TY - JOUR
A1 - Braun, Jean
A1 - Gemignani, Lorenzo
A1 - van der Beek, Pieter A.
T1 - Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands
JF - Earth surface dynamics
N2 - One of the main purposes of detrital thermochronology is to provide constraints on the regional-scale exhumation rate and its spatial variability in actively eroding mountain ranges. Procedures that use cooling age distributions coupled with hypsometry and thermal models have been developed in order to extract quantitative estimates of erosion rate and its spatial distribution, assuming steady state between tectonic uplift and erosion. This hypothesis precludes the use of these procedures to assess the likely transient response of mountain belts to changes in tectonic or climatic forcing. Other methods are based on an a priori knowledge of the in situ distribution of ages to interpret the detrital age distributions. In this paper, we describe a simple method that, using the observed detrital mineral age distributions collected along a river, allows us to extract information about the relative distribution of erosion rates in an eroding catchment without relying on a steady-state assumption, the value of thermal parameters or an a priori knowledge of in situ age distributions. The model is based on a relatively low number of parameters describing lithological variability among the various sub-catchments and their sizes and only uses the raw ages. The method we propose is tested against synthetic age distributions to demonstrate its accuracy and the optimum conditions for it use. In order to illustrate the method, we invert age distributions collected along the main trunk of the Tsangpo-Siang-Brahmaputra river system in the eastern Himalaya. From the inversion of the cooling age distributions we predict present-day erosion rates of the catchments along the Tsangpo-Siang-Brahmaputra river system, as well as some of its tributaries. We show that detrital age distributions contain dual information about present-day erosion rate, i. e., from the predicted distribution of surface ages within each catchment and from the relative contribution of any given catchment to the river distribution. The method additionally allows comparing modern erosion rates to long-term exhumation rates. We provide a simple implementation of the method in Python code within a Jupyter Notebook that includes the data used in this paper for illustration purposes.
Y1 - 2018
U6 - https://doi.org/10.5194/esurf-6-257-2018
SN - 2196-6311
SN - 2196-632X
VL - 6
IS - 1
SP - 257
EP - 270
PB - Copernicus
CY - Göttingen
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 - Fuchs, Matthias
A1 - Palmtag, Juri
A1 - Juhls, Bennet
A1 - Overduin, Pier Paul
A1 - Grosse, Guido
A1 - Abdelwahab, Ahmed
A1 - Bedington, Michael
A1 - Sanders, Tina
A1 - Ogneva, Olga
A1 - Fedorova, Irina
A1 - Zimov, Nikita S.
A1 - Mann, Paul J.
A1 - Strauss, Jens
T1 - High-resolution bathymetry models for the Lena Delta and Kolyma Gulf coastal zones
JF - Earth system science data
N2 - Arctic river deltas and deltaic near-shore zones represent important land-ocean transition zones influencing sediment dynamics and nutrient fluxes from permafrost-affected terrestrial ecosystems into the coastal Arctic Ocean. To accurately model fluvial carbon and freshwater export from rapidly changing river catchments as well as assess impacts of future change on the Arctic shelf and coastal ecosystems, we need to understand the sea floor characteristics and topographic variety of the coastal zones. To date, digital bathymetrical data from the poorly accessible, shallow, and large areas of the eastern Siberian Arctic shelves are sparse. We have digitized bathymetrical information for nearly 75 000 locations from large-scale (1 V 25000-1 V 500000) current and historical nautical maps of the Lena Delta and the Kolyma Gulf region in northeastern Siberia. We present the first detailed and seamless digital models of coastal zone bathymetry for both delta and gulf regions in 50 and 200m spatial resolution. We validated the resulting bathymetry layers using a combination of our own water depth measurements and a collection of available depth measurements, which showed a strong correlation (r>0.9). Our bathymetrical models will serve as an input for a high-resolution coupled hydrodynamic-ecosystem model to better quantify fluvial and coastal carbon fluxes to the Arctic Ocean, but they may be useful for a range of other studies related to Arctic delta and near-shore dynamics such as modeling of submarine permafrost, near-shore sea ice, or shelf sediment transport. The new digital high-resolution bathymetry products are available on the PANGAEA data set repository for the Lena Delta (https://doi.org/10.1594/PANGAEA.934045; Fuchs et al., 2021a) and Kolyma Gulf region (https://doi.org/10.1594/PANGAEA.934049; Fuchs et al., 2021b), respectively. Likewise, the depth validation data are available on PANGAEA as well (https://doi.org/10.1594/PANGAEA.933187; Fuchs et al., 2021c).
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-2279-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 5
SP - 2279
EP - 2301
PB - Copernicus
CY - Göttingen
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 - 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.
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.
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 - Smith, Taylor
A1 - Boers, Niklas
T1 - Global vegetation resilience linked to water availability and variability
JF - Nature Communications
N2 - Quantifying the resilience of vegetated ecosystems is key to constraining both present-day and future global impacts of anthropogenic climate change. Here we apply both empirical and theoretical resilience metrics to remotely-sensed vegetation data in order to examine the role of water availability and variability in controlling vegetation resilience at the global scale. We find a concise global relationship where vegetation resilience is greater in regions with higher water availability. We also reveal that resilience is lower in regions with more pronounced inter-annual precipitation variability, but find less concise relationships between vegetation resilience and intra-annual precipitation variability. Our results thus imply that the resilience of vegetation responds differently to water deficits at varying time scales. In view of projected increases in precipitation variability, our findings highlight the risk of ecosystem degradation under ongoing climate change.
Vegetation dynamics depend on both the amount of precipitation and its variability over time. Here, the authors show that vegetation resilience is greater where water availability is higher and where precipitation is more stable from year to year.
Y1 - 2023
U6 - https://doi.org/10.1038/s41467-023-36207-7
SN - 2041-1723
VL - 14
IS - 1
PB - Springer Nature
CY - London
ER -
TY - JOUR
A1 - Woutersen, Amber
A1 - Jardine, Phillip E.
A1 - Giovanni Bogota-Angel, Raul
A1 - Zhang, Hong-Xiang
A1 - Silvestro, Daniele
A1 - Antonelli, Alexandre
A1 - Gogna, Elena
A1 - Erkens, Roy H. J.
A1 - Gosling, William D.
A1 - Dupont-Nivet, Guillaume
A1 - Hoorn, Carina
T1 - A novel approach to study the morphology and chemistry of pollen in a phylogenetic context, applied to the halophytic taxon Nitraria L.(Nitrariaceae)
JF - PeerJ
N2 - Nitraria is a halophytic taxon (i.e., adapted to saline environments) that belongs to the plant family Nitrariaceae and is distributed from the Mediterranean, across Asia into the south-eastern tip of Australia. This taxon is thought to have originated in Asia during the Paleogene (66-23 Ma), alongside the proto-Paratethys epicontinental sea. The evolutionary history of Nitraria might hold important clues on the links between climatic and biotic evolution but limited taxonomic documentation of this taxon has thus far hindered this line of research. Here we investigate if the pollen morphology and the chemical composition of the pollen wall are informative of the evolutionary history of Nitraria and could explain if origination along the proto-Paratethys and dispersal to the Tibetan Plateau was simultaneous or a secondary process. To answer these questions, we applied a novel approach consisting of a combination of Fourier Transform Infrared spectroscopy (FTIR), to determine the chemical composition of the pollen wall, and pollen morphological analyses using Light Microscopy (LM) and Scanning Electron Microscopy (SEM). We analysed our data using ordinations (principal components analysis and non-metric multidimensional scaling), and directly mapped it on the Nitrariaceae phylogeny to produce a phylomorphospace and a phylochemospace. Our LM, SEM and FTIR analyses show clear morphological and chemical differences between the sister groups Peganum and Nitraria. Differences in the morphological and chemical characteristics of highland species (Nitraria schoberi, N. sphaerocarpa, N. sibirica and N. tangutorum) and lowland species (Nitraria billardierei and N. retusa) are very subtle, with phylogenetic history appearing to be a more important control on Nitraria pollen than local environmental conditions. Our approach shows a compelling consistency between the chemical and morphological characteristics of the eight studied Nitrariaceae species, and these traits are in agreement with the phylogenetic tree. Taken together, this demonstrates how novel methods for studying fossil pollen can facilitate the evolutionary investigation of living and extinct taxa, and the environments they represent.
KW - FTIR
KW - LM
KW - SEM
KW - Paratethys
KW - Tibet
KW - Sporopollenin
KW - Mediterranean
KW - Steppe-desert
KW - Australia
KW - Palynology
Y1 - 2018
U6 - https://doi.org/10.7717/peerj.5055
SN - 2167-8359
VL - 6
PB - PeerJ Inc.
CY - London
ER -
TY - JOUR
A1 - Toumoulin, Agathe
A1 - Tardif-Becquet, Delphine
A1 - Donnadieu, Yannick
A1 - Licht, Alexis
A1 - Ladant, Jean-Baptiste
A1 - Kunzmann, Lutz
A1 - Dupont-Nivet, Guillaume
T1 - Evolution of continental temperature seasonality from the Eocene greenhouse to the Oligocene icehouse
BT - a model-data comparison
JF - Climate of the past : an interactive open access journal of the European Geosciences Union
N2 - At the junction of greenhouse and icehouse climate states, the Eocene-Oligocene Transition (EOT) is a key moment in Cenozoic climate history. While it is associated with severe extinctions and biodiversity turnovers on land, the role of terrestrial climate evolution remains poorly resolved, especially the associated changes in seasonality. Some paleobotanical and geochemical continental records in parts of the Northern Hemisphere suggest the EOT is associated with a marked cooling in winter, leading to the development of more pronounced seasons (i.e., an increase in the mean annual range of temperature, MATR). However, the MATR increase has been barely studied by climate models and large uncertainties remain on its origin, geographical extent and impact. In order to better understand and describe temperature seasonality changes between the middle Eocene and the early Oligocene, we use the Earth system model IPSL-CM5A2 and a set of simulations reconstructing the EOT through three major climate forcings: pCO(2) decrease (1120, 840 and 560 ppm), the Antarctic ice-sheet (AIS) formation and the associated sea-level decrease. Our simulations suggest that pCO(2) lowering alone is not sufficient to explain the seasonality evolution described by the data through the EOT but rather that the combined effects of pCO(2) , AIS formation and increased continentality provide the best data-model agreement.pCO(2) decrease induces a zonal pattern with alternating increasing and decreasing seasonality bands particularly strong in the northern high latitudes (up to 8 degrees C MATR increase) due to sea-ice and surface albedo feedback. Conversely, the onset of the AIS is responsible for a more constant surface albedo yearly, which leads to a strong decrease in seasonality in the southern midlatitudes to high latitudes (> 40 degrees S). Finally, continental areas that emerged due to the sea-level lowering cause the largest increase in seasonality and explain most of the global heterogeneity in MATR changes (1MATR) patterns. The Delta MATR patterns we reconstruct are generally consistent with the variability of the EOT biotic crisis intensity across the Northern Hemisphere and provide insights on their underlying mechanisms.
Y1 - 2022
U6 - https://doi.org/10.5194/cp-18-341-2022
SN - 1814-9324
SN - 1814-9332
VL - 18
IS - 2
SP - 341
EP - 362
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Tardif-Becquet, Delphine
A1 - Fluteau, Frédéric
A1 - Donnadieu, Yannick
A1 - Le Hir, Guillaume
A1 - Ladant, Jean-Baptiste
A1 - Sepulchre, Pierre
A1 - Licht, Alexis
A1 - Poblete, Fernando
A1 - Dupont-Nivet, Guillaume
T1 - The origin of Asian monsoons
BT - a modelling perspective
JF - Climate of the Past
N2 - The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward.
KW - earth system model
KW - early eocene
KW - tibetan plateau
KW - climate-change
KW - oligocene climate
KW - summer monsoon
KW - global monsoon
KW - ice sheet
KW - part 1
KW - China
Y1 - 2020
U6 - https://doi.org/10.5194/cp-16-847-2020
SN - 1814-9332
SN - 1814-9324
VL - 16
IS - 3
SP - 847
EP - 865
PB - Copernicus Publications
CY - Göttingen
ER -
TY - JOUR
A1 - Haugk, Charlotte
A1 - Jongejans, Loeka L.
A1 - Mangelsdorf, Kai
A1 - Fuchs, Matthias
A1 - Ogneva, Olga
A1 - Palmtag, Juri
A1 - Mollenhauer, Gesine
A1 - Mann, Paul J.
A1 - Overduin, P. Paul
A1 - Grosse, Guido
A1 - Sanders, Tina
A1 - Tuerena, Robyn E.
A1 - Schirrmeister, Lutz
A1 - Wetterich, Sebastian
A1 - Kizyakov, Alexander
A1 - Karger, Cornelia
A1 - Strauss, Jens
T1 - Organic matter characteristics of a rapidly eroding permafrost cliff in NE Siberia (Lena Delta, Laptev Sea region)
JF - Biogeosciences
N2 - Organic carbon (OC) stored in Arctic permafrost represents one of Earth's largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coasts are particularly susceptible to thawing processes. Accelerating erosion of terrestrial permafrost along shorelines leads to increased transfer of organic matter (OM) to nearshore waters. However, the amount of terrestrial permafrost carbon and nitrogen as well as the OM quality in these deposits is still poorly quantified. We define the OM quality as the intrinsic potential for further transformation, decomposition and mineralisation. Here, we characterise the sources and the quality of OM supplied to the Lena River at a rapidly eroding permafrost river shoreline cliff in the eastern part of the delta (Sobo-Sise Island). Our multi-proxy approach captures bulk elemental, molecu- lar geochemical and carbon isotopic analyses of Late Pleistocene Yedoma permafrost and Holocene cover deposits, discontinuously spanning the last similar to 52 kyr. We showed that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt %). The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal ka BP) and are overlaid by last glacial MIS 2 (dated to 28 to 15 cal ka BP) and Holocene MIS 1 (dated to 7-0 cal ka BP) deposits. The relatively high average chain length (ACL) index of n-alkanes along the cliff profile indicates a predominant contribution of vascular plants to the OM composition. The elevated ratio of isoand anteiso-branched fatty acids (FAs) relative to mid- and long-chain (C >= 20) n-FAs in the interstadial MIS 3 and the interglacial MIS 1 deposits suggests stronger microbial activity and consequently higher input of bacterial biomass during these climatically warmer periods. The overall high carbon preference index (CPI) and higher plant fatty acid (HPFA) values as well as high C/N ratios point to a good quality of the preserved OM and thus to a high potential of the OM for decomposition upon thaw. A decrease in HPFA values downwards along the profile probably indicates stronger OM decomposition in the oldest (MIS 3) deposits of the cliff. The characterisation of OM from eroding permafrost leads to a better assessment of the greenhouse gas potential of the OC released into river and nearshore waters in the future.
Y1 - 2022
U6 - https://doi.org/10.5194/bg-19-2079-2022
SN - 1726-4170
SN - 1726-4189
VL - 19
IS - 7
SP - 2079
EP - 2094
PB - Copernicus
CY - Göttingen
ER -