TY - JOUR A1 - Esfahani, Reza Dokht Dolatabadi A1 - Gholami, Ali A1 - Ohrnberger, Matthias T1 - An inexact augmented Lagrangian method for nonlinear dispersion-curve inversion using Dix-type global linear approximation JF - Geophysics : a journal of general and applied geophysics N2 - Dispersion-curve inversion of Rayleigh waves to infer subsurface shear-wave velocity is a long-standing problem in seismology. Due to nonlinearity and ill-posedness, sophisticated regularization techniques are required to solve the problem for a stable velocity model. We have formulated the problem as a minimization problem with nonlinear operator constraint and then solve it by using an inexact augmented Lagrangian method, taking advantage of the Haney-Tsai Dix-type relation (a global linear approximation of the nonlinear forward operator). This replaces the original regularized nonlinear problem with iterative minimization of a more tractable regularized linear problem followed by a nonlinear update of the phase velocity (data) in which the update can be performed accurately with any forward modeling engine, for example, the finite-element method. The algorithm allows discretizing the medium with thin layers (for the finite-element method) and thus omitting the layer thicknesses from the unknowns and also allows incorporating arbitrary regularizations to shape the desired velocity model. In this research, we use total variation regularization to retrieve the shear-wave velocity model. We use two synthetic and two real data examples to illustrate the performance of the inversion algorithm with total variation regularization. We find that the method is fast and stable, and it converges to the solution of the original nonlinear problem. KW - surface wave KW - nonlinear KW - inversion KW - modeling KW - finite element Y1 - 2020 U6 - https://doi.org/10.1190/geo2019-0717.1 SN - 0016-8033 SN - 1942-2156 VL - 85 IS - 3 SP - EN77 EP - EN85 PB - GeoScienceWorld CY - Tulsa, Okla. ER - TY - GEN A1 - Wang, Wei-shi A1 - Oswald, Sascha A1 - Gräff, Thomas A1 - Lensing, Hermann-Josef A1 - Liu, Tie A1 - Strasser, Daniel A1 - Munz, Matthias T1 - Correction: Impact of river reconstruction on groundwater flow during bank filtration assessed by transient three-dimensional modelling of flow and heat transport. - Hydrogeology Journal. - Berlin: Springer. - 28 (2020) , S. 723. - https://doi.org/10.1007/s10040-019-02063-3 T2 - Hydrogeology journal : official journal of the International Association of Hydrogeologists T2 - Erratum: Impact de la reconstruction d’une rivière sur l’écoulement des eaux souterraines via la filtration sur berge évalué par un modèle tridimensionnel en régime transitoire de l’écoulement et du transport de chaleur. - Berlin: Springer. - 28 (2020) , S. 723. - https://doi.org/10.1007/s10040-019-02063-3 T2 - Erratum: Impacto de la restauración de un río en el flujo de agua subterránea durante la filtración en las márgenes, evaluado mediante la modelización tridimensional transitoria del flujo y el transporte de calor. - Berlin: Springer. - 28 (2020) , S. 723. - https://doi.org/10.1007/s10040-019-02063-3 Y1 - 2020 U6 - https://doi.org/10.1007/s10040-020-02221-y SN - 1431-2174 SN - 1435-0157 VL - 28 IS - 7 SP - 2633 EP - 2634 PB - Springer CY - Berlin ; Heidelberg ; New York, NY ER - TY - JOUR A1 - Ben Dor, Yoav A1 - Neugebauer, Ina A1 - Enzel, Yehouda A1 - Schwab, Markus J. A1 - Tjallingii, Rik A1 - Erel, Yigal A1 - Brauer, Achim T1 - Reply to comment on: Ben Dor, Yoav et al. : Varves of the Dead Sea sedimentary record. - In: Quaternary science reviews : the international multidisciplinary research and review journal. - 215 (2019), S. 173 - 184. - (ISSN: 0277-3791). - https://doi.org/10.1016/j.quascirev.2019.04.011 JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - In the comment on "Varves of the Dead Sea sedimentary record." Quaternary Science Reviews 215 (Ben Dor et al., 2019): 173-184. by R. Bookman, two recently published papers are suggested to prove that the interpretation of the laminated sedimentary sequence of the Dead Sea, deposited mostly during MIS2 and Holocene pluvials, as annual deposits (i.e., varves) is wrong. In the following response, we delineate several lines of evidence which coalesce to demonstrate that based on the vast majority of evidence, including some of the evidence provided in the comment itself, the interpretation of these sediments as varves is the more likely scientific conclusion. We further discuss the evidence brought up in the comment and its irrelevance and lack of robustness for addressing the question under discussion. Y1 - 2020 U6 - https://doi.org/10.1016/j.quascirev.2019.106063 SN - 0277-3791 VL - 231 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Kumar, Rohini A1 - Hesse, Fabienne A1 - Rao, P. Srinivasa A1 - Musolff, Andreas A1 - Jawitz, James A1 - Sarrazin, Francois A1 - Samaniego, Luis A1 - Fleckenstein, Jan H. A1 - Rakovec, Oldrich A1 - Thober, S. A1 - Attinger, Sabine T1 - Strong hydroclimatic controls on vulnerability to subsurface nitrate contamination across Europe JF - Nature Communications N2 - Subsurface contamination due to excessive nutrient surpluses is a persistent and widespread problem in agricultural areas across Europe. The vulnerability of a particular location to pollution from reactive solutes, such as nitrate, is determined by the interplay between hydrologic transport and biogeochemical transformations. Current studies on the controls of subsurface vulnerability do not consider the transient behaviour of transport dynamics in the root zone. Here, using state-of-the-art hydrologic simulations driven by observed hydroclimatic forcing, we demonstrate the strong spatiotemporal heterogeneity of hydrologic transport dynamics and reveal that these dynamics are primarily controlled by the hydroclimatic gradient of the aridity index across Europe. Contrasting the space-time dynamics of transport times with reactive timescales of denitrification in soil indicate that similar to 75% of the cultivated areas across Europe are potentially vulnerable to nitrate leaching for at least onethird of the year. We find that neglecting the transient nature of transport and reaction timescale results in a great underestimation of the extent of vulnerable regions by almost 50%. Therefore, future vulnerability and risk assessment studies must account for the transient behaviour of transport and biogeochemical transformation processes. KW - travel time distributions KW - groundwater vulnerability KW - flux tracking KW - transit-time KW - water age KW - nitrogen KW - model KW - dynamics KW - pollution KW - patterns Y1 - 2020 U6 - https://doi.org/10.1038/s41467-020-19955-8 SN - 2041-1723 VL - 11 IS - 1 SP - 1 EP - 10 PB - Nature Publishing Group UK CY - London ER - TY - JOUR A1 - Palmer, Matthew D. A1 - Gregory, Jonathan A1 - Bagge, Meike A1 - Calvert, Daley A1 - Hagedoorn, Jan Marius A1 - Howard, Tom A1 - Klemann, Volker A1 - Lowe, Jason A. A1 - Roberts, Chris A1 - Slangen, Aimee B. A. A1 - Spada, Giorgio T1 - Exploring the drivers of global and local sea‐level change over the 21st century and beyond JF - Earth's future N2 - We present a new set of global and local sea‐level projections at example tide gauge locations under the RCP2.6, RCP4.5, and RCP8.5 emissions scenarios. Compared to the CMIP5‐based sea‐level projections presented in IPCC AR5, we introduce a number of methodological innovations, including (i) more comprehensive treatment of uncertainties, (ii) direct traceability between global and local projections, and (iii) exploratory extended projections to 2300 based on emulation of individual CMIP5 models. Combining the projections with observed tide gauge records, we explore the contribution to total variance that arises from sea‐level variability, different emissions scenarios, and model uncertainty. For the period out to 2300 we further breakdown the model uncertainty by sea‐level component and consider the dependence on geographic location, time horizon, and emissions scenario. Our analysis highlights the importance of local variability for sea‐level change in the coming decades and the potential value of annual‐to‐decadal predictions of local sea‐level change. Projections to 2300 show a substantial degree of committed sea‐level rise under all emissions scenarios considered and highlight the reduced future risk associated with RCP2.6 and RCP4.5 compared to RCP8.5. Tide gauge locations can show large ( > 50%) departures from the global average, in some cases even reversing the sign of the change. While uncertainty in projections of the future Antarctic ice dynamic response tends to dominate post‐2100, we see substantial differences in the breakdown of model variance as a function of location, time scale, and emissions scenario. KW - climate change KW - CMIP5 models KW - RCP scenarios KW - sea-level projections KW - tide gauge observations Y1 - 2020 U6 - https://doi.org/10.1029/2019EF001413 SN - 2328-4277 VL - 8 IS - 9 SP - 1 EP - 25 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Jones, Benjamin M. A1 - Arp, Christopher D. A1 - Grosse, Guido A1 - Nitze, Ingmar A1 - Lara, Mark J. A1 - Whitman, Matthew S. A1 - Farquharson, Louise M. A1 - Kanevskiy, Mikhail A1 - Parsekian, Andrew D. A1 - Breen, Amy L. A1 - Ohara, Nori A1 - Rangel, Rodrigo Correa A1 - Hinkel, Kenneth M. T1 - Identifying historical and future potential lake drainage events on the western Arctic coastal plain of Alaska JF - Permafrost and Periglacial Processes N2 - Arctic lakes located in permafrost regions are susceptible to catastrophic drainage. In this study, we reconstructed historical lake drainage events on the western Arctic Coastal Plain of Alaska between 1955 and 2017 using USGS topographic maps, historical aerial photography (1955), and Landsat Imagery (ca. 1975, ca. 2000, and annually since 2000). We identified 98 lakes larger than 10 ha that partially (>25% of area) or completely drained during the 62-year period. Decadal-scale lake drainage rates progressively declined from 2.0 lakes/yr (1955-1975), to 1.6 lakes/yr (1975-2000), and to 1.2 lakes/yr (2000-2017) in the ~30,000-km(2) study area. Detailed Landsat trend analysis between 2000 and 2017 identified two years, 2004 and 2006, with a cluster (five or more) of lake drainages probably associated with bank overtopping or headward erosion. To identify future potential lake drainages, we combined the historical lake drainage observations with a geospatial dataset describing lake elevation, hydrologic connectivity, and adjacent lake margin topographic gradients developed with a 5-m-resolution digital surface model. We identified ~1900 lakes likely to be prone to drainage in the future. Of the 20 lakes that drained in the most recent study period, 85% were identified in this future lake drainage potential dataset. Our assessment of historical lake drainage magnitude, mechanisms and pathways, and identification of potential future lake drainages provides insights into how arctic lowland landscapes may change and evolve in the coming decades to centuries. KW - Arctic lakes KW - drained lake basins KW - lake drainage KW - permafrost regions KW - thermokarst lakes Y1 - 2020 U6 - https://doi.org/10.1002/ppp.2038 VL - 31 IS - 1 SP - 110 EP - 127 PB - Wiley CY - New York ER - TY - JOUR A1 - Foster, William J. A1 - Garvie, Christopher L. A1 - Weiss, Anna M. A1 - Muscente, A. Drew A1 - Aberhan, Martin A1 - Counts, John W. A1 - Martindale, Rowan C. T1 - Resilience of marine invertebrate communities during the early Cenozoic hyperthermals JF - Scientific Reports N2 - The hyperthermal events of the Cenozoic, including the Paleocene-Eocene Thermal Maximum, provide an opportunity to investigate the potential effects of climate warming on marine ecosystems. Here, we examine the shallow benthic marine communities preserved in the late Cretaceous to Eocene strata on the Gulf Coastal Plain (United States). In stark contrast to the ecological shifts following the end-Cretaceous mass extinction, our data show that the early Cenozoic hyperthermals did not have a long-term impact on the generic diversity nor composition of the Gulf Coastal Plain molluscan communities. We propose that these communities were resilient to climate change because molluscs are better adapted to high temperatures than other taxa, as demonstrated by their physiology and evolutionary history. In terms of resilience, these communities differ from other shallow-water carbonate ecosystems, such as reef communities, which record significant changes during the early Cenozoic hyperthermals. These data highlight the strikingly different responses of community types, i.e., the almost imperceptible response of molluscs versus the marked turnover of foraminifera and reef faunas. The impact on molluscan communities may have been low because detrimental conditions did not devastate the entire Gulf Coastal Plain, allowing molluscs to rapidly recolonise vacated areas once harsh environmental conditions ameliorated. KW - eocene thermal maximum KW - gulf coastal plain KW - climate-change KW - ocean acidification KW - extinction event KW - carbon-cycle KW - heat-stress KW - origination KW - ecosystems KW - diversity Y1 - 2020 U6 - https://doi.org/10.1038/s41598-020-58986-5 SN - 2045-2322 VL - 10 IS - 1 SP - 1 EP - 11 PB - Springer Nature CY - London ER - TY - JOUR A1 - Tardif, Delphine A1 - Fluteau, Frédéric A1 - Donnadieu, Yannick A1 - Le Hir, Guillaume A1 - Ladant, Jean-Baptiste A1 - Sepulchre, Pierre A1 - Licht, Alexis A1 - Poblete, Fernando A1 - Dupont-Nivet, Guillaume T1 - The origin of Asian monsoons BT - a modelling perspective JF - Climate of the Past N2 - The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward. KW - earth system model KW - early eocene KW - tibetan plateau KW - climate-change KW - oligocene climate KW - summer monsoon KW - global monsoon KW - ice sheet KW - part 1 KW - China Y1 - 2020 U6 - https://doi.org/10.5194/cp-16-847-2020 SN - 1814-9332 SN - 1814-9324 VL - 16 IS - 3 SP - 847 EP - 865 PB - Copernicus Publications CY - Göttingen ER - TY - JOUR A1 - Schuck, Bernhard A1 - Schleicher, Anja Maria A1 - Janssen, Christoph A1 - Toy, Virginia G. A1 - Dresen, Georg T1 - Fault zone architecture of a large plate-bounding strike-slip fault BT - A case study from the Alpine Fault, New Zealand JF - Solid Earth N2 - New Zealand's Alpine Fault is a large, platebounding strike-slip fault, which ruptures in large (M-w > 8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show that the young, largely unconsolidated sediments that constitute the footwall at shallow depths have a significant influence on fault gouge rheological properties and structure. KW - san andreas fault KW - thickness-displacement relationships KW - central south island KW - Ion-Beam (FIB) KW - internal structure KW - hanging wall KW - Fluid Flow KW - frictional properties KW - weakening mechanisms KW - strain localization Y1 - 2020 U6 - https://doi.org/10.5194/se-11-95-2020 SN - 1869-9529 VL - 11 IS - 1 SP - 95 EP - 124 PB - Copernicus Publications CY - Göttingen ER - TY - JOUR A1 - Olen, Stephanie M. A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Corrigendum to: Olen, Stephanie M.; Bookhagen, Bodo; Strecker, Manfred R. : Role of climate and vegetation density in modulating denudation rates in the Himalaya. - Earth and planetary science letters. - 445 (2016), S. 57 - 67. - doi: https://doi.org/10.1016/j.epsl.2016.03.047 JF - Earth and planetary science letters N2 - Vegetation has long been hypothesized to influence the nature and rates of surface processes. We test the possible impact of vegetation and climate on denudation rates at orogen scale by taking advantage of a pronounced along-strike gradient in rainfall and vegetation density in the Himalaya. We combine 12 new 10Be denudation rates from the Sutlej Valley and 123 published denudation rates from fluvially- dominated catchments in the Himalaya with remotely-sensed measures of vegetation density and rainfall metrics, and with tectonic and lithologic constraints. In addition, we perform topographic analyses to assess the contribution of vegetation and climate in modulating denudation rates along strike. We observe variations in denudation rates and the relationship between denudation and topography along strike that are most strongly controlled by local rainfall amount and vegetation density, and cannot be explained by along-strike differences in tectonics or lithology. A W–E along-strike decrease in denudation rate variability positively correlates with the seasonality of vegetation density (R = 0.95, p < 0.05), and negatively correlates with mean vegetation density (R = −0.84, p < 0.05). Vegetation density modulates the topographic response to changing denudation rates, such that the functional relationship between denudation rate and topographic steepness becomes increasingly linear as vegetation density increases. We suggest that while tectonic processes locally control the pattern of denudation rates across strike of the Himalaya (i.e., S–N), along strike of the orogen (i.e., E–W) climate exerts a measurable influence on how denudation rates scatter around long-term, tectonically-controlled erosion, and on the functional relationship between topography and denudation Y1 - 2020 U6 - https://doi.org/10.1016/j.epsl.2020.116252 SN - 0012-821X SN - 1385-013X VL - 540 PB - Elsevier CY - Amsterdam ER -