TY  - JOUR
A1  - Abdrakhmatov, Kanatbek E.
A1  - Walker, R. T.
A1  - Campbell, G. E.
A1  - Carr, A. S.
A1  - Elliott, A.
A1  - Hillemann, Christian
A1  - Hollingsworth, J.
A1  - Landgraf, Angela
A1  - Mackenzie, D.
A1  - Mukambayev, A.
A1  - Rizza, M.
A1  - Sloan, R. A.
T1  - Multisegment rupture in the 11 July 1889 Chilik earthquake (M-w 8.0-8.3), Kazakh Tien Shan, interpreted from remote sensing, field survey, and paleoseismic trenching
JF  - Journal of geophysical research : Solid earth
N2  - The 11 July 1889 Chilik earthquake (M-w 8.0-8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, similar to 100 km southeast of Almaty, Kazakhstan (similar to 2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the similar to 30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp-forming event, likely to be the 1889 earthquake, was the only surface-rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of similar to 175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left-lateral and right-lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard.
Y1  - 2016
U6  - https://doi.org/10.1002/2015JB012763
SN  - 2169-9313
SN  - 2169-9356
VL  - 121
SP  - 4615
EP  - 4640
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Abon, Catherine Cristobal
A1  - Kneis, David
A1  - Crisologo, Irene
A1  - Bronstert, Axel
A1  - David, Carlos Primo Constantino
A1  - Heistermann, Maik
T1  - Evaluating the potential of radar-based rainfall estimates for streamflow and flood simulations in the Philippines
JF  - GEOMATICS NATURAL HAZARDS & RISK
N2  - This case study evaluates the suitability of radar-based quantitative precipitation estimates (QPEs) for the simulation of streamflow in the Marikina River Basin (MRB), the Philippines. Hourly radar-based QPEs were produced from reflectivity that had been observed by an S-band radar located about 90 km from the MRB. Radar data processing and precipitation estimation were carried out using the open source library wradlib. To assess the added value of the radar-based QPE, we used spatially interpolated rain gauge observations (gauge-only (GO) product) as a benchmark. Rain gauge observations were also used to quantify rainfall estimation errors at the point scale. At the point scale, the radar-based QPE outperformed the GO product in 2012, while for 2013, the performance was similar. For both periods, estimation errors substantially increased from daily to the hourly accumulation intervals. Despite this fact, both rainfall estimation methods allowed for a good representation of observed streamflow when used to force a hydrological simulation model of the MRB. Furthermore, the results of the hydrological simulation were consistent with rainfall verification at the point scale: the radar-based QPE performed better than the GO product in 2012, and equivalently in 2013. Altogether, we could demonstrate that, in terms of streamflow simulation, the radar-based QPE can perform as good as or even better than the GO product - even for a basin such as the MRB which has a comparatively dense rain gauge network. This suggests good prospects for using radar-based QPE to simulate and forecast streamflow in other parts of the Philippines where rain gauge networks are not as dense.
Y1  - 2016
U6  - https://doi.org/10.1080/19475705.2015.1058862
SN  - 1947-5705
SN  - 1947-5713
VL  - 7
SP  - 1390
EP  - 1405
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Abouserie, Ahed
A1  - Zehbe, Kerstin
A1  - Metzner, Philipp
A1  - Kelling, Alexandra
A1  - Günter, Christina
A1  - Schilde, Uwe
A1  - Strauch, Peter
A1  - Körzdörfer, Thomas
A1  - Taubert, Andreas
T1  - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior
JF  - European journal of inorganic chemistry : a journal of ChemPubSoc Europe
N2  - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry.
KW  - Ionic liquids
KW  - Alkylpyridinium salts
KW  - Structure elucidation
KW  - Phase transitions
Y1  - 2017
U6  - https://doi.org/10.1002/ejic.201700826
SN  - 1434-1948
SN  - 1099-0682
SP  - 5640
EP  - 5649
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Abouserie, Ahed
A1  - Zehbe, Kerstin
A1  - Metzner, Philipp
A1  - Kelling, Alexandra
A1  - Günter, Christina
A1  - Schilde, Uwe
A1  - Strauch, Peter
A1  - Körzdörfer, Thomas
A1  - Taubert, Andreas
T1  - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior
JF  - European journal of inorganic chemistry : a journal of ChemPubSoc Europe
N2  - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry.
KW  - Ionic liquids
KW  - Alkylpyridinium salts
KW  - Structure elucidation
KW  - Phase transitions
Y1  - 2017
U6  - https://doi.org/10.1002/ejic.201700826
SN  - 1434-1948
SN  - 1099-0682
SP  - 5640
EP  - 5649
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Acosta, Veronica Torres
A1  - Schildgen, Taylor F.
A1  - Clarke, Brian A.
A1  - Scherler, Dirk
A1  - Bookhagen, Bodo
A1  - Wittmann, Hella
A1  - von Blanckenburg, Friedhelm
A1  - Strecker, Manfred
T1  - Effect of vegetation cover on millennial-scale landscape denudation rates in East Africa
JF  - Lithosphere
N2  - The mechanisms by which climate and vegetation affect erosion rates over various time scales lie at the heart of understanding landscape response to climate change. Plot-scale field experiments show that increased vegetation cover slows erosion, implying that faster erosion should occur under low to moderate vegetation cover. However, demonstrating this concept over long time scales and across landscapes has proven to be difficult, especially in settings complicated by tectonic forcing and variable slopes. We investigate this problem by measuring cosmogenic Be-10-derived catchment-mean denudation rates across a range of climate zones and hillslope gradients in the Kenya Rift, and by comparing our results with those published from the Rwenzori Mountains of Uganda. We find that denudation rates from sparsely vegetated parts of the Kenya Rift are up to 0.13 mm/yr, while those from humid and more densely vegetated parts of the Kenya Rift flanks and the Rwenzori Mountains reach a maximum of 0.08 mm/yr, despite higher median hillslope gradients. While differences in lithology and recent land-use changes likely affect the denudation rates and vegetation cover values in some of our studied catchments, hillslope gradient and vegetation cover appear to explain most of the variation in denudation rates across the study area. Our results support the idea that changing vegetation cover can contribute to complex erosional responses to climate or land-use change and that vegetation cover can play an important role in determining the steady-state slopes of mountain belts through its stabilizing effects on the land surface.
Y1  - 2015
U6  - https://doi.org/10.1130/L402.1
SN  - 1941-8264
SN  - 1947-4253
VL  - 7
IS  - 4
SP  - 408
EP  - 420
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Adhikari, Rishi Ram
A1  - Glombitza, Clemens
A1  - Nickel, Julia C.
A1  - Anderson, Chloe H.
A1  - Dunlea, Ann G.
A1  - Spivack, Arthur J.
A1  - Murray, Richard W.
A1  - Kallmeyer, Jens
T1  - Hydrogen Utilization Potential in Subsurface Sediments
JF  - Frontiers in microbiology
N2  - Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H(2)ases to successively higher concentrations of H-2 in successively deeper zones.
KW  - hydrogenase
KW  - tritium assay
KW  - deep biosphere
KW  - microbial activity
KW  - Lake Van
KW  - Barents Sea
KW  - Equatorial Pacific
KW  - Gulf of Mexico
Y1  - 2016
U6  - https://doi.org/10.3389/fmicb.2016.00008
SN  - 1664-302X
VL  - 7
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Adhikari, Rishi Ram
A1  - Kallmeyer, Jens
T1  - Detection and quantification of microbial activity in the subsurface
N2  - The subsurface harbors a large fraction of Earth's living biomass, forming complex microbial ecosystems. Without a profound knowledge of the ongoing biologically mediated processes and their reaction to anthropogenic changes it is difficult to assess the long-term stability and feasibility of any type of geotechnical utilization, as these influence subsurface ecosystems. Despite recent advances in many areas of subsurface microbiology, the direct quantification of turnover processes is still in its infancy, mainly due to the extremely low cell abundances. We provide an overview of the currently available techniques for the quantification of microbial turnover processes and discuss their specific strengths and limitations. Most techniques employed so far have focused on specific processes, e.g. sulfate reduction or methanogenesis. Recent studies show that processes that were previously thought to exclude each other can occur simultaneously, albeit at very low rates. Without the identification of the respective processes it is impossible to quantify total microbial activity. Even in cases where all simultaneously occurring processes can be identified, the typically very low rates prevent quantification. In many cases a simple measure of total microbial activity would be a better and more robust measure than assays for several specific processes. Enzyme or molecular assays provide a more general approach as they target key metabolic compounds. Depending on the compound targeted a broader spectrum of microbial processes can be quantified. The two most promising compounds are ATP and hydrogenase, as both are ubiquitous in microbes. Technical constraints limit the applicability of currently available ATP-assays for subsurface samples. A recently developed hydrogenase radiotracer assay has the potential to become a key tool for the quantification of subsurface microbial activity.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00092819
U6  - https://doi.org/10.1016/j.chemer.2010.05.003
SN  - 0009-2819
ER  - 
TY  - JOUR
A1  - Aerts, J. C. J. H.
A1  - Botzen, W. J. Wouter
A1  - Clarke, K. C.
A1  - Cutter, S. L.
A1  - Hall, J. W.
A1  - Merz, Bruno
A1  - Michel-Kerjan, E.
A1  - Mysiak, J.
A1  - Surminski, Swenja
A1  - Kunreuther, H.
T1  - Integrating human behaviour dynamics into flood disaster risk assessment
JF  - Nature climate change
N2  - The behaviour of individuals, businesses, and government entities before, during, and immediately after a disaster can dramatically affect the impact and recovery time. However, existing risk-assessment methods rarely include this critical factor. In this Perspective, we show why this is a concern, and demonstrate that although initial efforts have inevitably represented human behaviour in limited terms, innovations in flood-risk assessment that integrate societal behaviour and behavioural adaptation dynamics into such quantifications may lead to more accurate characterization of risks and improved assessment of the effectiveness of risk-management strategies and investments. Such multidisciplinary approaches can inform flood-risk management policy development.
Y1  - 2018
U6  - https://doi.org/10.1038/s41558-018-0085-1
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 3
SP  - 193
EP  - 199
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Agada, S.
A1  - Chen, F.
A1  - Geiger, S.
A1  - Toigulova, G.
A1  - Agar, Susan M.
A1  - Shekhar, R.
A1  - Benson, Gregory S.
A1  - Hehmeyer, O.
A1  - Amour, Frédéric
A1  - Mutti, Maria
A1  - Christ, Nicolas
A1  - Immenhauser, A.
T1  - Numerical simulation of fluid-flow processes in a 3D high-resolution carbonate reservoir analogue
JF  - Petroleum geoscience
N2  - A high-resolution three-dimensional (3D) outcrop model of a Jurassic carbonate ramp was used in order to perform a series of detailed and systematic flow simulations. The aim of this study was to test the impact of small- and large-scale geological features on reservoir performance and oil recovery. The digital outcrop model contains a wide range of sedimentological, diagenetic and structural features, including discontinuity surfaces, shoal bodies, mud mounds, oyster bioherms and fractures. Flow simulations are performed for numerical well testing and secondary oil recovery. Numerical well testing enables synthetic but systematic pressure responses to be generated for different geological features observed in the outcrops. This allows us to assess and rank the relative impact of specific geological features on reservoir performance. The outcome documents that, owing to the realistic representation of matrix heterogeneity, most diagenetic and structural features cannot be linked to a unique pressure signature. Instead, reservoir performance is controlled by subseismic faults and oyster bioherms acting as thief zones. Numerical simulations of secondary recovery processes reveal strong channelling of fluid flow into high-permeability layers as the primary control for oil recovery. However, appropriate reservoir-engineering solutions, such as optimizing well placement and injection fluid, can reduce channelling and increase oil recovery.
Y1  - 2014
U6  - https://doi.org/10.1144/petgeo2012-096
SN  - 1354-0793
VL  - 20
IS  - 1
SP  - 125
EP  - 142
PB  - Geological Soc. Publ. House
CY  - Bath
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Caesar, Levke
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Merz, Bruno
T1  - Network-based identification and characterization of teleconnections on different scales
JF  - Scientific Reports
N2  - Sea surface temperature (SST) patterns can – as surface climate forcing – affect weather and climate at large distances. One example is El Niño-Southern Oscillation (ENSO) that causes climate anomalies around the globe via teleconnections. Although several studies identified and characterized these teleconnections, our understanding of climate processes remains incomplete, since interactions and feedbacks are typically exhibited at unique or multiple temporal and spatial scales. This study characterizes the interactions between the cells of a global SST data set at different temporal and spatial scales using climate networks. These networks are constructed using wavelet multi-scale correlation that investigate the correlation between the SST time series at a range of scales allowing instantaneously deeper insights into the correlation patterns compared to traditional methods like empirical orthogonal functions or classical correlation analysis. This allows us to identify and visualise regions of – at a certain timescale – similarly evolving SSTs and distinguish them from those with long-range teleconnections to other ocean regions. Our findings re-confirm accepted knowledge about known highly linked SST patterns like ENSO and the Pacific Decadal Oscillation, but also suggest new insights into the characteristics and origins of long-range teleconnections like the connection between ENSO and Indian Ocean Dipole.
Y1  - 2019
U6  - https://doi.org/10.1038/s41598-019-45423-5
SN  - 2045-2322
VL  - 9
PB  - Macmillan Publishers Limited
CY  - London
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Guntu, Ravikumar
A1  - Banerjee, Abhirup
A1  - Gadhawe, Mayuri Ashokrao
A1  - Marwan, Norbert
T1  - A complex network approach to study the extreme precipitation patterns in a river basin
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - The quantification of spatial propagation of extreme precipitation events is vital in water resources planning and disaster mitigation. However, quantifying these extreme events has always been challenging as many traditional methods are insufficient to capture the nonlinear interrelationships between extreme event time series. Therefore, it is crucial to develop suitable methods for analyzing the dynamics of extreme events over a river basin with a diverse climate and complicated topography. Over the last decade, complex network analysis emerged as a powerful tool to study the intricate spatiotemporal relationship between many variables in a compact way. In this study, we employ two nonlinear concepts of event synchronization and edit distance to investigate the extreme precipitation pattern in the Ganga river basin. We use the network degree to understand the spatial synchronization pattern of extreme rainfall and identify essential sites in the river basin with respect to potential prediction skills. The study also attempts to quantify the influence of precipitation seasonality and topography on extreme events. The findings of the study reveal that (1) the network degree is decreased in the southwest to northwest direction, (2) the timing of 50th percentile precipitation within a year influences the spatial distribution of degree, (3) the timing is inversely related to elevation, and (4) the lower elevation greatly influences connectivity of the sites. The study highlights that edit distance could be a promising alternative to analyze event-like data by incorporating event time and amplitude and constructing complex networks of climate extremes.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0072520
SN  - 1054-1500
SN  - 1089-7682
VL  - 32
IS  - 1
PB  - American Institute of Physics
CY  - Woodbury, NY
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Maheswaran, Rathinasamy
A1  - Kurths, Jürgen
A1  - Khosa, R.
T1  - Wavelet Spectrum and Self-Organizing Maps-Based Approach for Hydrologic Regionalization -a Case Study in the Western United States
JF  - Water Resources Management
N2  - Hydrologic regionalization deals with the investigation of homogeneity in watersheds and provides a classification of watersheds for regional analysis. The classification thus obtained can be used as a basis for mapping data from gauged to ungauged sites and can improve extreme event prediction. This paper proposes a wavelet power spectrum (WPS) coupled with the self-organizing map method for clustering hydrologic catchments. The application of this technique is implemented for gauged catchments. As a test case study, monthly streamflow records observed at 117 selected catchments throughout the western United States from 1951 through 2002. Further, based on WPS of each station, catchments are classified into homogeneous clusters, which provides a representative WPS pattern for the streamflow stations in each cluster.
KW  - Wavelet power spectrum
KW  - Regionalization
KW  - Ungauged catchments
KW  - K-means technique
KW  - Self-organizing map
Y1  - 2016
U6  - https://doi.org/10.1007/s11269-016-1428-1
SN  - 0920-4741
SN  - 1573-1650
VL  - 30
SP  - 4399
EP  - 4413
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Merz, Bruno
A1  - Kurths, Jürgen
T1  - Multi-scale event synchronization analysis for unravelling climate processes: a wavelet-based approach
JF  - Nonlinear processes in geophysics
N2  - The temporal dynamics of climate processes are spread across different timescales and, as such, the study of these processes at only one selected timescale might not reveal the complete mechanisms and interactions within and between the (sub-) processes. To capture the non-linear interactions between climatic events, the method of event synchronization has found increasing attention recently. The main drawback with the present estimation of event synchronization is its restriction to analysing the time series at one reference timescale only. The study of event synchronization at multiple scales would be of great interest to comprehend the dynamics of the investigated climate processes. In this paper, the wavelet-based multi-scale event synchronization (MSES) method is proposed by combining the wavelet transform and event synchronization. Wavelets are used extensively to comprehend multi-scale processes and the dynamics of processes across various timescales. The proposed method allows the study of spatio-temporal patterns across different timescales. The method is tested on synthetic and real-world time series in order to check its replicability and applicability. The results indicate that MSES is able to capture relationships that exist between processes at different timescales.
Y1  - 2017
U6  - https://doi.org/10.5194/npg-24-599-2017
SN  - 1023-5809
VL  - 24
SP  - 599
EP  - 611
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Merz, Bruno
A1  - Kurths, Jürgen
T1  - Quantifying the roles of single stations within homogeneous regions using complex network analysis
JF  - Journal of hydrology
N2  - Regionalization and pooling stations to form homogeneous regions or communities are essential for reliable parameter transfer, prediction in ungauged basins, and estimation of missing information. Over the years, several clustering methods have been proposed for regional analysis. Most of these methods are able to quantify the study region in terms of homogeneity but fail to provide microscopic information about the interaction between communities, as well as about each station within the communities. We propose a complex network-based approach to extract this valuable information and demonstrate the potential of our approach using a rainfall network constructed from the Indian gridded daily precipitation data. The communities were identified using the network-theoretical community detection algorithm for maximizing the modularity. Further, the grid points (nodes) were classified into universal roles according to their pattern of within- and between-community connections. The method thus yields zoomed-in details of individual rainfall grids within each community.
KW  - Complex network
KW  - Event synchronization
KW  - Rainfall network
KW  - Z-P approach
Y1  - 2018
U6  - https://doi.org/10.1016/j.jhydrol.2018.06.050
SN  - 0022-1694
SN  - 1879-2707
VL  - 563
SP  - 802
EP  - 810
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Öztürk, Ugur
A1  - Kurths, Jürgen
A1  - Merz, Bruno
T1  - Optimal design of hydrometric station networks based on complex network analysis
JF  - Hydrology and Earth System Sciences
N2  - Hydrometric networks play a vital role in providing information for decision-making in water resource management. They should be set up optimally to provide as much information as possible that is as accurate as possible and, at the same time, be cost-effective. Although the design of hydrometric networks is a well-identified problem in hydrometeorology and has received considerable attention, there is still scope for further advancement. In this study, we use complex network analysis, defined as a collection of nodes interconnected by links, to propose a new measure that identifies critical nodes of station networks. The approach can support the design and redesign of hydrometric station networks. The science of complex networks is a relatively young field and has gained significant momentum over the last few years in different areas such as brain networks, social networks, technological networks, or climate networks. The identification of influential nodes in complex networks is an important field of research. We propose a new node-ranking measure – the weighted degree–betweenness (WDB) measure – to evaluate the importance of nodes in a network. It is compared to previously proposed measures used on synthetic sample networks and then applied to a real-world rain gauge network comprising 1229 stations across Germany to demonstrate its applicability. The proposed measure is evaluated using the decline rate of the network efficiency and the kriging error. The results suggest that WDB effectively quantifies the importance of rain gauges, although the benefits of the method need to be investigated in more detail.
KW  - identifying influential nodes
KW  - climate networks
KW  - rainfall
KW  - streamflow
KW  - synchronization
KW  - precipitation
KW  - classification
KW  - events
Y1  - 2020
U6  - https://doi.org/10.5194/hess-24-2235-2020
SN  - 1027-5606
SN  - 1607-7938
VL  - 24
IS  - 5
SP  - 2235
EP  - 2251
PB  - Copernicus Publ.
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, T.
A1  - Huang, S.
A1  - Tecklenburg, J.
A1  - Hoffmann, P.
A1  - Koch, H.
A1  - Fournet, S.
A1  - Krysanova, Valentina
A1  - Mueller, N.
A1  - Hattermann, Fred
T1  - Comparing impacts of climate change on streamflow in four large African river basins
JF  - Hydrology and earth system sciences : HESS
N2  - This study aims to compare impacts of climate change on streamflow in four large representative African river basins: the Niger, the Upper Blue Nile, the Oubangui and the Limpopo. We set up the eco-hydrological model SWIM (Soil and Water Integrated Model) for all four basins individually. The validation of the models for four basins shows results from adequate to very good, depending on the quality and availability of input and calibration data.
 For the climate impact assessment, we drive the model with outputs of five bias corrected Earth system models of Coupled Model Intercomparison Project Phase 5 (CMIP5) for the representative concentration pathways (RCPs) 2.6 and 8.5. This climate input is put into the context of climate trends of the whole African continent and compared to a CMIP5 ensemble of 19 models in order to test their representativeness. Subsequently, we compare the trends in mean discharges, seasonality and hydrological extremes in the 21st century. The uncertainty of results for all basins is high. Still, climate change impact is clearly visible for mean discharges but also for extremes in high and low flows. The uncertainty of the projections is the lowest in the Upper Blue Nile, where an increase in streamflow is most likely. In the Niger and the Limpopo basins, the magnitude of trends in both directions is high and has a wide range of uncertainty. In the Oubangui, impacts are the least significant. Our results confirm partly the findings of previous continental impact analyses for Africa. However, contradictory to these studies we find a tendency for increased streamflows in three of the four basins (not for the Oubangui). Guided by these results, we argue for attention to the possible risks of increasing high flows in the face of the dominant water scarcity in Africa. In conclusion, the study shows that impact intercomparisons have added value to the adaptation discussion and may be used for setting up adaptation plans in the context of a holistic approach.
Y1  - 2014
U6  - https://doi.org/10.5194/hess-18-1305-2014
SN  - 1027-5606
SN  - 1607-7938
VL  - 18
IS  - 4
SP  - 1305
EP  - 1321
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, Tobias
A1  - Andersson, Jafet C. M.
A1  - Müller, Eva Nora
A1  - Hattermann, Fred
T1  - Climate or Land Use?
BT  - Attribution of Changes in River Flooding in the Sahel Zone
JF  - Water
N2  - This study intends to contribute to the ongoing discussion on whether land use and land cover changes (LULC) or climate trends have the major influence on the observed increase of flood magnitudes in the Sahel. A simulation-based approach is used for attributing the observed trends to the postulated drivers. For this purpose, the ecohydrological model SWIM (Soil and Water Integrated Model) with a new, dynamic LULC module was set up for the Sahelian part of the Niger River until Niamey, including the main tributaries Sirba and Goroul. The model was driven with observed, reanalyzed climate and LULC data for the years 1950-2009. In order to quantify the shares of influence, one simulation was carried out with constant land cover as of 1950, and one including LULC. As quantitative measure, the gradients of the simulated trends were compared to the observed trend. The modeling studies showed that for the Sirba River only the simulation which included LULC was able to reproduce the observed trend. The simulation without LULC showed a positive trend for flood magnitudes, but underestimated the trend significantly. For the Goroul River and the local flood of the Niger River at Niamey, the simulations were only partly able to reproduce the observed trend. In conclusion, the new LULC module enabled some first quantitative insights into the relative influence of LULC and climatic changes. For the Sirba catchment, the results imply that LULC and climatic changes contribute in roughly equal shares to the observed increase in flooding. For the other parts of the subcatchment, the results are less clear but show, that climatic changes and LULC are drivers for the flood increase; however their shares cannot be quantified. Based on these modeling results, we argue for a two-pillar adaptation strategy to reduce current and future flood risk: Flood mitigation for reducing LULC-induced flood increase, and flood adaptation for a general reduction of flood vulnerability.
Y1  - 2015
U6  - https://doi.org/10.3390/w7062796
SN  - 2073-4441
VL  - 7
IS  - 6
SP  - 2796
EP  - 2820
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Zimmermann, Alexander
A1  - Elsenbeer, Helmut
T1  - Quantification and interpretation of suspended-sediment discharge hysteresis patterns: How much data do we need?
JF  - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution
N2  - Sediment-discharge hysteresis loops are frequently analyzed to facilitate the understanding of sediment transport processes. Hysteresis patterns, however, are often complex and their interpretation can be complicated. Particularly, quantifying hysteresis patterns remains a problematic issue. Moreover, it is currently unknown how much data is required for analyzing sediment-discharge hysteresis loops in a given area. These open questions and challenges motivated us to develop a new method for quantifying suspended-sediment hysteresis. Subsequently, we applied the new hysteresis index to three suspended-sediment and discharge datasets from a small tropical rainforest catchment. The datasets comprised a different number of events and sampling sites. Our analyses show three main findings: (1) datasets restricted to only few events, which is typical for rapid assessment surveys, were always sufficient to identify the dominating hysteresis pattern in our research area. Furthermore, some of these small datasets contained multiple-peak events that allowed identifying intra-event exhaustion effects and hence, limitations in sediment supply. (2) Datasets comprising complete hydrological years were particularly useful for analyzing seasonal dynamics of hysteresis. These analyses revealed an exhaustion of hysteresis on the inter-event scale which also points to a limited sediment supply. (3) Datasets comprising measurements from two consecutive gauges installed at the catchment outlet and on a slope within that catchment allowed analyzing the change of hysteresis patterns along the flowpath. On the slope, multiple-peak events showed a stronger intra-event exhaustion of hysteresis than at the catchment outlet. Furthermore, exhaustion of hysteresis on the inter-event scale was not evident on the slope but occurred at the catchment outlet. Our results indicate that even small sediment datasets can provide valuable insights into sediment transport processes of small catchments. Furthermore, our results may serve as a first guideline on what to expect from an analysis of hysteresis patterns for datasets of varying quality and quantity. (c) 2014 Elsevier B.V. All rights reserved.
KW  - Suspended sediment
KW  - Hysteresis index
KW  - Sediment monitoring
KW  - Overland flow
KW  - Tropical forest
Y1  - 2014
U6  - https://doi.org/10.1016/j.catena.2014.06.020
SN  - 0341-8162
SN  - 1872-6887
VL  - 122
SP  - 120
EP  - 129
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Bussian, Bernd M.
A1  - Lehnik-Habrink, Petra
A1  - Hein, Sebastian
T1  - Regionalized concentrations and fingerprints of polycyclic aromatic hydrocarbons (PAHs) in German forest soils
JF  - Environmental pollution
N2  - Samples of 474 forest stands in Germany were analysed for concentrations of polycyclic aromatic hydrocarbons (PAHs) in three sampling depths. Enhanced concentrations were mainly found at spots relatively close to densely industrialized and urbanized regions and at some topographically elevated areas. Average enrichment factors between mineral soil and humic layer depend on humus type i.e. decrease from mull via moder to more Based on their compound-patterns, the observed samples could be assigned to three main clusters. For some parts of our study area a uniform assignment of samples to clusters over larger regions could be identified. For instance, samples taken at vicinity to brown-coal strip-mining districts are characterized by high relative abundances of low-molecular-weight PAHs. These results suggest that PAHs are more likely originated from local and regional emitters rather than from long-range transport and that specific source-regions can be identified based on PAH fingerprints. (C) 2015 Elsevier Ltd. All rights reserved.
KW  - Organic pollutants
KW  - PAHs
KW  - Soil
KW  - Emissions
KW  - Long-range transport
KW  - Enrichment factor
KW  - Humic layer
KW  - Mineral soil
KW  - O horizon
Y1  - 2015
U6  - https://doi.org/10.1016/j.envpol.2015.03.026
SN  - 0269-7491
SN  - 1873-6424
VL  - 203
SP  - 31
EP  - 39
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Feakins, Sarah J.
A1  - Lee, J. E.
A1  - Herzschuh, Ulrike
A1  - Liu, X.
T1  - High-resolution leaf wax carbon and hydrogen isotopic record of the late Holocene paleoclimate in arid Central Asia
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Central Asia is located at the confluence of large-scale atmospheric circulation systems. It is thus likely to be highly susceptible to changes in the dynamics of those systems; however, little is still known about the regional paleoclimate history. Here we present carbon and hydrogen isotopic compositions of n-alkanoic acids from a late Holocene sediment core from Lake Karakuli (eastern Pamir, Xinjiang Province, China). Instrumental evidence and isotopeenabled climate model experiments with the Laboratoire de Meteorologie Dynamique Zoom model version 4 (LMDZ4) demonstrate that delta D values of precipitation in the region are influenced by both temperature and precipitation amount. We find that these parameters are inversely correlated on an annual scale, i.e., the climate has varied between relatively cool and wet and more warm and dry over the last 50 years. Since the isotopic signals of these changes are in the same direction and therefore additive, isotopes in precipitation are sensitive recorders of climatic changes in the region. Additionally, we infer that plants use year-round precipitation (including snowmelt), and thus leaf wax delta D values must also respond to shifts in the proportion of moisture derived from westerly storms during late winter and early spring. Downcore results give evidence for a gradual shift to cooler and wetter climates between 3.5 and 2.5 cal kyr BP, interrupted by a warm and dry episode between 3.0 and 2.7 kyr BP. Further cool and wet episodes occur between 1.9 and 1.5 and between 0.6 and 0.1 kyr BP, the latter coeval with the Little Ice Age. Warm and dry episodes from 2.5 to 1.9 and 1.5 to 0.6 kyr BP coincide with the Roman Warm Period and Medieval Climate Anomaly, respectively. Finally, we find a drying tend in recent decades. Regional comparisons lead us to infer that the strength and position of the westerlies, and wider northern hemispheric climate dynamics, control climatic shifts in arid Central Asia, leading to complex local responses. Our new archive from Lake Karakuli provides a detailed record of the local signatures of these climate transitions in the eastern Pamir.
Y1  - 2015
U6  - https://doi.org/10.5194/cp-11-619-2015
SN  - 1814-9324
SN  - 1814-9332
VL  - 11
IS  - 4
SP  - 619
EP  - 633
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Herzschuh, Ulrike
A1  - Wilkes, Heinz
A1  - Schulz, Hans-Martin
A1  - Wang, Yongbo
A1  - Plessen, Birgit
A1  - Mischke, Steffen
A1  - Diekmann, Bernhard
A1  - Zhang, Chengjun
T1  - Ecological development of Lake Donggi Cona, north-eastern Tibetan Plateau, since the late glacial on basis of organic geochemical proxies and non-pollen palynomorphs
JF  - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2  - Organic geochemical proxy data from surface sediment samples and a sediment core from Lake Donggi Cona were used to infer environmental changes on the northeastern Tibetan Plateau spanning the last 18.4 kyr. Long-chain n-alkanes dominate the aliphatic hydrocarbon fraction of the sediment extract from most surface sediment samples and the sediment core. Unsaturated mid-chain n-alkanes (nC(23:1) and nC(25:1)) have high abundances in some samples, especially in core samples from the late glacial and early Holocene. TOC contents, organic biomarker and non-pollen-palynomorph concentrations and results from organic petrologic analysis on selected samples suggest three major episodes in the history of Lake Donggi Cona. Before ca. 12.6 cal ka BP samples contain low amounts of organic matter due to cold and arid conditions during the late glacial. After 12.6 cal ka BP, relatively high contents of TOC and concentrations of Botryococcus fossils, as well as enhanced concentrations of mid-chain n-alkanes and n-alkenes suggest a higher primary and macrophyte productivity than at present This is supported by high contents of palynomorphs derived from higher plants and algae and was possibly triggered by a decrease of salinity and amelioration of climate during the early Holocene. Since 6.8 cal ka BP Lake Donggi Cona has been an oligotrophic freshwater lake. Proxy data suggest that variations in insolation drive ecological changes in the lake, with increased aquatic productivity during the early Holocene summer insolation maximum. Short-term drops of TOC contents or biomarker concentrations (at 9.9 cal ka BP, after 8.0 and between 3.5 and 1.7 cal ka BP) can possibly be related to relatively cool and dry episodes reported from other sites on the north-eastern Tibetan Plateau, which are hypothesized to occur in phase with Northern Hemisphere cooling events.
KW  - Biomarker
KW  - Holocene
KW  - n-alkanes
KW  - Total organic carbon
KW  - Organic matter
KW  - Macerals
KW  - Aquatic macrophytes
Y1  - 2012
U6  - https://doi.org/10.1016/j.palaeo.2011.10.015
SN  - 0031-0182
VL  - 313
IS  - 2
SP  - 140
EP  - 149
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Hilt, Sabine
A1  - Perillon, Cecile
A1  - Gillefalk, Mikael
A1  - Sachse, Dirk
T1  - Biosynthetic hydrogen isotopic fractionation factors during lipid synthesis in submerged aquatic macrophytes: Effect of groundwater discharge and salinity
JF  - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
N2  - Sedimentary lipid biomarkers have become widely used tools for reconstructing past climatic and ecological changes due to their ubiquitous occurrence in lake sediments. In particular, the hydrogen isotopic composition (expressed as delta D values) of leaf wax lipids derived from terrestrial plants has been a focus of research during the last two decades and the understanding of competing environmental and plant physiological factors influencing the delta D values has greatly improved. Comparatively less attention has been paid to lipid biomarkers derived from aquatic plants, although these compounds are abundant in many lacustrine sediments. We therefore conducted a field and laboratory experiment to study the effect of salinity and groundwater discharge on the isotopic composition of aquatic plant biomarkers. We analyzed samples of the common submerged plant species, Potamogeton pectinatus (sago pondweed), which has a wide geographic distribution and can tolerate high salinity. We tested the effect of groundwater discharge (characterized by more negative delta D values relative to lake water) and salinity on the delta D values of n-alkanes from P. pectinatus by comparing plants (i) collected from the oligotrophic freshwater Lake Stechlin (Germany) at shallow littoral depth from locations with and without groundwater discharge, and (ii) plants grown from tubers collected from the eutrophic Lake Muggelsee in nutrient solution at four salinity levels. Isotopically depleted groundwater did not have a significant influence on the delta D values of n-alkanes in Lake Stechlin P. pectinatus and calculated isotopic fractionation factors epsilon(l/w) between lake water and n-alkanes averaged -137 +/- 9%(n-C-23), -136 +/- 7%(n-C-25) and -131 +/- 6%(n-C-27), respectively. Similar epsilon values were calculated for plants from Lake Muggelsee grown in freshwater nutrient solution (-134 +/- 11% for n-C-23), while greater fractionation was observed at increased salinity values of 10 (163 +/- 12%) and 15(-172 +/- 15%). We therefore suggest an average e value of -136 +/- 9% between source water and the major n-alkanes in P. pectinatus grown under freshwater conditions. Our results demonstrate that isotopic fractionation can increase by 30-40% at salinity values 10 and 15. These results could be explained either by inhibited plant growth at higher salinity, or by metabolic adaptation to salt stress that remain to be elucidated. A potential salinity effect on dD values of aquatic lipids requires further examination, since this would impact on the interpretation of downcore isotopic data in paleohydrologic studies. (C) 2017 Elsevier Ltd. All rights reserved.
Y1  - 2017
U6  - https://doi.org/10.1016/j.orggeochem.2017.07.021
SN  - 0146-6380
VL  - 113
SP  - 10
EP  - 16
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Makhmudov, Zafar
A1  - Rajabov, Iljomjon
A1  - Zhang, Qiong
A1  - Pausata, Francesco Salvatore R.
A1  - Werner, Martin
A1  - Heinecke, Liv
A1  - Kuessner, Marie L.
A1  - Feakins, Sarah J.
A1  - Sachse, Dirk
A1  - Mischke, Steffen
T1  - Hydroclimate in the Pamirs Was Driven by Changes in Precipitation-Evaporation Seasonality Since theLast Glacial Period
JF  - Geophysical research letters
N2  - The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. delta D values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive delta D shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant.
KW  - climate
KW  - biomarker
KW  - geochemistry
KW  - modelling
KW  - paleoclimate
KW  - hydrology
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL085202
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13972
EP  - 13983
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Aiken, John M.
A1  - Aiken, Chastity
A1  - Cotton, Fabrice
T1  - A python library for teaching computation to seismology students
JF  - Seismological research letters
N2  - Python is at the forefront of scientific computation for seismologists and therefore should be introduced to students interested in becoming seismologists. On its own, Python is open source and well designed with extensive libraries. However, Python code can also be executed, visualized, and communicated to others with "Jupyter Notebooks". Thus, Jupyter Notebooks are ideal for teaching students Python and scientific computation. In this article, we designed an openly available Python library and collection of Jupyter Notebooks based on defined scientific computation learning goals for seismology students. The Notebooks cover topics from an introduction to Python to organizing data, earthquake catalog statistics, linear regression, and making maps. Our Python library and collection of Jupyter Notebooks are meant to be used as course materials for an upper-division data analysis course in an Earth Science Department, and the materials were tested in a Probabilistic Seismic Hazard course. However, seismologists or anyone else who is interested in Python for data analysis and map making can use these materials.
Y1  - 2018
U6  - https://doi.org/10.1785/0220170246
SN  - 0895-0695
SN  - 1938-2057
VL  - 89
IS  - 3
SP  - 1165
EP  - 1171
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Akal, Cuneyt
A1  - Koralay, O. Ersin
A1  - Candan, Osman
A1  - Oberhänsli, Roland
A1  - Chen, Fukun
T1  - Geodynamic significance of the early triassic karaburun granitoid (Western Turkey) for the opening history of Neo-Tethys
JF  - Turkish journal of earth sciences = Türk yerbilimleri dergisi
N2  - The Karaburun Peninsula, which is considered part of the Anatolide-Tauride Block of Turkey, contains clastic and carbonate sequences deposited on the northern margin of Gondwana. The Palaeozoic clastic sequence, which is intruded by the Early Triassic granitoid and tectonically overlies a Mesozoic melange sequence, can be divided into three subunits: a lower clastic subunit consisting of a sandstone-shale alternation, an upper clastic subunit consisting of black chert-bearing shales, sandstone and conglomerate, and a Permo-Carboniferous carbonate subunit. The lower Triassic Karaburun I-type granitoid has a high initial Sr-87/Sr-86 ratio (0.709021-0.709168), and low Nd-143/Nd-144 ratio (0.512004-0.512023) and epsilon Nd (-5.34 to -5.70) isotopic values. Geochronological data indicate a crystallization (intrusion) age of 247.1 +/- 2.0 Ma (Scythian). Geochemically, the acidic magmatism reflects a subduction-related continental-arc basin tectonic setting, which can be linked to the opening of the northern branch of Neo-Tethys as a continental back-arc rifting basin on the northern margin of Gondwana. This can be related to the closure through southward subduction of the Palaeotethys Ocean beneath Gondwana.
KW  - Karaburun
KW  - Neo-Tethys
KW  - Palaeo-Tethys
KW  - diorite
KW  - Triassic
KW  - magmatism
Y1  - 2011
U6  - https://doi.org/10.3906/yer-1008-1
SN  - 1300-0985
VL  - 20
IS  - 3
SP  - 255
EP  - 271
PB  - Tübitak
CY  - Ankara
ER  - 
TY  - JOUR
A1  - Akal, Cüneyt
A1  - Candan, Osman
A1  - Koralay, O. Ersin
A1  - Oberhänsli, Roland
A1  - Chen, Fukun
A1  - Prelevic, Dejan
T1  - Early Triassic potassic volcanism in the Afyon Zone of the Anatolides/Turkey - implications for the rifting of the Neo-Tethys
JF  - International journal of earth sciences
N2  - Afyon Zone, which was derived from the Anatolide-Tauride platform during closure of the Neo-Tethys, is made up of pre-Mesozoic basement and unconformably overlying Triassic-Early Tertiary cover series. The Afyon Zone contains widespread metavolcanic rocks, which are dominated by rhyolite, dacite, and trachyandesite. They form a distinct volcanic succession, which is separated from the underlying Silurian-Lower Carboniferous metacarbonates and meta-siliciclastics by a regional unconformity. Trachyandesitic metavolcanics are made up of massive lava flows, pyroclastics and epiclastics, less frequently, domes and dikes, which were developed on a deeply eroded subaerial landmass. U/Pb and Pb/Pb zircon geochronology yielded Lower Triassic (similar to 250 Ma) ages, which are interpreted as extrusion age of trachyandesitic volcanics. Based on the stratigraphic, geochronological, and geochemical data, we suggest that these Lower Triassic magmatic rocks represent an extensional tectonic setting on the northern active margin of the Gondwana, which led to the development of the northern branch of the Neo-Tethys.
KW  - Meta-trachyandesite
KW  - Afyon Zone
KW  - Turkey
KW  - Neo-Tethys
KW  - Paleo-tethys
Y1  - 2012
U6  - https://doi.org/10.1007/s00531-011-0654-2
SN  - 1437-3254
VL  - 101
IS  - 1
SP  - 177
EP  - 194
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Al Atik, Linda
A1  - Abrahamson, Norman A.
A1  - Bommer, Julian J.
A1  - Scherbaum, Frank
A1  - Cotton, Fabrice
A1  - Kuehn, Nicolas
T1  - The variability of ground-motion prediction models and its components
Y1  - 2010
UR  - http://srl.geoscienceworld.org/
U6  - https://doi.org/10.1785/gssrl.81.5.794
SN  - 0895-0695
ER  - 
TY  - JOUR
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Schöpfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Geomechanical modelling of sinkhole development using distinct elements
BT  - model verification for a single void space and application to the Dead Sea area
JF  - Solid earth
N2  - Mechanical and/or chemical removal of material from the subsurface may generate large subsurface cavities, the destabilisation of which can lead to ground collapse and the formation of sinkholes. Numerical simulation of the interaction of cavity growth, host material deformation and overburden collapse is desirable to better understand the sinkhole hazard but is a challenging task due to the involved high strains and material discontinuities. Here, we present 2-D distinct element method numerical simulations of cavity growth and sinkhole development. Firstly, we simulate cavity formation by quasi-static, stepwise removal of material in a single growing zone of an arbitrary geometry and depth. We benchmark this approach against analytical and boundary element method models of a deep void space in a linear elastic material. Secondly, we explore the effects of properties of different uniform materials on cavity stability and sinkhole development. We perform simulated biaxial tests to calibrate macroscopic geotechnical parameters of three model materials representative of those in which sinkholes develop at the Dead Sea shoreline: mud, alluvium and salt. We show that weak materials do not support large cavities, leading to gradual sagging or suffusion-style subsidence. Strong materials support quasi-stable to stable cavities, the overburdens of which may fail suddenly in a caprock or bedrock collapse style. Thirdly, we examine the consequences of layered arrangements of weak and strong materials. We find that these are more susceptible to sinkhole collapse than uniform materials not only due to a lower integrated strength of the overburden but also due to an inhibition of stabilising stress arching. Finally, we compare our model sinkhole geometries to observations at the Ghor Al-Haditha sinkhole site in Jordan. Sinkhole depth / diameter ratios of 0.15 in mud, 0.37 in alluvium and 0.33 in salt are reproduced successfully in the calibrated model materials. The model results suggest that the observed distribution of sinkhole depth / diameter values in each material type may partly reflect sinkhole growth trends.
Y1  - 2018
U6  - https://doi.org/10.5194/se-9-1341-2018
SN  - 1869-9510
SN  - 1869-9529
VL  - 9
IS  - 6
SP  - 1341
EP  - 1373
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Watson, Robert A.
A1  - Polom, Ulrich
A1  - Schoepfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Distinct element geomechanical modelling of the formation of sinkhole clusters within large-scale karstic depressions
JF  - Solid earth
N2  - The 2-D distinct element method (DEM) code (PFC2D_V5) is used here to simulate the evolution of subsidence-related karst landforms, such as single and clustered sinkholes, and associated larger-scale depressions. Subsurface material in the DEM model is removed progressively to produce an array of cavities; this simulates a network of subsurface groundwater conduits growing by chemical/mechanical erosion. The growth of the cavity array is coupled mechanically to the gravitationally loaded surroundings, such that cavities can grow also in part by material failure at their margins, which in the limit can produce individual collapse sinkholes. Two end-member growth scenarios of the cavity array and their impact on surface subsidence were examined in the models: (1) cavity growth at the same depth level and growth rate; (2) cavity growth at progressively deepening levels with varying growth rates. These growth scenarios are characterised by differing stress patterns across the cavity array and its overburden, which are in turn an important factor for the formation of sinkholes and uvalalike depressions. For growth scenario (1), a stable compression arch is established around the entire cavity array, hindering sinkhole collapse into individual cavities and favouring block-wise, relatively even subsidence across the whole cavity array. In contrast, for growth scenario (2), the stress system is more heterogeneous, such that local stress concentrations exist around individual cavities, leading to stress interactions and local wall/overburden fractures. Consequently, sinkhole collapses occur in individual cavities, which results in uneven, differential subsidence within a larger-scale depression. Depending on material properties of the cavity-hosting material and the overburden, the larger-scale depression forms either by sinkhole coalescence or by widespread subsidence linked geometrically to the entire cavity array. The results from models with growth scenario (2) are in close agreement with surface morphological and subsurface geophysical observations from an evaporite karst area on the eastern shore of the Dead Sea.
Y1  - 2019
U6  - https://doi.org/10.5194/se-10-1219-2019
SN  - 1869-9510
SN  - 1869-9529
VL  - 10
IS  - 4
SP  - 1219
EP  - 1241
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Al-Mashaikhi, K.
A1  - Oswald, Sascha
A1  - Attinger, Sabine
A1  - Büchel, G.
A1  - Knöller, K.
A1  - Strauch, G.
T1  - Evaluation of groundwater dynamics and quality in the Najd aquifers located in the Sultanate of Oman
JF  - Environmental earth sciences
N2  - The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, delta H-2 and delta O-18 variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region.
KW  - Environmental isotopes
KW  - Groundwater
KW  - Najd aquifer
KW  - Oman
KW  - Recharge
KW  - Water quality
Y1  - 2012
U6  - https://doi.org/10.1007/s12665-011-1331-2
SN  - 1866-6280
VL  - 66
IS  - 4
SP  - 1195
EP  - 1211
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Alawi, Mashal
A1  - Schneider, Beate
A1  - Kallmeyer, Jens
T1  - A procedure for separate recovery of extra- and intracellular DNA from a single marine sediment sample
JF  - Journal of microbiological methods
N2  - Extracellular DNA (eDNA) is a ubiquitous biological compound in aquatic sediment and soil. Previous studies suggested that eDNA plays an important role in biogeochemical element cycling, horizontal gene transfer and stabilization of biofilm structures. Previous methods for eDNA extraction were either not suitable for oligotrophic sediments or only allowed quantification but no genetic analyses. Our procedure is based on cell detachment and eDNA liberation from sediment particles by sequential washing with an alkaline sodium phosphate buffer followed by a separation of cells and eDNA. The separated eDNA is then bound onto silica particles and purified, whereas the intracellular DNA from the separated cells is extracted using a commercial kit. The method provides extra- and intracellular DNA of high purity that is suitable for downstream applications like PCR. Extracellular DNA was extracted from organic-rich shallow sediment of the Baltic Sea, glacially influenced sediment of the Barents Sea and from the oligotrophic South Pacific Gyre. The eDNA concentration in these samples varied from 23 to 626 ng g(-1) wet weight sediment. A number of experiments were performed to verify each processing step. Although extraction efficiency is higher than other published methods, it is not fully quantitative. (C) 2014 Elsevier B.V. All rights reserved.
KW  - Extracellular DNA
KW  - eDNA
KW  - Intracellular DNA
KW  - South Pacific Gyre
KW  - Ancient DNA
KW  - Fossil DNA
Y1  - 2014
U6  - https://doi.org/10.1016/j.mimet.2014.06.009
SN  - 0167-7012
SN  - 1872-8359
VL  - 104
SP  - 36
EP  - 42
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Albrecht, Tanja
A1  - Martin, M.
A1  - Haseloff, M.
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Parameterization for subgrid-scale motion of ice-shelf calving fronts
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - A parameterization for the motion of ice-shelf fronts on a Cartesian grid in finite-difference land-ice models is presented. The scheme prevents artificial thinning of the ice shelf at its edge, which occurs due to the finite resolution of the model. The intuitive numerical implementation diminishes numerical dispersion at the ice front and enables the application of physical boundary conditions to improve the calculation of stress and velocity fields throughout the ice-sheet-shelf system. Numerical properties of this subgrid modification are assessed in the Potsdam Parallel Ice Sheet Model (PISM-PIK) for different geometries in one and two horizontal dimensions and are verified against an analytical solution in a flow-line setup.
Y1  - 2011
U6  - https://doi.org/10.5194/tc-5-35-2011
SN  - 1994-0416
VL  - 5
IS  - 1
SP  - 35
EP  - 44
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)
BT  - Part 1: boundary conditions and climatic forcing
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Simulations of the glacial-interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also climatic forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. <br /> We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level forcing. Hence, this study serves as a "cookbook" for the growing community of PISM users and paleo-ice sheet modelers in general. <br /> For each of the different model uncertainties with regard to climatic forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-599-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 2
SP  - 599
EP  - 632
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrich, Sergi
A1  - Frijia, Gianluca
A1  - Parente, Mariano
A1  - Caus, Esmeralda
T1  - The evolution of the earliest representatives of the genus Orbitoides: Implications for Upper Cretaceous biostratigraphy
JF  - Cretaceous research
N2  - The biostratigraphy of Campanian-Maastrichtian carbonate platforms is largely based on the larger foraminiferal genus Orbitoides. However, while the taxonomy and the chronostratigraphic age of the younger species of this genus are well established, there are still many controversies on the earliest species. We have restudied their morphological characters using a large collection of samples from the type-localities and from continuous sections in the southern Pyrenees. Based on these new observations, the long forgotten species O. sanctae-pelagiae is reinstated, while O. dordoniensis is considered a junior synonym. Successive populations of O. hottingeri, O. sanctae-pelagiae and O. douvillei show gradual morphological changes in time marked by an increase in the size and complexity of the macrospheric embryonal apparatus, an increase of the size of the adult specimens of both generations and the progressive appearance and development of true lateral chamberlets. The Font de les Bagasses Unit in the southern Pyrenees preserves a high-resolution archive of the evolution of the earliest Orbitoides. Strontium isotope stratigraphy indicates that the oldest species, O. hottingeri, made its first appearance in the earliest Campanian, close to the Santonian-Campanian boundary, and was replaced by O. sanctae-pelagiae at a level closely corresponding to the boundary between the Placenticeras bidorsatum and Menabites delawarensis ammonite zones. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Larger foraminifera
KW  - Biostratigraphy
KW  - Strontium isotope stratigraphy
KW  - Late cretaceous
KW  - Orbitoides
Y1  - 2014
U6  - https://doi.org/10.1016/j.cretres.2014.04.013
SN  - 0195-6671
SN  - 1095-998X
VL  - 51
SP  - 22
EP  - 34
PB  - Elsevier
CY  - London
ER  - 
TY  - JOUR
A1  - Alemanno, Giulia
A1  - D'Amore, Maddalena
A1  - Maturilli, Alessandro
A1  - Helbert, Joern
A1  - Arnold, Gabriele
A1  - Korablev, Oleg
A1  - Ignatiev, Nikolay
A1  - Grigoriev, Alexei
A1  - Shakun, Alexey
A1  - Trokhimovskiy, Alexander
T1  - Martian atmospheric spectral end-members retrieval from ExoMars Thermal Infrared (TIRVIM) data
JF  - JGR / Planets
N2  - Key knowledge about planetary composition can be recovered from the study of thermal infrared spectral range datasets. 
This range has a huge diagnostic potential because it contains diagnostic absorptions from a planetary surface and atmosphere. The main goal of this study is to process and interpret the dataset from the Thermal Infrared channel (TIRVIM) which is part of the Atmospheric Chemistry Suite of the ExoMars2016 Trace Gas Orbiter mission to find and characterize dust and water ice clouds in the atmosphere. 
The method employed here is based on the application of principal component analysis and target transformation techniques to extract the independent variable components present in the analyzed dataset. Spectral shapes of both atmospheric dust and water ice aerosols have been recovered from the analysis of TIRVIM data. 
The comparison between our results with those previously obtained on Thermal Emission Spectrometer (TES) data and with previous analysis on TIRVIM data, validates the methodology here applied, showing that it allows to correctly recover the atmospheric spectral endmembers present in the TIRVIM data. 
Moreover, comparison with atmospheric retrievals on PFS, TES and IRIS data, allowed us to assess the temporal stability and homogeneity of dust and water ice components in the Martian atmosphere over a time period of almost 50 years.
Y1  - 2022
U6  - https://doi.org/10.1029/2022JE007429
SN  - 2169-9097
SN  - 2169-9100
VL  - 127
IS  - 9
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Ali, Saleem H.
A1  - Giurco, Damien
A1  - Arndt, Nicholas
A1  - Nickless, Edmund
A1  - Brown, Graham
A1  - Demetriades, Alecos
A1  - Durrheim, Ray
A1  - Enriquez, Maria Amelia
A1  - Kinnaird, Judith
A1  - Littleboy, Anna
A1  - Meinert, Lawrence D.
A1  - Oberhänsli, Roland
A1  - Salem, Janet
A1  - Schodde, Richard
A1  - Schneider, Gabi
A1  - Vidal, Olivier
A1  - Yakovleva, Natalia
T1  - Mineral supply for sustainable development requires resource governance
JF  - Nature : the international weekly journal of science
N2  - Successful delivery of the United Nations sustainable development goals and implementation of the Paris Agreement requires technologies that utilize a wide range of minerals in vast quantities. Metal recycling and technological change will contribute to sustaining supply, but mining must continue and grow for the foreseeable future to ensure that such minerals remain available to industry. New links are needed between existing institutional frameworks to oversee responsible sourcing of minerals, trajectories for mineral exploration, environmental practices, and consumer awareness of the effects of consumption. Here we present, through analysis of a comprehensive set of data and demand forecasts, an interdisciplinary perspective on how best to ensure ecologically viable continuity of global mineral supply over the coming decades.
Y1  - 2017
U6  - https://doi.org/10.1038/nature21359
SN  - 0028-0836
SN  - 1476-4687
VL  - 543
SP  - 367
EP  - 372
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Alinaghi, Alireza
A1  - Kruger, Frank
T1  - Seismic array analysis and redetermination of depths of earthquakes in Tien-Shan: implications for strength of the crust and lithosphere
JF  - Geophysical journal international
N2  - We have redetermined focal depths of moderate and major earthquakes with reported lower-crust and upper-mantle depths that have occurred in Tien-Shan, since the availability of broad-band array data. Records of earthquakes at global arrays have been used for identification and modelling of depth phases in order to make accurate estimation of focal depths. Our results show that half of the purportedly deep earthquakes are indeed originating from depths attributable to middle-crust and lower-crust regions. Also one exceptional event in the northern foreland of Tien-Shan in Junggar Basin is located in the upper mantle at the depth of 64 km. Such unusually deep earthquakes for intraplate continental tectonic domain are all located at the margin of Tien-Shan with its adjacent stable blocks and at least some of them have occurred where the brittle behaviour of continental rocks is not highly expected. The reverse mechanisms of all these earthquakes and their proximity to formerly subducting and later colliding and underplating stable blocks and their interactions with overlying Tien-Shan are clues to explain this extremity.
KW  - Earthquake source observations
KW  - Seismicity and tectonics
KW  - Body waves
Y1  - 2014
U6  - https://doi.org/10.1093/gji/ggu141
SN  - 0956-540X
SN  - 1365-246X
VL  - 198
IS  - 2
SP  - 1111
EP  - 1129
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Beiter, Daniel
A1  - Tronicke, Jens
T1  - Ground-penetrating radar monitoring of fast subsurface processes
JF  - Geophysics
N2  - Earth and environmental sciences rely on detailed information about subsurface processes. Whereas geophysical techniques typically provide highly resolved spatial images, monitoring subsurface processes is often associated with enormous effort and, therefore, is usually limited to point information in time or space. Thus, the development of spatial and temporal continuous field monitoring methods is a major challenge for the understanding of subsurface processes. We have developed a novel method for ground-penetrating-radar (GPR) reflection monitoring of subsurface flow processes under unsaturated conditions and applied it to a hydrological infiltration experiment performed across a periglacial slope deposit in northwest Luxembourg. Our approach relies on a spatial and temporal quasicontinuous data recording and processing, followed by an attribute analysis based on analyzing differences between individual time steps. The results demonstrate the ability of time-lapse GPR monitoring to visualize the spatial and temporal dynamics of preferential flow processes with a spatial resolution in the order of a few decimeters and temporal resolution in the order of a few minutes. We observe excellent agreement with water table information originating from different boreholes. This demonstrates the potential of surface-based GPR reflection monitoring to observe the spatiotemporal dynamics of water movements in the subsurface. It provides valuable, and so far not accessible, information for example in the field of hydrology and pedology that allows studying the actual subsurface processes rather than deducing them from point information.
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0737.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 3
SP  - A19
EP  - A23
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Heincke, Bjorn H.
A1  - Koyan, Philipp
A1  - Wheeler, Walter
A1  - Ronning, Jan S.
T1  - 3D ground-penetrating radar attribute classification
BT  - a case study from a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard
JF  - Geophysics
N2  - Ground-penetrating radar (GPR) is a method that can provide detailed information about the near subsurface in sedimentary and carbonate environments. 
The classical interpretation of GPR data (e.g., based on manual feature selection) often is labor-intensive and limited by the experience of the intercally used for seismic interpretation, can provide faster, more repeatable, and less biased interpretations. We have recorded a 3D GPD data set collected across a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard. After performing advanced processing, we compare the results of a classical GPR interpretation to the results of an attribute-based classification. 

Our attribute classification incorporates a selection of dip and textural attributes as the input for a k-means clustering approach. Similar to the results of the classical interpretation, the resulting classes differentiate between undisturbed strata and breccias or fault zones. 
The classes also reveal details inside the breccia pipe that are not discerned in the classical fer that the intrapipe GPR facies result from subtle differences, such as breccia lithology, clast size, or pore-space filling.
Y1  - 2022
U6  - https://doi.org/10.1190/GEO2021-0651.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 87
IS  - 4
SP  - WB19
EP  - WB30
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas Robin
A1  - Booth, Adam D.
A1  - Baker, Sandra E.
A1  - Ellwood, Stephen A.
A1  - Tronicke, Jens
T1  - High-resolution imaging and monitoring of animal tunnels using 3D ground-penetrating radar
JF  - Near surface geophysics
N2  - Ground-penetrating radar is widely used to provide highly resolved images of subsurface sedimentary structures, with implications for processes active in the vadose zone. Frequently overlooked among these structures are tunnels excavated by fossorial animals (e.g., moles). We present two repeated ground-penetrating radar surveys performed a year apart in 2016 and 2017. Careful three-dimensional data processing reveals, in each data set, a pattern of elongated structures that are interpreted as a subsurface mole tunnel network. Our data demonstrate the ability of three-dimensional ground-penetrating radar imaging to non-invasively delineate the small animal tunnels (similar to 5 cm diameter) at a higher spatial and geolocation resolution than has previously been achieved. In turn, this makes repeated surveys and, therefore, long-term monitoring possible. Our results offer valuable insight into the understanding of the near-surface and showcase a potential new application for a geophysical method as well as a non-invasive method of ecological surveying.
KW  - Ground-penetrating radar
KW  - Shallow subsurface
KW  - Environmental
Y1  - 2019
U6  - https://doi.org/10.1002/nsg.12039
SN  - 1569-4445
SN  - 1873-0604
VL  - 17
IS  - 3
SP  - 291
EP  - 298
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Tronicke, Jens
T1  - Attribute-based analysis of time-lapse ground-penetrating radar data
JF  - Geophysics
N2  - Analysis of time-lapse ground-penetrating radar (GPR) data can provide information regarding subsurface hydrological processes, such as preferential flow. However, the analysis of time-lapse data is often limited by data quality; for example, for noisy input data, the interpretation of difference images is often difficult. Motivated by modern image-processing tools, we have developed two robust GPR attributes, which allow us to distinguish amplitude (contrast similarity) and time-shift (structural similarity) variations related to differences between individual time-lapse GPR data sets. We tested and evaluated our attributes using synthetic data of different complexity. Afterward, we applied them to a field data example, in which subsurface flow was induced by an artificial rainfall event. For all examples, we identified our structural similarity attribute to be a robust measure for highlighting time-lapse changes also in data with low signal-to-noise ratios. We determined that our new attribute-based workflow is a promising tool to analyze time-lapse GPR data, especially for imaging subsurface hydrological processes.
Y1  - 2016
U6  - https://doi.org/10.1190/GEO2015-0171.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 81
SP  - H1
EP  - H8
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Tronicke, Jens
A1  - Delock, Marcel
A1  - Böniger, Urs
T1  - Topographic migration of 2D and 3D ground-penetrating radar data considering variable velocities
JF  - Near surface geophysics
N2  - We present a 2D/3D topographic migration scheme for ground-penetrating radar (GPR) data which is able to account for variable velocities by using the root mean square (rms) velocity approximation. We test our migration scheme using a synthetic 2D example and compare our migrated image to the results obtained using common GPR migration approaches. Furthermore, we apply it to 2D and 3D field data. These examples are recorded across common subsurface settings including surface topography and variations in the GPR subsurface velocity field caused by a shallow ground water table. In such field settings, our migration strategy provides well focused images of commonoffset GPR data without the need for a detailed interval velocity model. The synthetic and field examples demonstrate that our topographic migration scheme allows for accurate GPR imaging in the presence of variations in surface topography and subsurface velocity.
Y1  - 2015
U6  - https://doi.org/10.3997/1873-0604.2014037
SN  - 1569-4445
SN  - 1873-0604
VL  - 13
IS  - 3
PB  - European Association of Geoscientists & Engineers
CY  - Houten
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - van Schaik, N. Loes M. B.
A1  - Tronicke, Jens
T1  - 4D ground-penetrating radar during a plot scale dye tracer experiment
JF  - Journal of applied geophysics
N2  - Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500 MHz antennas. Such a survey setup requires accurate acquisition and processing techniquesto extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Ground penetrating radar
KW  - Time-lapse imaging
KW  - Brilliant blue
Y1  - 2015
U6  - https://doi.org/10.1016/j.jappgeo.2015.04.016
SN  - 0926-9851
SN  - 1879-1859
VL  - 118
SP  - 139
EP  - 144
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Alonso, Ricardo N.
A1  - Bookhagen, Bodo
A1  - Carrapa, Barbara
A1  - Coutand, Isabelle
A1  - Haschke, Michael
A1  - Hilley, George E.
A1  - Schoenbohm, Lindsay M.
A1  - Sobel, Edward
A1  - Strecker, Manfred
A1  - Trauth, Martin H.
A1  - Villanueva, Arturo
T1  - Tectonics, climate and landscape evolution of the Southern Central Andes : the Argentine Puna Plateau and adjacent regions between 22 and 30°S
Y1  - 2006
SN  - 978-3-540- 24329-8
ER  - 
TY  - JOUR
A1  - Alonzo, Michael
A1  - Bookhagen, Bodo
A1  - McFadden, Joseph P.
A1  - Sun, Alex
A1  - Roberts, Dar A.
T1  - Mapping urban forest leaf area index with airborne lidar using penetration metrics and allometry
JF  - Remote sensing of environment : an interdisciplinary journal
N2  - In urban areas, leaf area index (LAI) is a key ecosystem structural attribute with implications for energy and water balance, gas exchange, and anthropogenic energy use. In this study, we estimated LAI spatially using airborne lidar in downtown Santa Barbara, California, USA. We implemented two different modeling approaches. First, we directly estimated effective LAI (LAIe) using scan angle- and clump-corrected lidar laser penetration metrics (LPM). Second, we adapted existing allometric equations to estimate crown structural metrics including tree height and crown base height using lidar. The latter approach allowed for LAI estimates at the individual tree-crown scale. The LPM method, at both high and decimated point densities, resulted in good linear agreement with estimates from ground-based hemispherical photography (r(2) = 0.82, y = 0.99x) using a model that assumed a spherical leaf angle distribution. Within individual tree crown segments, the lidar estimates of crown structure closely paralleled field measurements (e.g., r(2) = 0.87 for crown length). LAI estimates based on the lidar crown measurements corresponded well with estimates from field measurements (r(2) = 0.84, y = 0.97x + 0.10). Consistency of the LPM and allometric lidar methods was also strong at 71 validation plots (r(2) = 0.88) and at 450 additional sample locations across the entire study area (r(2) = 0.72). This level of correspondence exceeded that of the canopy hemispherical photography and allometric, ground-based estimates (r(2) = 0.53). The first-order alignment of these two disparate methods may indicate that the error bounds for mapping LAI in cities are small enough to pursue large scale, spatially explicit estimation. (C) 2015 Elsevier Inc All rights reserved.
KW  - Airborne lidar
KW  - Leaf area index
KW  - Urban ecosystem analysis
KW  - Hemispherical photography
KW  - Allometry
KW  - Vegetation structure
Y1  - 2015
U6  - https://doi.org/10.1016/j.rse.2015.02.025
SN  - 0034-4257
SN  - 1879-0704
VL  - 162
SP  - 141
EP  - 153
PB  - Elsevier
CY  - New York
ER  - 
TY  - JOUR
A1  - Altenbach, Alexander V.
A1  - Pflaum, U.
A1  - Scheibel, Thomas R.
A1  - Thies, A.
A1  - Timm, M.
A1  - Trauth, Martin H.
T1  - Scaling percentages of benthic forminifera with flux rates of organic carbon
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Strain localization mechanisms in deep seated layered rocks
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Material transport in channelized fluids-examples from hightemperature shear zones and its comparsion with minor deformed ares of the Mid-European Variscan belt
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Fluid enhanced element redistribution, mass transport and volume changes in eclogite and amphibolite facies shear zones of different geological settings
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Cisterna, Clara
A1  - Günter, Christina
A1  - Gutiérrez, Adolfo Antonio
A1  - Rosales, J.
T1  - Tectono-metamorphic evolution of the proto-Andean margin of Gondwana
BT  - Evidence of internal high-grade metamorphism along the northern portion of the Famatinian orogen, Sierra de Aconquija, Sierras Pampeanas Orientales, Argentina
JF  - Journal of South American earth sciences
N2  - The present work gives a detailed analysis of the metamorphic and structural evolution of the back-arc portion of the Famatinian Orogen exposed in the southern Sierra de Aconquija (Cuesta de La Chilca segment) in the Sierras Pampeanas Orientales (Eastern Pampean Sierras). The Pampeanas Orientales include from north to south the Aconquija, Ambato and Ancasti mountains. They are mainly composed of middle to high grade metasedimentary units and magmatic rocks. 
At the south end of the Sierra de Aconquija, along an east to west segment extending over nearly 10 km (Cuesta de La Chilca), large volumes of metasedimentary rocks crop out. The eastern metasediments were defined as members of the El Portezuelo Metamorphic-Igneous Complex (EPMIC) or Eastern block and the western ones relate to the Quebrada del Molle Metamorphic Complex (QMMC) or Western block. The two blocks are divided by the La Chilca Shear Zone, which is reactivated as the Rio Chanarito fault. 
The EPMIC, forming the hanging wall, is composed of schists, gneisses and rare amphibolites, calc- silicate schists, marbles and migmatites. The rocks underwent multiple episodes of deformation and a late high strain-rate episode with gradually increasing mylonitization to the west. Metamorphism progrades from a M-1 phase to the peak M-3, characterized by the reactions: Qtz + Pl + Bt +/- Ms -> Grt + Bt(2) + Pl(2) +/- Sil +/- Kfs, Qtz + Bt + Sil -> Crd + Kfs and Qtz + Grt + Sil -> Crd. The M-3 assemblage is coeval with the dominant foliation related to a third deformational phase (D-3). 

The QMMC, forming the foot wall, is made up of fine-grained banded quartz - biotite schists with quartz veins and quartz-feldspar-rich pegmatites. To the east, schists are also overprinted by mylonitization. The M-3 peak assemblage is quartz + biotite + plagioclase +/- garnet +/- sillimanite +/- muscovite +/- ilmenite +/- magnetite +/- apatite. 

The studied segment suffered multiphase deformation and metamorphism. Some of these phases can be correlated between both blocks. D-1 is locally preserved in scarce outcrops in the EPMIC but is the dominant in the QMMC, where S-1 is nearly parallel to S-0. In the EPMIC, D-2 is represented by the S-2 foliation, related to the F-2 folding that overprints S-1, with dominant strike NNW - SSE and high angles dip to the E. D-3 in the EPMIC have F-3 folds with axis oblique to S-2; the S-3 foliation has striking NW - SE dipping steeply to the E or W and develops interference patterns. In the QMMC, S-2 (D-2) is a discontinuous cleavage oblique to S-1 and transposed by S-3 (D-3), subparallel to S-1. Such structures in the QMMC developed at subsolidus conditions and could be correlated to those of the EPMIC, which formed under higher P-T conditions. The penetrative deformation D-2 in the EPMIC occurred during a prograde path with syntectonic growth of garnet reaching P-T conditions of 640 degrees C and 0.54 GPa in the EPMIC. This stage was followed by a penetrative deformation D-3 with syn-kinematic growth of garnet, cordierite and plagioclase. Peak P-T conditions calculated for M-3 are 710 degrees C and 0.60 GPa, preserved in the western part of the EPMIC, west of the unnamed fault.
The schists from the QMMC suffered the early low grade M-1 metamorphism with minimum PT conditions of ca 400 degrees C and 0.35 GPa, comparable to the fine schists (M-1) outcropping to the east. The D-2 deformation is associated with the prograde M-2 metamorphism. The penetrative D-3 stage is related to a medium grade metamorphism M-3, with peak conditions at ca 590 degrees C and 0.55 GPa.
The superimposed stages of deformation and metamorphism reaching high P-T conditions followed by isothermal decompression, defining a clockwise orogenic P-T path. During the Lower Paleozoic, folds were superimposed and recrystallization as well as partial melting at peak conditions occurred. Similar characteristics were described from the basement from other Famatinian-dominated locations of the Sierra de Aconquija and other ranges of the Sierras Pampeanas Orientales.
KW  - Famatinian
KW  - Sierras Pampeanas Orientales
KW  - Cuesta de la chilca
KW  - PT path
Y1  - 2021
U6  - https://doi.org/10.1016/j.jsames.2021.103305
SN  - 0895-9811
VL  - 110
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Kruhl, J. H.
T1  - The long life of a thin and dry-temperature shear zone in the Hercynian lower crust of Calabria (s.Italy)
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Mejia Jimenez, D. M.
A1  - Günter, Christina
A1  - Sierra Rodriguez, G. I.
A1  - Scheffler, F.
A1  - Oberhänsli, Roland
T1  - The Garzn Massif, Colombia-a new ultrahigh-temperature metamorphic complex in the early Neoproterozoic of northern South America
JF  - Mineralogy and petrology
N2  - The Garzn Complex of the Garzn Massif in SW Colombia is composed of the Vergel Granulite Unit (VG) and the Las Margaritas Migmatite Unit (LMM). Previous studies reveal peak temperature conditions for the VG of about 740 A degrees C. The present study considers the remarkable exsolution phenomena in feldspars and pyroxenes and titanium-in-quartz thermometry. Recalculated ternary feldspar compositions indicate temperatures around 900-1,000 A degrees C just at or above the ultra-high temperature-metamorphism (UHTM) boundary of granulites. The calculated temperatures range of exsolved ortho- and clinopyroxenes also supports the existence of an UHTM event. In addition, titanium-in-quartz thermometry points towards ultra-high temperatures. It is the first known UHTM crustal segment in the northern part of South America. Although a mean geothermal gradient of ca 38 A degrees C km(-1) could imply additional heat supply in the lower crust controlling this extreme of peak metamorphism, an alternative model is suggested. The formation of the Vergel Granulite Unit is supposed to be formed in a continental back-arc environment with a thinned and weakened crust behind a magmatic arc (Guapotn-Mancagua Gneiss) followed by collision. In contrast, rocks of the adjacent Las Margaritas Migmatite Unit display "normal" granulite facies temperatures and are formed in a colder lower crust outside the arc, preserved by the Guapotn-Mancagu Gneiss. Back-arc formation was followed by inversion and thickening of the basin. The three units that form the modern-day Garzn Massif, were juxtaposed upon each other during collision (at ca. 1,000 Ma) and exhumation. The collision leading to the deformation of the studied area is part of the Grenville orogeny leading to the amalgamation of Rodinia.
Y1  - 2012
U6  - https://doi.org/10.1007/s00710-012-0202-1
SN  - 0930-0708
VL  - 105
IS  - 3-4
SP  - 171
EP  - 185
PB  - Springer
CY  - Wien
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Oberhänsli, Roland
A1  - Stein, Eckehard
A1  - Moghni, Mohsen
T1  - Geochemistry, tectonic setting and geodynamic position of late orogenic dikes in the Melibocus Massiv, Bergstraesser Odenwald
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Prosser, Giacomo
A1  - Grande, Atonella
A1  - Günter, Christina
A1  - Langone, Antonio
T1  - A seismogenic zone in the deep crust indicated by pseudotachylytes and ultramylonites in granulite-facies rocks of Calabria (Southern Italy)
JF  - Contributions to mineralogy and petrology
N2  - Pseudotachylyte veins frequently associated with mylonites and ultramylonites occur within migmatitic paragneisses, metamonzodiorites, as well as felsic and mafic granulites at the base of the section of the Hercynian lower crust exposed in Calabria (Southern Italy). The crustal section is tectonically superposed on lower grade units. Ultramylonites and pseudotachylytes are particularly well developed in migmatitic paragneisses, whereas sparse fault-related pseudotachylytes and thin mylonite/ultramylonite bands occur in granulite-facies rocks. The presence of sillimanite and clinopyroxene in ultramylonites and mylonites indicates that relatively high-temperature conditions preceded the formation of pseudotachylytes. We have analysed pseudotachylytes from different rock types to ascertain their deep crustal origin and to better understand the relationships between brittle and ductile processes during deformation of the deeper crust. Different protoliths were selected to test how lithology controls pseudotachylyte composition and textures. In migmatites and felsic granulites, euhedral or cauliflower-shaped garnets directly crystallized from pseudotachylyte melts of near andesitic composition. This indicates that pseudotachylytes originated at deep crustal conditions (> 0.75 GPa). In mafic protoliths, quenched needle-to-feather-shaped high-alumina orthopyroxene occurs in contact with newly crystallized plagioclase. The pyroxene crystallizes in garnet-free and garnet-bearing veins. The simultaneous growth of orthopyroxene and plagioclase as well as almandine, suggests lower crustal origin, with pressures in excess of 0.85 GPa. The existence of melts of different composition in the same vein indicates the stepwise, non-equilibrium conditions of frictional melting. Melt formed and intruded into pre-existing anisotropies. In mafic granulites, brittle faulting is localized in a previously formed thin high-temperature mylonite bands. migmatitic gneisses are deformed into ultramylonite domains characterized by s-c fabric. Small grain size and fluids lowered the effective stress on the c planes favouring a seismic event and the consequent melt generation. Microstructures and ductile deformation of pseudotachylytes suggest continuous ductile flow punctuated by episodes of high-strain rate, leading to seismic events and melting.
KW  - Pseudotachylyte
KW  - Calabria
KW  - Lower crust
KW  - Palaeo-seismicity
Y1  - 2013
U6  - https://doi.org/10.1007/s00410-013-0904-3
SN  - 0010-7999
VL  - 166
IS  - 4
SP  - 975
EP  - 994
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Wilhelm, Stefan
T1  - Ductile deformation of K-feldspar in eclogite facies shear zones in the Bergen Arcs, Norway : tectonophysics
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Aminov, Jovid
A1  - Ding, Lin
A1  - Mamadjonov, Yunus
A1  - Dupont-Nivet, Guillaume
A1  - Aminov, Jamshed
A1  - Zhang, Li-Yun
A1  - Yoqubov, Shokirjon
A1  - Aminov, Javhar
A1  - Abdulov, Sherzod
T1  - Pamir Plateau formation and crustal thickening before the India-Asia collision inferred from dating and petrology of the 110-92 Ma Southern Pamir volcanic sequence
JF  - Gondwana research : international geoscience journal ; official journal of the International Association for Gondwana Research
N2  - The formation of the Pamir is a key component of the India-Asia collision with major implications for lithospheric processes, plateau formation, land-sea configurations and associated climate changes. Although the formation of the Pamir is traditionally linked to Cenozoic processes associated with the India-Asia collision, the contribution of the Mesozoic tectonic evolution remains poorly understood. The Pamir was formed by the suturing of Gondwanan terranes to the south margin of Eurasia, however, the timing and tectonic mechanisms associated with this Mesozoic accretion remain poorly constrained. These processes are recorded by several igneous belts within these terranes, which are not well studied. Within the Southern Pamir, the Albian-Turonian volcanic rocks and comagmatic plutons of the Kyzylrabat Igneous Complex (KIC) provide an important and still unconstrained record of the Pamir evolution. Here we provide the age, origin and the geodynamic setting of the KIC volcanics by studying their petrology, zircon U-Pb geochronology, geochemistry and isotope composition.17 samples from the KIC volcanics yield U-Pb ages spanning from 92 to 110 Ma. The volcanics are intermediate to acidic in composition (SiO2 = 56-69 wt%) and exhibit high-K calc-alkaline and shoshonitic affinity (K2O/Na2O = 12.2 wt%). They show enrichment in LILE and LREE and depletion in HFSE and HREE with negative Ta, Ti and Nb anomalies, suggesting an arc-related tectonic setting for their formation. Low sNd(t) values (from 9.1 to 4.7), relatively high Sr-87/Sr-86(i) ratios (0.7069-0.7096) and broad range of zircon stif values (from 22.6 to 1.5) suggest a mixture of different magma sources. These features suggest that volcanics were derived by crustal under- or intraplating of an enriched subduction-related mantle shoshonitic magmas, by heating and partial melting of the lower crust, and by mixing of both magma components. Our results further imply that the KIC volcanics represent a shoshonitic suite typical of an evolution from active continental arc to post-collisional setting with a steepening of the Benioff zone and thickening of the crust toward the back-arc. This setting is best explained by the subduction- collision transition along the Shyok suture due to accretion of the Kohistan island arc to the Karakoram. This suggests that a significant part of the crustal shortening and thickening accommodated in the Pamir occurred in the Mesozoic before the India-Asia collision with implications for regional tectonic models. This further suggests the Pamir was already a major topographic feature with potentially important paleoclimate forcing such as the monsoonal circulation. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
KW  - Southern Pamir
KW  - Cretaceous
KW  - Volcanic rocks
KW  - Geochemistry
KW  - Geochronology
KW  - Petrogenesis
Y1  - 2017
U6  - https://doi.org/10.1016/j.gr.2017.08.003
SN  - 1342-937X
SN  - 1878-0571
VL  - 51
SP  - 310
EP  - 326
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Amour, Frederic
A1  - Mutti, Maria
A1  - Christ, Nicolas
A1  - Immenhauser, Adrian
A1  - Benson, Gregory S.
A1  - Agar, Susan M.
A1  - Tomas, Sara
A1  - Kabiri, Lahcen
T1  - Outcrop analog for an oolitic carbonate ramp reservoir a scale-dependent geologic modeling approach based on stratigraphic hierarchy
JF  - AAPG bulletin
N2  - Considerable effort has been devoted to the development of simulation algorithms for facies modeling, whereas a discussion of how to combine those techniques has not existed. The integration of multiple geologic data into a three-dimensional model, which requires the combination of simulation techniques, is yet a current challenge for reservoir modeling. This article presents a thought process that guides the acquisition and modeling of geologic data at various scales. Our work is based on outcrop data collected from a Jurassic carbonate ramp located in the High Atlas mountain range of Morocco. The study window is 1 km (0.6 mi) wide and 100 m (328.1 ft) thick. We describe and model the spatial and hierarchical arrangement of carbonate bodies spanning from largest to smallest: (1) stacking pattern of high-frequency depositional sequences, (2) facies association, and (3) lithofacies. Five sequence boundaries were modeled using differential global position system mapping and light detection and ranging data. The surface-based model shows a low-angle profile with modest paleotopographic relief at the inner-to-middle ramp transition. Facies associations were populated using truncated Gaussian simulation to preserve ordered trends between the inner, middle, and outer ramps. At the lithofacies scale, field observations and statistical analysis show a mosaiclike distribution that was simulated using a fully stochastic approach with sequential indicator simulation.
 This study observes that the use of one single simulation technique is unlikely to correctly model the natural patterns and variability of carbonate rocks. The selection and implementation of different techniques customized for each level of the stratigraphic hierarchy will provide the essential computing flexibility to model carbonate settings. This study demonstrates that a scale-dependent modeling approach should be a common procedure when building subsurface and outcrop models.
Y1  - 2013
U6  - https://doi.org/10.1306/10231212039
SN  - 0149-1423
VL  - 97
IS  - 5
SP  - 845
EP  - 871
PB  - American Association of Petroleum Geologists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Andermann, Christoff
A1  - Crave, Alain
A1  - Gloaguen, Richard
A1  - Davy, Philippe
A1  - Bonnet, Stephane
T1  - Connecting source and transport: Suspended sediments in the Nepal Himalayas
JF  - Earth & planetary science letters
N2  - Understanding the dynamics of sediment fluxes is a key issue to constrain modern erosion rates in mountain belts and determine the still debated level of control exerted by precipitation, topography and tectonics. The well defined monsoon seasonality in the Himalayas, together with active tectonics and strong relief provide an ideal environment to assess these possible interactions. For this purpose, we present a new compilation of daily suspended sediment data for 12 stations of the major rivers of the Nepal Himalayas. We analyze the relationships of sediment transport with daily river discharge and precipitation data as well as with morphometric parameters. We show that suspended sediment concentrations vary systematically through the seasons and asynchronously to river discharge displaying a hysteresis effect. This clockwise hysteresis effect disappears when suspended sediment fluxes are directly compared with direct storm discharge. Therefore we attribute the hysteresis effect to groundwater dilution rather than a sediment supply limitation. We infer a rating model to calculate erosion rates directly from long river discharge chronicles. We show that, when normalized by drainage area and mean sediment flux, all rivers exhibit the same trend. This similarity implies that all river basins have the same erosion behavior, independent of location, size and catchment characteristics. Erosion rates calculated from suspended sediment fluxes range between 0.1 and 2.8 mm/yr. The erosion rates of the three main basins of Nepal are in the range 0.9-1.5 mm/yr. Erosion rates in the Higher Himalayas are relatively low ( <0.5 mm/yr, except for Kali Gandaki), while in the Lesser Himalayas they range from 0.2 to 2 mm/yr. We propose that material transport in the rivers depends on hillslope sediment supply, which is, in turn, controlled by those rainfalls producing direct runoff. In other words, the rivers in the Nepal Himalayas are supply-limited and the hillsopes as a contributing source are transport-limited. We also show that erosion processes are not as much controlled by infrequently occurring extreme precipitation events, than by moderate ones with a high recurrence interval.
KW  - suspended sediment transport
KW  - Himalayas
KW  - erosion
KW  - sediment flux hysteresis
KW  - monsoon river hydrology
KW  - Himalayan rivers
Y1  - 2012
U6  - https://doi.org/10.1016/j.epsl.2012.06.059
SN  - 0012-821X
VL  - 351
SP  - 158
EP  - 170
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Andersen, Jane Lund
A1  - Egholm, D. L.
A1  - Knudsen, M. F.
A1  - Jansen, John D.
A1  - Nielsen, S. B.
T1  - The periglacial engine of mountain erosion - Part 1: Rates of frost cracking and frost creep
JF  - Earth surface dynamics
N2  - With accelerating climate cooling in the late Cenozoic, glacial and periglacial erosion became more widespread on the surface of the Earth. The resultant shift in erosion patterns significantly changed the large-scale morphology of many mountain ranges worldwide. Whereas the glacial fingerprint is easily distinguished by its characteristic fjords and U-shaped valleys, the periglacial fingerprint is more subtle but potentially prevails in some mid- to high-latitude landscapes. Previous models have advocated a frost-driven control on debris production at steep headwalls and glacial valley sides. Here we investigate the important role that periglacial processes also play in less steep parts of mountain landscapes. Understanding the influences of frost-driven processes in low-relief areas requires a focus on the consequences of an accreting soil mantle, which characterises such surfaces. We present a new model that quantifies two key physical processes: frost cracking and frost creep, as a function of both temperature and sediment thickness. Our results yield new insights into how climate and sediment transport properties combine to scale the intensity of periglacial processes. The thickness of the soil mantle strongly modulates the relation between climate and the intensity of mechanical weathering and sediment flux. Our results also point to an offset between the conditions that promote frost cracking and those that promote frost creep, indicating that a stable climate can provide optimal conditions for only one of those processes at a time. Finally, quantifying these relations also opens up the possibility of including periglacial processes in large-scale, long-term landscape evolution models, as demonstrated in a companion paper.
Y1  - 2015
U6  - https://doi.org/10.5194/esurf-3-447-2015
SN  - 2196-6311
SN  - 2196-632X
VL  - 3
IS  - 4
SP  - 447
EP  - 462
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Westermann, Sebastian
A1  - Tronicke, Jens
A1  - Strauss, Jens
A1  - Schirrmeister, Lutz
A1  - Biskaborn, Boris
A1  - Liebner, Susanne
A1  - Maksimov, Georgii
A1  - Grigoriev, Mikhail N.
A1  - Grosse, Guido
T1  - Thermokarst lake to lagoon transitions in Eastern Siberia
BT  - do submerged taliks refreeze?
JF  - Journal of geophysical research : Earth surface
N2  - As the Arctic coast erodes, it drains thermokarst lakes, transforming them into lagoons, and, eventually, integrates them into subsea permafrost. Lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions. In this research, borehole data, electrical resistivity surveying, and modeling of heat and salt diffusion were carried out at Polar Fox Lagoon on the Bykovsky Peninsula, Siberia. Polar Fox Lagoon is a seasonally isolated water body connected to Tiksi Bay through a channel, leading to hypersaline waters under the ice cover. The boreholes in the center of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik, a thin ice-bearing permafrost layer, and unfrozen ground. The bathymetry showed that most of the lagoon had bedfast ice in spring. In bedfast ice areas, the electrical resistivity profiles suggested that an unfrozen saline layer was underlain by a thick layer of refrozen talik. The modeling showed that thermokarst lake taliks can refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0 degrees C. This occurs, because the top-down chemical degradation of newly formed ice-bearing permafrost is slower than the refreezing of the talik. Hence, lagoons may precondition taliks with a layer of ice-bearing permafrost before encroachment by the sea, and this frozen layer may act as a cap on gas migration out of the underlying talik.
KW  - thermokarst lake
KW  - talik
KW  - lagoon
KW  - subsea permafrost
KW  - salt diffusion
KW  - Siberia
Y1  - 2020
U6  - https://doi.org/10.1029/2019JF005424
SN  - 2169-9003
SN  - 2169-9011
VL  - 125
IS  - 10
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Angelopoulos, Michael
A1  - Westermann, Sebastian
A1  - Overduin, Pier Paul
A1  - Faguet, Alexey
A1  - Olenchenko, Vladimir
A1  - Grosse, Guido
A1  - Grigoriev, Mikhail N.
T1  - Heat and salt flow in subsea permafrost modeled with CryoGRID2
JF  - Journal of geophysical research : Earth surface
N2  - Thawing of subsea permafrost can impact offshore infrastructure, affect coastal erosion, and release permafrost organic matter. Thawing is usually modeled as the result of heat transfer, although salt diffusion may play an important role in marine settings. To better quantify nearshore subsea permafrost thawing, we applied the CryoGRID2 heat diffusion model and coupled it to a salt diffusion model. We simulated coastline retreat and subsea permafrost evolution as it develops through successive stages of a thawing sequence at the Bykovsky Peninsula, Siberia. Sensitivity analyses for seawater salinity were performed to compare the results for the Bykovsky Peninsula with those of typical Arctic seawater. For the Bykovsky Peninsula, the modeled ice-bearing permafrost table (IBPT) for ice-rich sand and an erosion rate of 0.25m/year was 16.7 m below the seabed 350m offshore. The model outputs were compared to the IBPT depth estimated from coastline retreat and electrical resistivity surveys perpendicular to and crossing the shoreline of the Bykovsky Peninsula. The interpreted geoelectric data suggest that the IBPT dipped to 15-20m below the seabed at 350m offshore. Both results suggest that cold saline water forms beneath grounded ice and floating sea ice in shallow water, causing cryotic benthic temperatures. The freezing point depression produced by salt diffusion can delay or prevent ice formation in the sediment and enhance the IBPT degradation rate. Therefore, salt diffusion may facilitate the release of greenhouse gasses to the atmosphere and considerably affect the design of offshore and coastal infrastructure in subsea permafrost areas.
KW  - subsea permafrost
KW  - salt diffusion
KW  - CryoGRID
KW  - Lena Delta
KW  - Bykovsky Peninsula
KW  - electrical resistivity
Y1  - 2019
U6  - https://doi.org/10.1029/2018JF004823
SN  - 2169-9003
SN  - 2169-9011
VL  - 124
IS  - 4
SP  - 920
EP  - 937
PB  - American Geophysical Union
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Angermann, Lisa
A1  - Jackisch, Conrad
A1  - Allroggen, Niklas
A1  - Sprenger, Matthias
A1  - Zehe, Erwin
A1  - Tronicke, Jens
A1  - Weiler, Markus
A1  - Blume, Theresa
T1  - Form and function in hillslope hydrology: characterization of subsurface flow based on response observations
JF  - Hydrology and earth system sciences : HESS
N2  - The phrase form and function was established in architecture and biology and refers to the idea that form and functionality are closely correlated, influence each other, and co-evolve. We suggest transferring this idea to hydrological systems to separate and analyze their two main characteristics: their form, which is equivalent to the spatial structure and static properties, and their function, equivalent to internal responses and hydrological behavior. While this approach is not particularly new to hydrological field research, we want to employ this concept to explicitly pursue the question of what information is most advantageous to understand a hydrological system. We applied this concept to subsurface flow within a hillslope, with a methodological focus on function: we conducted observations during a natural storm event and followed this with a hillslope-scale irrigation experiment. The results are used to infer hydrological processes of the monitored system. Based on these findings, the explanatory power and conclusiveness of the data are discussed. The measurements included basic hydrological monitoring methods, like piezometers, soil moisture, and discharge measurements. These were accompanied by isotope sampling and a novel application of 2-D time-lapse GPR (ground-penetrating radar). The main finding regarding the processes in the hillslope was that preferential flow paths were established quickly, despite unsaturated conditions. These flow paths also caused a detectable signal in the catchment response following a natural rainfall event, showing that these processes are relevant also at the catchment scale. Thus, we conclude that response observations (dynamics and patterns, i.e., indicators of function) were well suited to describing processes at the observational scale. Especially the use of 2-D time-lapse GPR measurements, providing detailed subsurface response patterns, as well as the combination of stream-centered and hillslope-centered approaches, allowed us to link processes and put them in a larger context. Transfer to other scales beyond observational scale and generalizations, however, rely on the knowledge of structures (form) and remain speculative. The complementary approach with a methodological focus on form (i.e., structure exploration) is presented and discussed in the companion paper by Jackisch et al. (2017).
Y1  - 2017
U6  - https://doi.org/10.5194/hess-21-3727-2017
SN  - 1027-5606
SN  - 1607-7938
VL  - 21
SP  - 3727
EP  - 3748
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Anoop, A.
A1  - Prasad, S.
A1  - Basavaiah, Nathani
A1  - Brauer, Achim
A1  - Shahzad, F.
A1  - Deenadayalan, K.
T1  - Tectonic versus climate influence on landscape evolution: A case study from the upper Spiti valley, NW Himalaya
JF  - Geomorphology : an international journal on pure and applied geomorphology
N2  - We have undertaken structural, geomorphological, and morphometric analyses to investigate the role of tectonism and climate in the landscape evolution in the upper Spiti valley, NW Himalayas. Geomorphometric analyses coupled with field investigations reveal active tectonic deformation in the Spiti region. The calculated geomorphic indices (steepness, concavity and Hack) demonstrate uplift/subsidence along the Kaurik-Chango fault, whereas transverse topographic index (T-index) reveals basin tilting associated with active faulting near Hansa and Lingti valley. Investigation of well-dated Mane palaeolake sediments also provides evidence of regional tectonic instability. Four episodes (ca. 7.8, 7.4, 6.5 and 6.1 cal ka) of neotectonic activity have been identified during the period of the lake's existence. We have also compiled data on the regional climate variability and compared it with the age of the Mane palaeo-landslide. Our results indicate that the landslide occurred towards the end of the early Holocene intensified monsoon phase and is located near an active fault. Our data on regional tectonic instability and the coincidences of modern and palaeo-landslides with zones of active deformation suggest that tectonism is an important factor governing landscape stability in the Spiti region.
KW  - Geomorphic indices
KW  - Holocene
KW  - Palaeo-lake sediments
KW  - Palaeo-landslides
KW  - Monsoon
Y1  - 2012
U6  - https://doi.org/10.1016/j.geomorph.2011.10.028
SN  - 0169-555X
VL  - 145
IS  - 4
SP  - 32
EP  - 44
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Anoop, Ambili
A1  - Prasad, S.
A1  - Plessen, Birgit
A1  - Basavaiah, Nathani
A1  - Gaye, B.
A1  - Naumann, R.
A1  - Menzel, P.
A1  - Weise, S.
A1  - Brauer, Achim
T1  - Palaeoenvironmental implications of evaporative gaylussite crystals from Lonar Lake, central India
JF  - Journal of quaternary science
N2  - We have undertaken petrographic, mineralogical, geochemical and isotopic investigations on carbonate minerals found within a 10-m-long core from Lonar Lake, central India, with the aim of evaluating their potential as palaeoenvironmental proxies. The core encompasses the entire Holocene and is the first well-dated high-resolution record from central India. While calcite and/or aragonite were found throughout the core, the mineral gaylussite was found only in two specific intervals (46303890 and 2040560 cal a BP). Hydrochemical and isotope data from inflowing streams and lake waters indicate that evaporitic processes play a dominant role in the precipitation of carbonates within this lake. Isotopic (18O and 13C) studies on the evaporative gaylussite crystals and residual bulk carbonates (calcite) from the long core show that evaporation is the major control on 18O enrichment in both the minerals. However, in case of 13C additional mechanisms, for example methanogenesis (gaylussite) and phytoplankton productivity (calcium carbonate), play an additional important role in some intervals. We also discuss the relevance of our investigation for palaeoclimate reconstruction and late Holocene monsoon variability.
KW  - evaporites
KW  - gaylussite
KW  - isotopes
KW  - Lonar Lake
KW  - monsoon
Y1  - 2013
U6  - https://doi.org/10.1002/jqs.2625
SN  - 0267-8179
VL  - 28
IS  - 4
SP  - 349
EP  - 359
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Anoop, Ambili
A1  - Prasad, Sushma
A1  - Krishnan, R.
A1  - Naumann, Rudolf
A1  - Dulski, Peter
T1  - Intensified monsoon and spatiotemporal changes in precipitation patterns in the NW Himalaya during the early-mid holocene
JF  - Quaternary international : the journal of the International Union for Quaternary Research
N2  - We have undertaken a high resolution palaeoclimate reconstruction on radiocarbon dated palaeolake sediments from the Spiti valley, NW Himalaya. This site lies in the climatically sensitive winter westerlies and Indian Summer Monsoon (ISM) transitional regime and provides an opportunity to reconstruct the precipitation seasonality, and extreme precipitation events that are characterised by intensified erosion. The lake sediments reveal distinct lithofacies that provide evidence of changes in depositional environment and climate during early to mid Holocene (8.7-6.1 cal ka BP). We have identified three stages during the period of lake's existence: the Stage I (8.7-7.6 cal ka BP) is marked by lake establishment; Stage II (similar to 7.6-6.8 cal ka BP) by sustained cooler periods and weakened summer monsoon, and Stage III (similar to 6.8-6.1 cal ka BP) by a shift from colder to warmer climate with stronger ISM. We have identified several short term cooler periods at ca. 8.7, 8.5, 8.3 and 7.2-6.9 cal ka BP. Based on an overview of regional climate records we show that there is an abrupt switch in precipitation seasonality ca. 6.8 cal ka BP that is followed by the onset of the intensified monsoon in the NW Himalaya. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.
Y1  - 2013
U6  - https://doi.org/10.1016/j.quaint.2013.08.014
SN  - 1040-6182
VL  - 313
SP  - 74
EP  - 84
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Anthymidis, Marios
A1  - Papazachos, Costas
A1  - Ohrnberger, Matthias
A1  - Savvaidis, Alexandros
A1  - Theodoulidis, Nikos
A1  - Oikonomou, Dimitris
T1  - Evaluation of the 3D near-surface velocity structure in an urban environment from ambient noise array tomography: the case of the city of Thessaloniki (Northern Greece)
JF  - The bulletin of the Seismological Society of America : BSSA
N2  - We examine the implementation of ambient noise array tomography in an urban environment to assess the 3D near-surface shear wave velocity (VS) structure at an intermediate spatial scale (-1 km2, depth range 200-300 m). The application employs cross correlation traces of vertical component ambient noise recordings from a local network installed in Thessaloniki city (Northern Greece), allowing the determination of Rayleigh wave travel times for the frequency range of 1.5-14 Hz. The results confirm the presence of a complex subsurface with strong lateral variations in the geology, with travel times varying up to almost one order of magnitude. A surface wave travel time tomography approach was applied for each frequency to determine the spatial variability of the group velocity, involving the use of approximate Fresnel volumes, as well as damping and spatial smoothing constraints to stabilize the results. We also employed an interfrequency smoothing scheme to obtain smooth but data-compatible dispersion curves at the cost of inverting all travel time data simultaneously. Following the application of several quality cutoff criteria, we reconstructed local group slowness dispersion curves for a predefined tomographic grid in the study area. The final 3D velocity model was determined by a modified Monte Carlo inversion of these dispersion curves and the spatial integration of the obtained 1D VS profiles. Different model parameterizations were tested for the inversion to determine the optimal datafit. The final 3D velocity model is in a very good agreement with the local geology, previous larger scale studies, and other geophysical surveys, providing additional structural constraints (such as hidden fault identification) for the complex sedimentary deposits and bedrock formation in Thessaloniki, up to the depth of - 250-300 m. The introduction of the aforementioned modifications to the ambient noise array tomography suggests that it can be efficiently adjusted and employed as a reliable tool for imaging the 3D seismic structure in urban environments with complex geology.
Y1  - 2022
U6  - https://doi.org/10.1785/0120220004
SN  - 0037-1106
SN  - 1943-3573
VL  - 112
IS  - 5
SP  - 2587
EP  - 2605
PB  - Seismological Society of America
CY  - El Cerito, Calif.
ER  - 
TY  - JOUR
A1  - Apaestegui, James
A1  - Cruz, Francisco William
A1  - Vuille, Mathias
A1  - Fohlmeister, Jens Bernd
A1  - Carlo Espinoza, Jhan
A1  - Sifeddine, Abdelfettah
A1  - Strikis, Nicolas
A1  - Guyot, Jean Loup
A1  - Ventura, Roberto
A1  - Cheng, Hai
A1  - Edwards, R. Lawrence
T1  - Precipitation changes over the eastern Bolivian Andes inferred from speleothem (delta O-18) records for the last 1400 years
JF  - Earth & planetary science letters
N2  - Here we present high-resolution delta O-18 records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in delta O-18 during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative delta O-18 values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian delta O-18 record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased delta O-18 values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the delta O-18 reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA.
KW  - speleothems
KW  - stable isotopes
KW  - MCA
KW  - LIA
KW  - Bolivia
KW  - South American Monsoon
Y1  - 2018
U6  - https://doi.org/10.1016/j.epsl.2018.04.048
SN  - 0012-821X
SN  - 1385-013X
VL  - 494
SP  - 124
EP  - 134
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aramayo, Alejandro
A1  - Guzman, Silvina
A1  - Hongn, Fernando D.
A1  - del Papa, Cecilia
A1  - Montero-Lopez, Carolina
A1  - Sudo, Masafumi
T1  - A Middle Miocene (13.5-12 Ma) deformational event constrained by volcanism along the Puna-Eastern Cordillera border, NW Argentina
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - The features of Middle Miocene deposits in the Puna-Eastern Cordillera transition (Valles Calchaquies) indicate that Cenozoic deformation, sedimentation and volcanism follow a complex spatiotemporal relationship. The intense volcanic activity recorded in the eastern Puna border between 14 and 11.5 Ma coincides with the occurrence of one of the most important deformation events of the Neogene tectonic evolution in the region. Studies performed across the Puna-Eastern Cordillera transition show different relationships between volcanic deposits of ca. 13.5-12.1 Ma and the Oligocene-Miocene Angastaco Formation. In this paper we describe the ash-flow tuff deposits which are the first of this type found concordant in the sedimentary fill of Valles Calchaquies. Several analyses performed on these pyroclastic deposits allow a correlation to be made with the Alto de Las Lagunas Ignimbrite (ca. 13.5 Ma) of the Pucarilla-Cerro Tipillas Volcanic Complex located in the Puna. Outcrops of the ca. 13.5 Ma pyroclastic deposits are recognised within the Puna and the Valle Calchaqui. However, in the southern prolongation of the Valle de Hualfin (Tiopampa-Pucarilla depression) that separates the Puna from the Valle Calchaqui at these latitudes, these deposits are partially eroded and buried, and thus their occurrence is recorded only by abundant volcanic clasts included in conglomerates of the Angastaco Formation. The sedimentation of the Angastaco Formation was aborted at ca. 12 Ma in the Tiopampa-Pucarilla depression by the Pucarilla Ignimbrite, which unconformably covers the synorogenic units. On the contrary, in the Valle Calchaqui the sedimentation of the Angastaco Formation continued until the Late Miocene. The different relationships between the Miocene Angastaco Formation and the ignimbrites with ages of ca. 13.5 and ca. 12 Ma reveal that in this short period (-1.5 m.y.) a significant deformation event took place and resulted in marked palaeogeographic changes, as evidenced by stratigraphic-sedimentological and chronological records in the Angastaco Formation. (C) 2017 Elsevier B.V. All rights reserved.
KW  - Angastaco Formation
KW  - Miocene deformation
KW  - Alto de Las Lagunas Ignimbrite
KW  - Luingo caldera
KW  - Foreland
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2017.02.018
SN  - 0040-1951
SN  - 1879-3266
VL  - 703
SP  - 9
EP  - 22
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Araya Vargas, Jaime Andrés
A1  - Meqbel, Naser M.
A1  - Ritter, Oliver
A1  - Brasse, H.
A1  - Weckmann, Ute
A1  - Yanez, Gonzalo
A1  - Godoy, B.
T1  - Fluid Distribution in the Central Andes Subduction Zone Imaged With Magnetotellurics
JF  - Journal of geophysical research : Solid earth
N2  - We present a model of the electrical resistivity structure of the lithosphere in the Central Andes between 20 degrees and 24 degrees S from 3-D inversion of 56 long-period magnetotelluric sites. Our model shows a complex resistivity structure with significant variability parallel and perpendicular to the trench direction. The continental forearc is characterized mainly by high electrical resistivity (>1,000m), suggesting overall low volumes of fluids. However, low resistivity zones (LRZs, <5m) were found in the continental forearc below areas where major trench-parallel faults systems intersect NW-SE transverse faults. Forearc LRZs indicate circulation and accumulation of fluids in highly permeable fault zones. The continental crust along the arc shows three distinctive resistivity domains, which coincide with segmentation in the distribution of volcanoes. The northern domain (20 degrees-20.5 degrees S) is characterized by resistivities >1,000m and the absence of active volcanism, suggesting the presence of a low-permeability block in the continental crust. The central domain (20.5 degrees-23 degrees S) exhibits a number of LRZs at varying depths, indicating different levels of a magmatic plumbing system. The southern domain (23 degrees-24 degrees S) is characterized by resistivities >1,000m, suggesting the absence of large magma reservoirs below the volcanic chain at crustal depths. Magma reservoirs located below the base of the crust or in the backarc may fed active volcanism in the southern domain. In the subcontinental mantle, the model exhibits LRZs in the forearc mantle wedge and above clusters of intermediate-depth seismicity, likely related to fluids produced by serpentinization of the mantle and eclogitization of the slab, respectively.
KW  - Subduction Zone
KW  - Central Andes
KW  - Magnetotellurics
KW  - Seismotectonic segmentation
KW  - Fluid processes
Y1  - 2019
U6  - https://doi.org/10.1029/2018JB016933
SN  - 2169-9313
SN  - 2169-9356
VL  - 124
IS  - 4
SP  - 4017
EP  - 4034
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Arboleda-Zapata, Mauricio
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Grosse, Guido
A1  - Jones, Benjamin M.
A1  - Tronicke, Jens
T1  - Exploring the capabilities of electrical resistivity tomography to study subsea permafrost
JF  - The Cryosphere
N2  - Sea level rise and coastal erosion have inundated large areas of Arctic permafrost. Submergence by warm and saline waters increases the rate of inundated permafrost thaw compared to sub-aerial thawing on land. Studying the contact between the unfrozen and frozen sediments below the seabed, also known as the ice-bearing permafrost table (IBPT), provides valuable information to understand the evolution of sub-aquatic permafrost, which is key to improving and understanding coastal erosion prediction models and potential greenhouse gas emissions. In this study, we use data from 2D electrical resistivity tomography (ERT) collected in the nearshore coastal zone of two Arctic regions that differ in their environmental conditions (e.g., seawater depth and resistivity) to image and study the subsea permafrost. The inversion of 2D ERT data sets is commonly performed using deterministic approaches that favor smoothed solutions, which are typically interpreted using a user-specified resistivity threshold to identify the IBPT position. In contrast, to target the IBPT position directly during inversion, we use a layer-based model parameterization and a global optimization approach to invert our ERT data. This approach results in ensembles of layered 2D model solutions, which we use to identify the IBPT and estimate the resistivity of the unfrozen and frozen sediments, including estimates of uncertainties. Additionally, we globally invert 1D synthetic resistivity data and perform sensitivity analyses to study, in a simpler way, the correlations and influences of our model parameters. The set of methods provided in this study may help to further exploit ERT data collected in such permafrost environments as well as for the design of future field experiments.
Y1  - 2022
U6  - https://doi.org/10.5194/tc-16-4423-2022
SN  - 1994-0424
VL  - 16
SP  - 4423
EP  - 4445
PB  - Copernicus
CY  - Katlenburg-Lindau
ER  - 
TY  - JOUR
A1  - Arboleda-Zapata, Mauricio
A1  - Guillemoteau, Julien
A1  - Tronicke, Jens
T1  - A comprehensive workflow to analyze ensembles of globally inverted 2D electrical resistivity models
JF  - Journal of applied geophysics
N2  - Electrical resistivity tomography (ERT) aims at imaging the subsurface resistivity distribution and provides valuable information for different geological, engineering, and hydrological applications. To obtain a subsurface resistivity model from measured apparent resistivities, stochastic or deterministic inversion procedures may be employed. Typically, the inversion of ERT data results in non-unique solutions; i.e., an ensemble of different models explains the measured data equally well. In this study, we perform inference analysis of model ensembles generated using a well-established global inversion approach to assess uncertainties related to the nonuniqueness of the inverse problem. Our interpretation strategy starts by establishing model selection criteria based on different statistical descriptors calculated from the data residuals. Then, we perform cluster analysis considering the inverted resistivity models and the corresponding data residuals. Finally, we evaluate model uncertainties and residual distributions for each cluster. To illustrate the potential of our approach, we use a particle swarm optimization (PSO) algorithm to obtain an ensemble of 2D layer-based resistivity models from a synthetic data example and a field data set collected in Loon-Plage, France. Our strategy performs well for both synthetic and field data and allows us to extract different plausible model scenarios with their associated uncertainties and data residual distributions. Although we demonstrate our workflow using 2D ERT data and a PSObased inversion approach, the proposed strategy is general and can be adapted to analyze model ensembles generated from other kinds of geophysical data and using different global inversion approaches.
KW  - Near-surface geophysics
KW  - Electrical resistivity tomography
KW  - Non-uniqueness
KW  - Global inversion
KW  - Particle swarm optimization
KW  - Ensemble
KW  - analysis
Y1  - 2021
U6  - https://doi.org/10.1016/j.jappgeo.2021.104512
SN  - 0926-9851
SN  - 1879-1859
VL  - 196
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Arcay, Diane
A1  - Doin, Marie Pierre
A1  - Tric, Emmanuel
A1  - Bousquet, Romain
A1  - de Capitani, Christian
T1  - Overriding plate thinning in subduction zones : localized convection induced by slab dehydration
N2  - In subduction zones, many observations indicate that the backarc thermal state is particularly hot and that the upper lithosphere is thin, even if no recent extension episode has occurred. This might result from free thermal convection favored by low viscosities in the hydrated mantle wedge. We perform 2-D numerical experiments of the convective mantle wedge interaction with both the downgoing slab and the overriding plate to test this hypothesis, explore its physical mechanism, and assess its dependencies on some relevant rock properties. Water transfers across the subducting plate and the mantle wedge are explicitly modeled by including in the calculation realistic hydration/ dehydration reaction boundaries for a water-saturated mantle and oceanic crust. The rheology is non-Newtonian and temperature-, pressure-, and water content-dependent. For low strength reduction associated to water content, the upper plate is locally thinned by an enhanced corner flow. For larger strength reductions, small convection cells rapidly thin the upper plate ( in less than 15 Myr) over the area in the overriding lithosphere hydrated by slab-derived water fluxes. As a result, the thinned region location depends on the subducting plate thermal state, and it increases with high convergence rates and low subduction dip angles. Other simulations are performed to test the sole effect of hydrous rock weakening on the upper plate/mantle convective interaction. They show that the thinning process is not influenced by the corner flow, but develops at the favor of a decoupling level induced by the formation of hydroxylated minerals inside the hydrated lithosphere. The erosion mechanism identified in these simulations allows us to explain the characteristic duration of erosion as a function of the hydrous strength reduction. We find that the presence of amphibole in the upper lithosphere in significant proportions is required down to a temperature of about 980 degrees C, corresponding to an initial depth of similar to 70 km, to strongly decrease the strength of the base of the lithosphere and trigger a rapid erosion (< 15 Myr).
Y1  - 2006
UR  - http://g-cubed.org/
U6  - https://doi.org/10.1029/2005gc001061
SN  - 1525-2027
ER  - 
TY  - JOUR
A1  - Ariagno, Coline
A1  - Le Bouteiller, Caroline
A1  - van der Beek, Pieter A.
A1  - Klotz, Sébastien
T1  - Sediment export in marly badland catchments modulated by frost-cracking intensity, Draix–Bléone Critical Zone Observatory, SE France
JF  - Earth surface dynamics : ESURF ; an interactive open access journal of the European Geosciences Union
N2  - At the interface between the lithosphere and the atmosphere, the critical zone records the complex interactions between erosion, climate, geologic substrate, and life and can be directly monitored. Long data records (30 consecutive years for sediment yields) collected in the sparsely vegetated, steep, and small marly badland catchments of the Draix-Bleone Critical Zone Observatory (CZO), SE France, allow analyzing potential climatic controls on regolith dynamics and sediment export. Although widely accepted as a first-order control, rainfall variability does not fully explain the observed interannual variability in sediment export. Previous studies in this area have suggested that frost-weathering processes could drive regolith production and potentially modulate the observed pattern of sediment export. Here, we define sediment export anomalies as the residuals from a predictive model with annual rainfall intensity above a threshold as the control. We then use continuous soil temperature data recorded at different locations over multiple years to highlight the role of different frost-weathering processes (i.e., ice segregation versus volumetric expansion) in regolith production. Several proxies for different frost-weathering processes have been calculated from these data and compared to the sediment export anomalies, with careful consideration of field data quality. Our results suggest that frost-cracking intensity (linked to ice segregation) can explain about half (47 %-64 %) of the sediment export anomalies. In contrast, the number of freeze-thaw cycles (linked to volumetric expansion) has only a minor impact on catchment sediment response. The time spent below 0 degrees C also correlates well with the sediment export anomalies and requires fewer field data to be calculated than the frost-cracking intensity. Thus, frost-weathering processes modulate sediment export by controlling regolith production in these catchments and should be taken into account when building predictive models of sediment export from these badlands under a changing climate.
Y1  - 2022
U6  - https://doi.org/10.5194/esurf-10-81-2022
SN  - 2196-6311
SN  - 2196-632X
VL  - 10
IS  - 1
SP  - 81
EP  - 96
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Armbruster, Thomas
A1  - Bermance, V.
A1  - Zebec, M.
A1  - Oberhänsli, Roland
T1  - Titanium and iron poor zincohögbomite-16H, Zn14(al,Fe3+,Ti,Mg)8Al24O62(OH)2, from Nezilovo, Macedonia: occurrence and crystal structure of a new polysome
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Armstrong, Michael R.
A1  - Radousky, Harry B.
A1  - Austin, Ryan A.
A1  - Tschauner, Oliver
A1  - Brown, Shaughnessy
A1  - Gleason, Arianna E.
A1  - Goldman, Nir
A1  - Granados, Eduardo
A1  - Grivickas, Paulius
A1  - Holtgrewe, Nicholas
A1  - Kroonblawd, Matthew P.
A1  - Lee, Hae Ja
A1  - Lobanov, Sergey S.
A1  - Nagler, Bob
A1  - Nam, Inhyuk
A1  - Prakapenka, Vitali
A1  - Prescher, Clemens
A1  - Reed, Evan J.
A1  - Stavrou, Elissaios
A1  - Walter, Peter
A1  - Goncharov, Alexander F.
A1  - Belof, Jonathan L.
T1  - Highly ordered graphite (HOPG) to hexagonal diamond (lonsdaleite) phase transition observed on picosecond time scales using ultrafast x-ray diffraction
JF  - Journal of applied physics
N2  - The response of rapidly compressed highly oriented pyrolytic graphite (HOPG) normal to its basal plane was investigated at a pressure of & SIM;80 GPa. Ultrafast x-ray diffraction using & SIM;100 fs pulses at the Materials Under Extreme Conditions sector of the Linac Coherent Light Source was used to probe the changes in crystal structure resulting from picosecond timescale compression at laser drive energies ranging from 2.5 to 250 mJ. A phase transformation from HOPG to a highly textured hexagonal diamond structure is observed at the highest energy, followed by relaxation to a still highly oriented, but distorted graphite structure following release. We observe the formation of a highly oriented lonsdaleite within 20 ps, subsequent to compression. This suggests that a diffusionless martensitic mechanism may play a fundamental role in phase transition, as speculated in an early work on this system, and more recent static studies of diamonds formed in impact events. Published by AIP Publishing.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0085297
SN  - 0021-8979
SN  - 1089-7550
VL  - 132
IS  - 5
PB  - AIP Publishing
CY  - Melville
ER  - 
TY  - JOUR
A1  - Arnous, Ahmad
A1  - Zeckra, Martin
A1  - Venerdini, Agostina
A1  - Alvarado, Patricia
A1  - Arrowsmith, Ramón
A1  - Guillemoteau, Julien
A1  - Landgraf, Angela
A1  - Gutiérrez, Adolfo Antonio
A1  - Strecker, Manfred
T1  - Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)
JF  - Lithosphere
N2  - Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.
Y1  - 2019
U6  - https://doi.org/10.2113/2020/8888588
SN  - 1947-4253
SN  - 1941-8264
VL  - 2020
IS  - 1
SP  - 1
EP  - 25
PB  - GSA
CY  - Boulder, Colo.
ER  - 
TY  - JOUR
A1  - Arrowsmith, J. Ramon
A1  - Crosby, Christopher J.
A1  - Korzhenkov, Andrey M.
A1  - Mamyrov, Ernest
A1  - Povolotskaya, Irina
A1  - Guralnik, Benny
A1  - Landgraf, Angela
T1  - Surface rupture of the 1911 Kebin (Chon-Kemin) earthquake, Northern Tien Shan, Kyrgyzstan
JF  - Seismicity, fault rupture and earthquake hazards in slowly deforming regions
N2  - The 1911 Chon-Kemin (Kebin) earthquake culminated c. 30 years of remarkable earthquakes in the northern Tien Shan (Kyrgyzstan and Kazakhstan). Building on prior mapping of the event, we traced its rupture in the field and measured more than 50 offset landforms. Cumulative fault rupture length is >155-195 km along 13 fault patches comprising six sections. The patches are separated by changes of dip magnitude or dip direction, or by 4-10 km-wide stepovers. One <40 km section overlaps and is parallel to the main north-dipping rupture but is 7 km north and dips opposite (south). Both ends of the rupture are along mountain front thrust faults demonstrating late Quaternary activity. We computed the moment from each fault patch using the surface fault traces, dip inferred from the traces, 20 km seismogenic thickness, rigidity of 3.3 x 10(10) N m(-2) and dip slip converted from our observations of the largely reverse sense of motion vertical offsets. The discontinuous patches with c. 3-4 m average slip and peak slip of <14 m yield a seismic moment of 4.6 x 10(20) Nm (M-w 7.78) to 7.4 x 10(20) Nm (M-w 7.91). The majority of moment was released along the inner eastern rupture segments. This geological moment is lower by a factor of 1.5 from that determined from teleseismic data.
Y1  - 2016
SN  - 978-1-86239-745-3
SN  - 978-1-86239-964-8
U6  - https://doi.org/10.1144/SP432.10
SN  - 0305-8719
VL  - 432
SP  - 233
EP  - 253
PB  - The Geological Society
CY  - London
ER  - 
TY  - JOUR
A1  - Arrowsmith, J. Ramón
A1  - Strecker, Manfred
T1  - Seismotectonic range-front segmentation and mountain-belt growth in the Pamir-Alai region, Kyrgyzstan (India- Eurasia collision zone)
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Asari, Seiki
A1  - Wardinski, Ingo
T1  - Interannual fluctuations of the core angular momentum inferred from geomagnetic field models
JF  - Magnetic Fields in the Solar System : Planets, Moons and Solar Wind Interactions
Y1  - 2018
SN  - 978-3-319-64292-5
SN  - 978-3-319-64291-8
U6  - https://doi.org/10.1007/978-3-319-64292-5_4
SN  - 0067-0057
VL  - 448
SP  - 111
EP  - 123
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Aseev, Nikita
A1  - Shprits, Yuri
A1  - Wang, Dedong
A1  - Wygant, John
A1  - Drozdov, Alexander
A1  - Kellerman, Adam C.
A1  - Reeves, Geoffrey D.
T1  - Transport and loss of ring current electrons inside geosynchronous orbit during the 17 March 2013 storm
JF  - Journal of geophysical research : Space physics
N2  - Ring current electrons (1–100 keV) have received significant attention in recent decades, but many questions regarding their major transport and loss mechanisms remain open. In this study, we use the four‐dimensional Versatile Electron Radiation Belt code to model the enhancement of phase space density that occurred during the 17 March 2013 storm. Our model includes global convection, radial diffusion, and scattering into the Earth's atmosphere driven by whistler‐mode hiss and chorus waves. We study the sensitivity of the model to the boundary conditions, global electric field, the electric field associated with subauroral polarization streams, electron loss rates, and radial diffusion coefficients. The results of the code are almost insensitive to the model parameters above 4.5 RERE, which indicates that the general dynamics of the electrons between 4.5 RE and the geostationary orbit can be explained by global convection. We found that the major discrepancies between the model and data can stem from the inaccurate electric field model and uncertainties in lifetimes. We show that additional mechanisms that are responsible for radial transport are required to explain the dynamics of ≥40‐keV electrons, and the inclusion of the radial diffusion rates that are typically assumed in radiation belt studies leads to a better agreement with the data. The overall effect of subauroral polarization streams on the electron phase space density profiles seems to be smaller than the uncertainties in other input parameters. This study is an initial step toward understanding the dynamics of these particles inside the geostationary orbit.
KW  - ring current electrons
KW  - magnetospheric convection
KW  - ensemble modeling
KW  - inner magnetosphere
KW  - electron transport
KW  - wave-particle interactions
Y1  - 2019
U6  - https://doi.org/10.1029/2018JA026031
SN  - 2169-9380
SN  - 2169-9402
VL  - 124
IS  - 2
SP  - 915
EP  - 933
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Asgarimehr, Milad
A1  - Wickert, Jens
A1  - Reich, Sebastian
T1  - TDS-1 GNSS Reflectometry
BT  - Development and Validation of Forward Scattering Winds
JF  - IEEE journal of selected topics in applied earth observations and remote sensing
N2  - This study presents the development and a systematic evaluation study of GNSS reflectometry wind speeds. After establishing a wind speed retrieval algorithm, UK TechDemoSat-1 (TDS-1) derived winds, from May 2015 to July 2017, are compared to the Advanced Scatterometer (ASCAT). ERA-Interim wind fields of the European Centre for Medium-range Weather Forecasts (ECMWF) and in situ observation from Tropical Atmosphere Ocean buoy array in the Pacific are taken as reference. One-year averaged TDS-1 global winds demonstrate small differences with ECMWF in a majority of areas as well as discuss under- and overestimations. The pioneering TDS-1 winds demonstrate a root-mean-squared error (RMSE) and bias of 2.77 and -0.33 m/s, which are comparable to the RMSE and bias derived by ASCAT winds, as large as 2.31 and 0.25 m/s, respectively. Using buoys measurements as reference, RMSE and bias of 2.23 and -0.03 m/s for TDS-1 as well as 1.40 and -0.68 m/s for ASCAT are obtained. Utilizing rain microwave-infrared estimates of the Tropical Rainfall Measuring Mission, rain-affected observation of both ASCAT and TDS-1 are collected and evaluated. Although ASCAT winds show a significant performance degradation resulting in an RMSE and bias of 3.16 and 1.03 m/s, respectively, during rain condition, TDS-1 shows a more reliable performance with an RMSE and bias of 2.94 and -0.21 m/s, respectively, which indicates the promising capability of GNSS forward scattering for wind retrievals during rain. A decrease in TDS-1-derived bistatic radar cross sections during rain events, at weak winds, is also demonstrated.
KW  - Advanced scatterometer (ASCAT)
KW  - European Centre for Medium-Range Weather Forecasts (ECMWF)
KW  - GNSS forward scatterometry
KW  - GNSS reflectometry
KW  - TechDemoSat-1 (TDS-1)
KW  - wind speed
Y1  - 2018
U6  - https://doi.org/10.1109/JSTARS.2018.2873241
SN  - 1939-1404
SN  - 2151-1535
VL  - 11
IS  - 11
SP  - 4534
EP  - 4541
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Asgarimehr, Milad
A1  - Wickert, Jens
A1  - Reich, Sebastian
T1  - Evaluating impact of rain attenuation on space-borne GNSS reflectometry wind speeds
JF  - Remote Sensing
N2  - The novel space-borne Global Navigation Satellite System Reflectometry (GNSS-R) technique has recently shown promise in monitoring the ocean state and surface wind speed with high spatial coverage and unprecedented sampling rate. The L-band signals of GNSS are structurally able to provide a higher quality of observations from areas covered by dense clouds and under intense precipitation, compared to those signals at higher frequencies from conventional ocean scatterometers. As a result, studying the inner core of cyclones and improvement of severe weather forecasting and cyclone tracking have turned into the main objectives of GNSS-R satellite missions such as Cyclone Global Navigation Satellite System (CYGNSS). Nevertheless, the rain attenuation impact on GNSS-R wind speed products is not yet well documented. Evaluating the rain attenuation effects on this technique is significant since a small change in the GNSS-R can potentially cause a considerable bias in the resultant wind products at intense wind speeds. Based on both empirical evidence and theory, wind speed is inversely proportional to derived bistatic radar cross section with a natural logarithmic relation, which introduces high condition numbers (similar to ill-posed conditions) at the inversions to high wind speeds. This paper presents an evaluation of the rain signal attenuation impact on the bistatic radar cross section and the derived wind speed. This study is conducted simulating GNSS-R delay-Doppler maps at different rain rates and reflection geometries, considering that an empirical data analysis at extreme wind intensities and rain rates is impossible due to the insufficient number of observations from these severe conditions. Finally, the study demonstrates that at a wind speed of 30 m/s and incidence angle of 30 degrees, rain at rates of 10, 15, and 20 mm/h might cause overestimation as large as approximate to 0.65 m/s (2%), 1.00 m/s (3%), and 1.3 m/s (4%), respectively, which are still smaller than the CYGNSS required uncertainty threshold. The simulations are conducted in a pessimistic condition (severe continuous rainfall below the freezing height and over the entire glistening zone) and the bias is expected to be smaller in size in real environments.
KW  - GNSS Reflectometry
KW  - wind speed
KW  - rain effect
KW  - rain attenuation
KW  - DDM simulation
Y1  - 2019
U6  - https://doi.org/10.3390/rs11091048
SN  - 2072-4292
VL  - 11
IS  - 9
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Asgarimehr, Milad
A1  - Zavorotny, Valery
A1  - Wickert, Jens
A1  - Reich, Sebastian
T1  - Can GNSS Reflectometry Detect Precipitation Over Oceans?
JF  - Geophysical research letters
N2  - For the first time, a rain signature in Global Navigation Satellite System Reflectometry (GNSS-R) observations is demonstrated. Based on the argument that the forward quasi-specular scattering relies upon surface gravity waves with lengths larger than several wavelengths of the reflected signal, a commonly made conclusion is that the scatterometric GNSS-R measurements are not sensitive to the surface small-scale roughness generated by raindrops impinging on the ocean surface. On the contrary, this study presents an evidence that the bistatic radar cross section sigma(0) derived from TechDemoSat-1 data is reduced due to rain at weak winds, lower than approximate to 6 m/s. The decrease is as large as approximate to 0.7 dB at the wind speed of 3 m/s due to a precipitation of 0-2 mm/hr. The simulations based on the recently published scattering theory provide a plausible explanation for this phenomenon which potentially enables the GNSS-R technique to detect precipitation over oceans at low winds.
KW  - GNSS Reflectometry
KW  - rain detection
KW  - rain splash
KW  - TDS-1
KW  - ocean surface
KW  - electromagnetic scattering
Y1  - 2018
U6  - https://doi.org/10.1029/2018GL079708
SN  - 0094-8276
SN  - 1944-8007
VL  - 45
IS  - 22
SP  - 12585
EP  - 12592
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ashastina, Kseniia
A1  - Kuzmina, Svetlana
A1  - Rudaya, Natalia
A1  - Troeva, Elena I.
A1  - Schoch, Werner H.
A1  - Roemermann, Christine
A1  - Reinecke, Jennifer
A1  - Otte, Volker
A1  - Savvinov, Grigoriy
A1  - Wesche, Karsten
A1  - Kienast, Frank
T1  - Woodlands and steppes
BT  - Pleistocene vegetation in Yakutia's most continental part recorded in the Batagay permafrost sequence
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - Based on fossil organism remains including plant macrofossils, charcoal, pollen, and invertebrates preserved in syngenetic deposits of the Batagay permafrost sequence in the Siberian Yana Highlands, we reconstructed the environmental history during marine isotope stages (MIS) 6 to 2. Two fossil assemblages, exceptionally rich in plant remains, allowed for a detailed description of the palaeo-vegetation during two climate extremes of the Late Pleistocene, the onset of the last glacial maximum (LGM) and the last interglacial. In addition, altogether 41 assemblages were used to outline the vegetation history since the penultimate cold stage of MIS 6. Accordingly, meadow steppes analogue to modern communities of the phytosociological order Festucetalia lenensis formed the primary vegetation during the Saalian and Weichselian cold stages. Cold-resistant tundra-steppe communities (Carici rupestris-Kobresietea bellardii) as they occur above the treeline today were, in contrast to more northern locations, mostly lacking. During the last interglacial, open coniferous woodland similar to modern larch taiga was the primary vegetation at the site. Abundant charcoal indicates wildfire events during the last interglacial. Zoogenic disturbances of the local vegetation were indicated by the presence of ruderal plants, especially by abundant Urtica dioica, suggesting that the area was an interglacial refugium for large herbivores. Meadow steppes, which formed the primary vegetation during cold stages and provided potentially suitable pastures for herbivores, were a significant constituent of the plant cover in the Yana Highlands also under the full warm stage conditions of the last interglacial. Consequently, meadow steppes occurred in the Yana Highlands during the entire investigated timespan from MIS 6 to MIS 2 documenting a remarkable environmental stability. Thus, the proportion of meadow steppe vegetation merely shifted in response to the respectively prevailing climatic conditions. Their persistence indicates low precipitation and a relatively warm growing season throughout and beyond the late Pleistocene. The studied fossil record also proves that modern steppe occurrences in the Yana Highlands did not establish as late as in the Holocene but instead are relicts of a formerly continuous steppe belt extending from Central Siberia to Northeast Yakutia during the Pleistocene. The persistence of plants and invertebrates characteristic of meadow steppe vegetation in interior Yakutia throughout the late Quaternary indicates climatic continuity and documents the suitability of this region as a refugium also for other organisms of the Pleistocene mammoth steppe including the iconic large herbivores. (C)2018 Elsevier Ltd. All rights reserved.
KW  - Palaeo-vegetation
KW  - Plant macrofossils
KW  - Invertebrates
KW  - Modern analogues
KW  - Pollen
KW  - Ground squirrel nest
KW  - Last cold stage
KW  - Eemian
KW  - Beringia
Y1  - 2018
U6  - https://doi.org/10.1016/j.quascirev.2018.07.032
SN  - 0277-3791
VL  - 196
SP  - 38
EP  - 61
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Astudillo-Sotomayor, Luis
A1  - Jara Muñoz, Julius
A1  - Melnick, Daniel
A1  - Cortés‐Aranda, Joaquín
A1  - Tassara, Andrés
A1  - Strecker, Manfred
T1  - Fast Holocene slip and localized strain along the Liquiñe-Ofqui strike-slip fault system, Chile
JF  - Scientific reports
N2  - In active tectonic settings dominated by strike-slip kinematics, slip partitioning across subparallel faults is a common feature; therefore, assessing the degree of partitioning and strain localization is paramount for seismic hazard assessments. Here, we estimate a slip rate of 18.8 +/- 2.0 mm/year over the past 9.0 +/- 0.1 ka for a single strand of the Liquirie-Ofqui Fault System, which straddles the Main Cordillera in Southern Chile. This Holocene rate accounts for similar to 82% of the trench-parallel component of oblique plate convergence and is similar to million-year estimates integrated over the entire fault system. Our results imply that strain localizes on a single fault at millennial time scale but over longer time scales strain localization is not sustained. The fast millennial slip rate in the absence of historical Mw> 6.5 earthquakes along the Liquine-Ofqui Fault System implies either a component of aseismic slip or Mw similar to 7 earthquakes involving multi-trace ruptures and > 150-year repeat times. Our results have implications for the understanding of strike-slip fault system dynamics within volcanic arcs and seismic hazard assessments.
KW  - Geodynamics
KW  - Geomorphology
KW  - Tectonics
Y1  - 2021
U6  - https://doi.org/10.1038/s41598-021-85036-5
SN  - 2045-2322
VL  - 11
IS  - 1
PB  - Macmillan Publishers Limited, part of Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Atmani, Farid
A1  - Bookhagen, Bodo
A1  - Smith, Taylor
T1  - Measuring vegetation heights and their seasonal changes in the Western Namibian Savanna using spaceborne lidars
JF  - Remote sensing / Molecular Diversity Preservation International (MDPI)
N2  - The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) with its land and vegetation height data product (ATL08), and Global Ecosystem Dynamics Investigation (GEDI) with its terrain elevation and height metrics data product (GEDI Level 2A) missions have great potential to globally map ground and canopy heights. Canopy height is a key factor in estimating above-ground biomass and its seasonal changes; these satellite missions can also improve estimated above-ground carbon stocks. This study presents a novel Sparse Vegetation Detection Algorithm (SVDA) which uses ICESat-2 (ATL03, geolocated photons) data to map tree and vegetation heights in a sparsely vegetated savanna ecosystem. The SVDA consists of three main steps: First, noise photons are filtered using the signal confidence flag from ATL03 data and local point statistics. Second, we classify ground photons based on photon height percentiles. Third, tree and grass photons are classified based on the number of neighbors. We validated tree heights with field measurements (n = 55), finding a root-mean-square error (RMSE) of 1.82 m using SVDA, GEDI Level 2A (Geolocated Elevation and Height Metrics product): 1.33 m, and ATL08: 5.59 m. Our results indicate that the SVDA is effective in identifying canopy photons in savanna ecosystems, where ATL08 performs poorly. We further identify seasonal vegetation height changes with an emphasis on vegetation below 3 m; widespread height changes in this class from two wet-dry cycles show maximum seasonal changes of 1 m, possibly related to seasonal grass-height differences. Our study shows the difficulties of vegetation measurements in savanna ecosystems but provides the first estimates of seasonal biomass changes.
KW  - ICESat-2
KW  - GEDI
KW  - canopy height
KW  - lidar
KW  - savanna
Y1  - 2022
U6  - https://doi.org/10.3390/rs14122928
SN  - 2072-4292
VL  - 14
IS  - 12
SP  - 1
EP  - 20
PB  - MDPI
CY  - Basel, Schweiz
ET  - 12
ER  - 
TY  - JOUR
A1  - Atsawawaranunt, Kamolphat
A1  - Comas-Bru, Laia
A1  - Mozhdehi, Sahar Amirnezhad
A1  - Deininger, Michael
A1  - Harrison, Sandy P.
A1  - Baker, Andy
A1  - Boyd, Meighan
A1  - Kaushal, Nikita
A1  - Ahmad, Syed Masood
A1  - Brahim, Yassine Ait
A1  - Arienzo, Monica
A1  - Bajo, Petra
A1  - Braun, Kerstin
A1  - Burstyn, Yuval
A1  - Chawchai, Sakonvan
A1  - Duan, Wuhui
A1  - Hatvani, Istvan Gabor
A1  - Hu, Jun
A1  - Kern, Zoltan
A1  - Labuhn, Inga
A1  - Lachniet, Matthew
A1  - Lechleitner, Franziska A.
A1  - Lorrey, Andrew
A1  - Perez-Mejias, Carlos
A1  - Pickering, Robyn
A1  - Scroxton, Nick
A1  - Atkinson, Tim
A1  - Ayalon, Avner
A1  - Baldini, James
A1  - Bar-Matthews, Miriam
A1  - Pablo Bernal, Juan
A1  - Breitenbach, Sebastian Franz Martin
A1  - Boch, Ronny
A1  - Borsato, Andrea
A1  - Cai, Yanjun
A1  - Carolin, Stacy
A1  - Cheng, Hai
A1  - Columbu, Andrea
A1  - Couchoud, Isabelle
A1  - Cruz, Francisco
A1  - Demeny, Attila
A1  - Dominguez-Villar, David
A1  - Dragusin, Virgil
A1  - Drysdale, Russell
A1  - Ersek, Vasile
A1  - Finne, Martin
A1  - Fleitmann, Dominik
A1  - Fohlmeister, Jens Bernd
A1  - Frappier, Amy
A1  - Genty, Dominique
A1  - Holzkamper, Steffen
A1  - Hopley, Philip
A1  - Kathayat, Gayatri
A1  - Keenan-Jones, Duncan
A1  - Koltai, Gabriella
A1  - Luetscher, Marc
A1  - Li, Ting-Yong
A1  - Lone, Mahjoor Ahmad
A1  - Markowska, Monika
A1  - Mattey, Dave
A1  - McDermott, Frank
A1  - Moreno, Ana
A1  - Moseley, Gina
A1  - Nehme, Carole
A1  - Novello, Valdir F.
A1  - Psomiadis, David
A1  - Rehfeld, Kira
A1  - Ruan, Jiaoyang
A1  - Sekhon, Natasha
A1  - Sha, Lijuan
A1  - Sholz, Denis
A1  - Shopov, Yavor
A1  - Smith, Andrew
A1  - Strikis, Nicolas
A1  - Treble, Pauline
A1  - Unal-Imer, Ezgi
A1  - Vaks, Anton
A1  - Vansteenberge, Stef
A1  - Veiga-Pires, Cristina
A1  - Voarintsoa, Ny Riavo
A1  - Wang, Xianfeng
A1  - Wong, Corinne
A1  - Wortham, Barbara
A1  - Wurtzel, Jennifer
A1  - Zong, Baoyun
T1  - The SISAL database
BT  - a global resource to document oxygen and carbon isotope records from speleothems
JF  - Earth System Science Data
N2  - Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide "out-of-sample" evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (delta O-18, delta C-13) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data.
Y1  - 2018
U6  - https://doi.org/10.5194/essd-10-1687-2018
SN  - 1866-3508
SN  - 1866-3516
VL  - 10
IS  - 3
SP  - 1687
EP  - 1713
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Awais, Muhammad
A1  - Ahmad, Rafiq
A1  - Khan, Nadeem
A1  - Garapati, Prashanth
A1  - Shahzad, Muhammad
A1  - Afroz, Amber
A1  - Rashid, Umer
A1  - Khan, Sabaz Ali
T1  - Transformation of tomato variety rio grande with drought resistant transcription factor gene ATAF1 and its molecular analysis
JF  - Pakistan Journal of Botany
N2  - Tomato (Solanum lycopersicum L.) being an important vegetable is cultivated and used throughout the world. It not only contributes in fulfilling the basic nutritional requirements of the human body but also has many health benefits due to its rich biochemical composition. However, its production at large scale is hampered by many limiting factors such as biotic and abiotic stresses. Among the different abiotic stresses, drought poses drastic impact on tomato yield. Drought stress is genetically regulated by many transcription factors that not only regulate the stress responsive mechanism but also facilitate the growth and development of tomato plants. NAC is an important stress related transcription factor genes family, and the ATAF1 gene, a member of this family, is involved in ABA signaling and stress response. In this study, tomato variety Rio Drande was transformed with drought resistant ATAF1 gene via Agrobacterium mediated gene transformation method. The ATAF1 gene was first cloned in the pK7WFG2 vector having kanamycin selectable marker and then it was introduced in the Agrobacterium tumefaciens strain GV3101 through heat shock method. The tomato cotyledon and hypocotyl ex-plants of variety "Rio Ggrande" were cultured on callus induction medium (MS + 2.5 mg/L IAA + 2 mg/L BAP). The calli were then infected with Agrobacterium tumefaciens strain GV3101 containing ATAF1 gene and selection was carried out on the kanamycin selectable medium (MS + 100 mg/L Kan), and were regenerated on MS medium with 1 mg/L IAA + 1 mg/L BAP. Out of 216 putative transformed calli, 13 calli were able to regenerate on the selection medium. Of the 13 calli, three transgenic tomato plantlets were recovered, and these were confirmed through PCR analysis for the presence of 432 bp fragment of ATAF1 gene. The transformation protocol reported here can be used to generate drought resistant tomato plants in future.
KW  - Agrobacterium tumefaciens
KW  - drought stress
KW  - NAC transcription factor ATAF1
KW  - plant transformation
KW  - Rio Grande
KW  - tomato
Y1  - 2018
SN  - 0556-3321
SN  - 2070-3368
VL  - 50
IS  - 5
SP  - 1811
EP  - 1820
PB  - Pakistan botanic soc
CY  - Karachi
ER  - 
TY  - JOUR
A1  - Aygül, Mesut
A1  - Oberhänsli, Roland
T1  - Tectonic Stacking of HP/LT Metamorphic Rocks in Accretionary Wedges and the Role of Shallowing Slab-Mantle Decoupling
JF  - Tectonics
N2  - High-pressure/low-temperature (HP/LT) chloritoid-bearing micaschists crop out widely in the central part of northern Turkey and represent deep-seated subduction-accretionary complexes. Three peak metamorphic assemblages are identified in the area studied: (1) garnet-chloritoid-glaucophane with pseudomorphs after lawsonite; (2) chloritoid with pseudomorphs after glaucophane; and (3) chloritoid with pseudomorphs after jadeite in addition to phengite, paragonite, quartz, chlorite, rutile, and apatite. The latter is interpreted as transformation of a chloritoid + glaucophane assemblage to chloritoid + jadeite with increasing pressure; PT modeling indicates similar to 17 and 22-25 kbars for the two peak parageneses. The diversity of peak metamorphic assemblages and the PT estimates suggest that basal accretion occurred at different depths within the wedge. The depth of the basal accretion is possibly controlled by the slab-mantle decoupling depth. Stretching and thinning of the lithospheric fore arc induced by the slab rollback possibly caused shallowing of the slab-mantle decoupling depth which limited depth of the basal accretion from 70-80km to similar to 55km within the subduction channel. A slab-mantle coupling depth-controlled basal accretion may also explain the scarcity of eclogite and high-grade blueschist facies metamorphic rocks in active intraoceanic subduction zones. Because the overriding plate is young and hot in intraoceanic subductions, the slab and mantle are coupled at a relatively shallow depth before eclogitization of the oceanic crust. This prevents accretion and exhumation of eclogite along the subduction channel.
KW  - chloritoid micaschist
KW  - accretionary complex
KW  - slab-mantle decoupling
KW  - basal accretion
Y1  - 2017
U6  - https://doi.org/10.1002/2017TC004689
SN  - 0278-7407
SN  - 1944-9194
VL  - 36
SP  - 2332
EP  - 2346
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Aygül, Mesut
A1  - Okay, Aral I.
A1  - Oberhänsli, Roland
A1  - Schmidt, Alexander
A1  - Sudo, Masafumi
T1  - Late Cretaceous infant intra-oceanic arc volcanism, the Central Pontides, Turkey: Petrogenetic and tectonic implications
JF  - Journal of Asian earth sciences
N2  - A tectonic slice of an arc sequence consisting of low-grade metavolcanic rocks and overlying metasedimentary succession is exposed in the Central Pontides north of the Izmir-Ankara-Erzincan suture separating Laurasia from Gondwana-derived terranes. The metavolcanic rocks mainly consist of basaltic andesite/andesite and mafic cognate xenolith-bearing rhyolite with their pyroclastic equivalents, which are interbedded with recrystallized pelagic limestone and chert. The metasedimentary succession comprises recrystallized micritic limestone with rare volcanogenic metaclastic rocks and stratigraphically overlies the metavolcanic rocks. The geochemistry of the metavolcanic rocks indicates an arc setting evidenced by depletion of HFSE (Ti, P and Nb) and enrichment of fluid mobile LILE. Identical trace and rare earth elements compositions of basaltic andesites/andesites and rhyolites suggest that they are cogenetic and derived from a common parental magma. The arc sequence crops out between an Albian-Turonian subduction-accretionary complex representing the Laurasian active margin and an ophiolitic melange. Absence of continent derived detritus in the arc sequence and its tectonic setting in a wide Cretaceous accretionary complex suggest that the Kosdag Arc was intra-oceanic. Zircons from two metarhyolite samples give Late Cretaceous (93.8 +/- 1.9 and 94.4 +/- 1.9 Ma) U/Pb ages. These ages are the same as the age of the supra-subduction ophiolites in western Turkey, which implies that that the Kosdag Arc may represent part of the incipient arc formed during the generation of the supra-subduction ophiolites. The low-grade regional metamorphism in the Kosdag Arc is constrained to 69.9 +/- 0.4 Ma by Ar-40/Ar-39 muscovite dating indicating that the arc sequence became part of a wide Tethyan Cretaceous accretionary complex by the latest Cretaceous. Non-collisional cessation of the arc volcanism is possibly associated with southward migration of the magmatism as in the Izu-Bonin-Mariana arc system. (c) 2015 Elsevier Ltd. All rights reserved.
KW  - Intra-oceanic subduction
KW  - Felsic volcanism
KW  - Arc accretion
KW  - Ophiolite obduction
Y1  - 2015
U6  - https://doi.org/10.1016/j.jseaes.2015.07.005
SN  - 1367-9120
SN  - 1878-5786
VL  - 111
SP  - 312
EP  - 327
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aygül, Mesut
A1  - Okay, Aral I.
A1  - Oberhänsli, Roland
A1  - Ziemann, Martin Andreas
T1  - Thermal structure of low-grade accreted Lower Cretaceous distal turbidites, the Central Pontides, Turkey: insights for tectonic thickening of an accretionary wedge
JF  - Turkish journal of earth sciences = Türk yerbilimleri dergisi
N2  - Albian-Turonian subduction-accretionary complexes are exposed widely in the Central Pontides. A major portion of the accretionary complexes is made up of a metaflysch sequence consisting of slate/phyllite and metasandstone intercalation with blocks of marble, Na-amphibole bearing metabasite, and serpentinite. The metaflysch sequence represents distal parts of a large Lower Cretaceous submarine turbidite fan deposited on the Laurasian active continental margin that was subsequently accreted and metamorphosed during the Albian. Raman spectra of carbonaceous material of the metapelitic rocks revealed that the metaflysch consists of metamorphic packets with distinct peak metamorphic temperatures. The majority of the metapelites are low-temperature (ca. 330 degrees C) slates characterized by lack of differentiation of the graphite (G) and D2 defect bands. They possibly represent offscraped distal turbidites along the toe of the Albian accretionary wedge. Other phyllites are characterized by a slightly pronounced G band with a D2 defect band occurring on its shoulder. Peak metamorphic temperatures of these phyllites are constrained to 370-385 degrees C. The phyllites are associated with a strip of incipient blueschist facies metabasites and are found as a sliver within the offscraped distal turbidites. We interpret the phyllites as underplated continental sediments together with oceanic crustal basalt along the basal decollement. Tectonic emplacement of the underplated rocks into the offscraped distal turbidites was possibly achieved by out-of-sequence thrusting causing tectonic thickening and uplift of the wedge.
KW  - Pontides
KW  - distal turbidites
KW  - offscraping
KW  - underplating
KW  - low-grade metamorphism
KW  - graphitization
KW  - Raman microspectroscopy
Y1  - 2015
U6  - https://doi.org/10.3906/yer-1504-4
SN  - 1300-0985
VL  - 24
IS  - 5
SP  - 461
EP  - 474
PB  - Tübitak
CY  - Ankara
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy
A1  - Scheffer, Tobias
A1  - Heistermann, Maik
T1  - RainNet v1.0
BT  - a convolutional neural network for radar-based precipitation nowcasting
JF  - Geoscientific Model Development
N2  - In this study, we present RainNet, a deep convolutional neural network for radar-based precipitation nowcasting. Its design was inspired by the U-Net and SegNet families of deep learning models, which were originally designed for binary segmentation tasks. RainNet was trained to predict continuous precipitation intensities at a lead time of 5min, using several years of quality-controlled weather radar composites provided by the German Weather Service (DWD). That data set covers Germany with a spatial domain of 900km × 900km and has a resolution of 1km in space and 5min in time. Independent verification experiments were carried out on 11 summer precipitation events from 2016 to 2017. In order to achieve a lead time of 1h, a recursive approach was implemented by using RainNet predictions at 5min lead times as model inputs for longer lead times. In the verification experiments, trivial Eulerian persistence and a conventional model based on optical flow served as benchmarks. The latter is available in the rainymotion library and had previously been shown to outperform DWD's operational nowcasting model for the same set of verification events.

RainNet significantly outperforms the benchmark models at all lead times up to 60min for the routine verification metrics mean absolute error (MAE) and the critical success index (CSI) at intensity thresholds of 0.125, 1, and 5mm h⁻¹. However, rainymotion turned out to be superior in predicting the exceedance of higher intensity thresholds (here 10 and 15mm h⁻¹). The limited ability of RainNet to predict heavy rainfall intensities is an undesirable property which we attribute to a high level of spatial smoothing introduced by the model. At a lead time of 5min, an analysis of power spectral density confirmed a significant loss of spectral power at length scales of 16km and below. Obviously, RainNet had learned an optimal level of smoothing to produce a nowcast at 5min lead time. In that sense, the loss of spectral power at small scales is informative, too, as it reflects the limits of predictability as a function of spatial scale. Beyond the lead time of 5min, however, the increasing level of smoothing is a mere artifact – an analogue to numerical diffusion – that is not a property of RainNet itself but of its recursive application. In the context of early warning, the smoothing is particularly unfavorable since pronounced features of intense precipitation tend to get lost over longer lead times. Hence, we propose several options to address this issue in prospective research, including an adjustment of the loss function for model training, model training for longer lead times, and the prediction of threshold exceedance in terms of a binary segmentation task. Furthermore, we suggest additional input data that could help to better identify situations with imminent precipitation dynamics. The model code, pretrained weights, and training data are provided in open repositories as an input for such future studies.
KW  - weather
KW  - models
KW  - skill
Y1  - 2020
U6  - https://doi.org/10.5194/gmd-13-2631-2020
SN  - 1991-959X
SN  - 1991-9603
VL  - 13
IS  - 6
SP  - 2631
EP  - 2644
PB  - Copernicus Publ.
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy V.
T1  - Runoff predictions in ungauged arctic basins using conceptual models forced by reanalysis data
JF  - Water Resources
N2  - Due to global warming, the problem of assessing water resources and their vulnerability to climate drivers in the Arctic region has become a focus in the recent years. This study is aimed at investigating three lumped hydrological models to predict daily runoff of large-scale Arctic basins in the case of substantial data scarcity. All models were driven only by meteorological forcing reanalysis dataset without any additional information about landscape, soil, or vegetation cover properties of the studied basins. Model parameter regionalization based on transferring the whole parameter set showed good efficiency for predictions in ungauged basins. We run a blind test of the proposed methodology for ensemble runoff predictions on five sub-basins, for which only monthly observations were available, and obtained promising results for current water resources assessment for a broad domain of ungauged basins in the Russian Arctic.
KW  - hydrologic modeling
KW  - runoff
KW  - ungauged basins
KW  - reanalysis
KW  - Arctic
Y1  - 2018
U6  - https://doi.org/10.1134/S0097807818060180
SN  - 0097-8078
SN  - 1608-344X
VL  - 45
SP  - S1
EP  - S7
PB  - Pleiades Publ.
CY  - New York
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy
A1  - Varentsova, Natalia
A1  - Erina, Oxana
A1  - Sokolov, Dmitriy
A1  - Kurochkina, Liubov
A1  - Moreydo, Vsevolod
T1  - OpenForecast
BT  - The First Open-Source Operational Runoff Forecasting System in Russia
JF  - Water : Molecular Diversity Preservation International
N2  - The development and deployment of new operational runoff forecasting systems are a strong focus of the scientific community due to the crucial importance of reliable and timely runoff predictions for early warnings of floods and flashfloods for local businesses and communities. OpenForecast, the first operational runoff forecasting system in Russia, open for public use, is presented in this study. We developed OpenForecast based only on open-source software and data-GR4J hydrological model, ERA-Interim meteorological reanalysis, and ICON deterministic short-range meteorological forecasts. Daily forecasts were generated for two basins in the European part of Russia. Simulation results showed a limited efficiency in reproducing the spring flood of 2019. Although the simulations managed to capture the timing of flood peaks, they failed in estimating flood volume. However, further implementation of the parsimonious data assimilation technique significantly alleviates simulation errors. The revealed limitations of the proposed operational runoff forecasting system provided a foundation to outline its further development and improvement.
KW  - OpenForecast
KW  - open
KW  - operational service
KW  - runoff
KW  - forecasting
KW  - Russia
Y1  - 2019
U6  - https://doi.org/10.3390/w11081546
SN  - 2073-4441
VL  - 11
IS  - 8
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Bachmann, Raik
A1  - Oncken, Onno
A1  - Glodny, Johannes
A1  - Seifert, Wolfgang
A1  - Georgieva, Viktoria
A1  - Sudo, Masafumi
T1  - Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone
N2  - We present observations from a continuous exposure of an ancient plate interface in the depth range of its former seismogenic zone in the central Alps of Europe related to Late Cretaceous-early Tertiary subduction and accretion of the South Penninic lower plate underneath the Adriatic upper plate. The material forming the exposed plate interface zone has experienced flow and fracturing over an extended period of time followed by syncollisional exhumation, thus reflecting a multistage evolution. Fabric formation and metamorphism, however, chiefly record the deformation conditions of the precollisional setting along the plate interface. We identify an unstable slip domain from pseudotachylytes occurring in the temperature range between 200 and 300 degrees C. This zone coincides with a domain of intense veining in the subduction melange with mineral growth into open cavities, indicating fast, possibly seismic, rupture. Evidence for transient near-lithostatic fluid pressure as well as brittle fractures competing with mylonitic shear zones continues into the region below the occurrence of pseudotachylytes, possibly reflecting a zone of conditionally stable slip. The zone above the unstable slip area is devoid of veins but displays ample evidence of fluid-assisted processes similar to the deeper zone: solution-precipitation creep and dehydration reactions in the melange matrix, hydration, and sealing of the base of the upper plate. Seismic rupture here is possibly expressed by ubiquitous localized deformation zones. We hypothesize that trenchward sealing of parts of the plate interface as well as reaction-enhanced destruction of upper plate permeability is an important component, localizing the unstable slip zone. This relation may result from the competition of the pervasive, presumably interseismic, pressure solution creep destroying permeability and building elevated fluid pressure until the strength threshold is reached with seismic failure.
Y1  - 2009
UR  - http://www.agu.org/journals/jb/
U6  - https://doi.org/10.1029/2008jb005927
SN  - 0148-0227
ER  - 
TY  - JOUR
A1  - Back, Stefan
A1  - De Batist, Marc
A1  - Strecker, Manfred
T1  - The Frolikha Fan : a large Pleistocene glaciolacustrine outwash fan in northern Lake Baikal, Siberia
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Back, Stefan
A1  - De Batist, Marc
A1  - Strecker, Manfred
A1  - Vanhauwaert, P.
T1  - Quaternary depositional systems in northern Lake Baikal, Siberia
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Back, Stefan
A1  - Strecker, Manfred
T1  - Asymmetric late Pleistocene glaciations in the North Basin of the Baikal Rift, Russia
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Baes, Marzieh
A1  - Gerya, Taras V.
A1  - Sobolev, Stephan
T1  - 3-D thermo-mechanical modeling of plume-induced subduction initiation
JF  - Earth & planetary science letters
N2  - Here, we study the 3-D subduction initiation process induced by the interaction between a hot thermochemical mantle plume and oceanic lithosphere using thermo-mechanical viscoplastic finite difference marker-in-cell models. Our numerical modeling results show that self-sustaining subduction is induced by plume-lithosphere interaction when the plume is sufficiently buoyant, the oceanic lithosphere is sufficiently old and the plate is weak enough to allow the buoyant plume to. pass through it. Subduction initiation occurs following penetration of the lithosphere by the hot plume and the downward displacement of broken, nearly circular segments of lithosphere (proto-slabs) as a result of partially molten plume rocks overriding the proto-slabs. Our experiments show four different deformation regimes in response to plume-lithosphere interaction: a) self-sustaining subduction initiation, in which subduction becomes self-sustaining; b) frozen subduction initiation, in which subduction stops at shallow depths; c) slab break-off, in which the subducting circular slab breaks off soon after formation; and d) plume underplating, in which the plume does not pass through the lithosphere and instead spreads beneath it (i.e., failed subduction initiation). These regimes depend on several parameters, such as the size, composition, and temperature of the plume, the brittle/plastic strength and age of the oceanic lithosphere, and the presence/absence of lithospheric heterogeneities. The results show that subduction initiates and becomes self-sustaining when the lithosphere is older than 10 Myr and the non dimensional ratio of the plume buoyancy force and lithospheric strength above the plume is higher than approximately 2. The outcomes of our numerical experiments are applicable for subduction initiation in the modern and Precambrian Earth and for the origin of plume-related corona structures on Venus. (C) 2016 Elsevier B.V. All rights reserved.
KW  - subduction initiation
KW  - mantle plume
KW  - oceanic lithosphere
KW  - numerical models
Y1  - 2016
U6  - https://doi.org/10.1016/j.epsl.2016.08.023
SN  - 0012-821X
SN  - 1385-013X
VL  - 453
SP  - 193
EP  - 203
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Baes, Marzieh
A1  - Sobolev, Stephan
T1  - Mantle Flow as a Trigger for Subduction Initiation: A Missing Element of the Wilson Cycle Concept
JF  - Geochemistry, geophysics, geosystems
N2  - The classical Wilson Cycle concept, describing repeated opening and closing of ocean basins, hypothesizes spontaneous conversion of passive continental margins into subduction zones. This process, however, is impeded by the high strength of passive margins, and it has never occurred in Cenozoic times. Here using thermomechanical models, we show that additional forcing, provided by mantle flow, which is induced by neighboring subduction zones and midmantle slab remnants, can convert a passive margin into a subduction zone. Models suggest that this is a long-term process, thus explaining the lack of Cenozoic examples. We speculate that new subduction zones may form in the next few tens of millions of years along the Argentine passive margin and the U.S. East Coast. Mantle suction force can similarly trigger subduction initiation along large oceanic fracture zones. We propose that new subduction zones will preferentially originate where subduction zones were active in the past, thus explaining the remarkable colocation of subduction zones during at least the last 400 Myr.
Y1  - 2017
U6  - https://doi.org/10.1002/2017GC006962
SN  - 1525-2027
VL  - 18
SP  - 4469
EP  - 4486
PB  - American Geophysical Union
CY  - Washington
ER  -