TY  - JOUR
A1  - Crisologo, Irene
A1  - Heistermann, Maik
T1  - Using ground radar overlaps to verify the retrieval of calibration bias estimates from spaceborne platforms
JF  - Atmospheric measurement techniques : an interactive open access journal of the European Geosciences Union
N2  - Many institutions struggle to tap into the potential of their large archives of radar reflectivity: these data are often affected by miscalibration, yet the bias is typically unknown and temporally volatile. Still, relative calibration techniques can be used to correct the measurements a posteriori. For that purpose, the usage of spaceborne reflectivity observations from the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) platforms has become increasingly popular: the calibration bias of a ground radar (GR) is estimated from its average reflectivity difference to the spaceborne radar (SR). Recently, Crisologo et al. (2018) introduced a formal procedure to enhance the reliability of such estimates: each match between SR and GR observations is assigned a quality index, and the calibration bias is inferred as a quality-weighted average of the differences between SR and GR. The relevance of quality was exemplified for the Subic S-band radar in the Philippines, which is greatly affected by partial beam blockage. The present study extends the concept of quality-weighted averaging by accounting for path-integrated attenuation (PIA) in addition to beam blockage. This extension becomes vital for radars that operate at the C or X band. Correspondingly, the study setup includes a C-band radar that substantially overlaps with the S-band radar. Based on the extended quality-weighting approach, we retrieve, for each of the two ground radars, a time series of calibration bias estimates from suitable SR overpasses. As a result of applying these estimates to correct the ground radar observations, the consistency between the ground radars in the region of overlap increased substantially. Furthermore, we investigated if the bias estimates can be interpolated in time, so that ground radar observations can be corrected even in the absence of prompt SR overpasses. We found that a moving average approach was most suitable for that purpose, although limited by the absence of explicit records of radar maintenance operations.
Y1  - 2020
U6  - https://doi.org/10.5194/amt-13-645-2020
SN  - 1867-1381
SN  - 1867-8548
VL  - 13
IS  - 2
SP  - 645
EP  - 659
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Crisologo, Irene
A1  - Heistermann, Maik
T1  - Using ground radar overlaps to verify the retrieval of calibration bias estimates from spaceborne platforms
JF  - Atmospheric Measurement Techniques
N2  - Many institutions struggle to tap into the potential of their large archives of radar reflectivity: these data are often affected by miscalibration, yet the bias is typically unknown and temporally volatile. Still, relative calibration techniques can be used to correct the measurements a posteriori. For that purpose, the usage of spaceborne reflectivity observations from the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) platforms has become increasingly popular: the calibration bias of a ground radar (GR) is estimated from its average reflectivity difference to the spaceborne radar (SR). Recently, Crisologo et al. (2018) introduced a formal procedure to enhance the reliability of such estimates: each match between SR and GR observations is assigned a quality index, and the calibration bias is inferred as a quality-weighted average of the differences between SR and GR. The relevance of quality was exemplified for the Subic S-band radar in the Philippines, which is greatly affected by partial beam blockage.

The present study extends the concept of quality-weighted averaging by accounting for path-integrated attenuation (PIA) in addition to beam blockage. This extension becomes vital for radars that operate at the C or X band. Correspondingly, the study setup includes a C-band radar that substantially overlaps with the S-band radar. Based on the extended quality-weighting approach, we retrieve, for each of the two ground radars, a time series of calibration bias estimates from suitable SR overpasses. As a result of applying these estimates to correct the ground radar observations, the consistency between the ground radars in the region of overlap increased substantially. Furthermore, we investigated if the bias estimates can be interpolated in time, so that ground radar observations can be corrected even in the absence of prompt SR overpasses. We found that a moving average approach was most suitable for that purpose, although limited by the absence of explicit records of radar maintenance operations.
KW  - Weather
KW  - Band
KW  - Reflectivity
KW  - Algorithm
KW  - Uncertainties
KW  - Methodology
KW  - Kwajalein
Y1  - 2020
U6  - https://doi.org/10.5194/amt-13-645-2020
SN  - 1867-1381
SN  - 1867-8548
VL  - 13
IS  - 2
SP  - 645
EP  - 659
PB  - Copernicus Publications
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Dahm, Torsten
A1  - Stiller, Manfred
A1  - Mechie, James
A1  - Heimann, Sebastian
A1  - Hensch, Martin
A1  - Woith, Heiko
A1  - Schmidt, Bernd
A1  - Gabriel, Gerald
A1  - Weber, Michael
T1  - Seismological and geophysical signatures of the deep crustal magma systems of the cenozoic volcanic fields Beneath the Eifel, Germany
JF  - Geochemistry, geophysics, geosystems
N2  - The Quaternary volcanic fields of the Eifel (Rhineland-Palatinate, Germany) had their last eruptions less than 13,000 years ago. Recently, deep low-frequency (DLF) earthquakes were detected beneath one of the volcanic fields showing evidence of ongoing magmatic activity in the lower crust and upper mantle. In this work, seismic wide- and steep-angle experiments from 1978/1979 and 1987/1988 are compiled, partially reprocessed and interpreted, together with other data to better determine the location, size, shape, and state of magmatic reservoirs in the Eifel region near the crust-mantle boundary. We discuss seismic evidence for a low-velocity gradient layer from 30-36 km depth, which has developed over a large region under all Quaternary volcanic fields of the Rhenish Massif and can be explained by the presence of partial melts. We show that the DLF earthquakes connect the postulated upper mantle reservoir with the upper crust at a depth of about 8 km, directly below one of the youngest phonolitic volcanic centers in the Eifel, where CO(2)originating from the mantle is massively outgassing. A bright spot in the West Eifel between 6 and 10 km depth represents a Tertiary magma reservoir and is seen as a model for a differentiated reservoir beneath the young phonolitic center today. We find that the distribution of volcanic fields is controlled by the Variscan lithospheric structures and terrane boundaries as a whole, which is reflected by an offset of the Moho depth, a wedge-shaped transparent zone in the lower crust and the system of thrusts over about 120 km length.
KW  - magma reservoirs
KW  - distributed volcanic fields
KW  - reflection seismic
KW  - crustal magma chamber
KW  - deep low-frequency earthquakes
KW  - low velocity zone
Y1  - 2020
U6  - https://doi.org/10.1029/2020GC009062
SN  - 1525-2027
VL  - 21
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Dommain, René
A1  - Andama, Morgan
A1  - McDonough, Molly M.
A1  - Prado, Natalia A.
A1  - Goldhammer, Tobias
A1  - Potts, Richard
A1  - Maldonado, Jesús E.
A1  - Nkurunungi, John Bosco
A1  - Campana, Michael G.
T1  - The Challenges of Reconstructing Tropical Biodiversity With Sedimentary Ancient DNA
BT  - A 2200-Year-Long Metagenomic Record From Bwindi Impenetrable Forest, Uganda
JF  - Frontiers in Ecology and Evolution
N2  - Sedimentary ancient DNA has been proposed as a key methodology for reconstructing biodiversity over time. Yet, despite the concentration of Earth’s biodiversity in the tropics, this method has rarely been applied in this region. Moreover, the taphonomy of sedimentary DNA, especially in tropical environments, is poorly understood. This study elucidates challenges and opportunities of sedimentary ancient DNA approaches for reconstructing tropical biodiversity. We present shotgun-sequenced metagenomic profiles and DNA degradation patterns from multiple sediment cores from Mubwindi Swamp, located in Bwindi Impenetrable Forest (Uganda), one of the most diverse forests in Africa. We describe the taxonomic composition of the sediments covering the past 2200 years and compare the sedimentary DNA data with a comprehensive set of environmental and sedimentological parameters to unravel the conditions of DNA degradation. Consistent with the preservation of authentic ancient DNA in tropical swamp sediments, DNA concentration and mean fragment length declined exponentially with age and depth, while terminal deamination increased with age. DNA preservation patterns cannot be explained by any environmental parameter alone, but age seems to be the primary driver of DNA degradation in the swamp. Besides degradation, the presence of living microbial communities in the sediment also affects DNA quantity. Critically, 92.3% of our metagenomic data of a total 81.8 million unique, merged reads cannot be taxonomically identified due to the absence of genomic references in public databases. Of the remaining 7.7%, most of the data (93.0%) derive from Bacteria and Archaea, whereas only 0–5.8% are from Metazoa and 0–6.9% from Viridiplantae, in part due to unbalanced taxa representation in the reference data. The plant DNA record at ordinal level agrees well with local pollen data but resolves less diversity. Our animal DNA record reveals the presence of 41 native taxa (16 orders) including Afrotheria, Carnivora, and Ruminantia at Bwindi during the past 2200 years. Overall, we observe no decline in taxonomic richness with increasing age suggesting that several-thousand-year-old information on past biodiversity can be retrieved from tropical sediments. However, comprehensive genomic surveys of tropical biota need prioritization for sedimentary DNA to be a viable methodology for future tropical biodiversity studies.
KW  - sedimentary ancient DNA
KW  - tropical biodiversity
KW  - DNA preservation
KW  - sediment
KW  - tropical swamp
KW  - shotgun sequencing
KW  - metagenomic analysis
Y1  - 2019
U6  - https://doi.org/10.3389/fevo.2020.00218
SN  - 2296-701X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Durand, Virginie
A1  - Bentz, Stephan
A1  - Kwiatek, Grzegorz
A1  - Dresen, Georg
A1  - Wollin, Christopher
A1  - Heidbach, Oliver
A1  - Martinez-Garzon, Patricia
A1  - Cotton, Fabrice
A1  - Nurlu, Murat
A1  - Bohnhoff, Marco
T1  - A two-scale preparation phase preceded an M-w 5.8 earthquake in the sea of marmara offshore Istanbul, Turkey
JF  - Seismological research letters
N2  - We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an M-w 4.7 foreshock and M-w 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.
Y1  - 2020
U6  - https://doi.org/10.1785/0220200110
SN  - 0895-0695
SN  - 1938-2057
VL  - 91
IS  - 6
SP  - 3139
EP  - 3147
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Engels, Stefan
A1  - Medeiros, Andrew S.
A1  - Axford, Yarrow
A1  - Brooks, Steve
A1  - Heiri, Oliver
A1  - Luoto, Tomi P.
A1  - Nazarova, Larisa B.
A1  - Porinchu, David F.
A1  - Quinlan, Roberto
A1  - Self, Angela E.
T1  - Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity
JF  - Global change biology
N2  - Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a metadata analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric data sets overall consisting of 837 lakes. Our results indicate that in most of our data sets, summer temperature (T-jul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing T-jul in regions with present-day T-jul between 2.5 and 14 degrees C. In some areas with T-jul > 14 degrees C, chironomid diversity stabilizes or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (similar to 15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites.
KW  - Arctic
KW  - biodiversity
KW  - climate warming
KW  - freshwater ecosystems
KW  - insects
KW  - palaeoecology
KW  - Quaternary
Y1  - 2019
U6  - https://doi.org/10.1111/gcb.14862
SN  - 1354-1013
SN  - 1365-2486
VL  - 26
IS  - 3
SP  - 1155
EP  - 1169
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Esfahani, Reza Dokht Dolatabadi
A1  - Gholami, Ali
A1  - Ohrnberger, Matthias
T1  - An inexact augmented Lagrangian method for nonlinear dispersion-curve inversion using Dix-type global linear approximation
JF  - Geophysics : a journal of general and applied geophysics
N2  - Dispersion-curve inversion of Rayleigh waves to infer subsurface shear-wave velocity is a long-standing problem in seismology. Due to nonlinearity and ill-posedness, sophisticated regularization techniques are required to solve the problem for a stable velocity model. We have formulated the problem as a minimization problem with nonlinear operator constraint and then solve it by using an inexact augmented Lagrangian method, taking advantage of the Haney-Tsai Dix-type relation (a global linear approximation of the nonlinear forward operator). This replaces the original regularized nonlinear problem with iterative minimization of a more tractable regularized linear problem followed by a nonlinear update of the phase velocity (data) in which the update can be performed accurately with any forward modeling engine, for example, the finite-element method. The algorithm allows discretizing the medium with thin layers (for the finite-element method) and thus omitting the layer thicknesses from the unknowns and also allows incorporating arbitrary regularizations to shape the desired velocity model. In this research, we use total variation regularization to retrieve the shear-wave velocity model. We use two synthetic and two real data examples to illustrate the performance of the inversion algorithm with total variation regularization. We find that the method is fast and stable, and it converges to the solution of the original nonlinear problem.
KW  - surface wave
KW  - nonlinear
KW  - inversion
KW  - modeling
KW  - finite element
Y1  - 2020
U6  - https://doi.org/10.1190/geo2019-0717.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 3
SP  - EN77
EP  - EN85
PB  - GeoScienceWorld
CY  - Tulsa, Okla.
ER  - 
TY  - JOUR
A1  - Figueroa Villegas, Sara
A1  - Weiss, Jonathan R.
A1  - Hongn, Fernando D.
A1  - Pingel, Heiko
A1  - Escalante, Leonardo
A1  - Elías, Leonardo
A1  - Aranda-Viana, R. Germán
A1  - Strecker, Manfred
T1  - Late pleistocene to recent deformation in the thick-skinned fold-and-thrust belt of Northwestern Argentina (Central Calchaqui Valley, 26 degrees S)
JF  - Tectonics / American Geophysical Union, AGU ; European Geophysical Society, EGS
N2  - The thick-skinned fold-and-thrust belt on the eastern flank of the Andean Plateau in northwestern Argentina (NWA) is a zone of active contractional deformation characterized by fault-bounded mountain ranges with no systematic spatiotemporal pattern of tectonic activity. In contrast, the thin-skinned Subandean fold-and-thrust belt of northern Argentina and southern Bolivia is characterized primarily by in-sequence (i.e., west to east) fault progression, with a narrow zone of Quaternary deformation focused at the front of the orogenic wedge. To better understand how recent deformation is accommodated across these mountain ranges and the Argentinian portion of the orogen in particular, estimating and comparing deformation rates and patterns across different timescales is essential. We present Late Pleistocene shortening rates for the central Calchaqui intermontane valley in NWA associated with at least three episodes of deformation. Global Positioning System data for the same region reveal a gradual decrease in horizontal surface velocities from the Eastern Cordillera toward the foreland, which contrasts with the rapid velocity gradient associated with a locked decollement in the Subandean Ranges of southern Bolivia. Our new results represent a small view of regional deformation that, when considered in combination with the shallow crustal seismicity and decadal-scale surface velocities, support the notion that strain release in NWA is associated with numerous slowly deforming structures that are distributed throughout the orogen.
Y1  - 2020
U6  - https://doi.org/10.1029/2020TC006394
SN  - 0278-7407
SN  - 1944-9194
VL  - 40
IS  - 1
PB  - American Geophysical Union
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Forbriger, Thomas
A1  - Gao, Lingli
A1  - Malischewsky, Peter
A1  - Ohrnberger, Matthias
A1  - Pan, Yudi
T1  - A single Rayleigh mode may exist with multiple values of phase-velocity at one frequency
JF  - Geophysical journal international
N2  - Other than commonly assumed in seismology, the phase velocity of Rayleigh waves is not necessarily a single-valued function of frequency. In fact, a single Rayleigh mode can exist with three different values of phase velocity at one frequency. We demonstrate this for the first higher mode on a realistic shallow seismic structure of a homogeneous layer of unconsolidated sediments on top of a half-space of solid rock (LOH). In the case of LOH a significant contrast to the half-space is required to produce the phenomenon. In a simpler structure of a homogeneous layer with fixed (rigid) bottom (LFB) the phenomenon exists for values of Poisson's ratio between 0.19 and 0.5 and is most pronounced for P-wave velocity being three times S-wave velocity (Poisson's ratio of 0.4375). A pavement-like structure (PAV) of two layers on top of a half-space produces the multivaluedness for the fundamental mode. Programs for the computation of synthetic dispersion curves are prone to trouble in such cases. Many of them use mode-follower algorithms which loose track of the dispersion curve and miss the multivalued section. We show results for well established programs. Their inability to properly handle these cases might be one reason why the phenomenon of multivaluedness went unnoticed in seismological Rayleigh wave research for so long. For the very same reason methods of dispersion analysis must fail if they imply wave number k(l)(omega) for the lth Rayleigh mode to be a single-valued function of frequency.. This applies in particular to deconvolution methods like phase-matched filters. We demonstrate that a slant-stack analysis fails in the multivalued section, while a Fourier-Bessel transformation captures the complete Rayleigh-wave signal. Waves of finite bandwidth in the multivalued section propagate with positive group-velocity and negative phase-velocity. Their eigenfunctions appear conventional and contain no conspicuous feature.
KW  - Surface waves and free oscillations
KW  - Theoretical seismology
KW  - Wave
KW  - propagation
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa123
SN  - 0956-540X
SN  - 1365-246X
VL  - 222
IS  - 1
SP  - 582
EP  - 594
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Foster, William J.
A1  - Garvie, Christopher L.
A1  - Weiss, Anna M.
A1  - Muscente, A. Drew
A1  - Aberhan, Martin
A1  - Counts, John W.
A1  - Martindale, Rowan C.
T1  - Resilience of marine invertebrate communities during the early Cenozoic hyperthermals
JF  - Scientific Reports
N2  - The hyperthermal events of the Cenozoic, including the Paleocene-Eocene Thermal Maximum, provide an opportunity to investigate the potential effects of climate warming on marine ecosystems. Here, we examine the shallow benthic marine communities preserved in the late Cretaceous to Eocene strata on the Gulf Coastal Plain (United States). In stark contrast to the ecological shifts following the end-Cretaceous mass extinction, our data show that the early Cenozoic hyperthermals did not have a long-term impact on the generic diversity nor composition of the Gulf Coastal Plain molluscan communities. We propose that these communities were resilient to climate change because molluscs are better adapted to high temperatures than other taxa, as demonstrated by their physiology and evolutionary history. In terms of resilience, these communities differ from other shallow-water carbonate ecosystems, such as reef communities, which record significant changes during the early Cenozoic hyperthermals. These data highlight the strikingly different responses of community types, i.e., the almost imperceptible response of molluscs versus the marked turnover of foraminifera and reef faunas. The impact on molluscan communities may have been low because detrimental conditions did not devastate the entire Gulf Coastal Plain, allowing molluscs to rapidly recolonise vacated areas once harsh environmental conditions ameliorated.
KW  - eocene thermal maximum
KW  - gulf coastal plain
KW  - climate-change
KW  - ocean acidification
KW  - extinction event
KW  - carbon-cycle
KW  - heat-stress
KW  - origination
KW  - ecosystems
KW  - diversity
Y1  - 2020
U6  - https://doi.org/10.1038/s41598-020-58986-5
SN  - 2045-2322
VL  - 10
IS  - 1
SP  - 1
EP  - 11
PB  - Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Ganguli, Poulomi
A1  - Paprotny, Dominik
A1  - Hasan, Mehedi
A1  - Güntner, Andreas
A1  - Merz, Bruno
T1  - Projected changes in compound flood hazard from riverine and coastal floods in northwestern Europe
JF  - Earth's future
N2  - Compound flooding in coastal regions, that is, the simultaneous or successive occurrence of high sea levels and high river flows, is expected to increase in a warmer world. To date, however, there is no robust evidence on projected changes in compound flooding for northwestern Europe. We combine projected storm surges and river floods with probabilistic, localized relative sea-level rise (SLR) scenarios to assess the future compound flood hazard over northwestern coastal Europe in the high (RCP8.5) emission scenario. We use high-resolution, dynamically downscaled regional climate models (RCM) to drive a storm surge model and a hydrological model, and analyze the joint occurrence of high coastal water levels and associated river peaks in a multivariate copula-based approach. The RCM-forced multimodel mean reasonably represents the observed spatial pattern of the dependence strength between annual maxima surge and peak river discharge, although substantial discrepancies exist between observed and simulated dependence strength. All models overestimate the dependence strength, possibly due to limitations in model parameterizations. This bias affects compound flood hazard estimates and requires further investigation. While our results suggest decreasing compound flood hazard over the majority of sites by 2050s (2040-2069) compared to the reference period (1985-2005), an increase in projected compound flood hazard is limited to around 34% of the sites. Further, we show the substantial role of SLR, a driver of compound floods, which has frequently been neglected. Our findings highlight the need to be aware of the limitations of the current generation of Earth system models in simulating coastal compound floods.
KW  - compound flood
KW  - storm surge
KW  - river floods
KW  - sea level rise
KW  - climate
KW  - change
KW  - Europe
Y1  - 2020
U6  - https://doi.org/10.1029/2020EF001752
SN  - 2328-4277
VL  - 8
IS  - 11
PB  - Wiley-Blackwell
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Ghani, Humaad
A1  - Sobel, Edward
A1  - Zeilinger, Gerold
A1  - Glodny, Johannes
A1  - Zapata, Sebastian
A1  - Irum, Irum
T1  - Palaeozoic and Pliocene tectonic evolution of the Salt Range constrained by low-temperature thermochronology
JF  - Terra nova
N2  - The Salt Range in Pakistan exposes Precambrian to Pleistocene strata outcropping along the Salt Range Thrust (SRT). To better understand the in-situ Cambrian and Pliocene tectonic evolution of the Pakistan Subhimalaya, we have conducted low-temperature thermochronological analysis using apatite (U-Th-Sm)/He and fission track dating. We combine cooling ages from different samples located along the thrust front of the SRT into a thermal model that shows two major cooling events associated with rifting and regional erosion in the Late Palaeozoic and SRT activity since the Pliocene. Our results suggest that the SRT maintained a long-term average shortening rate of similar to 5-6 mm/yr and a high exhumation rate above the SRT ramp since similar to 4 Ma.
KW  - exhumation
KW  - fault bend fold
KW  - ramp
KW  - Salt Range
Y1  - 2020
U6  - https://doi.org/10.1111/ter.12515
SN  - 0954-4879
SN  - 1365-3121
VL  - 33
IS  - 3
SP  - 293
EP  - 305
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Giarolla, Emanuel
A1  - Veiga, Sandro F.
A1  - Nobre, Paulo
A1  - Silva, Manoel B.
A1  - Capistrano, Vinicius B.
A1  - Callegare, Andyara O.
T1  - Sea surface height trends in the southern hemisphere oceans simulated by the Brazilian Earth System Model under RCP4.5 and RCP8.5 scenarios
JF  - Journal of southern hemisphere earth systems science
N2  - The Brazilian Earth System Model (BESM-OA2.5), while simulating the historical period proposed by the fifth phase of the Coupled Model Intercomparison Project (CMIP5), detects an increasing trend in the sea surface height (SSH) on the southern hemisphere oceans relative to that of the pre-industrial era. The increasing trend is accentuated in the CMIP5 RCP4.5 and RCP8.5 future scenarios with higher concentrations of greenhouse gases in the atmosphere. This study sheds light on the sources of such trends in these regions. The results suggest an association with the thermal expansion of the oceans in the upper 700 m due to a gradual warming inflicted by those future scenarios. BESM-OA2.5 presents a surface height increase of 0.11 m in the historical period of 1850-2005. Concerning future projections, BESM-OA2.5 projects SSH increases of 0.14 and 0.23 m (relative to the historical 2005 value) for RCP4.5 and RCP8.5, respectively, by the end of 2100. These increases are predominantly in a band of latitude within 35-60 degrees S in the Atlantic and Indian oceans. The reproducibility of the trend signal detected in the BESM-OA2.5 simulations is confirmed by the results of three other CMIP5 models.
KW  - Brazilian Earth System Model
KW  - CMIP5
KW  - IPCC AR5 scenarios
KW  - RCP4.5
KW  - RCP8.5
KW  - sea level trends
KW  - sea surface height
KW  - southern hemisphere oceans
Y1  - 2020
U6  - https://doi.org/10.1071/ES19042
SN  - 2206-5865
VL  - 70
IS  - 1
SP  - 280
EP  - 289
PB  - CSIRO
CY  - Clayton
ER  - 
TY  - JOUR
A1  - Glerum, Anne
A1  - Brune, Sascha
A1  - Stamps, D. Sarah
A1  - Strecker, Manfred
T1  - Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift
JF  - Nature Communications
N2  - The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria's rotation is primarily controlled by the distribution of rheologically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria's GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress. One of the largest continental microplates on Earth is situated in the center of the East African Rift System, and oddly, the Victoria microplate rotates counterclockwise with respect to the neighboring African tectonic plate. Here, the authors' modelling results suggest that Victoria microplate rotation is caused by edge-driven lithospheric processes related to the specific geometry of rheologically weak and strong regions.
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-16176-x
SN  - 2041-1723
VL  - 11
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Govin, Gwladys
A1  - van der Beek, Pieter A.
A1  - Najman, Yani
A1  - Millar, Ian
A1  - Gemignani, Lorenzo
A1  - Huyghe, Pascale
A1  - Dupont-Nivet, Guillaume
A1  - Bernet, Matthias
A1  - Mark, Chris
A1  - Wijbrans, Jan
T1  - Early onset and late acceleration of rapid exhumation in the Namche Barwa syntaxis, eastern Himalaya
JF  - Geology
N2  - The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface erosion initiated in the late Miocene (8-10 Ma). Recent studies, in contrast, suggest a Quaternary onset of rapid exhumation linked to a purely tectonic mechanism. We report new multisystem detrital thermochronology data from the most proximal Neogene clastic sediments downstream of Namche Barwa and use a thermo-kinematic model constrained by new and published data to explore its exhumation history. Modeling results show that exhumation accelerated to similar to 4 km/m.y. at ca. 8 Ma and to similar to 9 km/m.y. after ca. 2 Ma. This three-stage history reconciles apparently contradictory evidence for early and late onset of rapid exhumation and suggests efficient coupling between tectonics and erosion since the late Miocene. Quaternary acceleration of exhumation is consistent with river-profile evolution and may be linked to a Quaternary river-capture event.
Y1  - 2020
U6  - https://doi.org/10.1130/G47720.1
SN  - 0091-7613
SN  - 1943-2682
VL  - 48
IS  - 12
SP  - 1139
EP  - 1143
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Grotheer, Hendrik
A1  - Meyer, Vera
A1  - Riedel, Theran
A1  - Pfalz, Gregor
A1  - Mathieu, Lucie
A1  - Hefter, Jens H.
A1  - Gentz, Torben
A1  - Lantuit, Hugues
A1  - Mollennauer, Gesine
A1  - Fritz, Michael
T1  - Burial and origin of permafrost-derived carbon in the nearshore zone of the southern Canadian Beaufort Sea
JF  - Geophysical research letters
N2  - Detailed organic geochemical and carbon isotopic (delta C-13 and Delta C-14) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea) and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end-member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that similar to 40% of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs, and canyons for the carbon sequestration in previously poorly investigated, nearshore areas. 

Plain Language Summary Increasing air and sea surface temperatures at high latitudes leads to accelerated thaw, destabilization, and erosion of perennially frozen soils (i.e., permafrost), which are often rich in organic carbon. Coastal erosion leads to an increased mobilization of organic carbon into the Arctic Ocean, which there can be converted into greenhouse gases and may therefore contribute to further warming. Carbon decomposition can be limited if organic matter is efficiently deposited on the seafloor, buried in marine sediments, and thus removed from the short-term carbon cycle. Basins, canyons, and troughs near the coastline can serve as sediment traps and potentially accommodate large quantities of organic carbon along the Arctic coast. Here we use biomarkers (source-specific molecules), stable carbon isotopes, and radiocarbon to identify the sources of organic carbon in the nearshore zone of the southern Canadian Beaufort Sea near Herschel Island. We quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget of the area and estimate that more than a third of all carbon released by local permafrost erosion is efficiently trapped in marine sediments. This highlights the importance of regional sediment traps for carbon sequestration.
Y1  - 2020
U6  - https://doi.org/10.1029/2019GL085897
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 3
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Guzman, Diego A.
A1  - Samprogna Mohor, Guilherme
A1  - Mendiondo, Eduardo Mario
T1  - Multi-year index-based insurance for adapting Water Utility Companies to hydrological drought
BT  - case study of a water supply system of the Sao Paulo metropolitan region, Brazil
JF  - Water
N2  - The sustainability of water utility companies is threatened by non-stationary drivers, such as climate and anthropogenic changes. To cope with potential economic losses, instruments such as insurance are useful for planning scenarios and mitigating impacts, but data limitations and risk uncertainties affect premium estimation and, consequently, business sustainability. This research estimated the possible economic impacts of business interruption to the Sao Paulo Water Utility Company derived from hydrological drought and how this could be mitigated with an insurance scheme. Multi-year insurance (MYI) was proposed through a set of "change" drivers: the climate driver, through forcing the water evaluation and planning system (WEAP) hydrological tool; the anthropogenic driver, through water demand projections; and the economic driver, associated with recent water price policies adopted by the utility company during water scarcity periods. In our study case, the evaluated indices showed that MYI contracts that cover only longer droughts, regardless of the magnitude, offer better financial performance than contracts that cover all events (in terms of drought duration). Moreover, through MYI contracts, we demonstrate solvency for the insurance fund in the long term and an annual average actuarially fair premium close to the total expected revenue reduction.
KW  - multi-year insurance
KW  - climate change
KW  - hydrological drought
KW  - water
KW  - security and economy
Y1  - 2020
U6  - https://doi.org/10.3390/w12112954
SN  - 2073-4441
VL  - 12
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Heeschen, Katja U.
A1  - Janocha, Julian
A1  - Spangenberg, Erik
A1  - Schicks, Judith Maria
A1  - Giese, Ronny
T1  - The impact of ice on the tensile strength of unconsolidated sand
BT  - a model for gas hydrate-bearing sands?
JF  - Marine and petroleum geology
N2  - Tensile strength is an important parameter when it comes to predictions of potential fracturing of sediments by natural processes such as the emplacement of ice or gas hydrate lenses, as well as anthropogenic fracturing or else the stability of engineering constructions such as boreholes. Yet, tensile strength (sigma(tau)) measurements of unconsolidated ice-bearing or gas hydrate-bearing sands are scarce and affected by a large variability. <br /> In the course of the SUGAR project we successfully used ice as a model for pore-filling and "load-bearing" gas hydrate in sand to determine compressional wave velocity. We were thus able to verify comparable formation characteristics and morphologies of ice and gas hydrate within the pore space. As these are important values for the tensile strength of ice/hydrate-bearing sands, ice was also used as a model for hydrate-bearing sands, despite differences in the mechanical behavior and strength of pure ice and gas hydrate. Water-saturated sand cores with ice saturations (S-ice) between 0 and 100% were tested at -6.8 degrees C. The varying S-ice were a result of the freezing point depression caused by saline solutions of different concentrations. The sigma(tau) was directly determined using a sleeve-fracturing test with an internal pressure that was created within the frozen samples. The setup was also adapted to fit a pressure vessel for tests using confining pressure. <br /> The correlation of S-ice - sigma(tau) shows an exponential increase of sigma(tau) with S-ice. Whereas at S-ice < 60% the increase is small, it is large at S-ice > 80%. In conjunction with the change in strength, the viscoelastic behavior changes. A clear peak strength occurs at S-ice > 80%. We conclude that given 60% < S-ice < 80% the pore-filling morphology of the ice converts into a frame-building habitus and at S-ice > 80% the frame gains strength while the amount of residual water decreases. Tensile failure and cracking now exceed grain boundary sliding as the prevailing failure mode. The ice morphology in the sand is non-cementing and comparable to a gas hydrate-sand mixture.
KW  - tensile strength
KW  - ice-grain mixture
KW  - gas hydrate
KW  - saline permafrost
KW  - ice
KW  - frozen soil
Y1  - 2020
U6  - https://doi.org/10.1016/j.marpetgeo.2020.104607
SN  - 0264-8172
SN  - 1873-4073
VL  - 122
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Hennig, Theresa
A1  - Stockmann, Madlen
A1  - Kühn, Michael
T1  - Simulation of diffusive uranium transport and sorption processes in the Opalinus Clay
JF  - Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry
N2  - Diffusive transport and sorption processes of uranium in the Swiss Opalinus Clay were investigated as a function of partial pressure of carbon dioxide pCO(2), varying mineralogy in the facies and associated changes in porewater composition. Simulations were conducted in one-dimensional diffusion models on the 100 m-scale for a time of one million years using a bottom-up approach based on mechanistic surface complexation models as well as cation exchange to quantify sorption. Speciation calculations have shown, uranium is mainly present as U(VI) and must therefore be considered as mobile for in-situ conditions. Uranium migrated up to 26 m in both, the sandy and the carbonate-rich facies, whereas in the shaly facies 16 m was the maximum. The main species was the anionic complex CaUO2(CO3)(3)(2-) . Hence, anion exclusion was taken into account and further reduced the migration distances by 30 %. The concentrations of calcium and carbonates reflected by the set pCO(2) determine speciation and activity of uranium and consequently the sorption behaviour. Our simulation results allow for the first time to prioritize on the far-field scale the governing parameters for diffusion and sorption of uranium and hence outline the sensitivity of the system. Sorption processes are controlled in descending priority by the carbonate and calcium concentrations, pH, pe and the clay mineral content. Therefore, the variation in porewater composition resulting from the heterogeneity of the facies in the Opalinus Clay formation needs to be considered in the assessment of uranium migration in the far field of a potential repository.
KW  - reactive transport
KW  - facies
KW  - heterogeneity
KW  - carbonate
KW  - PHREEQC
KW  - Mont Terri
KW  - speciation
Y1  - 2020
U6  - https://doi.org/10.1016/j.apgeochem.2020.104777
SN  - 0883-2927
SN  - 1872-9134
VL  - 123
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Huang, Sichao
A1  - Herzschuh, Ulrike
A1  - Pestryakova, Luidmila Agafyevna
A1  - Zimmermann, Heike Hildegard
A1  - Davydova, Paraskovya
A1  - Biskaborn, Boris
A1  - Shevtsova, Iuliia
A1  - Stoof-Leichsenring, Kathleen Rosemarie
T1  - Genetic and morphologic determination of diatom community composition in surface sediments from glacial and thermokarst lakes in the Siberian Arctic
JF  - Journal of paleolimnolog
N2  - Lakes cover large parts of the climatically sensitive Arctic landscape and respond rapidly to environmental change. Arctic lakes have different origins and include the predominant thermokarst lakes, which are small, young and highly dynamic, as well as large, old and stable glacial lakes. Freshwater diatoms dominate the primary producer community in these lakes and can be used to detect biotic responses to climate and environmental change. We used specific diatom metabarcoding on sedimentary DNA, combined with next-generation sequencing and diatom morphology, to assess diatom diversity in five glacial and 15 thermokarst lakes within the easternmost expanse of the Siberian treeline ecotone in Chukotka, Russia. We obtained 163 verified diatom sequence types and identified 176 diatom species morphologically. Although there were large differences in taxonomic assignment using the two approaches, they showed similar high abundances and diversity of Fragilariceae and Aulacoseiraceae. In particular, the genetic approach detected hidden within-lake variations of fragilarioids in glacial lakes and dominance of centric Aulacoseira species, whereas Lindavia ocellata was predominant using morphology. In thermokarst lakes, sequence types and valve counts also detected high diversity of Fragilariaceae, which followed the vegetation gradient along the treeline. Ordination analyses of the genetic data from glacial and thermokarst lakes suggest that concentrations of sulfate (SO42-), an indicator of the activity of sulfate-reducing microbes under anoxic conditions, and bicarbonate (HCO3-), which relates to surrounding vegetation, have a significant influence on diatom community composition. For thermokarst lakes, we also identified lake depth as an important variable, but SO42- best explains diatom diversity derived from genetic data, whereas HCO3- best explains the data from valve counts. Higher diatom diversity was detected in glacial lakes, most likely related to greater lake age and different edaphic settings, which gave rise to diversification and endemism. In contrast, small, dynamic thermokarst lakes are inhabited by stress-tolerant fragilarioids and are related to different vegetation types along the treeline ecotone. Our study demonstrated that genetic investigations of lake sediments can be used to interpret climate and environmental responses of diatoms. It also showed how lake type affects diatom diversity, and that such genetic analyses can be used to track diatom community changes under ongoing warming in the Arctic.
KW  - diatoms
KW  - diversity
KW  - glacial lakes
KW  - sedimentary DNA
KW  - Siberian arctic
KW  - thermokarst
Y1  - 2020
U6  - https://doi.org/10.1007/s10933-020-00133-1
SN  - 0921-2728
SN  - 1573-0417
VL  - 64
IS  - 3
SP  - 225
EP  - 242
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Hudson, Paul
T1  - The affordability of flood risk property-level adaptation measures
JF  - Risk Analysis
N2  - The affordability of property-level adaptation measures against flooding is crucial due to the movement toward integrated flood risk management, which requires the individuals threatened by flooding to actively manage flooding. It is surprising to find that affordability is not often discussed, given the important roles that affordability and social justice play regarding flood risk management. This article provides a starting point for investigating the potential rate of unaffordability of flood risk property-level adaptation measures across Europe using two definitions of affordability, which are combined with two different affordability thresholds from within flood risk research. It uses concepts of investment and payment affordability, with affordability thresholds based on residual income and expenditure definitions of unaffordability. These concepts, in turn, are linked with social justice through fairness concerns, in that, all should have equal capability to act, of which affordability is one avenue. In doing so, it was found that, for a large proportion of Europe, property owners generally cannot afford to make one-time payment of the cost of protective measures. These can be made affordable with installment payment mechanisms or similar mechanisms that spread costs over time. Therefore, the movement toward greater obligations for flood-prone residents to actively adapt to flooding should be accompanied by socially accessible financing mechanisms.
KW  - Affordability
KW  - flood risk
KW  - social justice
KW  - risk reduction
Y1  - 2020
U6  - https://doi.org/10.1111/risa.13465
SN  - 0272-4332
SN  - 1539-6924
VL  - 40
IS  - 6
SP  - 1151
EP  - 1167
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Izgi, Gizem
A1  - Eken, Tuna
A1  - Gaebler, Peter
A1  - Eulenfeld, Tom
A1  - Taymaz, Tuncay
T1  - Crustal seismic attenuation parameters in the western region of the North Anatolian Fault Zone
JF  - Journal of geodynamics
N2  - Detailed knowledge of the crustal structure along the North Anatolian Fault Zone can help in understanding past and present tectonic processes in relation to the deformation history. To estimate the frequency-dependent crustal attenuation parameters beneath the western part of the North Anatolian Fault Zone we apply acoustic radiative transfer theory under the assumption of multiple isotropic scattering to generate synthetic seismogram envelopes. The inversion depends on finding an optimal fit between observed and synthetically computed coda wave envelopes in five frequency bands. 2-D lateral variation of intrinsic and scattering attenuation at various frequencies tends to three crustal blocks (i.e., Armutlu-Almacik, Istanbul-Zonguldak and Sakarya Zones) separated by the southern and northern branches of the western part of the North Anatolian Fault Zone. Overall, scattering attenuation appears to be dominant over intrinsic attenuation in the study area at lower frequencies. Relatively low attenuation properties are observed beneath the older Istanbul Zone whereas higher attenuation properties are found for the younger Sakarya Zone. The Armutlu Almacik Zone exhibits more complex lateral variations. Very high attenuation values towards the west characterize the area of the Kuzuluk Basin, a pull-apart basin formed under west-east extension. Our coda-derived moment magnitudes are similar to the local magnitude estimates that were previously calculated for the same earthquakes. For smaller earthquakes (M-L < 2.5), however, the relation between local and moment magnitudes appears to lose its coherency. This may stem from various reasons including the use of seismic data recorded in finite sampling interval, possible biases in local magnitude estimates of earthquake catalogues as well as biases due to wrong assumptions to consider anelastic attenuation terms.
Y1  - 2020
U6  - https://doi.org/10.1016/j.jog.2020.101694
SN  - 0264-3707
VL  - 134
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Jones, Benjamin M.
A1  - Arp, Christopher D.
A1  - Grosse, Guido
A1  - Nitze, Ingmar
A1  - Lara, Mark J.
A1  - Whitman, Matthew S.
A1  - Farquharson, Louise M.
A1  - Kanevskiy, Mikhail
A1  - Parsekian, Andrew D.
A1  - Breen, Amy L.
A1  - Ohara, Nori
A1  - Rangel, Rodrigo Correa
A1  - Hinkel, Kenneth M.
T1  - Identifying historical and future potential lake drainage events on the western Arctic coastal plain of Alaska
JF  - Permafrost and Periglacial Processes
N2  - Arctic lakes located in permafrost regions are susceptible to catastrophic drainage. In this study, we reconstructed historical lake drainage events on the western Arctic Coastal Plain of Alaska between 1955 and 2017 using USGS topographic maps, historical aerial photography (1955), and Landsat Imagery (ca. 1975, ca. 2000, and annually since 2000). We identified 98 lakes larger than 10 ha that partially (>25% of area) or completely drained during the 62-year period. Decadal-scale lake drainage rates progressively declined from 2.0 lakes/yr (1955-1975), to 1.6 lakes/yr (1975-2000), and to 1.2 lakes/yr (2000-2017) in the ~30,000-km(2) study area. Detailed Landsat trend analysis between 2000 and 2017 identified two years, 2004 and 2006, with a cluster (five or more) of lake drainages probably associated with bank overtopping or headward erosion. To identify future potential lake drainages, we combined the historical lake drainage observations with a geospatial dataset describing lake elevation, hydrologic connectivity, and adjacent lake margin topographic gradients developed with a 5-m-resolution digital surface model. We identified ~1900 lakes likely to be prone to drainage in the future. Of the 20 lakes that drained in the most recent study period, 85% were identified in this future lake drainage potential dataset. Our assessment of historical lake drainage magnitude, mechanisms and pathways, and identification of potential future lake drainages provides insights into how arctic lowland landscapes may change and evolve in the coming decades to centuries.
KW  - Arctic lakes
KW  - drained lake basins
KW  - lake drainage
KW  - permafrost regions
KW  - thermokarst lakes
Y1  - 2020
U6  - https://doi.org/10.1002/ppp.2038
VL  - 31
IS  - 1
SP  - 110
EP  - 127
PB  - Wiley
CY  - New York
ER  - 
TY  - JOUR
A1  - Karamzadeh Toularoud, Nasim
A1  - Heimann, Sebastian
A1  - Dahm, Torsten
A1  - Krüger, Frank
T1  - Earthquake source arrays
BT  - optimal configuration and applications in crustal structure studies
JF  - Geophysical journal international
N2  - A collection of earthquake sources recorded at a single station, under specific conditions, are considered as a source array (SA), that is interpreted as if earthquake sources originate at the station location and are recorded at the source location. Then, array processing methods, that is array beamforming, are applicable to analyse the recorded signals. A possible application is to use source array multiple event techniques to locate and characterize near-source scatterers and structural interfaces. In this work the aim is to facilitate the use of earthquake source arrays by presenting an automatic search algorithm to configure the source array elements. We developed a procedure to search for an optimal source array element distribution given an earthquake catalogue including accurate origin time and hypocentre locations. The objective function of the optimization process can be flexibly defined for each application to ensure the prerequisites (criteria) of making a source array. We formulated four quantitative criteria as subfunctions and used the weighted sum technique to combine them in one single scalar function. The criteria are: (1) to control the accuracy of the slowness vector estimation using the time domain beamforming method, (2) to measure the waveform coherency of the array elements, (3) to select events with lower location error and (4) to select traces with high energy of specific phases, that is, sp- or ps-phases. The proposed procedure is verified using synthetic data as well as real examples for the Vogtland region in Northwest Bohemia. We discussed the possible application of the optimized source arrays to identify the location of scatterers in the velocity model by presenting a synthetic test and an example using real waveforms.
KW  - location of scatterers
KW  - optimization
KW  - source array design
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa002
SN  - 0956-540X
SN  - 1365-246X
VL  - 221
IS  - 1
SP  - 352
EP  - 370
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kaya, Mustafa Yuecel
A1  - Dupont-Nivet, Guillaume
A1  - Proust, Jean-Noël
A1  - Roperch, Pierrick
A1  - Meijer, Niels
A1  - Frieling, Joost
A1  - Fioroni, Chiara
A1  - Altiner, Sevinç Özkan
A1  - Stoica, Marius
A1  - Aminov, Jovid
A1  - Mamtimin, Mehmut
A1  - Guo, Zhaojie
T1  - Cretaceous evolution of the Central Asian Proto-Paratethys Sea
BT  - tectonic, eustatic, and climatic controls
JF  - Tectonics
N2  - The timing and mechanisms of the Cretaceous sea incursions into Central Asia are still poorly constrained. We provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of Cretaceous records of the proto-Paratethys Sea fluctuations in the Tajik and Tarim basins. The Early Cretaceous marine incursion in the western Tajik Basin was followed by major marine incursions during the Cenomanian (ca. 100 Ma) and Santonian (ca. 86 Ma) that reached far into the eastern Tajik and Tarim basins. These marine incursions were separated by a Turonian-Coniacian (ca. 92-86 Ma) regression. Basin-wide tectonic subsidence analyses imply that the Early Cretaceous sea incursion into the Tajik Basin was related to increased Pamir tectonism. We find that thrusting along the northern edge of the Pamir at ca. 130-90 Ma resulted in increased subsidence in a retro-arc basin setting. This tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the Cenomanian (ca. 100 Ma). The following Turonian-Coniacian (ca. 92-86 Ma) major regression, driven by eustasy, coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting. The Santonian (ca. 86 Ma) major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west Siberian Basin. An early Maastrichtian cooling (ca. 71-70 Ma), potentially connected to global Late Cretaceous trends, is inferred from the replacement of mollusk-rich limestones by bryozoan- and echinoderm-rich limestones.
Y1  - 2020
U6  - https://doi.org/10.1029/2019TC005983
SN  - 0278-7407
SN  - 1944-9194
VL  - 39
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Klose, Tim
A1  - Chaparro, M. Carme
A1  - Schilling, Frank
A1  - Butscher, Christoph
A1  - Klumbach, Steffen
A1  - Blum, Philipp
T1  - Fluid flow simulations of a large-scale borehole leakage experiment
JF  - Transport in Porous Media
N2  - Borehole leakage is a common and complex issue. Understanding the fluid flow characteristics of a cemented area inside a borehole is crucial to monitor and quantify the wellbore integrity as well as to find solutions to minimise existing leakages. In order to improve our understanding of the flow behaviour of cemented boreholes, we investigated experimental data of a large-scale borehole leakage tests by means of numerical modelling using three different conceptual models. The experiment was performed with an autoclave system consisting of two vessels bridged by a cement-filled casing. After a partial bleed-off at the well-head, a sustained casing pressure was observed due to fluid flow through the cementsteel composite. The aim of our simulations is to investigate and quantify the permeability of the cement-steel composite. From our model results, we conclude that the flow occurred along a preferential flow path at the cement-steel interface. Thus, the inner part of the cement core was impermeable during the duration of the experiment. The preferential flow path can be described as a highly permeable and highly porous area with an aperture of about 5 mu m and a permeability of 3 . 10(-12) m(2) (3 Darcy). It follows that the fluid flow characteristics of a cemented area inside a borehole cannot be described using one permeability value for the entire cement-steel composite. Furthermore, it can be concluded that the quality of the cement and the filling process regarding the cement-steel interface is crucial to minimize possible well leakages.
KW  - borehole leakage
KW  - sustained casing pressure
KW  - permeability test
KW  - cement
KW  - modelling
Y1  - 2020
U6  - https://doi.org/10.1007/s11242-020-01504-y
SN  - 0169-3913
SN  - 1573-1634
VL  - 136
IS  - 1
SP  - 125
EP  - 145
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Koyan, Philipp
A1  - Tronicke, Jens
T1  - 3D modeling of ground-penetrating radar data across a realistic sedimentary model
JF  - Computers & geosciences : an international journal devoted to the publication of papers on all aspects of geocomputation and to the distribution of computer programs and test data sets ; an official journal of the International Association for Mathematical Geology
N2  - Ground-penetrating radar (GPR) is an established geophysical tool to explore a wide range of near-surface environments. Today, the use of synthetic GPR data is largely limited to 2D because 3D modeling is computationally more expensive. In fact, only recent developments of modeling tools and powerful hardware allow for a time-efficient computation of extensive 3D data sets. Thus, 3D subsurface models and resulting GPR data sets, which are of great interest to develop and evaluate novel approaches in data analysis and interpretation, have not been made publicly available up to now. <br /> We use a published hydrofacies data set of an aquifer-analog study within fluvio-glacial deposits to infer a realistic 3D porosity model showing heterogeneities at multiple spatial scales. Assuming fresh-water saturated sediments, we generate synthetic 3D GPR data across this model using novel GPU-acceleration included in the open-source software gprMax. We present a numerical approach to examine 3D wave-propagation effects in modeled GPR data. Using the results of this examination study, we conduct a spatial model decomposition to enable a computationally efficient 3D simulation of a typical GPR reflection data set across the entire model surface. We process the resulting GPR data set using a standard 3D structural imaging sequence and compare the results to selected input data to demonstrate the feasibility and potential of the presented modeling studies. We conclude on conceivable applications of our 3D GPR reflection data set and the underlying porosity model, which are both publicly available and, thus, can support future methodological developments in GPR and other near-surface geophysical techniques.
KW  - Applied geophysics
KW  - Ground-penetrating radar
KW  - 3D modeling
Y1  - 2020
U6  - https://doi.org/10.1016/j.cageo.2020.104422
SN  - 0098-3004
SN  - 1873-7803
VL  - 137
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Krmíček, Lukáš
A1  - Timmerman, Martin Jan
A1  - Ziemann, Martin Andreas
A1  - Sudo, Masafumi
A1  - Ulrych, Jaromir
T1  - 40Ar/39Ar step-heating dating of phlogopite and kaersutite megacrysts from the Železná hůrka (Eisenbühl) Pleistocene scoria cone, Czech Republic
JF  - Geologica Carpathica
N2  - (40)A/Ar-39 step-heating of mica and amphibole megacrysts from hauyne-bearing olivine melilitite scoria/tephra from the Zelezna hurka yielded a 435 +/- 108 ka isotope correlation age for phlogopite and a more imprecise 1.55 Ma total gas age of the kaersutite megacryst. The amphibole megacrysts may constitute the first, and the younger phlogopite megacrysts the later phase of mafic, hydrous melilitic magma crystallization. It cannot be ruled out that the amphibole megacrysts are petrogenetically unrelated to tephra and phlogopite megacrysts and were derived from mantle xenoliths or disaggregated older, deep crustal pegmatites. This is in line both with the rarity of amphibole at Zelezna hurka and with the observed signs of magmatic resorption at the edges of amphibole crystals.
KW  - Bohemian Massif
KW  - Zelezna hurka
KW  - Eisenbuhl
KW  - argon dating
KW  - mica
KW  - amphibole
KW  - melilitite
Y1  - 2020
U6  - https://doi.org/10.31577/GeolCarp.71.4.6
SN  - 1335-0552
SN  - 1336-8052
VL  - 71
IS  - 4
SP  - 382
EP  - 387
PB  - Veda
CY  - Bratislava
ER  - 
TY  - JOUR
A1  - Kruse, Stefan
A1  - Kolmogorov, Aleksey I.
A1  - Pestryakova, Luidmila Agafyevna
A1  - Herzschuh, Ulrike
T1  - Long-lived larch clones may conserve adaptations that could restrict treeline migration in northern Siberia
JF  - Ecology and evolution
N2  - The occurrence of refugia beyond the arctic treeline and genetic adaptation therein play a crucial role of largely unknown effect size. While refugia have potential for rapidly colonizing the tundra under global warming, the taxa may be maladapted to the new environmental conditions. Understanding the genetic composition and age of refugia is thus crucial for predicting any migration response. 
Here, we genotype 194 larch individuals from an similar to 1.8 km(2)area in northcentral Siberia on the southern Taimyr Peninsula by applying an assay of 16 nuclear microsatellite markers. For estimating the age of clonal individuals, we counted tree rings at sections along branches to establish a lateral growth rate that was then combined with geographic distance.
Findings reveal that the predominant reproduction type is clonal (58.76%) by short distance spreading of ramets. One outlier of clones 1 km apart could have been dispersed by reindeer. In clonal groups and within individuals, we find that somatic mutations accumulate with geographic distance. Clonal groups of two or more individuals are observed. Clonal age estimates regularly suggest individuals as old as 2,200 years, which coincides with a major environmental change that forced a treeline retreat in the region. 
We conclude that individuals with clonal growth mode were naturally selected as it lowers the likely risk of extinction under a harsh environment. We discuss this legacy from the past that might now be a maladaptation and hinder expansion under currently strongly increasing temperatures.
KW  - adaptation
KW  - clonal growth
KW  - growth rate
KW  - Larix
KW  - leading edge
KW  - treeline
KW  - migration
Y1  - 2020
U6  - https://doi.org/10.1002/ece3.6660
SN  - 2045-7758
VL  - 10
IS  - 18
SP  - 10017
EP  - 10030
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Krüger, Frank
A1  - Dahm, Torsten
A1  - Hannemann, Katrin
T1  - Mapping of Eastern North Atlantic Ocean seismicity from Po/So observations at a mid-aperture seismological broad-band deep sea array
JF  - Geophysical journal international
N2  - A mid-aperture broad-band test array (OBS array DOCTAR) was deployed from June 2011 to April 2012 about 100 km north of the Gloria fault in the Eastern North Atlantic in about 5000 m water depth. In addition arrays were installed on Madeira Island and in western Portugal mainland. For the first time in the Eastern North Atlantic, we recorded a large number of high frequency Po and So waves from local and regional small and moderate earthquakes (M-L < 4). An incoherent beamforming method was adapted to scan continuous data for such Po and So arrivals applying a sliding window waveform migration and frequency-wavenumber technique. We identify about 320 Po and 1550 So arrivals and compare the phase onsets with the ISC catalogue (ISC 2015) for the same time span. Up to a distance of 6 degrees to the DOCTAR stations all events listed in the ISC catalogue could be associated to Po and So phases. Arrivals from events in more than 10 degrees distance could be identified only in some cases. Only few Po and/or So arrivals were detected for earthquakes from the European and African continental area, the continental shelf regions and for earthquakes within or northwest of the Azores plateau. Unexpectedly, earthquake clusters are detected within the oceanic plates north and south of the Gloria fault and far from plate boundaries, indicating active intraplate structures. We also observe and locate numerous small magnitude earthquakes on the segment of the Gloria fault directly south of DOCTAR, which likely coincides with the rupture of the 25 November 1941 event. Local small magnitude earthquakes located beneath DOCTAR show hypocentres up to 30 km depth and strike-slip focal mechanisms. A comparison with detections at temporary mid-aperture arrays on Madeira and in western Portugal shows that the deep ocean array performs much better than the island and the continental array regarding the detection threshold for events in the oceanic plates. 
 We conclude that sparsely distributed mid-aperture seismic arrays in the deep ocean could decrease the detection and location threshold for seismicity with M-L < 4 in the oceanic plate and might constitute a valuable tool to monitor oceanic plate seismicity.
KW  - body waves
KW  - earthquake source observations
KW  - seismicity and tectonics
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa054
SN  - 0956-540X
SN  - 1365-246X
VL  - 221
IS  - 2
SP  - 1055
EP  - 1080
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kumar, Rohini
A1  - Hesse, Fabienne
A1  - Rao, P. Srinivasa
A1  - Musolff, Andreas
A1  - Jawitz, James
A1  - Sarrazin, Francois
A1  - Samaniego, Luis
A1  - Fleckenstein, Jan H.
A1  - Rakovec, Oldrich
A1  - Thober, S.
A1  - Attinger, Sabine
T1  - Strong hydroclimatic controls on vulnerability to subsurface nitrate contamination across Europe
JF  - Nature Communications
N2  - Subsurface contamination due to excessive nutrient surpluses is a persistent and widespread problem in agricultural areas across Europe. The vulnerability of a particular location to pollution from reactive solutes, such as nitrate, is determined by the interplay between hydrologic transport and biogeochemical transformations. Current studies on the controls of subsurface vulnerability do not consider the transient behaviour of transport dynamics in the root zone. Here, using state-of-the-art hydrologic simulations driven by observed hydroclimatic forcing, we demonstrate the strong spatiotemporal heterogeneity of hydrologic transport dynamics and reveal that these dynamics are primarily controlled by the hydroclimatic gradient of the aridity index across Europe. Contrasting the space-time dynamics of transport times with reactive timescales of denitrification in soil indicate that similar to 75% of the cultivated areas across Europe are potentially vulnerable to nitrate leaching for at least onethird of the year. We find that neglecting the transient nature of transport and reaction timescale results in a great underestimation of the extent of vulnerable regions by almost 50%. Therefore, future vulnerability and risk assessment studies must account for the transient behaviour of transport and biogeochemical transformation processes.
KW  - travel time distributions
KW  - groundwater vulnerability
KW  - flux tracking
KW  - transit-time
KW  - water age
KW  - nitrogen
KW  - model
KW  - dynamics
KW  - pollution
KW  - patterns
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-19955-8
SN  - 2041-1723
VL  - 11
IS  - 1
SP  - 1
EP  - 10
PB  - Nature Publishing Group UK
CY  - London
ER  - 
TY  - JOUR
A1  - Ladeira, Guenia
A1  - Marwan, Norbert
A1  - Destro-Filho, Joao-Batista
A1  - Ramos, Camila Davi
A1  - Lima, Gabriela
T1  - Frequency spectrum recurrence analysis
JF  - Scientific reports
N2  - In this paper, we present the new frequency spectrum recurrence analysis technique by means of electro-encephalon signals (EES) analyses. The technique is suitable for time series analysis with noise and disturbances. EES were collected, and alpha waves of the occipital region were analysed by comparing the signals from participants in two states, eyes open and eyes closed. Firstly, EES were characterized and analysed by means of techniques already known to compare with the results of the innovative technique that we present here. We verified that, standard recurrence quantification analysis by means of EES time series cannot statistically distinguish the two states. However, the new frequency spectrum recurrence quantification exhibit quantitatively whether the participants have their eyes open or closed. In sequence, new quantifiers are created for analysing the recurrence concentration on frequency bands. These analyses show that EES with similar frequency spectrum have different recurrence levels revealing different behaviours of the nervous system. The technique can be used to deepen the study on depression, stress, concentration level and other neurological issues and also can be used in any complex system.
KW  - Biomedical engineering
KW  - Brain injuries
KW  - Computational models
KW  - Computational neuroscience
KW  - Data acquisition
KW  - Data processing
KW  - Electrical and electronic engineering
KW  - Neural circuits
KW  - Visual system
Y1  - 2020
U6  - https://doi.org/10.1038/s41598-020-77903-4
SN  - 2045-2322
VL  - 10
IS  - 1
PB  - Nature portfolio
CY  - Berlin
ER  - 
TY  - JOUR
A1  - León, Ena Mercedes Matienzo
T1  - Observaciones sobre el clima de Lima y sus influencias en los seres   organizados, en especial el hombre
JF  - Iberoamericana
N2  - Una extraordinaria edición actualizada de Observaciones sobre el clima de Lima y sus influencias en los seres organizados, en especial el hombre de José Hipólito Unanue y Pavón ha sido publicado en el 2018  y merece ser anunciado a la comunidad académica peruana e internacional. Este libro incluye un exhaustivo estudio in troductorio del destacado historiador Lizardo Seiner Lizárraga. Esta introducción está conformada de tres partes encabezadas por los siguientes títulos: a) Unanue: una historiografía de amplio espectro b) Textos, registros y referencias: una indagación en la biblioteca de Unanue y c) Observaciones sobre el clima de Lima: una obra en dos tiempos.
Y1  - 2020
U6  - https://doi.org/10.18441/ibam.20.2020.74.279-394
SN  - 1577-3388
SN  - 2255-520X
VL  - 20
IS  - 74
SP  - 305
EP  - 308
PB  - Vervuert
CY  - Frankfurt, Main
ER  - 
TY  - JOUR
A1  - Liu, Qi
A1  - Adler, Karsten
A1  - Lipus, Daniel
A1  - Kämpf, Horst
A1  - Bussert, Robert
A1  - Plessen, Birgit
A1  - Schulz, Hans-Martin
A1  - Krauze, Patryk
A1  - Horn, Fabian
A1  - Wagner, Dirk
A1  - Mangelsdorf, Kai
A1  - Alawi, Mashal
T1  - Microbial signatures in deep CO2-saturated miocene sediments of the active Hartousov mofette system (NW Czech Republic)
JF  - Frontiers in microbiology
N2  - The Hartousov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system.
KW  - geo-bio interaction
KW  - CO2
KW  - mofette systems
KW  - Eger Rift
KW  - microbial lipid
KW  - biomarker
KW  - microbial diversity
KW  - deep biosphere
KW  - saline groundwater
Y1  - 2020
U6  - https://doi.org/10.3389/fmicb.2020.543260
SN  - 1664-302X
VL  - 11
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Lu, Yin
A1  - Dewald, Nico
A1  - Koutsodendris, Andreas
A1  - Kaboth-Bahr, Stefanie
A1  - Rösler, Wolfgang
A1  - Fang, Xiaomin
A1  - Pross, Jörg
A1  - Appel, Erwin
A1  - Friedrich, Oliver
T1  - Sedimentological evidence for pronounced glacial-interglacial climate fluctuations in NE Tibet in the latest Pliocene to early Pleistocene
JF  - Paleoceanography and Paleoclimatology
N2  - The intensification of Northern Hemisphere glaciation (iNHG) and uplift of the Tibetan Plateau have been argued to be among the main drivers of climate change in midlatitude Central Asia during the Pliocene/Pleistocene. While most proxy records that support this hypothesis are from regions outside the Tibetan Plateau (such as from the Chinese Loess Plateau), detailed paleoclimatic information for the plateau itself during that time has yet remained elusive. Here we present a temporally highly resolved (similar to 500 years) sedimentological record from the Qaidam Basin situated on the northeastern Tibetan Plateau that shows pronounced glacial-interglacial climate variability during the interval from 2.7 to 2.1 Ma. Glacial (interglacial) intervals are generally characterized by coarser (finer) grain size, minima (maxima) in organic matter content, and maxima (minima) in carbonate content. Comparison of our results with Earth's orbital parameters and proxy records from the Chinese Loess Plateau suggests that the observed climate fluctuations were mainly driven by changes in the Siberian High/East Asian winter monsoon system as a response to the iNHG. They are further proposed to be enhanced by the topography of the Tibetan Plateau and its impact on the position and intensity of the westerlies.
KW  - Western Qaidam Basin
KW  - grain-size distribution
KW  - lake Donggi Cona
KW  - Chinese loess
KW  - Central-Asia
KW  - transport processes
KW  - Qilian mountains
KW  - dust sources
KW  - plateau
KW  - record
Y1  - 2020
VL  - 35
IS  - 5
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Marcisz, Katarzyna
A1  - Jassey, Vincent E. J.
A1  - Kosakyan, Anush
A1  - Krashevska, Valentyna
A1  - Lahr, Daniel J. G.
A1  - Lara, Enrique
A1  - Lamentowicz, Lukasz
A1  - Lamentowicz, Mariusz
A1  - Macumber, Andrew
A1  - Mazei, Yuri
A1  - Mitchell, Edward A. D.
A1  - Nasser, Nawaf A.
A1  - Patterson, R. Timothy
A1  - Roe, Helen M.
A1  - Singer, David
A1  - Tsyganov, Andrey N.
A1  - Fournier, Bertrand
T1  - Testate amoeba functional traits and their use in paleoecology
JF  - Frontiers in Ecology and Evolution
N2  - This review provides a synthesis of current knowledge on the morphological and functional traits of testate amoebae, a polyphyletic group of protists commonly used as proxies of past hydrological changes in paleoecological investigations from peatland, lake sediment and soil archives. A trait-based approach to understanding testate amoebae ecology and paleoecology has gained in popularity in recent years, with research showing that morphological characteristics provide complementary information to the commonly used environmental inferences based on testate amoeba (morpho-)species data. We provide a broad overview of testate amoeba morphological and functional traits and trait-environment relationships in the context of ecology, evolution, genetics, biogeography, and paleoecology. As examples we report upon previous ecological and paleoecological studies that used trait-based approaches, and describe key testate amoebae traits that can be used to improve the interpretation of environmental studies. We also highlight knowledge gaps and speculate on potential future directions for the application of trait-based approaches in testate amoeba research.
KW  - protists
KW  - functional traits
KW  - morphological traits
KW  - ecology
KW  - peatlands
KW  - lakes
KW  - soils
KW  - trait-based approaches
Y1  - 2020
U6  - https://doi.org/10.3389/fevo.2020.575966
SN  - 2296-701X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Menges, Johanna
A1  - Hovius, Niels
A1  - Andermann, Christoff
A1  - Lupker, Maarten
A1  - Haghipour, Negar
A1  - Märki, Lena
A1  - Sachse, Dirk
T1  - Variations in organic carbon sourcing along a trans-Himalayan river determined by a Bayesian mixing approach
JF  - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society
N2  - Rivers transfer particulate organic carbon (POC) from eroding mountains into geological sinks. Organic carbon source composition and selective mobilization have been shown to affect the type and quantity of POC export, but their combined effects across complex mountain ranges remain underexplored. Here, we examine the variation in organic carbon sourcing and transport in the trans-Himalayan Kali Gandaki River catchment, along strong gradients in precipitation, rock type and vegetation. Combining bulk stable nitrogen, and stable and radioactive organic carbon isotopic composition of bedrock, litter, soil and river sediment samples with a Bayesian end-member mixing approach, we differentiate POC sources along the river and quantify their export. Our analysis shows that POC export from the Tibetan segment of the catchment, where carbon bearing shales are partially covered by aged and modern soils, is dominated by petrogenic POC. Based on our data we re-assess the presence of aged biospheric OC in this part of the catchment, and its contribution to the river load. In the High Himalayan segment, we observed low inputs of petrogenic and biospheric POC, likely due to very low organic carbon concentrations in the metamorphic bedrock, combined with erosion dominated by deep-seated landslides. Our findings show that along the Kali Gandaki River, the sourcing of sediment and organic carbon are decoupled, due to differences in rock organic carbon content, soil and above ground carbon stocks, and geomorphic process activity. While the fast eroding High Himalayas are the principal source of river sediment, the Tibetan headwaters, where erosion rates are lower, are the principal source of organic carbon. To robustly estimate organic carbon export from the Himalayas, the mountain range should be divided into tectono-physiographic zones with distinct organic carbon yields due to differences in substrate and erosion processes and rates.
KW  - particulate organic carbon
KW  - Himalaya
KW  - rivers
KW  - carbon cycle
KW  - stable
KW  - isotopes
KW  - erosion
KW  - end-member mixing
Y1  - 2020
U6  - https://doi.org/10.1016/j.gca.2020.07.003
SN  - 0016-7037
VL  - 286
SP  - 159
EP  - 176
PB  - Elsevier
CY  - New York [u.a.]
ER  - 
TY  - JOUR
A1  - Merz, Bruno
A1  - Kuhlicke, Christian
A1  - Kunz, Michael
A1  - Pittore, Massimiliano
A1  - Babeyko, Andrey
A1  - Bresch, David N.
A1  - Domeisen, Daniela I.
A1  - Feser, Frauke
A1  - Koszalka, Inga
A1  - Kreibich, Heidi
A1  - Pantillon, Florian
A1  - Parolai, Stefano
A1  - Pinto, Joaquim G.
A1  - Punge, Heinz Jürgen
A1  - Rivalta, Eleonora
A1  - Schröter, Kai
A1  - Strehlow, Karen
A1  - Weisse, Ralf
A1  - Wurpts, Andreas
T1  - Impact forecasting to support emergency management of natural hazards
JF  - Reviews of geophysics
N2  - Forecasting and early warning systems are important investments to protect lives, properties, and livelihood. While early warning systems are frequently used to predict the magnitude, location, and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services, or financial loss. Complementing early warning systems with impact forecasts has a twofold advantage: It would provide decision makers with richer information to take informed decisions about emergency measures and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multihazard early warning systems. This review discusses the state of the art in impact forecasting for a wide range of natural hazards. We outline the added value of impact-based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe.
KW  - impact forecasting
KW  - natural hazards
KW  - early warning
Y1  - 2020
U6  - https://doi.org/10.1029/2020RG000704
SN  - 8755-1209
SN  - 1944-9208
VL  - 58
IS  - 4
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Milewski, Robert
A1  - Chabrillat, Sabine
A1  - Bookhagen, Bodo
T1  - Analyses of Namibian Seasonal Salt Pan Crust Dynamics and Climatic Drivers Using Landsat 8 Time-Series and Ground Data
JF  - Remote Sensing
N2  - Salt pans are highly dynamic environments that are difficult to study by in situ methods because of their harsh climatic conditions and large spatial areas. Remote sensing can help to elucidate their environmental dynamics and provide important constraints regarding their sedimentological, mineralogical, and hydrological evolution. This study utilizes spaceborne multitemporal multispectral optical data combined with spectral endmembers to document spatial distribution of surface crust types over time on the Omongwa pan located in the Namibian Kalahari. For this purpose, 49 surface samples were collected for spectral and mineralogical characterization during three field campaigns (2014–2016) reflecting different seasons and surface conditions of the salt pan. An approach was developed to allow the spatiotemporal analysis of the salt pan crust dynamics in a dense time-series consisting of 77 Landsat 8 cloud-free scenes between 2014 and 2017, covering at least three major wet–dry cycles. The established spectral analysis technique Sequential Maximum Angle Convex Cone (SMACC) extraction method was used to derive image endmembers from the Landsat time-series stack. Evaluation of the extracted endmember set revealed that the multispectral data allowed the differentiation of four endmembers associated with mineralogical mixtures of the crust’s composition in dry conditions and three endmembers associated with flooded or muddy pan conditions. The dry crust endmember spectra have been identified in relation to visible, near infrared, and short-wave infrared (VNIR–SWIR) spectroscopy and X-ray diffraction (XRD) analyses of the collected surface samples. According these results, the spectral endmembers are interpreted as efflorescent halite crust, mixed halite–gypsum crust, mixed calcite quartz sepiolite crust, and gypsum crust. For each Landsat scene the spatial distribution of these crust types was mapped with the Spectral Angle Mapper (SAM) method and significant spatiotemporal dynamics of the major surface crust types were observed. Further, the surface crust dynamics were analyzed in comparison with the pan’s moisture regime and other climatic parameters. The results show that the crust dynamics are mainly driven by flooding events in the wet season, but are also influenced by temperature and aeolian activity in the dry season. The approach utilized in this study combines the advantages of multitemporal satellite data for temporal event characterization with advantages from hyperspectral methods for the image and ground data analyses that allow improved mineralogical differentiation and characterization.
KW  - salt pan
KW  - playa
KW  - spectral analysis
KW  - crust
KW  - saline pan cycle
KW  - evaporites
KW  - time-series mapping
Y1  - 2019
U6  - https://doi.org/10.3390/rs12030474
SN  - 2072-4292
IS  - 3
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Mogrovejo Arias, Diana Carolina
A1  - Brill, Florian H. H.
A1  - Wagner, Dirk
T1  - Potentially pathogenic bacteria isolated from diverse habitats in Spitsbergen, Svalbard
JF  - Environmental earth sciences
N2  - The Arctic ecosystem, a reservoir of genetic microbial diversity, represents a virtually unlimited source of microorganisms that could interact with human beings. Despite continuous exploration of Arctic habitats and description of their microbial communities, bacterial phenotypes commonly associated with pathogenicity, such as hemolytic activity, have rarely been reported. In this study, samples of snow, fresh and marine water, soil, and sediment from several habitats in the Arctic archipelago of Svalbard were collected during Summer, 2017. Bacterial isolates were obtained after incubation on oligotrophic media at different temperatures and their hemolytic potential was assessed on sheep blood agar plates. Partial (alpha) or true (beta) hemolysis was observed in 32 out of 78 bacterial species. Genes expressing cytolytic compounds, such as hemolysins, likely increase the general fitness of the producing microorganisms and confer a competitive advantage over the availability of nutrients in natural habitats. In environmental species, the nutrient-acquisition function of these compounds presumably precedes their function as toxins for mammalian erythrocytes. However, in the light of global warming, the presence of hemolytic bacteria in Arctic environments highlights the possible risks associated with these microorganisms in the event of habitat melting/destruction, ecosystem transition, and re-colonization.
KW  - Arctic
KW  - Svalbard
KW  - hemolysins
KW  - climate change
KW  - pathogens
KW  - virulence
Y1  - 2020
U6  - https://doi.org/10.1007/s12665-020-8853-4
SN  - 1866-6280
SN  - 1866-6299
VL  - 79
IS  - 5
PB  - Springer
CY  - Berlin ; Heidelberg
ER  - 
TY  - JOUR
A1  - Montero-Lopez, Carolina
A1  - Hongn, Fernando D.
A1  - Lopez Steinmetz, Romina L.
A1  - Aramayo, Alejandro
A1  - Pingel, Heiko
A1  - Strecker, Manfred
A1  - Cottle, John
A1  - Bianchi, Carlos
T1  - Development of an incipient Paleogene topography between the present-day Eastern Andean Plateau (Puna) and the Eastern Cordillera, southern Central Andes, NW Argentina
JF  - Basin research / publ. in conjunction with the European Association of Geoscientists & Engineers and the International Association of Sedimentologists
N2  - The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13 degrees S and 27 degrees S) is part of the Andean Plateau, which is the world's second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the present-day transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts.
KW  - Andean Plateau
KW  - Eastern Cordillera
KW  - Eocene deformation
KW  - growth structures
KW  - northern Puna
KW  - north-western Argentina
KW  - southern Central Andes
Y1  - 2020
U6  - https://doi.org/10.1111/bre.12510
SN  - 0950-091X
SN  - 1365-2117
VL  - 33
IS  - 2
SP  - 1194
EP  - 1217
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Morgenstern, Anne
A1  - Overduin, Pier Paul
A1  - Günther, Frank
A1  - Stettner, Samuel
A1  - Ramage, Justine
A1  - Schirrmeister, Lutz
A1  - Grigoriev, Mikhail N.
A1  - Grosse, Guido
T1  - Thermo-erosional valleys in Siberian ice-rich permafrost
JF  - Permafrost and Periglacial Processes
N2  - Thermal erosion is a major mechanism of permafrost degradation, resulting in characteristic landforms. We inventory thermo-erosional valleys in ice-rich coastal lowlands adjacent to the Siberian Laptev Sea based on remote sensing, Geographic Information System (GIS), and field investigations for a first regional assessment of their spatial distribution and characteristics. Three study areas with similar geological (Yedoma Ice Complex) but diverse geomorphological conditions vary in valley areal extent, incision depth, and branching geometry. The most extensive valley networks are incised deeply (up to 35 m) into the broad inclined lowland around Mamontov Klyk. The flat, low-lying plain forming the Buor Khaya Peninsula is more degraded by thermokarst and characterized by long valleys of lower depth with short tributaries. Small, isolated Yedoma Ice Complex remnants in the Lena River Delta predominantly exhibit shorter but deep valleys. Based on these hydrographical network and topography assessments, we discuss geomorphological and hydrological connections to erosion processes. Relative catchment size along with regional slope interact with other Holocene relief-forming processes such as thermokarst and neotectonics. Our findings suggest that thermo-erosional valleys are prominent, hitherto overlooked permafrost degradation landforms that add to impacts on biogeochemical cycling, sediment transport, and hydrology in the degrading Siberian Yedoma Ice Complex.
KW  - geomorphology
KW  - periglacial landscapes
KW  - permafrost degradation
KW  - thermal
KW  - erosion
KW  - valley distribution
KW  - Yedoma Ice Complex
Y1  - 2020
U6  - https://doi.org/10.1002/ppp.2087
SN  - 1045-6740
SN  - 1099-1530
VL  - 32
IS  - 1
SP  - 59
EP  - 75
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Morishita, Yu
A1  - Lazecky, Milan
A1  - Wright, Tim J.
A1  - Weiss, Jonathan R.
A1  - Elliott, John R.
A1  - Hooper, Andy
T1  - LiCSBAS
BT  - an open-source InSAR time series analysis package integrated with the LiCSAR automated Sentinel-1 InSAR processor
JF  - Remote sensing
N2  - For the past five years, the 2-satellite Sentinel-1 constellation has provided abundant and useful Synthetic Aperture Radar (SAR) data, which have the potential to reveal global ground surface deformation at high spatial and temporal resolutions. However, for most users, fully exploiting the large amount of associated data is challenging, especially over wide areas. To help address this challenge, we have developed LiCSBAS, an open-source SAR interferometry (InSAR) time series analysis package that integrates with the automated Sentinel-1 InSAR processor (LiCSAR). LiCSBAS utilizes freely available LiCSAR products, and users can save processing time and disk space while obtaining the results of InSAR time series analysis. In the LiCSBAS processing scheme, interferograms with many unwrapping errors are automatically identified by loop closure and removed. Reliable time series and velocities are derived with the aid of masking using several noise indices. The easy implementation of atmospheric corrections to reduce noise is achieved with the Generic Atmospheric Correction Online Service for InSAR (GACOS). Using case studies in southern Tohoku and the Echigo Plain, Japan, we demonstrate that LiCSBAS applied to LiCSAR products can detect both large-scale (>100 km) and localized (similar to km) relative displacements with an accuracy of <1 cm/epoch and similar to 2 mm/yr. We detect displacements with different temporal characteristics, including linear, periodic, and episodic, in Niigata, Ojiya, and Sanjo City, respectively. LiCSBAS and LiCSAR products facilitate greater exploitation of globally available and abundant SAR datasets and enhance their applications for scientific research and societal benefit.
KW  - InSAR
KW  - Sentinel-1
KW  - time series analysis
KW  - deformation monitoring
KW  - tectonics
KW  - subsidence
KW  - automatic processing
KW  - global
Y1  - 2020
U6  - https://doi.org/10.3390/rs12030424
SN  - 2072-4292
VL  - 12
IS  - 3
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Mtilatila, Lucy Mphatso Ng'ombe
A1  - Bronstert, Axel
A1  - Bürger, Gerd
A1  - Vormoor, Klaus Josef
T1  - Meteorological and hydrological drought assessment in Lake Malawi and Shire River basins (1970-2013)
JF  - Hydrological sciences journal = Journal des sciences hydrologiques
N2  - The study assesses the variability and trends of both meteorological and hydrological droughts from 1970 to 2013 in Lake Malawi and Shire River basins using the standardized precipitation index (SPI) and standardized precipitation and evaporation index (SPEI) for meteorological droughts and the lake level change index (LLCI) for hydrological droughts. Trends and slopes in droughts and drought drivers are estimated using Mann-Kendall test and Sen's slope, respectively. Results suggest that meteorological droughts are increasing due to a decrease in precipitation which is exacerbated by an increase in temperature (potential evapotranspiration). The hydrological system of Lake Malawi seems to have a >24-month memory towards meteorological conditions, since the 36-month SPEI can predict hydrological droughts 10 months in advance. The study has found the critical lake level that would trigger hydrological drought to be 474.1 m a.s.l. The increase in drought is a concern as this will have serious impacts on water resources and hydropower supply in Malawi.
KW  - Lake Malawi basin
KW  - Shire River basin
KW  - meteorological drought
KW  - hydrological drought
KW  - SPEI
KW  - SPI
KW  - trend analysis
Y1  - 2020
U6  - https://doi.org/10.1080/02626667.2020.1837384
SN  - 0262-6667
SN  - 2150-3435
VL  - 65
IS  - 16
SP  - 2750
EP  - 2764
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Muldashev, Iskander A.
A1  - Sobolev, Stephan
T1  - What controls maximum magnitudes of giant subduction earthquakes?
JF  - Geochemistry, geophysics, geosystems
N2  - Giant earthquakes with magnitudes above 8.5 occur only in subduction zones. Despite the developments made in observing large subduction zone earthquakes with geophysical instruments, the factors controlling the maximum size of these earthquakes are still poorly understood. Previous studies have suggested the importance of slab shape, roughness of the plate interface contact, state of the strain in the upper plate, thickness of sediments filling the trenches, and subduction rate. Here, we present 2-D cross-scale numerical models of seismic cycles for subduction zones with various geometries, subduction channel friction configurations, and subduction rates. We found that low-angle subduction and thick sediments in the subduction channel are the necessary conditions for generating giant earthquakes, while the subduction rate has a negligible effect. We suggest that these key parameters determine the maximum magnitude of a subduction earthquake by controlling the seismogenic zone width and smoothness of the subduction interface. This interpretation supports previous studies that are based upon observations and scaling laws. Our modeling results also suggest that low static friction in the sediment-filled subduction channel results in neutral or moderate compressive deformation in the overriding plate for low-angle subduction zones hosting giant earthquakes. These modeling results agree well with observations for the largest earthquakes. Based on our models we predict maximum magnitudes of subduction earthquakes worldwide, demonstrating the fit to magnitudes of all giant earthquakes of the 20th and 21st centuries and good agreement with the predictions based on statistical analyses of observations.
KW  - giant earthquakes
KW  - earthquake modeling
KW  - subduction
Y1  - 2020
U6  - https://doi.org/10.1029/2020GC009145
SN  - 1525-2027
VL  - 21
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Naliboff, John B.
A1  - Glerum, Anne
A1  - Brune, Sascha
A1  - Péron-Pinvidic, G.
A1  - Wrona, Thilo
T1  - Development of 3-D rift heterogeneity through fault network evolution
JF  - Geophysical Research Letters
N2  - Observations of rift and rifted margin architecture suggest that significant spatial and temporal structural heterogeneity develops during the multiphase evolution of continental rifting. Inheritance is often invoked to explain this heterogeneity, such as preexisting anisotropies in rock composition, rheology, and deformation. Here, we use high-resolution 3-D thermal-mechanical numerical models of continental extension to demonstrate that rift-parallel heterogeneity may develop solely through fault network evolution during the transition from distributed to localized deformation. In our models, the initial phase of distributed normal faulting is seeded through randomized initial strength perturbations in an otherwise laterally homogeneous lithosphere extending at a constant rate. Continued extension localizes deformation onto lithosphere-scale faults, which are laterally offset by tens of km and discontinuous along-strike. These results demonstrate that rift- and margin-parallel heterogeneity of large-scale fault patterns may in-part be a natural byproduct of fault network coalescence.
KW  - magma-poor
KW  - continental lithosphere
KW  - extension
KW  - insights
KW  - margins
KW  - architecture
KW  - systems
KW  - models
KW  - sea
KW  - reactivation
Y1  - 2019
VL  - 47
IS  - 13
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Nardini, Livia
A1  - Rybacki, Erik
A1  - Krause, Michael
A1  - Morales, Luiz F.G.
A1  - Dresen, Georg
T1  - Control of the geometric arrangement of material heterogeneities on strain localization at the brittle-to-ductile transition in experimentally deformed carbonate rocks
JF  - Journal of Structural Geology
N2  - Triaxial high temperature (900 °C) deformation experiments were conducted at constant strain rate in a Paterson-type deformation apparatus on cylinders of Carrara marble with two right or left stepping, non-overlapping weak inclusions of Solnhofen limestone, oriented at 45° to the cylinders’ longitudinal axes. Applying different values of confinement (30, 50, 100 and 300 MPa) we induced various amounts of brittle deformation in the marble matrix and investigated the effect of brittle precursors on the initiation and development of heterogeneity-induced high temperature shear zones.

Viscosity contrast between the matrix and the inclusions induces local stress concentration at the tips of these latter. The initial arrangement of the inclusions results in either an overpressured (contractional) or underpressured (extensional) domain in the step-over region of the sample. At low confinement (30 and 50 MPa) abundant brittle deformation is observed, but the spatial distribution of microfractures is dependent on the kinematics of the step-over region: microcracks occur either along the shearing plane between inclusions (in extensional bridge samples), or broadly distributed outside the step-over region (contractional bridge samples). Accordingly, ductile deformation localizes along the inclusions plane in the extensional bridge samples as opposed to distributing over large areas of the matrix in the contractional bridge samples. If microcracking is suppressed (high confinement), strain is accommodated by viscous creep and strain progressively de-localizes in extensional bridge samples. Our experiments demonstrate that brittle precursors enhance the degree of localization in the ductile deformation regime, but only if the interaction of pre-existing heterogeneities induces an extensional mean stress regime in between.
KW  - High-temperature shear zones
KW  - Triaxial deformation
KW  - Brittle precursors
KW  - Strain localization Carrara marble
Y1  - 2019
U6  - https://doi.org/10.1016/j.jsg.2020.104038
SN  - 0191-8141
VL  - 135
PB  - Pergamon Press
CY  - Oxford ; Frankfurt, M.
ER  - 
TY  - JOUR
A1  - Niemz, Peter
A1  - Cesca, Simone
A1  - Heimann, Sebastian
A1  - Grigoli, Francesco
A1  - von Specht, Sebastian
A1  - Hammer, Conny
A1  - Zang, Arno
A1  - Dahm, Torsten
T1  - Full-waveform-based characterization of acoustic emission activity in a mine-scale experiment
BT  - a comparison of conventional and advanced hydraulic fracturing schemes
JF  - Geophysical journal international / the Royal Astronomical Society, the Deutsche Geophysikalische Gesellschaft and the European Geophysical Society
N2  - Understanding fracturing processes and the hydromechanical relation to induced seismicity is a key question for enhanced geothermal systems (EGS). Commonly massive fluid injection, predominately causing hydroshearing, are used in large-scale EGS but also hydraulic fracturing approaches were discussed. To evaluate the applicability of hydraulic fracturing techniques in EGS, six in situ, multistage hydraulic fracturing experiments with three different injection schemes were performed under controlled conditions in crystalline rock at the Aspo Hard Rock Laboratory (Sweden). During the experiments the near-field ground motion was continuously recorded by 11 piezoelectric borehole sensors with a sampling rate of 1 MHz. The sensor network covered a volume of 30x30x30 m around a horizontal, 28-m-long injection borehole at a depth of 410 m. To extract and characterize massive, induced, high-frequency acoustic emission (AE) activity from continuous recordings, a semi-automated workflow was developed relying on full waveform based detection, classification and location procedures. The approach extended the AE catalogue from 196 triggered events in previous studies to more than 19600 located AEs. The enhanced catalogue, for the first time, allows a detailed analysis of induced seismicity during single hydraulic fracturing experiments, including the individual fracturing stages and the comparison between injection schemes. Beside the detailed study of the spatio-temporal patterns, event clusters and the growth of seismic clouds, we estimate relative magnitudes and b-values of AEs for conventional, cyclic progressive and dynamic pulse injection schemes, the latter two being fatigue hydraulic fracturing techniques. While the conventional fracturing leads to AE patterns clustered in planar regions, indicating the generation of a single main fracture plane, the cyclic progressive injection scheme results in a more diffuse, cloud-like AE distribution, indicating the activation of a more complex fracture network. For a given amount of hydraulic energy (pressure multiplied by injected volume) pumped into the system, the cyclic progressive scheme is characterized by a lower rate of seismicity, lower maximum magnitudes and significantly larger b-values, implying an increased number of small events relative to the large ones. To our knowledge, this is the first direct comparison of high resolution seismicity in a mine-scale experiment induced by different hydraulic fracturing schemes.
KW  - Fracture and flow
KW  - Spatial analysis
KW  - Statistical methods
KW  - Time-series analysis
KW  - Induced seismicity
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa127
SN  - 0955-419X
SN  - 1365-246X
VL  - 222
IS  - 1
SP  - 189
EP  - 206
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Oberhänsli, Roland
T1  - Deep-time Digital Earth (DDE) the first IUGS big science program
JF  - Journal of the Geological Society of India
Y1  - 2020
U6  - https://doi.org/10.1007/s12594-020-1420-5
SN  - 0016-7622
SN  - 0974-6889
VL  - 95
IS  - 3
SP  - 223
EP  - 226
PB  - Springer India
CY  - New Delhi
ER  - 
TY  - JOUR
A1  - Obreht, Igor
A1  - Wörmer, Lars
A1  - Brauer, Achim
A1  - Wendt, Jenny
A1  - Alfken, Susanne
A1  - De Vleeschouwer, David
A1  - Elvert, Marcus
A1  - Hinrichs, Kai-Uwe
T1  - An annually resolved record of Western European vegetation response to Younger Dryas cooling
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - The regional patterns and timing of the Younger Dryas cooling in the North Atlantic realm were complex and are mechanistically incompletely understood. To enhance understanding of regional climate patterns, we present molecular biomarker records at subannual to annual resolution by mass spectrometry imaging (MSI) of sediments from the Lake Meerfelder Maar covering the Allerod-Younger Dryas transition. These analyses are supported by conventional extraction-based molecular-isotopic analyses, which both validate the imaging results and constrain the sources of the target compounds. The targeted fatty acid biomarkers serve as a gauge of the response of the local aquatic and terrestrial ecosystem to climate change. Based on the comparison of our data with existing data from Meerfelder Maar, we analyse the short-term environmental evolution in Western Europe during the studied time interval and confirm the previously reported delayed hydrological response to Greenland cooling. However, despite a detected delay of Western European environmental change of similar to 135 years, our biomarker data show statistically significant correlation with deuterium excess in Greenland ice core at - annual resolution during this time-transgressive cooling. This suggests a coherent atmospheric forcing across the North Atlantic realm during this transition. We propose that Western European cooling was postponed due to major reorganization of the westerlies that were intermittently forcing warmer and wetter air masses from lower latitudes to Western Europe and thus resulted in delayed cooling relative to Greenland.
KW  - lateglacial
KW  - paleoclimatology
KW  - Western Europe
KW  - Meerfelder Maar
KW  - high-resolution biomarkers
KW  - fatty acids
KW  - FT-ICR-MS
KW  - mass spectrometry
KW  - imaging
Y1  - 2020
U6  - https://doi.org/10.1016/j.quascirev.2020.106198
SN  - 0277-3791
VL  - 231
PB  - Elsevier
CY  - Amsterdam [u.a.]
ER  - 
TY  - JOUR
A1  - Olen, Stephanie M.
A1  - Bookhagen, Bodo
T1  - Applications of SAR interferometric coherence time series
BT  - satiotemporal dynamics of geomorphic transitions in the South-Central Andes
JF  - Journal of geophysical research : Earth surface
N2  - Sediment transport domains in mountain landscapes are characterized by fundamentally different processes and rates depending on several factors, including geology, climate, and biota. Accurately identifying where transitions between transport domains occur is an important step to quantify the past, present, and future contribution of varying erosion and sedimentation processes and enhance our predictive capabilities. We propose a new methodology based on time series of synthetic aperture radar (SAR) interferometric coherence images to map sediment transport regimes across arid and semiarid landscapes. Using 4 years of Sentinel-1 data, we analyze sediment transport regimes for the south-central Andes in northwestern Argentina characterized by steep topographic and climatic gradients. We observe seasonally low coherence during the regional wet season, particularly on hillslopes and in alluvial channels. The spatial distribution of coherence is compared to drainage areas extracted from digital topography to identify two distinct transitions within watersheds: (a) a hillslope-to-fluvial and (b) a fluvial-to-alluvial transition. While transitions within a given basin can be well-constrained, the relative role of each sediment transport domain varies widely over the climatic and topographic gradients. In semiarid regions, we observe larger relative contributions from hillslopes compared to arid regions. Across regional gradients, the range of coherence within basins positively correlates to previously published millennial catchment-wide erosion rates and to topographic metrics used to indicate long-term uplift. Our study suggests that a dense time series of interferometric coherence can be used as a proxy for surface sediment movement and landscape stability in vegetation-free settings at event to decadal timescales.
KW  - Copernicus
KW  - SAR
KW  - critical infrastructure resilience
KW  - early warning
KW  - landslides
Y1  - 2020
U6  - https://doi.org/10.1029/2019JF005141
SN  - 2169-9003
SN  - 2169-9011
VL  - 125
IS  - 3
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Olen, Stephanie M.
A1  - Bookhagen, Bodo
A1  - Strecker, Manfred
T1  - Corrigendum to:  Olen, Stephanie M.; Bookhagen, Bodo; Strecker, Manfred R. : Role of climate and vegetation density in modulating denudation rates in the Himalaya. - Earth and planetary science letters. - 445 (2016), S. 57 - 67. - doi: https://doi.org/10.1016/j.epsl.2016.03.047
JF  - Earth and planetary science letters
N2  - Vegetation has long been hypothesized to influence the nature and rates of surface processes. We test the possible impact of vegetation and climate on denudation rates at orogen scale by taking advantage of a pronounced along-strike gradient in rainfall and vegetation density in the Himalaya. We combine 12 new 10Be denudation rates from the Sutlej Valley and 123 published denudation rates from fluvially- dominated catchments in the Himalaya with remotely-sensed measures of vegetation density and rainfall metrics, and with tectonic and lithologic constraints. In addition, we perform topographic analyses to assess the contribution of vegetation and climate in modulating denudation rates along strike. We observe variations in denudation rates and the relationship between denudation and topography along strike that are most strongly controlled by local rainfall amount and vegetation density, and cannot be explained by along-strike differences in tectonics or lithology. A W–E along-strike decrease in denudation rate variability positively correlates with the seasonality of vegetation density (R = 0.95, p < 0.05), and negatively correlates with mean vegetation density (R = −0.84, p < 0.05). Vegetation density modulates the topographic response to changing denudation rates, such that the functional relationship between denudation rate and topographic steepness becomes increasingly linear as vegetation density increases. We suggest that while tectonic processes locally control the pattern of denudation rates across strike of the Himalaya (i.e., S–N), along strike of the orogen (i.e., E–W) climate exerts a measurable influence on how denudation rates scatter around long-term, tectonically-controlled erosion, and on the functional relationship between topography and denudation
Y1  - 2020
U6  - https://doi.org/10.1016/j.epsl.2020.116252
SN  - 0012-821X
SN  - 1385-013X
VL  - 540
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Otto, Christopher
A1  - Kempka, Thomas
T1  - Synthesis gas composition prediction for underground coal gasification using a thermochemical equilibrium modeling approach
JF  - Energies
N2  - Underground coal gasification (UCG) is an in situ conversion technique that enables the production of high-calorific synthesis gas from resources that are economically not minable by conventional methods. A broad range of end-use options is available for the synthesis gas, including fuels and chemical feedstock production. Furthermore, UCG also offers a high potential for integration with Carbon Capture and Storage (CCS) to mitigate greenhouse gas emissions. In the present study, a stoichiometric equilibrium model, based on minimization of the Gibbs function has been used to estimate the equilibrium composition of the synthesis gas. Thereto, we further developed and applied a proven thermodynamic equilibrium model to simulate the relevant thermochemical coal conversion processes (pyrolysis and gasification). Our modeling approach has been validated against thermodynamic models, laboratory gasification experiments and UCG field trial data reported in the literature. The synthesis gas compositions have been found to be in good agreement under a wide range of different operating conditions. Consequently, the presented modeling approach enables an efficient quantification of synthesis gas quality resulting from UCG, considering varying coal and oxidizer compositions at deposit-specific pressures and temperatures.
KW  - underground coal gasification
KW  - Cantera
KW  - thermodynamic equilibrium
KW  - composition
KW  - synthesis gas
KW  - oxidizer
Y1  - 2020
U6  - https://doi.org/10.3390/en13051171
SN  - 1996-1073
VL  - 13
IS  - 5
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Ou, Qi
A1  - Kulikova, Galina
A1  - Yu, Jingxing
A1  - Elliott, Austin
A1  - Parsons, Bethany
A1  - Walker, Richard
T1  - Magnitude of the 1920 Haiyuan earthquake reestimated using seismological and geomorphological methods
JF  - Journal of geophysical research : Solid earth
N2  - Reported magnitudes ranging between 7.8 and 8.7 highlight a confusion about the true size of the 1920 Haiyuan earthquake, the largest earthquake recorded in the northeast Tibetan Plateau. We compiled a global data set of previously unlooked-at historical seismograms and performed modern computational analyses on the digitized seismic records. We found the epicenter to be near Haiyuan town and obtained a moment magnitude of M-W=7.90.2. Following traditional approaches, we obtained m(B)=7.90.3 with data from 21 stations and M-S(20)=8.10.2 with data from three stations. Geomorphologically, we mapped the surface rupture and horizontal offsets on high-resolution Pleiades satellite and drone imagery that covered the entire western and middle sections of the 1920 Haiyuan earthquake rupture and compiled offsets reported on the eastern section from field measurements in the 1980s. Careful discrimination between single-event and cumulative offsets suggests average horizontal slips of 3.01.0m on the western section, 4.51.5m on the middle section, and 3.5 +/- 0.5m on the eastern section, indicating a total moment magnitude of M-W=7.8 +/- 0.1. Thus, the seismological and geomorphological results agree within the uncertainties, a weighted average giving a moment magnitude of M-W=7.9 +/- 0.2 for the 1920 Haiyuan earthquake. It is likely that earthquake magnitudes based on the historical M were systematically overestimated. <br /> Plain Language Summary Earthquakes are the main mechanism by which elastic energy accumulating due to tectonic motion is released. As the earthquake magnitude scale is logarithmic, major earthquakes control the bulk of this energy budget and are often the most destructive, like the 1920 Haiyuan earthquake with similar to 230,000 casualties. However, major earthquakes tend to have recurrence periods of several hundred years, longer than our instrumental records. To obtain knowledge of historic major earthquakes, paleoseismologists measure geomorphic offsets and map surface ruptures left by past events and estimate the shaking intensity from historical writings. However, in the case of the Haiyuan earthquake, which happened in the late historic, early instrumental period, the magnitudes reported from these two communities differed significantly. In order to constrain the magnitude of this earthquake for seismic hazard assessment and to reconcile the differences between published magnitudes, we reestimated its magnitude from both newly compiled and digitized seismological records and modern satellite and drone imagery. The results show that the early seismological magnitudes were overestimated, which may affect historical magnitudes systematically. The 1920 Haiyuan earthquake was of a similar magnitude to the 2001 Kokoxili and 2008 Wenchuan earthquakes that also occurred in and around the Tibetan Plateau, instead of more than half a magnitude larger.
Y1  - 2020
U6  - https://doi.org/10.1029/2019JB019244
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Palmer, Matthew D.
A1  - Gregory, Jonathan
A1  - Bagge, Meike
A1  - Calvert, Daley
A1  - Hagedoorn, Jan Marius
A1  - Howard, Tom
A1  - Klemann, Volker
A1  - Lowe, Jason A.
A1  - Roberts, Chris
A1  - Slangen, Aimee B. A.
A1  - Spada, Giorgio
T1  - Exploring the drivers of global and local sea‐level change over the 21st century and beyond
JF  - Earth's future
N2  - We present a new set of global and local sea‐level projections at example tide gauge locations under the RCP2.6, RCP4.5, and RCP8.5 emissions scenarios. Compared to the CMIP5‐based sea‐level projections presented in IPCC AR5, we introduce a number of methodological innovations, including (i) more comprehensive treatment of uncertainties, (ii) direct traceability between global and local projections, and (iii) exploratory extended projections to 2300 based on emulation of individual CMIP5 models. Combining the projections with observed tide gauge records, we explore the contribution to total variance that arises from sea‐level variability, different emissions scenarios, and model uncertainty. For the period out to 2300 we further breakdown the model uncertainty by sea‐level component and consider the dependence on geographic location, time horizon, and emissions scenario. Our analysis highlights the importance of local variability for sea‐level change in the coming decades and the potential value of annual‐to‐decadal predictions of local sea‐level change. Projections to 2300 show a substantial degree of committed sea‐level rise under all emissions scenarios considered and highlight the reduced future risk associated with RCP2.6 and RCP4.5 compared to RCP8.5. Tide gauge locations can show large ( > 50%) departures from the global average, in some cases even reversing the sign of the change. While uncertainty in projections of the future Antarctic ice dynamic response tends to dominate post‐2100, we see substantial differences in the breakdown of model variance as a function of location, time scale, and emissions scenario.
KW  - climate change
KW  - CMIP5 models
KW  - RCP scenarios
KW  - sea-level projections
KW  - tide gauge observations
Y1  - 2020
U6  - https://doi.org/10.1029/2019EF001413
SN  - 2328-4277
VL  - 8
IS  - 9
SP  - 1
EP  - 25
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Paprotny, Dominik
A1  - Kreibich, Heidi
A1  - Morales-Napoles, Oswaldo
A1  - Wagenaar, Dennis
A1  - Castellarin, Attilio
A1  - Carisi, Francesca
A1  - Bertin, Xavier
A1  - Merz, Bruno
A1  - Schröter, Kai
T1  - A probabilistic approach to estimating residential losses from different flood types
JF  - Natural hazards : journal of the International Society for the Prevention and Mitigation of Natural Hazards
N2  - Residential assets, comprising buildings and household contents, are a major source of direct flood losses. Existing damage models are mostly deterministic and limited to particular countries or flood types. Here, we compile building-level losses from Germany, Italy and the Netherlands covering a wide range of fluvial and pluvial flood events. Utilizing a Bayesian network (BN) for continuous variables, we find that relative losses (i.e. loss relative to exposure) to building structure and its contents could be estimated with five variables: water depth, flow velocity, event return period, building usable floor space area and regional disposable income per capita. The model's ability to predict flood losses is validated for the 11 flood events contained in the sample. Predictions for the German and Italian fluvial floods were better than for pluvial floods or the 1993 Meuse river flood. Further, a case study of a 2010 coastal flood in France is used to test the BN model's performance for a type of flood not included in the survey dataset. Overall, the BN model achieved better results than any of 10 alternative damage models for reproducing average losses for the 2010 flood. An additional case study of a 2013 fluvial flood has also shown good performance of the model. The study shows that data from many flood events can be combined to derive most important factors driving flood losses across regions and time, and that resulting damage models could be applied in an open data framework.
KW  - fluvial floods
KW  - coastal floods
KW  - pluvial floods
KW  - Bayesian networks
KW  - flood
KW  - damage surveys
Y1  - 2020
U6  - https://doi.org/10.1007/s11069-020-04413-x
SN  - 0921-030X
SN  - 1573-0840
VL  - 105
IS  - 3
SP  - 2569
EP  - 2601
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Pilz, Marco
A1  - Cotton, Fabrice
A1  - Razafindrakoto, Hoby Njara Tendrisoa
A1  - Weatherill, Graeme
A1  - Spies, Thomas
T1  - Regional broad-band ground-shaking modelling over extended and thick sedimentary basins
BT  - An example from the Lower Rhine Embayment (Germany)
JF  - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering
N2  - The simulation of broad-band (0.1 to 10 + Hz) ground-shaking over deep and spatially extended sedimentary basins at regional scales is challenging. We evaluate the ground-shaking of a potential M 6.5 earthquake in the southern Lower Rhine Embayment, one of the most important areas of earthquake recurrence north of the Alps, close to the city of Cologne in Germany. In a first step, information from geological investigations, seismic experiments and boreholes is combined for deriving a harmonized 3D velocity and attenuation model of the sedimentary layers. Three alternative approaches are then applied and compared to evaluate the impact of the sedimentary cover on ground-motion amplification. The first approach builds on existing response spectra ground-motion models whose amplification factors empirically take into account the influence of the sedimentary layers through a standard parameterization. In the second approach, site-specific 1D amplification functions are computed from the 3D basin model. Using a random vibration theory approach, we adjust the empirical response spectra predicted for soft rock conditions by local site amplification factors: amplifications and associated ground-motions are predicted both in the Fourier and in the response spectra domain. In the third approach, hybrid physics-based ground-motion simulations are used to predict time histories for soft rock conditions which are subsequently modified using the 1D site-specific amplification functions computed in method 2. For large distances and at short periods, the differences between the three approaches become less notable due to the significant attenuation of the sedimentary layers. At intermediate and long periods, generic empirical ground-motion models provide lower levels of amplification from sedimentary soils compared to methods taking into account site-specific 1D amplification functions. In the near-source region, hybrid physics-based ground-motions models illustrate the potentially large variability of ground-motion due to finite source effects.
KW  - ground-motion modelling
KW  - site effects
KW  - scenario
KW  - random vibration
KW  - theory
KW  - hybrid modelling
Y1  - 2020
U6  - https://doi.org/10.1007/s10518-020-01004-w
SN  - 1570-761X
SN  - 1573-1456
VL  - 19
IS  - 2
SP  - 581
EP  - 603
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Pilz, Tobias
A1  - Francke, Till
A1  - Baroni, Gabriele
A1  - Bronstert, Axel
T1  - How to Tailor my process-based hydrological model?
BT  - dynamic identifiability analysis of flexible model structures
JF  - Water resources research
N2  - In the field of hydrological modeling, many alternative representations of natural processes exist. Choosing specific process formulations when building a hydrological model is therefore associated with a high degree of ambiguity and subjectivity. In addition, the numerical integration of the underlying differential equations and parametrization of model structures influence model performance. Identifiability analysis may provide guidance by constraining the a priori range of alternatives based on observations. In this work, a flexible simulation environment is used to build an ensemble of semidistributed, process-based hydrological model configurations with alternative process representations, numerical integration schemes, and model parametrizations in an integrated manner. The flexible simulation environment is coupled with an approach for dynamic identifiability analysis. The objective is to investigate the applicability of the framework to identify the most adequate model. While an optimal model configuration could not be clearly distinguished, interesting results were obtained when relating model identifiability with hydro-meteorological boundary conditions. For instance, we tested the Penman-Monteith and Shuttleworth & Wallace evapotranspiration models and found that the former performs better under wet and the latter under dry conditions. Parametrization of model structures plays a dominant role as it can compensate for inadequate process representations and poor numerical solvers. Therefore, it was found that numerical solvers of high order of accuracy do often, though not necessarily, lead to better model performance. The proposed coupled framework proved to be a straightforward diagnostic tool for model building and hypotheses testing and shows potential for more in-depth analysis of process implementations and catchment functioning.
KW  - identifiability analysis
KW  - flexible model
KW  - numerics
KW  - model structure
KW  - WASA-SED
KW  - ECHSE
Y1  - 2020
U6  - https://doi.org/10.1029/2020WR028042
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Powali, Debarchan
A1  - Sharma, Shubham
A1  - Mandal, Riddhi
A1  - Mitra, Supriyo
T1  - A reappraisal of the 2005 Kashmir (M-w 7.6) earthquake and its aftershocks
BT  - seismotectonics of NW Himalaya
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - We study the source properties of the 2005 Kashmir earthquake and its aftershocks to unravel the seismotectonics of the NW Himalayan syntaxis. The mainshock and larger aftershocks have been simultaneously relocated using phase data. We use back-projection of high-frequency energy from multiple teleseismic arrays to model the spatio-temporal evolution of the mainshock rupture. Our analysis reveal a bilateral rupture, which initially propagated SE and then NW of the epicenter, with an average rupture velocity of similar to 2 km s(-1). The area of maximum energy release is parallel to and bound by the surface rupture. Incorporating rupture propagation and velocity, we model the mainshock as a line source using P- and SH-waveform inversion. Our result confirms that the mainshock occurred on a NE dipping (similar to 35 degrees) fault plane, with centroid depth of similar to 10 km. Integrated source time function show that majority of the energy was released in the first similar to 20 s, and was confined above the hypocenter. From waveform inverted fault dimension and seismic moment, we argue that the mainshock had an additional similar to 25 km blind rupture beyond the NW Himalayan syntaxis. Combining this with findings from previous studies, we conjecture that the blind rupture propagated NW of the syntaxis underneath a weak detachment overlain by infra-Cambrian salt layer, and terminated in a wedge thrust. All moderate-to-large aftershocks, NW of the mainshock rupture, are concentrated at the edge of the blind rupture termination. Source modeling of these aftershocks reveal thrust mechanism with centroid depths of 2-10 km, and fault planes oriented subparallel to the mainshock rupture. To study the influence of mainshock rupture on aftershock occurrence, we compute Coulomb failure stress on aftershock faults. All these aftershocks lie in the positive Coulomb stress change region. This suggest that the aftershocks have been triggered by either co-seismic or post-seismic slip on the mainshock fault.
KW  - Kashmir earthquake
KW  - Aftershocks
KW  - High frequency back-projection
KW  - Source
KW  - mechanism
KW  - Coulomb failure stress
KW  - Seismo-tectonics
Y1  - 2020
U6  - https://doi.org/10.1016/j.tecto.2020.228501
SN  - 0040-1951
SN  - 1879-3266
VL  - 789
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Pradhan, Prajal
A1  - Kriewald, Steffen
A1  - Costa, Luís Fílípe Carvalho da
A1  - Rybski, Diego
A1  - Benton, Tim G.
A1  - Fischer, Günther
A1  - Kropp, Jürgen
T1  - Urban food systems: how regionalization can contribute to climate change mitigation
JF  - Environmental science & technology
N2  - Cities will play a key role in the grand challenge of nourishing a growing global population, because, due to their population density, they set the demand. To ensure that food systems are sustainable, as well as nourishing, one solution often suggested is to shorten their supply chains toward a regional rather than a global basis. While such regional systems may have a range of costs and benefits, we investigate the mitigation potential of regionalized urban food systems by examining the greenhouse gas emissions associated with food transport. Using data on food consumption for 7108 urban administrative units (UAUs), we simulate total transport emissions for both regionalized and globalized supply chains. In regionalized systems, the UAUs' demands are fulfilled by peripheral food production, whereas to simulate global supply chains, food demand is met from an international pool (where the origin can be any location globally). We estimate that regionalized systems could reduce current emissions from food transport. However, because longer supply chains benefit from maximizing comparative advantage, this emission reduction would require closing yield gaps, reducing food waste, shifting toward diversified farming, and consuming seasonal produce. Regionalization of food systems will be an essential component to limit global warming to well below 2 degrees C in the future.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.est.0c02739
SN  - 0013-936X
SN  - 1520-5851
VL  - 54
IS  - 17
SP  - 10551
EP  - 10560
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Putra, Muhammad Panji Islam Fajar
A1  - Pradhan, Prajal
A1  - Kropp, Jürgen
T1  - A systematic analysis of Water-Energy-Food security nexus
BT  - a South Asian case study
JF  - The science of the total environment : an international journal for scientific research into the environment and its relationship with man
N2  - Most South Asian countries have challenges in ensuring water, energy, and food (WEF) security, which are often interacting positively or negatively. To address these challenges, the nexus approach provides a framework to identify the interactions of the WEF sectors as an integrated system. However, most nexus studies only qualitatively discuss the interactions between these sectors. This study conducts a systematic analysis of the WEF security nexus in South Asia by using open data sources at the country scale. We analyze interactions between the WEF sectors statistically, defining positive and negative correlations between the WEF security indicators as synergies and trade-offs, respectively. By creating networks of the synergies and trade-offs, we further identify most positively and negatively influencing indicators in the WEF security nexus. We observe a larger share of trade-offs than synergies within the water and energy sectors and a larger share of synergies than trade-offs among the WEF sectors for South Asia. However, these observations vary across the South Asian countries. Our analysis highlights that strategies on promoting sustainable energy and discouraging fossil fuel use could have overall positive effects on the WEF security nexus in the countries. This study provides evidence for considering the WEF security nexus as an integrated system rather than just a combination of three different sectors or securities.
KW  - water security
KW  - food security
KW  - energy security
KW  - network analysis
KW  - water-energy-food nexus
KW  - sustainable development
Y1  - 2020
U6  - https://doi.org/10.1016/j.scitotenv.2020.138451
SN  - 0048-9697
SN  - 1879-1026
VL  - 728
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Racano, Simone
A1  - Jara Muñoz, Julius
A1  - Cosentino, Domenico
A1  - Melnick, Daniel
T1  - Variable quaternary uplift along the Southern Margin of the Central Anatolian Plateau inferred from modeling Marine Terrace sequences
JF  - Tectonics
N2  - The southern margin of the Central Anatolian Plateau (CAP) records a strong uplift phase after the early Middle Pleistocene, which has been related to the slab break-off of the subducting Arabian plate beneath the Anatolian microplate. During the last 450 kyr the area underwent an uplift phase at a mean rate of similar to 3.2 m/kyr, as suggested by Middle Pleistocene marine sediments exposed at similar to 1,500 m above sea level. These values are significantly higher than the 1.0-1.5 m/kyr estimated since the Late Pleistocene, suggesting temporal variations in uplift rate. To estimate changes in uplift rate during the Pleistocene we studied the marine terraces along the CAP southern margin, mapping the remnants of the platforms and their associated deposits in the field, and used the TerraceM software to identify the position and elevation of associated shoreline angles. We used shoreline angles and the timing of Quaternary marine sedimentation as constrains for a Landscape Evolution Model that simulates wave erosion of an uplifting coast. We applied random optimization algorithms and minimization statistics to find the input parameters that better reproduce the morphology of CAP marine terraces. The best-fitting uplift rate history suggests a significative increase from 1.9 to 3.5 m/kyr between 500 and 200 kyr, followed by an abrupt decrease to 1.4 m/kyr until the present. Our results agree with slab break-off models, which suggest a strong uplift pulse during slab rupture followed by a smoother decrease.
Y1  - 2020
U6  - https://doi.org/10.1029/2019TC005921
SN  - 0278-7407
SN  - 1944-9194
VL  - 39
IS  - 12
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Rajaonarison, Tahiry A.
A1  - Stamps, D. Sarah
A1  - Fishwick, Stewart
A1  - Brune, Sascha
A1  - Glerum, Anne
A1  - Hu, Jiashun
T1  - Numerical modeling of mantle flow beneath Madagascar to constrain upper mantle rheology beneath continental regions
JF  - Journal of geophysical research : Solid earth
N2  - Over the past few decades, azimuthal seismic anisotropy measurements have been widely used proxy to study past and present-day deformation of the lithosphere and to characterize convection in the mantle. Beneath continental regions, distinguishing between shallow and deep sources of anisotropy remains difficult due to poor depth constraints of measurements and a lack of regional-scale geodynamic modeling. Here, we constrain the sources of seismic anisotropy beneath Madagascar where a complex pattern cannot be explained by a single process such as absolute plate motion, global mantle flow, or geology. We test the hypotheses that either Edge-Driven Convection (EDC) or mantle flow derived from mantle wind interactions with lithospheric topography is the dominant source of anisotropy beneath Madagascar. We, therefore, simulate two sets of mantle convection models using regional-scale 3-D computational modeling. We then calculate Lattice Preferred Orientation that develops along pathlines of the mantle flow models and use them to calculate synthetic splitting parameters. Comparison of predicted with observed seismic anisotropy shows a good fit in northern and southern Madagascar for the EDC model, but the mantle wind case only fits well in northern Madagascar. This result suggests the dominant control of the measured anisotropy may be from EDC, but the role of localized fossil anisotropy in narrow shear zones cannot be ruled out in southern Madagascar. Our results suggest that the asthenosphere beneath northern and southern Madagascar is dominated by dislocation creep. Dislocation creep rheology may be dominant in the upper asthenosphere beneath other regions of continental lithosphere.
KW  - seismic anisotropy
KW  - edge-driven convection
KW  - mantle flow modeling
KW  - lattice preferred orientations
KW  - lithosphere-mantle wind interactions
KW  - splitting parameters
Y1  - 2019
U6  - https://doi.org/10.1029/2019JB018560
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 2
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ramachandran, Srikanthan
A1  - Rupakheti, Maheswar
A1  - Lawrence, Mark
T1  - Black carbon dominates the aerosol absorption over the Indo-Gangetic Plain and the Himalayan foothills
JF  - Environment international : a journal of science, technology, health, monitoring and policy
N2  - This study, based on new and high quality in situ observations, quantifies for the first time, the individual contributions of light-absorbing aerosols (black carbon (BC), brown carbon (BrC) and dust) to aerosol absorption over the Indo-Gangetic Plain (IGP) and the Himalayan foothill region, a relatively poorly studied region with several sensitive ecosystems of global importance, as well as highly vulnerable populations. The annual and seasonal average single scattering albedo (SSA) over Kathmandu is the lowest of all the locations. The SSA over Kathmandu is < 0.89 during all seasons, which confirms the dominance of light-absorbing carbonaceous aerosols from local and regional sources over Kathmandu. It is observed here that the SSA decreases with increasing elevation, confirming the dominance of light absorbing carbonaceous aerosols at higher elevations. In contrast, the SSA over the IGP does not exhibit a pronounced spatial variation. BC dominates (>= 75%) the aerosol absorption over the IGP and the Himalayan foothills throughout the year. Higher BC concentration at elevated locations in the Himalayas leads to lower SSA at elevated locations in the Himalayas. The contribution of dust to aerosol absorption is higher throughout the year over the IGP than over the Himalayan foothills. The aerosol absorption over South Asia is very high, exceeding available observations over East Asia, and also exceeds previous model estimates. This quantification will be valuable as observational constraints to help improve regional simulations of climate change, impacts on the glaciers and the hydrological cycle, and will help to direct the focus towards BC as the main contributor to aerosol-induced warming in the region.
KW  - atmospheric aerosols
KW  - characteristics
KW  - absorption
KW  - black carbon
KW  - brown
KW  - carbon
KW  - dust
KW  - Himalayas
KW  - IGP
KW  - South Asia
Y1  - 2020
U6  - https://doi.org/10.1016/j.envint.2020.105814
SN  - 0160-4120
SN  - 1873-6750
VL  - 142
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Rein, Theresa
A1  - Hannemann, Katrin
A1  - Thomas, Christine
A1  - Korn, Michael
T1  - Location and characteristics of the X-discontinuity beneath SW Morocco and the adjacent shelf area using P-wave receiver functions
JF  - Geophysical journal international
N2  - Receiver function approaches have proven to be valuable for the investigation of crustal and upper mantle discontinuities whose sharp changes in seismic velocities cause wave conversions. While the crustal and mantle transition zone discontinuities are largely understood, the X-discontinuity at 250-350 km depth is still an object of controversial debate. The origin and global distribution of this structure with a velocity jump of 1.5-4.8% for compressional and shear waves is still unexplained. Although the crustal and mantle transition zone discontinuities beneath SW Morocco and surroundings have been investigated, only a few studies observed the X-discontinuity and place the depth at 260-370 km beneath the region of western Morocco. In order to better locate and characterize the X-discontinuity beneath southwest Morocco, we create P-wave receiver functions using data recorded by the Morocco-Munster array and detect the X-discontinuity at apparent depths of 285-350 km. In the western part of our study region we find apparent depths of similar to 310-340 km. The eastern part of the study area appears more complex: we locate two velocity jumps at apparent depths of around 285-295 km and 330-350 km in the northeast, and in the southeast we find a discontinuity at apparent depths of 340-350 km. Due to the large depth range and the twofold appearance of the X-discontinuity, we suggest that two different phase transitions cause the X-discontinuity beneath SW Morocco. The velocity contrasts at larger depths likely point to the coesite-stishovite phase transition occurring in deep eclogitic pools. The shallower depths can be explained by the transition from orthoenstatite to high-pressure clinoenstatite which requires the reaction between eclogite and peridotite to form orthopyroxene-rich peridotite. This reaction is likely related to previously proposed small-scale mantle upwellings beneath SW Morocco. Since both phase transitions require eclogite occurrence, the location of the X-discontinuity in this region can be used to indicate the location of recycled oceanic crust.
KW  - body waves
KW  - mantle discontinuities
KW  - NW Morocco
KW  - P-waves
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa379
SN  - 0956-540X
SN  - 1365-246X
VL  - 223
IS  - 3
SP  - 1780
EP  - 1793
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Repasch, Marisa
A1  - Wittmann, Hella
A1  - Scheingross, Joel S.
A1  - Sachse, Dirk
A1  - Szupiany, Ricardo
A1  - Orfeo, Oscar
A1  - Fuchs, Margret
A1  - Hovius, Niels
T1  - Sediment Transit Time and Floodplain Storage Dynamics in Alluvial Rivers Revealed by Meteoric 10Be
JF  - Journal of Geophysical Research: Earth Surface
N2  - Quantifying the time scales of sediment transport and storage through river systems is fundamental for understanding weathering processes, biogeochemical cycling, and improving watershed management, but measuring sediment transit time is challenging. Here we provide the first systematic test of measuring cosmogenic meteoric Beryllium-10 (10Bem) in the sediment load of a large alluvial river to quantify sediment transit times. We take advantage of a natural experiment in the Rio Bermejo, a lowland alluvial river traversing the east Andean foreland basin in northern Argentina. This river has no tributaries along its trunk channel for nearly 1,300 km downstream from the mountain front. We sampled suspended sediment depth profiles along the channel and measured the concentrations of 10Bem in the chemically extracted grain coatings. We calculated depth-integrated 10Bem concentrations using sediment flux data and found that 10Bem concentrations increase 230% from upstream to downstream, indicating a mean total sediment transit time of 8.4 ± 2.2 kyr. Bulk sediment budget-based estimates of channel belt and fan storage times suggest that the 10Bem tracer records mixing of old and young sediment reservoirs. On a reach scale, 10Bem transit times are shorter where the channel is braided and superelevated above the floodplain, and longer where the channel is incised and meandering, suggesting that transit time is controlled by channel morphodynamics. This is the first systematic application of 10Bem as a sediment transit time tracer and highlights the method's potential for inferring sediment routing and storage dynamics in large river systems.
KW  - meteoric 10Be
KW  - sediment transit time
KW  - river sediment
KW  - floodplains
KW  - sediment routing
Y1  - 2019
U6  - https://doi.org/10.1029/2019JF005419
SN  - 2169-9011
SN  - 2169-9003
VL  - 125
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Reschke, Maria
A1  - Kröner, Igor
A1  - Laepple, Thomas
T1  - Testing the consistency of Holocene and Last Glacial Maximum spatial correlations in temperature proxy records
JF  - Journal of quaternary science : JQS
N2  - Holocene temperature proxy records are commonly used in quantitative synthesis and model-data comparisons. However, comparing correlations between time series from records collected in proximity to one another with the expected correlations based on climate model simulations indicates either regional or noisy climate signals in Holocene temperature proxy records. In this study, we evaluate the consistency of spatial correlations present in Holocene proxy records with those found in data from the Last Glacial Maximum (LGM). Specifically, we predict correlations expected in LGM proxy records if the only difference to Holocene correlations would be due to more time uncertainty and more climate variability in the LGM. We compare this simple prediction to the actual correlation structure in the LGM proxy records. We found that time series data of ice-core stable isotope records and planktonic foraminifera Mg/Ca ratios were consistent between the Holocene and LGM periods, while time series of Uk'37 proxy records were not as we found no correlation between nearby LGM records. Our results support the finding of highly regional or noisy marine proxy records in the compilation analysed here and suggest the need for further studies on the role of climate proxies and the processes of climate signal recording and preservation.
KW  - Holocene
KW  - LGM
KW  - spatial correlation
KW  - temperature
KW  - Uk'37
Y1  - 2020
U6  - https://doi.org/10.1002/jqs.3245
SN  - 0267-8179
SN  - 1099-1417
VL  - 36
IS  - 1
SP  - 20
EP  - 28
PB  - Wiley
CY  - New York
ER  - 
TY  - JOUR
A1  - Richter, Gudrun
A1  - Hainzl, Sebastian
A1  - Dahm, Torsten
A1  - Zöller, Gert
T1  - Stress-based, statistical modeling of the induced seismicity at the Groningen gas field
BT  - the Netherlands
JF  - Environmental earth sciences
N2  - Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with ML=3.6 was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity.
KW  - induced seismicity
KW  - modeling
KW  - statistical seismology
KW  - forecast
Y1  - 2020
U6  - https://doi.org/10.1007/s12665-020-08941-4
SN  - 1866-6280
SN  - 1866-6299
VL  - 79
IS  - 11
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Riedl, Simon
A1  - Melnick, Daniel
A1  - Mibei, Geoffrey K.
A1  - Njue, Lucy
A1  - Strecker, Manfred
T1  - Continental rifting at magmatic centres
BT  - structural implications from the Late Quaternary Menengai Caldera, central Kenya Rift
JF  - Journal of the geological society
N2  - The structural evolution of calderas in rifts helps to characterize the spatiotemporal relationships between magmatism, long wavelength crustal deformation and the formation of tectonic deformation zones along the rift axis. We document the structural characteristics of the c. 36 ka old Menengai Caldera located within a young zone of extension in the central Kenya Rift. Field mapping and high-resolution digital surface models show that NNE-striking Holocene normal faults perpendicular to the regional ESE-WNWextension direction dominate the interior sectors of the rift. Inside the caldera, these structures are overprinted by post-collapse doming and faulting of the magmatic centre, resulting in obliquely slipping normal faults bounding a resurgence horst. Radiocarbon dating of faulted units as young as 5 ka cal BP and the palaeo-shorelines of a lake formed during the African Humid Period in the Nakuru Basin indicate that volcanism and fault activity inside and in the vicinity of Menengai must have been sustained during the Holocene. Our analysis confirms that the caldera is located at the centre of an extending rift segment and suggests that other magmatic centres and young zones of faulting along the volcano-tectonic axis of the Kenya Rift may constitute nucleation points of faulting that ultimately foster future continental break-up.
Y1  - 2020
U6  - https://doi.org/10.1144/jgs2019-021
SN  - 0016-7649
SN  - 2041-479X
VL  - 177
IS  - 1
SP  - 153
EP  - 169
PB  - Geological Soc. Publ. House
CY  - Bath
ER  - 
TY  - JOUR
A1  - Rodriguez Piceda, Constanza
A1  - Scheck Wenderoth, Magdalena
A1  - Gomez Dacal, Maria Laura
A1  - Bott, Judith
A1  - Prezzi, Claudia Beatriz
A1  - Strecker, Manfred
T1  - Lithospheric density structure of the southern Central Andes constrained by 3D data-integrative gravity modelling
JF  - International journal of earth sciences
N2  - The southern Central Andes (SCA) (between 27 degrees S and 40 degrees S) is bordered to the west by the convergent margin between the continental South American Plate and the oceanic Nazca Plate. The subduction angle along this margin is variable, as is the deformation of the upper plate. Between 33 degrees S and 35 degrees S, the subduction angle of the Nazca plate increases from sub-horizontal (< 5 degrees) in the north to relatively steep (similar to 30 degrees) in the south. The SCA contain inherited lithological and structural heterogeneities within the crust that have been reactivated and overprinted since the onset of subduction and associated Cenozoic deformation within the Andean orogen. The distribution of the deformation within the SCA has often been attributed to the variations in the subduction angle and the reactivation of these inherited heterogeneities. However, the possible influence that the thickness and composition of the continental crust have had on both short-term and long-term deformation of the SCA is yet to be thoroughly investigated. For our investigations, we have derived density distributions and thicknesses for various layers that make up the lithosphere and evaluated their relationships with tectonic events that occurred over the history of the Andean orogeny and, in particular, investigated the short- and long-term nature of the present-day deformation processes. We established a 3D model of lithosphere beneath the orogen and its foreland (29 degrees S-39 degrees S) that is consistent with currently available geological and geophysical data, including the gravity data. The modelled crustal configuration and density distribution reveal spatial relationships with different tectonic domains: the crystalline crust in the orogen (the magmatic arc and the main orogenic wedge) is thicker (similar to 55 km) and less dense (similar to 2900 kg/m(3)) than in the forearc (similar to 35 km, similar to 2975 kg/m(3)) and foreland (similar to 30 km, similar to 3000 kg/m(3)). Crustal thickening in the orogen probably occurred as a result of stacking of low-density domains, while density and thickness variations beneath the forearc and foreland most likely reflect differences in the tectonic evolution of each area following crustal accretion. No clear spatial relationship exists between the density distribution within the lithosphere and previously proposed boundaries of crustal terranes accreted during the early Paleozoic. Areas with ongoing deformation show a spatial correlation with those areas that have the highest topographic gradients and where there are abrupt changes in the average crustal-density contrast. This suggests that the short-term deformation within the interior of the Andean orogen and its foreland is fundamentally influenced by the crustal composition and the relative thickness of different crustal layers. A thicker, denser, and potentially stronger lithosphere beneath the northern part of the SCA foreland is interpreted to have favoured a strong coupling between the Nazca and South American plates, facilitating the development of a sub-horizontal slab.
KW  - Central andes
KW  - Lithospheric structure
KW  - Crustal density
KW  - Gravity
KW  - modelling
KW  - Subduction
Y1  - 2020
U6  - https://doi.org/10.1007/s00531-020-01962-1
SN  - 1437-3254
SN  - 1437-3262
VL  - 110
IS  - 7
SP  - 2333
EP  - 2359
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Rolfes, Manfred
A1  - Wilhelm, Jan Lorenz
T1  - Urban complexity and urban change
BT  - Co-irritation, co-evolution and co-design with the Potsdam lodestar approach
JF  - Urban Change and Citizenship in Times of Crisis
N2  - The chapter illustrates how cities can be understood from a system–theory perspective as complex social systems. It argues that the classical and linear intervention methods are often no (longer) suitable for the complex structure, temporal dynamics and multifaceted processuality of urban development. It offers a systemic and systems theory-inspired method as an alternative approach, which allows for extended possibilities that are more appropriate for dealing with urban development processes. The method was developed on the basis of practical experience and theoretical insights. The approach should demonstrate for local decision-makers potential areas of activity for organising urban changes through co-design.
Y1  - 2020
SN  - 978-0-429-26226-5
SN  - 978-0-367-20562-1
SP  - 135
EP  - 155
PB  - Routledge
CY  - London
ER  - 
TY  - JOUR
A1  - Runge, Alexandra
A1  - Grosse, Guido
T1  - Mosaicking Landsat and Sentinel-2 Data to Enhance LandTrendr Time Series Analysis in Northern High Latitude Permafrost Regions
JF  - Remote Sensing
N2  - Permafrost is warming in the northern high latitudes, inducing highly dynamic thaw-related permafrost disturbances across the terrestrial Arctic. Monitoring and tracking of permafrost disturbances is important as they impact surrounding landscapes, ecosystems and infrastructure. Remote sensing provides the means to detect, map, and quantify these changes homogeneously across large regions and time scales. Existing Landsat-based algorithms assess different types of disturbances with similar spatiotemporal requirements. However, Landsat-based analyses are restricted in northern high latitudes due to the long repeat interval and frequent clouds, in particular at Arctic coastal sites. We therefore propose to combine Landsat and Sentinel-2 data for enhanced data coverage and present a combined annual mosaic workflow, expanding currently available algorithms, such as LandTrendr, to achieve more reliable time series analysis. We exemplary test the workflow for twelve sites across the northern high latitudes in Siberia. We assessed the number of images and cloud-free pixels, the spatial mosaic coverage and the mosaic quality with spectral comparisons. The number of available images increased steadily from 1999 to 2019 but especially from 2016 onward with the addition of Sentinel-2 images. Consequently, we have an increased number of cloud-free pixels even under challenging environmental conditions, which then serve as the input to the mosaicking process. In a comparison of annual mosaics, the Landsat+Sentinel-2 mosaics always fully covered the study areas (99.9–100 %), while Landsat-only mosaics contained data-gaps in the same years, only reaching coverage percentages of 27.2 %, 58.1 %, and 69.7 % for Sobo Sise, East Taymyr, and Kurungnakh in 2017, respectively. The spectral comparison of Landsat image, Sentinel-2 image, and Landsat+Sentinel-2 mosaic showed high correlation between the input images and mosaic bands (e.g., for Kurungnakh 0.91–0.97 between Landsat and Landsat+Sentinel-2 mosaic and 0.92–0.98 between Sentinel-2 and Landsat+Sentinel-2 mosaic) across all twelve study sites, testifying good quality mosaic results. Our results show that especially the results for northern, coastal areas was substantially improved with the Landsat+Sentinel-2 mosaics. By combining Landsat and Sentinel-2 data we accomplished to create reliably high spatial resolution input mosaics for time series analyses. Our approach allows to apply a high temporal continuous time series analysis to northern high latitude permafrost regions for the first time, overcoming substantial data gaps, and assess permafrost disturbance dynamics on an annual scale across large regions with algorithms such as LandTrendr by deriving the location, timing and progression of permafrost thaw disturbances
KW  - time series analysis
KW  - data fusion
KW  - disturbance tracking
KW  - permafrost
KW  - permafrost thaw
Y1  - 2020
U6  - https://doi.org/10.3390/rs12152471
SN  - 2072-4292
VL  - 12
IS  - 15
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Rybski, Diego
A1  - Dawson, Richard J.
A1  - Kropp, Jürgen
T1  - Comparing generic and case study damage functions
BT  - London storm-surge example
JF  - Natural hazards review
N2  - Two different approaches are used to assess the impacts associated with natural hazards and climate change in cities. A bottom-up approach uses high resolution data on constituent assets within the urban area. In contrast, a top-down approach uses less detailed information but is consequently more readily transferable. Here, we compare damage curves generated by each approach for coastal flooding in London. To compare them, we fit a log-logistic regression with three parameters to the calculated damage curves. We find that the functions are remarkably similar in their shape, albeit with different inflection points and a maximum damage that differs by 13%-25%. If rescaled, the curves agree almost exactly, which enables damage assessment to be undertaken following the calculation of the three parameters.
Y1  - 2020
U6  - https://doi.org/10.1061/(ASCE)NH.1527-6996.0000336
SN  - 1527-6988
SN  - 1527-6996
VL  - 21
IS  - 1
PB  - American Society of Civil Engineers
CY  - Reston
ER  - 
TY  - JOUR
A1  - Rötzler, Jochen
A1  - Timmerman, Martin Jan
T1  - Geochronological and petrological constraints from the evolution in the Saxon Granulite Massif, Germany, on the Variscan continental collision orogeny
JF  - Journal of metamorphic geology
N2  - Controversy over the plate tectonic affinity and evolution of the Saxon granulites in a two- or multi-plate setting during inter- or intracontinental collision makes the Saxon Granulite Massif a key area for the understanding of the Palaeozoic Variscan orogeny. The massif is a large dome structure in which tectonic slivers of metapelite and metaophiolite units occur along a shear zone separating a diapir-like body of high-Pgranulite below from low-Pmetasedimentary rocks above. Each of the upper structural units records a different metamorphic evolution until its assembly with the exhuming granulite body. New age and petrologic data suggest that the metaophiolites developed from early Cambrian protoliths during high-Pamphibolite facies metamorphism in the mid- to late-Devonian and thermal overprinting by the exhuming hot granulite body in the early Carboniferous. A correlation of new Ar-Ar biotite ages with publishedP-T-tdata for the granulites implies that exhumation and cooling of the granulite body occurred at average rates of similar to 8 mm/year and similar to 80 degrees C/Ma, with a drop in exhumation rate from similar to 20 to similar to 2.5 mm/year and a slight rise in cooling rate between early and late stages of exhumation. A time lag ofc. 2 Ma between cooling through the closure temperatures for argon diffusion in hornblende and biotite indicates a cooling rate of 90 degrees C/Ma when all units had assembled into the massif. A two-plate model of the Variscan orogeny in which the above evolution is related to a short-lived intra-Gondwana subduction zone conflicts with the oceanic affinity of the metaophiolites and the timescale ofc. 50 Ma for the metamorphism. Alternative models focusing on the internal Variscan belt assume distinctly different material paths through the lower or upper crust for strikingly similar granulite massifs. An earlier proposed model of bilateral subduction below the internal Variscan belt may solve this problem.
KW  - geochronology
KW  - granulite
KW  - high-Pmetamorphism
KW  - metaophiolite
KW  - Variscan
KW  - orogeny
Y1  - 2020
U6  - https://doi.org/10.1111/jmg.12559
SN  - 0263-4929
SN  - 1525-1314
VL  - 39
IS  - 1
SP  - 3
EP  - 38
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Saki, Adel
A1  - Miri, Mirmohammad
A1  - Oberhänsli, Roland
T1  - High temperature - low pressure metamorphism during subduction of Neo-Tethys beneath the Iranian plate
BT  - evidence for mafic migmatite formation in the Alvand complex (western Iran)
JF  - Mineralogy and petrology
N2  - Subduction of Neo-Tethys oceanic lithosphere beneath the Iranian plate during the Mesozoic formed several igneous bodies of ultramafic to intermediate and felsic composition. Intrusion of these magmas into a regional metamorphic sequence (the Sanandaj-Sirjan Zone) caused partial melting and formation of migmatites with meta-pelitic protoliths. The Alvand complex (west Iran) is a unique area comprising migmatites of both mafic and pelitic protoliths. In this area, the gabbroic rocks contain veins of leucosome at their contact with pyroxenite and olivine gabbro. These leucosomes are geochemically and mineralogically different from leucosomes of the meta-pelitic migmatites and clearly show properties of I-type granites. Microscopic observations and whole rock compositions of the mafic migmatite leucosomes show that migmatization occurred through partial melting of biotite, hornblende and plagioclase. Thermobarometric calculations indicate 800 degrees C and 3.7 kbar for partial melting, although phase diagram modeling demonstrates that the presence of water could decrease the solidus temperature by about 40 degrees C. Our results suggest an asthenospheric magma upwelling as the source of heat for partial melting of the gabbroic rock during subduction of Neo-Tethys oceanic crust under the western edge of the Iranian plate. The present study also reveals relationships between migmatization and formation of S- and I -type granites in the area.
KW  - partial melting
KW  - mafic migmatite
KW  - pelitic migmatite
KW  - Neo-Tethys
KW  - subduction
KW  - Gabbroic rocks
Y1  - 2020
U6  - https://doi.org/10.1007/s00710-020-00721-z
SN  - 0930-0708
SN  - 1438-1168
VL  - 114
IS  - 6
SP  - 539
EP  - 557
PB  - Springer
CY  - Wien [u.a.]
ER  - 
TY  - JOUR
A1  - Samprogna Mohor, Guilherme
A1  - Hudson, Paul
A1  - Thieken, Annegret
T1  - A comparison of factors driving flood losses in households affected by different flood types
JF  - Water resources research
N2  - Flood loss data collection and modeling are not standardized, and previous work has indicated that losses from different flood types (e.g., riverine and groundwater) may follow different driving forces. However, different flood types may occur within a single flood event, which is known as a compound flood event. Therefore, we aimed to identify statistical similarities between loss-driving factors across flood types and test whether the corresponding losses should be modeled separately. In this study, we used empirical data from 4,418 respondents from four survey campaigns studying households in Germany that experienced flooding. These surveys sought to investigate several features of the impact process (hazard, socioeconomic, preparedness, and building characteristics, as well as flood type). While the level of most of these features differed across flood type subsamples (e.g., degree of preparedness), they did so in a nonregular pattern. A variable selection process indicates that besides hazard and building characteristics, information on property-level preparedness was also selected as a relevant predictor of the loss ratio. These variables represent information, which is rarely adopted in loss modeling. Models shall be refined with further data collection and other statistical methods. To save costs, data collection efforts should be steered toward the most relevant predictors to enhance data availability and increase the statistical power of results. Understanding that losses from different flood types are driven by different factors is a crucial step toward targeted data collection and model development and will finally clarify conditions that allow us to transfer loss models in space and time. <br /> Key Points <br /> Survey data of flood-affected households show different concurrent flood types, undermining the use of a single-flood-type loss model Thirteen variables addressing flood hazard, the building, and property level preparedness are significant predictors of the building loss ratio Flood type-specific models show varying significance across the predictor variables, indicating a hindrance to model transferability
KW  - Loss modeling
KW  - Riverine floods
KW  - Surface floods
KW  - Groundwater
KW  - Levee
KW  - breaches
KW  - Compound flood event
Y1  - 2020
U6  - https://doi.org/10.1029/2019WR025943
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 4
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Scharf, Andreas
A1  - Sudo, Masafumi
A1  - Pracejus, Bernhard
A1  - Mattern, Frank
A1  - Callegari, Ivan
A1  - Bauer, Wilfried
A1  - Scharf, Katharina
T1  - Late Lutetian (Eocene) mafic intrusion into shallow marine platform deposits north of the Oman Mountains (Rusayl Embayment) and its tectonic significance
JF  - Journal of African earth sciences
N2  - A silica undersaturated alkali-olivine basanitic magma intruded the late Paleocene/early Eocene Jafnayn Formation near Muscat. Geochemical analyses indicate that a significant amount of host rock (limestone) was assimilated into the magma. We dated the basanite as 42.7 +/- 1.0 Ma (2 sigma error; late Lutetian), using the whole rock Ar-40/Ar-39 step-wise heating technique. Intrusion occurred in the hanging wall of a major regional extensional shear zone (Frontal Range Fault, FRF) bounding the northern margin of two domes within the Oman Mountains (Jabal Akhdar and Saih Hatat domes). Two shear intervals along the FRF have been documented. The first interval lasted immediately after emplacement of the Semail Ophiolite (latest Cretaceous-early Eocene) while the second and poorly constrained interval was assumed to have occurred during the Oligocene. 

The proximity of the basanite to the FRF suggests that magma used extensional faults for the upper part of its ascent path. Reactivated Permian rift faults of the Pangaea rift or other preexisting faults may have been used for the lower ascent part. 

We conclude that the basanite intrusion coincided with the onset of the second deformation interval along the FRF, because (1) the position of the basanite is near a dextral releasing bend, associated with the second shear interval, (2) the overlap of our Ar-40/Ar-39 age with the cooling curves for rocks from the nearby Jabal Akhdar Dome, and (3) the basanite postdates the first FRF deformation episode by > 10 Ma. Thus, the second interval along the FRF had started already during the late Lutetian and probably lasted into the Miocene.
KW  - Ar-40/Ar-39 age
KW  - Jafnayn formation
KW  - gravitational collapse
KW  - Basanite
KW  - extension
KW  - Limestone assimilation in basanite
Y1  - 2020
U6  - https://doi.org/10.1016/j.jafrearsci.2020.103941
SN  - 1464-343X
SN  - 1879-1956
VL  - 170
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Scherler, Dirk
A1  - Schwanghart, Wolfgang
T1  - Drainage divide networks
BT  - Part 2: Response to perturbations
JF  - Earth surface dynamics
N2  - Drainage divides are organized into tree-like networks that may record information about drainage divide mobility. However, views diverge about how to best assess divide mobility. Here, we apply a new approach of automatically extracting and ordering drainage divide networks from digital elevation models to results from landscape evolution model experiments. We compared landscapes perturbed by strike-slip faulting and spatiotemporal variations in erodibility to a reference model to assess which topographic metrics (hillslope relief, flow distance, and chi) are diagnostic of divide mobility. Results show that divide segments that are a minimum distance of similar to 5 km from river confluences strive to attain constant values of hillslope relief and flow distance to the nearest stream. Disruptions of such patterns can be related to mobile divides that are lower than stable divides, closer to streams, and often asymmetric in shape. In general, we observe that drainage divides high up in the network, i.e., at great distances from river confluences, are more susceptible to disruptions than divides closer to these confluences and are thus more likely to record disturbance for a longer time period. We found that across-divide differences in hillslope relief proved more useful for assessing divide migration than other tested metrics. However, even stable drainage divide networks exhibit across-divide differences in any of the studied topographic metrics. Finally, we propose a new metric to quantify the connectivity of divide junctions.
KW  - dynamics
KW  - landscape evolution
KW  - low-relief
KW  - patterns
KW  - river
KW  - scale
KW  - tectonics
Y1  - 2020
U6  - https://doi.org/10.5194/esurf-8-261-2020
SN  - 2196-6311
SN  - 2196-632X
VL  - 8
IS  - 2
SP  - 261
EP  - 274
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schmidt, Lennart
A1  - Hesse, Falk
A1  - Attinger, Sabine
A1  - Kumar, Rohini
T1  - Challenges in applying machine learning models for hydrological inference
BT  - a case study for flooding events across Germany
JF  - Water resources research
N2  - Machine learning (ML) algorithms are being increasingly used in Earth and Environmental modeling studies owing to the ever-increasing availability of diverse data sets and computational resources as well as advancement in ML algorithms. Despite advances in their predictive accuracy, the usefulness of ML algorithms for inference remains elusive. In this study, we employ two popular ML algorithms, artificial neural networks and random forest, to analyze a large data set of flood events across Germany with the goals to analyze their predictive accuracy and their usability to provide insights to hydrologic system functioning. The results of the ML algorithms are contrasted against a parametric approach based on multiple linear regression. For analysis, we employ a model-agnostic framework named Permuted Feature Importance to derive the influence of models' predictors. This allows us to compare the results of different algorithms for the first time in the context of hydrology. Our main findings are that (1) the ML models achieve higher prediction accuracy than linear regression, (2) the results reflect basic hydrological principles, but (3) further inference is hindered by the heterogeneity of results across algorithms. Thus, we conclude that the problem of equifinality as known from classical hydrological modeling also exists for ML and severely hampers its potential for inference. To account for the observed problems, we propose that when employing ML for inference, this should be made by using multiple algorithms and multiple methods, of which the latter should be embedded in a cross-validation routine.
KW  - machine learning
KW  - inference
KW  - floods
Y1  - 2020
U6  - https://doi.org/10.1029/2019WR025924
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 5
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schoppa, Lukas
A1  - Sieg, Tobias
A1  - Vogel, Kristin
A1  - Zöller, Gert
A1  - Kreibich, Heidi
T1  - Probabilistic flood loss models for companies
JF  - Water resources research
N2  - Flood loss modeling is a central component of flood risk analysis. Conventionally, this involves univariable and deterministic stage-damage functions. Recent advancements in the field promote the use of multivariable and probabilistic loss models, which consider variables beyond inundation depth and account for prediction uncertainty. Although companies contribute significantly to total loss figures, novel modeling approaches for companies are lacking. Scarce data and the heterogeneity among companies impede the development of company flood loss models. We present three multivariable flood loss models for companies from the manufacturing, commercial, financial, and service sector that intrinsically quantify prediction uncertainty. Based on object-level loss data (n = 1,306), we comparatively evaluate the predictive capacity of Bayesian networks, Bayesian regression, and random forest in relation to deterministic and probabilistic stage-damage functions, serving as benchmarks. The company loss data stem from four postevent surveys in Germany between 2002 and 2013 and include information on flood intensity, company characteristics, emergency response, private precaution, and resulting loss to building, equipment, and goods and stock. We find that the multivariable probabilistic models successfully identify and reproduce essential relationships of flood damage processes in the data. The assessment of model skill focuses on the precision of the probabilistic predictions and reveals that the candidate models outperform the stage-damage functions, while differences among the proposed models are negligible. Although the combination of multivariable and probabilistic loss estimation improves predictive accuracy over the entire data set, wide predictive distributions stress the necessity for the quantification of uncertainty.
KW  - flood loss estimation
KW  - probabilistic modeling
KW  - companies
KW  - multivariable
KW  - models
Y1  - 2020
U6  - https://doi.org/10.1029/2020WR027649
SN  - 0043-1397
SN  - 1944-7973
VL  - 56
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schuck, Bernhard
A1  - Schleicher, Anja Maria
A1  - Janssen, Christoph
A1  - Toy, Virginia G.
A1  - Dresen, Georg
T1  - Fault zone architecture of a large plate-bounding strike-slip fault
BT  - A case study from the Alpine Fault, New Zealand
JF  - Solid Earth
N2  - New Zealand's Alpine Fault is a large, platebounding strike-slip fault, which ruptures in large (M-w > 8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show that the young, largely unconsolidated sediments that constitute the footwall at shallow depths have a significant influence on fault gouge rheological properties and structure.
KW  - san andreas fault
KW  - thickness-displacement relationships
KW  - central south island
KW  - Ion-Beam (FIB)
KW  - internal structure
KW  - hanging wall
KW  - Fluid Flow
KW  - frictional properties
KW  - weakening mechanisms
KW  - strain localization
Y1  - 2020
U6  - https://doi.org/10.5194/se-11-95-2020
SN  - 1869-9529
VL  - 11
IS  - 1
SP  - 95
EP  - 124
PB  - Copernicus Publications
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Schönfeldt, Elisabeth
A1  - Pánek, Tomáš
A1  - Winocur, Diego
A1  - Silhan, Karel
A1  - Korup, Oliver
T1  - Postglacial Patagonian mass movement
BT  - from rotational slides and spreads to earthflows
JF  - Geomorphology : an international journal on pure and applied geomorphology
N2  - Many of the volcanic plateau margins of the eastern, formerly glaciated, foreland of the Patagonian Andes are undermined by giant landslides (>= 10(8) m(3)). One cluster of such landslides extends along the margin of the Meseta del Lago Buenos Aires (MLBA) plateau that is formed mainly by Neogene-Quaternary basalts. The dry climate is at odds with numerous >2-km long earthflows nested within older and larger compound landslides. We present a hydrological analysis, a detailed geomorphic map, interpretations of exposed landslide interiors, and radiocarbon dating of the El Mirador landslide, which is one of the largest and morphologically most representative landslide. We find that the presence of lakes on top of the plateau, causing low infiltration rates, correlates negatively with the abundance of earthflows on compound landslides along the plateau margins. Field outcrops show that the pattern of compound landslides and earthflows is likely controlled by groundwater seepage at the contact between the basalts and underlying soft Miocene molasse. Numerous peat bogs store water and sediment and are more abundant in earthflow-affected areas than in their contributing catchment areas. <br /> Radiocarbon dates indicate that these earthflows displaced metre-thick layers of peat in the late Holocene (<2.5 ka). We conclude that earthflows of the MLBA plateau might be promising proxies of past hydroclimatic conditions in the Patagonian foreland, if strong earthquakes or gradual crustal stress changes due to glacioisostatic rebound can be ruled out.
KW  - landslide
KW  - lateral spread
KW  - earthflow
KW  - Patagonia
Y1  - 2020
U6  - https://doi.org/10.1016/j.geomorph.2020.107316
SN  - 0169-555X
SN  - 1872-695X
VL  - 367
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Sharma, Shubham
A1  - Hainzl, Sebastian
A1  - Zöller, Gert
A1  - Holschneider, Matthias
T1  - Is Coulomb stress the best choice for aftershock forecasting?
JF  - Journal of geophysical research : Solid earth
N2  - The Coulomb failure stress (CFS) criterion is the most commonly used method for predicting spatial distributions of aftershocks following large earthquakes. However, large uncertainties are always associated with the calculation of Coulomb stress change. The uncertainties mainly arise due to nonunique slip inversions and unknown receiver faults; especially for the latter, results are highly dependent on the choice of the assumed receiver mechanism. Based on binary tests (aftershocks yes/no), recent studies suggest that alternative stress quantities, a distance-slip probabilistic model as well as deep neural network (DNN) approaches, all are superior to CFS with predefined receiver mechanism. To challenge this conclusion, which might have large implications, we use 289 slip inversions from SRCMOD database to calculate more realistic CFS values for a layered half-space and variable receiver mechanisms. We also analyze the effect of the magnitude cutoff, grid size variation, and aftershock duration to verify the use of receiver operating characteristic (ROC) analysis for the ranking of stress metrics. The observations suggest that introducing a layered half-space does not improve the stress maps and ROC curves. However, results significantly improve for larger aftershocks and shorter time periods but without changing the ranking. We also go beyond binary testing and apply alternative statistics to test the ability to estimate aftershock numbers, which confirm that simple stress metrics perform better than the classic Coulomb failure stress calculations and are also better than the distance-slip probabilistic model.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JB019553
SN  - 2169-9313
SN  - 2169-9356
VL  - 125
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Sieber, Melanie Jutta
A1  - Brink, Frank J.
A1  - Leys, Clyde
A1  - King, Penelope L.
A1  - Henley, Richard W.
T1  - Prograde and retrograde metasomatic reactions in mineralised magnesium- silicate skarn in the Cu-Au Ertsberg East Skarn System, Ertsberg, Papua Province, Indonesia
JF  - Ore geology reviews
N2  - The 2.7-2.9 Ma Ertsberg East Skarn System (EESS) is a world-class Cu-Au skarn that formed within and adjacent to an intrusion within a paleodepth of 0.5 km and > 2.5 km. Its economic mineralisation developed by sustained reaction of magmatic fluid with contact metamorphosed siliciclastic and carbonate rocks at the margin of the adjacent Ertsberg quartz monzodiorite intrusion. Based on high-resolution mineral mapping, chemical analysis and thermodynamic calculations, the multistage formation processes of the exoskarn components of the EESS are examined in the context of changing pressure, temperature, fluid composition and fluid phase. We show that contact metamorphism of dolomitic sediments occurred at 51 +/- 5 MPa, between 700 degrees C and 800 degrees C and in the presence of a H2O-CO2-fluid containing similar to 10 to similar to 70 mol% CO2. This prograde metamorphism formed a forsterite + diopside + calcite + phlogopite + spinel assemblage. Such forsterite-dominated skarns account for similar to 55 vol% of the EESS exoskarns. Rare pargasite (previously unrecognized in this deposit) formed locally in the metamorphosed carbonate sequence where the protolith was composed of supratidal evaporites with dolomitic carbonate and interlayered calc-silicate rocks. The subsequent flux of a lower pressure magmatic gas containing SO2(g) caused sulphate metasomatism. This high temperature gas alteration of the metamorphic assemblage also caused skarn Cu-Fe-sulphide mineralisation. The influx of a SO2 gas through fracture permeability occurred at a temperature between similar to 600 and 700 degrees C and caused calcite to be replaced by anhydrite, with the coupled release of H2S(g). This in-situ release of H2S(g) scavenged trace Cu from the gas phase to deposit Cu-Fe-sulphides, which make the economic value of the distinct. We demonstrate that the formation of metal sulphides within forsterite skarns of the Ertsberg East Skarn System required a minimum flux of similar to 1,050 Mt SO2(g) and show that volcanic degassing may have occurred over a time span of similar to 3,900 years. As the system waned, the ambient fluid resulted in partial retrograde serpentinization of olivine and diopside without carbonation, and at temperatures sufficiently high to preserve anhydrite.
KW  - porphyry Cu-Au deposit
KW  - magnesium silicate skarn
KW  - pargasite
KW  - gas-solid
KW  - reaction
KW  - sulphate metasomatism
Y1  - 2020
U6  - https://doi.org/10.1016/j.oregeorev.2020.103697
SN  - 0169-1368
SN  - 1872-7360
VL  - 125
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Sieber, Melanie Jutta
A1  - Yaxley, Gregory M.
A1  - Hermann, Jörg
T1  - Investigation of fluid-driven carbonation of a hydrated, forearc mantle wedge using serpentinite cores in high-pressure experiments
JF  - Journal of petrology
N2  - High-pressure experiments were performed to investigate the effectiveness, rate and mechanism of carbonation of serpentinites by a carbon-saturated COH fluid at 1.5-2.5 GPa and 375-700 degrees C. This allows a better understanding of the fate and redistribution of slab-derived carbonic fluids when they react with the partially hydrated mantle within and above the subducting slab under pressure and temperature conditions corresponding to the forearc mantle. Interactions between carbon-saturated CO2-H2O-CH4 fluids and serpentinite were investigated using natural serpentinite cylinders with natural grain sizes and shapes in piston-cylinder experiments. The volatile composition of post-run fluids was quantified by gas chromatography. Solid phases were examined by Raman spectroscopy, electron microscopy and laser ablation inductively coupled plasma mass spectrometry. Textures, porosity and phase abundances of recovered rock cores were visualized and quantified by three-dimensional, high-resolution computed tomography. We find that carbonation of serpentinites is efficient at sequestering CO2 from the interacting fluid into newly formed magnesite. Time-series experiments demonstrate that carbonation is completed within similar to 96 h at 2 GPa and 600 degrees C. With decreasing CO2, aq antigorite is replaced first by magnesite + quartz followed by magnesite + talc + chlorite in distinct, metasomatic fronts. Above antigorite stability magnesite + enstatite + talc + chlorite occur additionally. The formation of fluid-permeable reaction zones enhances the reaction rate and efficiency of carbonation. Carbonation probably occurs via an interface-coupled replacement process, whereby interconnected porosity is present within reaction zones after the experiment. Consequently, carbonation of serpentinites is self-promoting and efficient even if fluid flow is channelized into veins. We conclude that significant amounts of carbonates may accumulate, over time, in the hydrated forearc mantle.
KW  - serpentinite carbonation
KW  - deep carbon cycle
KW  - COH fluid
KW  - forearc
KW  - CO2
KW  - sequestration
Y1  - 2020
U6  - https://doi.org/10.1093/petrology/egaa035
SN  - 0022-3530
SN  - 1460-2415
VL  - 61
IS  - 3
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Smirnov, Artem G.
A1  - Kronberg, Elena A.
A1  - Daly, Patrick W.
A1  - Aseev, Nikita
A1  - Shprits, Yuri
A1  - Kellerman, Adam C.
T1  - Adiabatic Invariants Calculations for Cluster Mission: A Long-Term Product for Radiation Belts Studies
JF  - Journal of Geophysical Research: Space Physics
N2  - The Cluster mission has produced a large data set of electron flux measurements in the Earth's magnetosphere since its launch in late 2000. Electron fluxes are measured using Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector as a function of energy, pitch angle, spacecraft position, and time. However, no adiabatic invariants have been calculated for Cluster so far. In this paper we present a step-by-step guide to calculations of adiabatic invariants and conversion of the electron flux to phase space density (PSD) in these coordinates. The electron flux is measured in two RAPID/IES energy channels providing pitch angle distribution at energies 39.2-50.5 and 68.1-94.5 keV in nominal mode since 2004. A fitting method allows to expand the conversion of the differential fluxes to the range from 40 to 150 keV. Best data coverage for phase space density in adiabatic invariant coordinates can be obtained for values of second adiabatic invariant, K, similar to 10(2), and values of the first adiabatic invariant mu in the range approximate to 5-20 MeV/G. Furthermore, we describe the production of a new data product "LSTAR," equivalent to the third adiabatic invariant, available through the Cluster Science Archive for years 2001-2018 with 1-min resolution. The produced data set adds to the availability of observations in Earth's radiation belts region and can be used for long-term statistical purposes.
KW  - L-Asterisk
KW  - magnetosphere
KW  - electrons
KW  - model
Y1  - 2019
VL  - 125
IS  - 2
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Smith, Taylor
A1  - Bookhagen, Bodo
T1  - Assessing Multi-Temporal Snow-Volume Trends in High Mountain Asia From 1987 to 2016 Using High-Resolution Passive Microwave Data
JF  - Frontiers in Earth Science
N2  - High Mountain Asia (HMA) is dependent upon both the amount and timing of snow and glacier meltwater. Previous model studies and coarse resolution (0.25° × 0.25°, ∼25 km × 25 km) passive microwave assessments of trends in the volume and timing of snowfall, snowmelt, and glacier melt in HMA have identified key spatial and seasonal heterogeneities in the response of snow to changes in regional climate. Here we use recently developed, continuous, internally consistent, and high-resolution passive microwave data (3.125 km × 3.125 km, 1987–2016) from the special sensor microwave imager instrument family to refine and extend previous estimates of changes in the snow regime of HMA. We find an overall decline in snow volume across HMA; however, there exist spatially contiguous regions of increasing snow volume—particularly during the winter season in the Pamir, Karakoram, Hindu Kush, and Kunlun Shan. Detailed analysis of changes in snow-volume trends through time reveal a large step change from negative trends during the period 1987–1997, to much more positive trends across large regions of HMA during the periods 1997–2007 and 2007–2016. We also find that changes in high percentile monthly snow-water volume exhibit steeper trends than changes in low percentile snow-water volume, which suggests a reduction in the frequency of high snow-water volumes in much of HMA. Regions with positive snow-water storage trends generally correspond to regions of positive glacier mass balances.
KW  - snow
KW  - glacier
KW  - climate change
KW  - passive microwave
KW  - special sensor microwave imager
KW  - special sensor microwave imager/sounder
Y1  - 2020
U6  - https://doi.org/10.3389/feart.2020.559175
SN  - 2296-6463
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Soares, Gabriel Brando
A1  - Yamazaki, Yosuke
A1  - Cnossen, Ingrid
A1  - Matzka, Jürgen
A1  - Pinheiro, Katia J.
A1  - Morschhauser, Achim
A1  - Alken, Patrick
A1  - Stolle, Claudia
T1  - Evolution of the geomagnetic daily variation at Tatuoca, Brazil, From 1957 to 2019
BT  - a transition from Sq to EEJ
JF  - Journal of geophysical research : Space physics
N2  - The magnetic equator in the Brazilian region has moved over 1,100 km northward since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of long-term changes in the daily variation due to the influence of secular variation, solar activity, season, and lunar phase. The H day-to-day variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quiet-time daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and day-to-day variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that long-term changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JA028109
SN  - 2169-9380
SN  - 2169-9402
VL  - 125
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Specht, Sebastian von
T1  - ICBM Integrated Combined Baseline Modification
BT  - an algorithm for segmented baseline estimation
JF  - Seismological research letters
N2  - Accelerograms are the primary source for characterizing strong ground motion. It is therefore of paramount interest to have high-quality recordings free from any nonphysical contamination. Frequently, accelerograms are affected by baseline jumps and drifts, either related to the instrument and/or a major earthquake. In this work, I propose a correction method for these undesired baseline drifts based on segmented linear least squares. The algorithm operates on the integrated waveforms and combines all three instrument components to estimate a model that modifies the baseline to be at zero continuously. The procedure consists of two steps: first a suite of models with variable numbers of discontinuities is derived for all three instrument components. During this process, the number of discontinuities is reduced in a parsimonious way, for example, two very close discontinuities are merged into a single one. In the second step, the optimal model is selected on the basis of the Bayesian information criterion. I exemplify the application on synthetic waveforms with known discontinuities and on observed waveforms from a unified strong-motion database of the Japan Meteorological Agency (JMA) and the National Research Institute for Earth Science and Disaster Prevention (NIED, Japan) networks for the major events of the 2016 Kumamoto earthquakes. After the baseline jump correction, the waveforms are furthermore corrected for displacement according to Wang et al.(2011). The resulting displacements are comparable to the Interferometric Synthetic Aperture Radar-derived displacement estimates for the Kumamoto earthquake sequence.
Y1  - 2019
U6  - https://doi.org/10.1785/0220190134
SN  - 0895-0695
SN  - 1938-2057
VL  - 91
IS  - 1
SP  - 475
EP  - 487
PB  - Seismological Society of America, Eastern Section
CY  - Boulder, Colo.
ER  - 
TY  - JOUR
A1  - Steinberg, Andreas
A1  - Sudhaus, Henriette
A1  - Heimann, Sebastian
A1  - Krüger, Frank
T1  - Sensitivity of InSAR and teleseismic observations to earthquake rupture segmentation
JF  - Geophysical journal international
N2  - Earthquakes often rupture across more than one fault segment. If such rupture segmentation occurs on a significant scale, a simple point-source or one-fault model may not represent the rupture process well. As a consequence earthquake characteristics inferred, based on one-source assumptions, may become systematically wrong. This might have effects on follow-up analyses, for example regional stress field inversions and seismic hazard assessments. While rupture segmentation is evident for most M-w > 7 earthquakes, also smaller ones with 5.5 < M-w < 7 can be segmented. We investigate the sensitivity of globally available data sets to rupture segmentation and their resolution to reliably estimate the mechanisms in presence of segmentation. We focus on the sensitivity of InSAR (Interferometric Synthetic Aperture Radar) data in the static near-field and seismic waveforms in the far-field of the rupture and carry out non-linear and Bayesian optimizations of single-source and two-sources kinematic models (double-couple point sources and finite, rectangular sources) using InSAR and teleseismic waveforms separately. Our case studies comprises of four M-w 6-7 earthquakes: the 2009 L'Aquila and 2016 Amatrice (Italy) and the 2005 and 2008 Zhongba (Tibet) earthquakes. We contrast the data misfits of different source complexity by using the Akaike informational criterion (AIC). We find that the AIC method is well suited for data-driven inferences on significant rupture segmentation for the given data sets. This is based on our observation that an AIC-stated significant improvement of data fit for two-segment models over one-segment models correlates with significantly different mechanisms of the two source segments and their average compared to the single-segment mechanism. We attribute these modelled differences to a sufficient sensitivity of the data to resolve rupture segmentation. Our results show that near-field data are generally more sensitive to rupture segmentation of shallow earthquakes than far-field data but that also teleseismic data can resolve rupture segmentation in the studied magnitude range. We further conclude that a significant difference in the modelled source mechanisms for different segmentations shows that an appropriate choice of model segmentation matters for a robust estimation of source mechanisms. It reduces systematic biases and trade-off and thereby improves the knowledge on the rupture. Our study presents a strategy and method to detect significant rupture segmentation such that an appropriate model complexity can be used in the source mechanism inference. A similar, systematic investigation of earthquakes in the range of M-w 5.5-7 could provide important hazard-relevant statistics on rupture segmentation. In these cases single-source models introduce a systematic bias. Consideration of rupture segmentation therefore matters for a robust estimation of source mechanisms of the studied earthquakes.
KW  - radar interferometry
KW  - waveform inversion
KW  - earthquake source observations
Y1  - 2020
U6  - https://doi.org/10.1093/gji/ggaa351
SN  - 0956-540X
SN  - 1365-246X
VL  - 223
IS  - 2
SP  - 875
EP  - 907
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Stich, Daniel
A1  - Martin, Rosa
A1  - Morales, Jose
A1  - Lopez-Comino, Jose Angel
A1  - Mancilla, Flor de Lis
T1  - Slip partitioning in the 2016 Alboran Sea earthquake sequence (western Mediterranean)
JF  - Frontiers in Earth Science
N2  - AM(W)= 5.1 earthquake on January 21st, 2016 marked the beginning of a significant seismic sequence in the southern Alboran Sea, culminating in aM(W)= 6.3 earthquake on January 25th, and continuing with further moderate magnitude earthquakes until March. We use data from 35 seismic broadband stations in Spain, Morocco and Portugal to relocate the seismicity, estimate seismic moment tensors, and isolate regional apparent source time functions for the main earthquake. Relocation and regional moment tensor inversion consistently yield very shallow depths for the majority of events. We obtain 50 moment tensors for the sequence, showing a mixture of strike-slip faulting for the foreshock and the main event and reverse faulting for the major aftershocks. The leading role of reverse focal mechanisms among the aftershocks may be explained by the geometry of the fault network. The mainshock nucleates at a bend along the left-lateral Al-Idrisi fault, introducing local transpression within the transtensional Alboran Basin. The shallow depths of the 2016 Alboran Sea earthquakes may favor slip-partitioning on the involved faults. Apparent source durations for the main event suggest a similar to 21 km long, asymmetric rupture that propagates primarily toward NE into the restraining fault segment, with fast rupture speed of similar to 3.0 km/s. Consistently, the inversion for laterally variable fault displacement situates the main slip in the restraining segment. The partitioning into strike-slip rupture and dip-slip aftershocks confirms a non-optimal orientation of this segment, and suggests that the 2016 event settled a slip deficit from previous ruptures that could not propagate into the stronger restraining segment.
KW  - slip partitioning
KW  - fault bend
KW  - moment tensor
KW  - source time function
KW  - shallow earthquakes
Y1  - 2020
U6  - https://doi.org/10.3389/feart.2020.587356
SN  - 2296-6463
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Streck, Charlotte
T1  - Filling in for Governments?
BT  - the role of the private actors in the International Climate Regime
JF  - Journal for European Environmental & Planning Law
N2  - The 2015 Paris Agreement on climate change abandons the Kyoto Protocol's paradigm of binding emissions targets and relies instead on countries' voluntary contributions. However, the Paris Agreement encourages not only governments but also sub-national governments, corporations and civil society to contribute to reaching ambitious climate goals. In a transition from the regulated architecture of the Kyoto Protocol to the open system of the Paris Agreement, the Agreement seeks to integrate non-state actors into the treaty-based climate regime. In 2014 the secretariat of the United Nations Framework Convention on Climate Change Peru and France created the Non-State Actor Zone for Climate Action (and launched the Global Climate Action portal). In December 2019, this portal recorded more than twenty thousand climate-commitments of private and public non-state entities, making the non-state venues of international climate meetings decisively more exciting than the formal negotiation space. This level engagement and governments' response to it raises a flurry of questions in relation to the evolving nature of the climate regime and climate change governance, including the role of private actors as standard setters and the lack of accountability mechanisms for non-state actions. This paper takes these developments as occasion to discuss the changing role of private actors in the climate regime.
KW  - climate action
KW  - Paris Agreement
KW  - non-state actors
KW  - soft law
KW  - accountability
KW  - private governance
Y1  - 2020
U6  - https://doi.org/10.1163/18760104-01701003
SN  - 1613-7272
SN  - 1876-0104
VL  - 17
IS  - 1
SP  - 5
EP  - 28
PB  - Martinus Nijhoff Pub
CY  - Leiden
ER  - 
TY  - JOUR
A1  - Tardif-Becquet, Delphine
A1  - Fluteau, Frédéric
A1  - Donnadieu, Yannick
A1  - Le Hir, Guillaume
A1  - Ladant, Jean-Baptiste
A1  - Sepulchre, Pierre
A1  - Licht, Alexis
A1  - Poblete, Fernando
A1  - Dupont-Nivet, Guillaume
T1  - The origin of Asian monsoons
BT  - a modelling perspective
JF  - Climate of the Past
N2  - The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward.
KW  - earth system model
KW  - early eocene
KW  - tibetan plateau
KW  - climate-change
KW  - oligocene climate
KW  - summer monsoon
KW  - global monsoon
KW  - ice sheet
KW  - part 1
KW  - China
Y1  - 2020
U6  - https://doi.org/10.5194/cp-16-847-2020
SN  - 1814-9332
SN  - 1814-9324
VL  - 16
IS  - 3
SP  - 847
EP  - 865
PB  - Copernicus Publications
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Tofelde, Stefanie
A1  - Bernhardt, Anne
A1  - Guerit, Laure
A1  - Romans, Brian W.
T1  - Times Associated With Source-to-Sink Propagation of Environmental Signals During Landscape Transience
JF  - Frontiers in Earth Science
N2  - Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ‘signal’ and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ‘times’ and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.
KW  - signal propagation
KW  - landscape transience
KW  - source-to-sink
KW  - stratigraphy
KW  - response time
Y1  - 2021
U6  - https://doi.org/10.3389/feart.2021.628315
SN  - 2296-6463
VL  - 9
SP  - 1
EP  - 26
PB  - Frontiers Media
CY  - Lausanne, Schweiz
ER  - 
TY  - JOUR
A1  - Tranter, Morgan Alan
A1  - De Lucia, Marco
A1  - Wolfgramm, Markus
A1  - Kühn, Michael
T1  - Barite scale formation and injectivity loss models for geothermal systems
JF  - Water
N2  - Barite scales in geothermal installations are a highly unwanted effect of circulating deep saline fluids. They build up in the reservoir if supersaturated fluids are re-injected, leading to irreversible loss of injectivity. A model is presented for calculating the total expected barite precipitation. To determine the related injectivity decline over time, the spatial precipitation distribution in the subsurface near the injection well is assessed by modelling barite growth kinetics in a radially diverging Darcy flow domain. Flow and reservoir properties as well as fluid chemistry are chosen to represent reservoirs subject to geothermal exploration located in the North German Basin (NGB) and the Upper Rhine Graben (URG) in Germany. Fluids encountered at similar depths are hotter in the URG, while they are more saline in the NGB. The associated scaling amount normalised to flow rate is similar for both regions. The predicted injectivity decline after 10 years, on the other hand, is far greater for the NGB (64%) compared to the URG (24%), due to the temperature- and salinity-dependent precipitation rate. The systems in the NGB are at higher risk. Finally, a lightweight score is developed for approximating the injectivity loss using the Damkohler number, flow rate and total barite scaling potential. This formula can be easily applied to geothermal installations without running complex reactive transport simulations.
KW  - reactive transport
KW  - radial flow
KW  - geothermal energy
KW  - scaling
KW  - phreeqc
KW  - formation damage
Y1  - 2020
U6  - https://doi.org/10.3390/w12113078
SN  - 2073-4441
VL  - 12
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Tronicke, Jens
A1  - Allroggen, Niklas
A1  - Biermann, Felix
A1  - Fanselow, Florian
A1  - Guillemoteau, Julien
A1  - Krauskopf, Christof
A1  - Lück, Erika
T1  - Rapid multiscale analysis of near-surface geophysical anomaly maps
BT  - application to an archaeogeophysical data set
JF  - Geophysics
N2  - In near- surface geophysics, ground-based mapping surveys are routinely used in a variety of applications including those from archaeology, civil engineering, hydrology, and soil science. The resulting geophysical anomaly maps of, for example, magnetic or electrical parameters are usually interpreted to laterally delineate subsurface structures such as those related to the remains of past human activities, subsurface utilities and other installations, hydrological properties, or different soil types. To ease the interpretation of such data sets, we have developed a multiscale processing, analysis, and visualization strategy. Our approach relies on a discrete redundant wavelet transform (RWT) implemented using cubic-spline filters and the a trous algorithm, which allows to efficiently compute a multiscale decomposition of 2D data using a series of 1D convolutions. The basic idea of the approach is presented using a synthetic test image, whereas our archaeogeophysical case study from northeast Germany demonstrates its potential to analyze and process rather typical geophysical anomaly maps including magnetic and topographic data. Our vertical-gradient magnetic data show amplitude variations over several orders of magnitude, complex anomaly patterns at various spatial scales, and typical noise patterns, whereas our topographic data show a distinct hill structure superimposed by a microtopographic stripe pattern and random noise. Our results demonstrate that the RWT approach is capable to successfully separate these components and that selected wavelet planes can be scaled and combined so that the reconstructed images allow for a detailed, multiscale structural interpretation also using integrated visualizations of magnetic and topographic data. Because our analysis approach is straightforward to implement without laborious parameter testing and tuning, computationally efficient, and easily adaptable to other geophysical data sets, we believe that it can help to rapidly analyze and interpret different geophysical mapping data collected to address a variety of near-surface applications from engineering practice and research.
KW  - archaeology
KW  - case history
KW  - near surface
KW  - magnetics
KW  - decomposition
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0564.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 4
SP  - B109
EP  - B118
PB  - Society of Exploration Geophysicists
CY  - Tulsa, Okla.
ER  - 
TY  - JOUR
A1  - Vogt-Vincent, Noam
A1  - Lippold, Jörg
A1  - Kaboth-Bahr, Stefanie
A1  - Blaser, Patrick
T1  - Ice-rafted debris as a source of non-conservative behaviour for the epsilon Nd palaeotracer
BT  - insights from a simple model
JF  - Geo-marine letters : an international journal of marine geology
N2  - Neodymium isotopic composition (epsilon Nd) has enjoyed widespread use as a palaeotracer, principally because it behaves quasi-conservatively in the modern ocean. However, recent bottom water epsilon Nd reconstructions from the eastern North Atlantic are difficult to interpret under assumptions of conservative behaviour. The observation that this apparent departure from conservative behaviour increases with enhanced ice-rafted debris (IRD) fluxes has resulted in the suggestion that IRD leads to the overprinting of bottom water epsilon Nd through reversible scavenging. In this study, a simple water column model successfully reproduces epsilon Nd reconstructions from the eastern North Atlantic at the Last Glacial Maximum and Heinrich Stadial 1, and demonstrates that the changes in scavenging intensity required for good model-data fit is in good agreement with changes in the observed IRD flux. Although uncertainties in model parameters preclude a more definitive conclusion, the results indicate that the suggestion of IRD as a source of non-conservative behaviour in the epsilon Nd tracer is reasonable and that further research into the fundamental chemistry underlying the marine neodymium cycle is necessary to increase confidence in assumptions of conservative epsilon Nd behaviour in the past.
KW  - Neodymium isotopes
KW  - epsilon Nd
KW  - ice-rafted debris
KW  - IRD
KW  - last glacial
KW  - maximum
KW  - LGM
KW  - Heinrich event
KW  - Palaeoceanography
KW  - Paleoceanography
KW  - model
KW  - reversible scavenging
KW  - conservative
KW  - ocean circulation
KW  - atlantic
KW  - meridional overturning circulation
KW  - geochemical cycling
Y1  - 2020
U6  - https://doi.org/10.1007/s00367-020-00643-x
SN  - 0276-0460
SN  - 1432-1157
VL  - 40
IS  - 3
SP  - 325
EP  - 340
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Volante, Silvia
A1  - Pourteau, Amaury
A1  - Collins, William J.
A1  - Blereau, Eleanore
A1  - Li, Zheng-Xiang
A1  - Smit, Matthijs Arjen
A1  - Evans, Noreen
A1  - Nordsvan, Adam R.
A1  - Spencer, Chris J.
A1  - McDonald, Brad J.
A1  - Li, Jiangyu
A1  - Günter, Christina
T1  - Multiple P-T-d-t paths reveal the evolution of the final Nuna assembly in northeast Australia
JF  - Journal of metamorphic geology
N2  - The final assembly of the Mesoproterozoic supercontinent Nuna was marked by the collision of Laurentia and Australia at 1.60 Ga, which is recorded in the Georgetown Inlier of NE Australia. Here, we decipher the metamorphic evolution of this final Nuna collisional event using petrostructural analysis, major and trace element compositions of key minerals, thermodynamic modelling, and multi-method geochronology. The Georgetown Inlier is characterised by deformed and metamorphosed 1.70-1.62 Ga sedimentary and mafic rocks, which were intruded byc. 1.56 Ga old S-type granites. Garnet Lu-Hf and monazite U-Pb isotopic analyses distinguish two major metamorphic events (M1 atc. 1.60 Ga and M2 atc. 1.55 Ga), which allows at least two composite fabrics to be identified at the regional scale-c. 1.60 Ga S1 (consisting in fabrics S1a and S1b) andc. 1.55 Ga S2 (including fabrics S2a and S2b). Also, three tectono-metamorphic domains are distinguished: (a) the western domain, with S1 defined by low-P(LP) greenschist facies assemblages; (b) the central domain, where S1 fabric is preserved as medium-P(MP) amphibolite facies relicts, and locally as inclusion trails in garnet wrapped by the regionally dominant low-Pamphibolite facies S2 fabric; and (c) the eastern domain dominated by upper amphibolite to granulite facies S2 foliation. In the central domain, 1.60 GaMP-medium-T(MT) metamorphism (M1) developed within the staurolite-garnet stability field, with conditions ranging from 530-550 degrees C at 6-7 kbar (garnet cores) to 620-650 degrees C at 8-9 kbar (garnet rims), and it is associated with S1 fabric. The onset of 1.55 GaLP-high-T(HT) metamorphism (M2) is marked by replacement of staurolite by andalusite (M2a/D2a), which was subsequently pseudomorphed by sillimanite (M2b/D2b) where granite and migmatite are abundant.P-Tconditions ranged from 600 to 680 degrees C and 4-6 kbar for the M2b sillimanite stage. 1.60 Ga garnet relicts within the S2 foliation highlight the progressive obliteration of the S1 fabric by regional S2 in the central zone during peak M2 metamorphism. In the eastern migmatitic complex, partial melting of paragneiss and amphibolite occurred syn- to post-S2, at 730-770 degrees C and 6-8 kbar, and at 750-790 degrees C and 6 kbar, respectively. The pressure-temperature-deformation-time paths reconstructed for the Georgetown Inlier suggest ac. 1.60 Ga M1/D1 event recorded under greenschist facies conditions in the western domain and under medium-Pand medium-Tconditions in the central domain. This event was followed by the regional 1.56-1.54 Ga low-Pand high-Tphase (M2/D2), extensively recorded in the central and eastern domains. Decompression between these two metamorphic events is ascribed to an episode of exhumation. The two-stage evolution supports the previous hypothesis that the Georgetown Inlier preserves continental collisional and subsequent thermal perturbation associated with granite emplacement.
KW  - continental collision
KW  - Lu-Hf in garnet
KW  - petrostructural analysis
KW  - P-T-d-tpaths
KW  - supercontinent Nuna
Y1  - 2020
U6  - https://doi.org/10.1111/jmg.12532
SN  - 0263-4929
SN  - 1525-1314
VL  - 38
IS  - 6
SP  - 593
EP  - 627
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  - 
TY  - JOUR
A1  - von Specht, Sebastian
A1  - Cotton, Fabrice
T1  - A link between machine learning and optimization in ground-motion model development
BT  - weighted mixed-effects regression with data-driven probabilistic earthquake classification
JF  - Bulletin of the Seismological Society of America
N2  - The steady increase of ground-motion data not only allows new possibilities but also comes with new challenges in the development of ground-motion models (GMMs). Data classification techniques (e.g., cluster analysis) do not only produce deterministic classifications but also probabilistic classifications (e.g., probabilities for each datum to belong to a given class or cluster). One challenge is the integration of such continuous classification in regressions for GMM development such as the widely used mixed-effects model. We address this issue by introducing an extension of the mixed-effects model to incorporate data weighting. The parameter estimation of the mixed-effects model, that is, fixed-effects coefficients of the GMMs and the random-effects variances, are based on the weighted likelihood function, which also provides analytic uncertainty estimates. The data weighting permits for earthquake classification beyond the classical, expert-driven, binary classification based, for example, on event depth, distance to trench, style of faulting, and fault dip angle. We apply Angular Classification with Expectation-maximization, an algorithm to identify clusters of nodal planes from focal mechanisms to differentiate between, for example, interface- and intraslab-type events. Classification is continuous, that is, no event belongs completely to one class, which is taken into account in the ground-motion modeling. The theoretical framework described in this article allows for a fully automatic calibration of ground-motion models using large databases with automated classification and processing of earthquake and ground-motion data. As an example, we developed a GMM on the basis of the GMM by Montalva et al. (2017) with data from the strong-motion flat file of Bastias and Montalva (2016) with similar to 2400 records from 319 events in the Chilean subduction zone. Our GMM with the data-driven classification is comparable to the expert-classification-based model. Furthermore, the model shows temporal variations of the between-event residuals before and after large earthquakes in the region.
Y1  - 2020
U6  - https://doi.org/10.1785/0120190133
SN  - 0037-1106
SN  - 1943-3573
VL  - 110
IS  - 6
SP  - 2777
EP  - 2800
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Voss, Katalyn A.
A1  - Bookhagen, Bodo
A1  - Sachse, Dirk
A1  - Chadwick, Oliver A.
T1  - Variation of deuterium excess in surface waters across a 5000-m elevation gradient in eastern Nepal
JF  - Journal of hydrology
N2  - The strong elevation gradient of the Himalaya allows for investigation of altitude and orographic impacts on surface water delta O-18 and delta D stable isotope values. This study differentiates the time- and altitude-variable contributions of source waters to the Arun River in eastern Nepal. It provides isotope data along a 5000-m gradient collected from tributaries as well as groundwater, snow, and glacial-sourced surface waters and time-series data from April to October 2016. We find nonlinear trends in delta O-18 and delta D lapse rates with high-elevation lapse rates (4000-6000 masl) 5-7 times more negative than low-elevation lapse rates (1000-3000 masl). A distinct seasonal signal in delta O-18 and delta D lapse rates indicates time-variable source-water contributions from glacial and snow meltwater as well as precipitation transitions between the Indian Summer Monsoon and Winter Westerly Disturbances. Deuterium excess correlates with the extent of snowpack and tracks melt events during the Indian Summer Monsoon season. Our analysis identifies the influence of snow and glacial melt waters on river composition during low-flow conditions before the monsoon (April/May 2016) followed by a 5-week transition to the Indian Summer Monsoon-sourced rainfall around mid-June 2016. In the post-monsoon season, we find continued influence from glacial melt waters as well as ISM-sourced groundwater.
KW  - stable isotopes
KW  - Himalaya
KW  - glacier
KW  - snow
KW  - precipitation
KW  - seasonality
Y1  - 2020
U6  - https://doi.org/10.1016/j.jhydrol.2020.124802
SN  - 0022-1694
SN  - 1879-2707
VL  - 586
PB  - Elsevier
CY  - Amsterdam
ER  -