bluuebunny/crossref_metadata_2025 huggingface dataset:
Synergetic use of L- and C-band SAR data in Earth Sciences – The JAXA-ESA mutual cooperation
Authors: Kubanek Julia , Davidson Malcolm , Borgeaud Maurice , Sobue Shin-ichi , Tadono Takeo
Published: March 2021

Within the “Cooperation for the Use of Synthetic Aperture Radar Satellites in Earth Science and Applications”, the Japanese Aerospace Exploration Agency (JAXA) and the European Space Agency (ESA) agreed to mutually share C-band data from ESA’s Sentinel-1 mission and L-band data from JAXA’s ALOS-2 PALSAR-2 mission over selected test sites. Applications include wetland monitoring, hurricanes, sea ice, snow water equivalent and surface deformation.

The aim of the collaboration is to develop a better understanding of the benefits of combining L- and C-band data over various areas and for the different thematic applications. The findings of the different European, Japanese and international projects will help to develop future SAR satellite missions, such as JAXA’s ALOS-4, and ESA’s Copernicus mission ROSE-L and Sentinel-1 Next Generation.

This presentation will give an overview of the ongoing ESA-JAXA cooperation and will show highlights and first results of the different test sites and applications.
The Gröbminger Mitterberg (Austria): A time machine to the pre-LGM?
Authors: Griesmeier Gerit E.U. , Reitner Jürgen M. , Le Heron Daniel P.
Published: March 2021

The Last Glacial Maximum (LGM) is well understood in many parts of the European Alps, but open questions remain concerning glacial phases prior to the LGM as the record is fragmentary. The Gröbminger Mitterberg (GM), located among the Enns Valley in Styria (Austria) is one such location where pre-LGM glacial and paraglacial processes can be studied. The GM emerges roughly 200 m from the Enns Valley floor and is situated between unmetamorphosed Mesozoic carbonates in the north and crystalline basement units in the south. Strata occur below a cover of up to more than 10 m thick basal till attributed to the LGM. The sedimentary record rests on the phyllites and greenschists that crop out at the steep southern flank of the GM. The sediment consists of an assortment of pebble-sand deposits with individual sand lenses, sand bodies with climbing ripples and undulose bedding, and fine-sand/silt laminated strata. In grain-supported intervals, cracked pebbles occur, which are interpreted to record subglacial loading. Cross-bedding orientations, together with the limited amount of unmetamorphosed carbonate pebbles in the sequence, imply that sediment was sourced from the GM and deposited at its margins, rather than from surrounding mountains towards the centre of the Enns Valley. Three depositional regimes have been recognised: deltaic sediment (both distal sands with ripples and proximal, cross-bedded gravel), lake bottom sediment (laminated fine-sand and silt) and fluvial deposits (channels with basal lag deposits and local cross bedding). The delta facies testify to the presence of lacustrine conditions. By analogy to the Unterangerberg in the Inn Valley (Tyrol, Austria; Starnberger et al. 2013), the following sequence of events is proposed. Before the LGM, sediment derived from the wider catchment area accumulated in the Enns Valley in lakes and rivers. Aggradation within the whole Enns valley resulted in deposition on the present day GM. During the LGM, the large Enns Glacier eroded much of the sediment record, especially around the GM. Deposits on top of the GM were then concealed by > 10 m thick diamicts and thereby preserved. Future age dating of the sediments will provide a better-constrained chronology to the sequence of events proposed above.
Analyzing the propagation of drought through water storages using global scale GRACE-based data assimilation
Authors: Gerdener Helena , Schulze Kerstin , Engels Olga , Kusche Jürgen , Müller Schmied Hannes , Niemann Christoph , Ackermann Sebastian , Döll Petra
Published: March 2021

The frequency and severity of drought increase in many regions of the world, which emphasizes the need for sufficient research to better monitor and trigger management plans. An important role hereby plays hydrological drought, because it affects water supply and crop yields that are necessary to ensure food security. Typically, hydrological drought detection is based on in-situ observations of fluxes or storages at the surface. However, this neglects the fact that drought might occur in multiple storages with different timing and severity.  The use of subsurface storage, e.g. groundwater, is rare because the available in-situ well level monitoring is irregularly distributed in space and time and access might be restricted, for example due to national security reasons or problems in converting them to storage estimates.

The satellite mission Gravity Recovery and Climate Experiment (GRACE) and its successor GRACE-FO offer a great possibility to observe the total water storage, i.e. the sum of surface and subsurface storages, on a global scale from space. However, GRACE is restricted to monthly data on a spatial resolution of about 300 km and the vertical sum of the storages. Hydrological models present another possibility to derive global storage information with a finer spatial (~50km), temporal and vertical resolution than GRACE but they do not perfectly represent the reality because they are underlying assumptions and are affected by uncertainty of forcing data. Therefore, to enable downscaling of GRACE while improving the models realism, the GRACE measurements are assimilated into a hydrological model.

In previous works we used a framework that assimilates GRACE into the WaterGAP Global Hydrological Model (WGHM) regionally or basin-wise. In this work we present a new framework that globally assimilates GRACE on a 4 degree grid with full uncertainty information from 2003 to 2018. The framework enables to assimilate about 95% of the global WGHM land surface except Greenland. With regard to vertical and spatial resolution the performance of model, observation and assimilation is compared. Global GRACE based drought indicators are applied and its development in the different compartments of surface water, soil and groundwater is analyzed to identify new insights into the propagation of drought. We expect that by including GRACE we derive new information especially for groundwater droughts, which might reveal time lags and a different severity as compared to surface water droughts for some regions.
Multi-GNSS real-time orbit and clock quality changes over time 
Authors: Kazmierski Kamil , Zajdel Radoslaw , Sośnica Krzysztof
Published: March 2021

Navigation systems have substantially evolved in the last decade. The multi-GNSS constellation including GPS, GLONASS, Galileo, and BeiDou consists of more than a hundred active satellites. To fully exploit their potential, users should be able to take advantage of those systems not only in postprocessing mode employing final solutions but also in real-time. It is also important to make satellite signals highly useful in a real-time regime not only in standard positioning mode but also with the precise positioning technique. That is why real-time products are highly desirable. One of the IGS Analysis Centers that support multi-GNSS real-time solution is CNES which provides not only orbits and clocks but also code and phase biases and VTEC global maps. Over the last few years, real-time products have been changing similarly to navigation systems, which come along with observation availability and calculation strategy changes.

We utilize the signal-in-space ranging error (SISRE) as the main orbit and clock quality indicator. Additionally, SLR observations are used as an independent source of information about orbit quality. Three years of data, between 2017 and 2020, are used to check the progress in the quality of the delivered products to the users through the internet streams provided by CNES.

The progress in the product quality in the test period is obvious and it depends on the satellite system, block or satellite type, time, and the height of the Sun above the orbital plane. The most accurate orbits are available for GPS, however, the very stable atomic clocks of Galileo compensate for systematic errors in Galileo orbits. Consequently, the SISRE for Galileo is lower than that for GPS, equaling 1.6 and 2.3 cm for Galileo and GPS, respectively. The SISRE value for GLONASS, despite the good quality of the orbits, is disturbed by the lower quality of the onboard clocks and is equal to 4-6 cm. The same quality level is for BeiDou-2 MEO and IGSO satellites. Products for BeiDou-2 GEO satellites are less accurate and with poor availability due to a large number of satellite maneuvers, thus they are not very useful for real-time positioning.

For positioning purposes, the presented results may be interesting especially in the context of the proper observation weighting in the multi-GNSS combinations. It is worth mentioning that the quality of the real-time products is not constant and neglecting this fact may bring undesirable positioning errors, especially for long processing campaigns.
Timing of fault gouge formation and fluid-rock interaction during tectonic inversion of the Penninic Frontal Thrust (SW Alps)
Authors: Bilau Antonin , Rolland Yann , Schwartz Stéphane , Godeau Nicolas , Guihou Abel , Deschamps Pierre , Gautheron Cécile , Pinna-Jamme Rosella , Brigaud Benjamin , Mangenot Xavier , Noret Aurélie , Melleton Jérémie , Dumont Thierry
Published: March 2021

In the last decade, important improvements in dating methods have been made and make it possible to go into the details of fault gouge formation and evolution. Common minerals like calcite and hematite can now bring detailed information on timing of fault development and fluid-rock interaction. We applied those novel techniques to a tectonically well constrains alpine context, though still lacking key chronological constrains. The targeted fault zone is the Penninic Frontal Thrust (PFT) of SW Alps, which is a major tectonic boundary that juxtaposed the metamorphic internal Alps over the unmetamorphosed external Alps, primarily as a thrust during the Oligocene (Simon-Labric et al., 2009). The PFT was later reactivated as an extensional detachment in the Mio-Pliocene, though the age of this reactivation remained unconstrained. Sue and Tricart (2003) showed that ongoing extensional seismic activity along the PFT, corresponding to the High-Durance Fault System (HDFS), is characterized at the surface, by an extensional fault network. In this context, the HDFS corresponds to extensional reactivation of the PFT as a consequence of Pelvoux external crystalline massif exhumation.

In this study, we coupled field tectonic, in-situ calcite U-Pb and hematite (U-Th-Sm)/He dating to stable and clumped isotope analysis to infer the HDFS activation age and to investigate the related fluid circulations. Isotopic signature (δ13C and δ18O) of compressional veins, en-echelon extensional veins and cataclasite fault gouge have been determined (Bilau et al., 2020).

This study allows pinpointing the evolution of deformation and fluid-rock interaction in the PFT footwall during its progressive extensional exhumation. The older U-Pb ages obtained on the cement of the gouge fault range between 5 to 3.5 Ma and taking into consideration uplift rate, comparison to currently seismicity depth and calcite brittle/ductile transition temperature, calcite crystallization may have occurred between 5 to 2 km. The hematite crystallization appears at shallower levels in the latest stages of the fault displacement at 3-1 km depth. A transition in the nature of fluids, controlling the redox state, can be highlighted here. This transition occurs between the calcite and hematite forming events at 2-3 km depth, which is probably related to a significant influx of meteoric fluids into the drainage of the fault system.
Assessing the effect of the geomorphological complexity of glacier forefields on the multi-temporal water dynamics will provide better future models
Authors: Müller Tom , Schaefli Bettina , Lane Stuart
Published: March 2021

The river discharge of recently deglaciated headwater catchments shows strong variations at daily, seasonal and annual time-scales. These cycles are susceptible to changes in the near future due to rapid glacier retreat combined with warmer winters and earlier snowmelt. Low discharges, in particular, are not only driven by climatic conditions but are filtered by a number of geomorphological features, which are also rapidly evolving with glacier debuttressing, sediment transport and vegetation onset. Future water availability as well as discharge extremes of future deglaciated forefields can therefore only be explained by considering the co-evolution of both local climate and catchment geomorphology. Many hydrological predictions for high Alpine catchments fail to take into account such combined effects, which are relevant in better predicting winter low flow, as well as the recession behavior in autumn and potentially even peak flow events induced by later summer rainfall. These extremes are however of significant importance for ecosystem development on proglacial margins as well as for the management of hydropower, in particular of high elevation water.  In this study, we propose a detailed analysis of the yearly groundwater and river stage fluctuations of the proglacial zone of the Otemma glacier, one of the largest glaciers of the Swiss Alps. By decomposing the water fluctuations and comparing them with climate forcing, we analyze the role of key landscape features in smoothing and delaying the different water inputs. Using additional datasets of daily water electrical conductivity and water isotopes a finer description of the hydrological functions of these features is achieved. A perceptual model is then proposed, showing how the different water signals driven by climate are modified by the local geomorphology. We finally propose a new metric which encapsulates the hydrological effects of these landscape features and should allow for a better assessment of the filtering effect at the  catchment-scale of the different water input signals. Using such a simple metric and the perceptual model should help in building or assessing more realistic hydrological models where the complex hydro-geomorphological interactions are better represented.
Statistical investigations of polar patch occurrence during high solar activity
Authors: Sieradzki Rafal , Paziewski Jacek
Published: March 2021

The circumpolar ionosphere is recognised as one of the most disturbed region of the ionized part of the atmosphere. The reasons for that are mainly dynamic conditions in the coupled system of the magnetosphere and the ionosphere as well as feeding of the polar plasma from the mid-latitude reservoir. One of the consequences of these phenomenon is the occurrence of large-scale ionospheric structures called polar patches. These are commonly defined as the enhancement of the F-region plasma characterized with a foreground-to-background density ratio larger than 2 and a size up to several hundred kilometres.

In this work we present GNSS-based characteristics of a patch occurrence in the northern hemisphere. The study covers a period of January–May 2014 corresponding to the maximum of the solar activity. The detection of structures was performed with a relative STEC value that is defined as a difference between epoch-wise L4 data and 4th order polynomial corresponding to background variations of the ionosphere. In order to ensure a continuous monitoring of the ionosphere over the north pole, we used data from ~45 permanent stations. The results prove that ground-based GNSS data can be successfully used in the climatological investigations of polar patches. We found a strong seasonal effect in the occurrence of these structures with the maximum at the turn of February and March and the minimum in May. Such outcomes correspond to variations of a TEC gradient between subauroral and polar regions. This parameter seems to be also responsible for a subdaily pattern of patches observed for particular months. The comparison of GNSS-based results with in-situ SWARM data revealed some differences, which are probably related to different characteristics of the ionosphere provided by both techniques. Furthermore, the study confirms that most of the patches are observed for the negative values of IMF Bz,  whereas IMF By component has no significant impact on the number of analysed structures. 
Shrubs covered by snow in the high Arctic cool down permafrost in winter by thermal bridging through frozen branches
Authors: Dominé Florent , Fourteau Kevin , Picard Ghislain
Published: March 2021

Warming-induced shrub expansion on Arctic tundra is generally thought to warm up permafrost, as shrubs trap blowing snow and increase the thermal insulation effect of snow, limiting permafrost winter cooling. We have monitored the thermal regime of permafrost on Bylot Island, 73°N in the Canadian high Arctic at nearby herb tundra and shrub tundra sites. Once adjusted for differences in air temperature, we find that shrubs actually cool permafrost by 0.6°C over November-March 2019, despite a snowpack twice as insulating in shrubs. By simulating the rate of propagation of thermal perturbations and using finite element calculations, we show that heat conduction through frozen shrub branches have a winter cooling effect of 1.5°C which compensates the warming effect induced by the more insulating snow in shrubs. In spring shrub branches under snow absorb solar radiation and accelerate permafrost warming. Over the whole snow season, simulations indicate that heat and radiation transfer through shrub branches result in a 0.3°C cooling effect. This is contrary to many previous studies, which concluded to a warming effect, sometimes based on environmental manipulations that may perturb the natural environment. The impact of shrubs on the permafrost thermal regime may need to be re-evaluated.
Rise and fall of rotaliids in the Paleocene-Eocene: the influence of climate and trophic competition
Authors: Benedetti Andrea , Papazzoni Cesare Andrea , Bosellini Francesca Romana
Published: March 2021

It is largely accepted that climate plays a pivotal role in the diversification of shallow-water communities, with special regards to larger foraminifera (LF), also because increase of surface water temperatures is often accompanied by change in trophic conditions. The shift from widespread eutrophic to oligotrophic conditions in shallow seas probably contributed to the LF differentiation during Paleocene-Eocene times. However, there are few recent attempts to quantify the changes in biodiversity and to correlate them with the global climatic events of the Paleogene. We concentrated our attention on the group of rotaliids, resilient taxa that partially survived after the mass extinction occurred at the end of the Cretaceous.

Our data show that their differentiation at genus level was very rapid, reaching its maximum already in the late Danian SB2 Zone. Specific diversification, instead, culminated in late Thanetian SB4 Zone. A second peak in specific diversity is recorded during the Cuisian (upper part of the Ypresian), then rotaliid diversity steadily declined, as long as other groups of larger foraminifers, especially Alveolina and Nummulites, became more competitive and proliferated with a large number of species up to the Bartonian SB17 Zone, when a significant drop in rotaliid biodiversity is recorded.

Differently to other taxonomic groups, i.e., alveolinids and nummulitids, for which a single genus during the whole Eocene generated numerous species, rotaliid genera are usually characterized by a low number of species, possibly due to the re-opening of ecological niches after the abrupt decrease of diversity that followed the PETM event. The competition with other K-strategist LF probably contributed to the decline of rotaliids in the middle Eocene up to the MECO event, where a last dramatic drop is recorded.

The major changes appear strictly linked to warming events such as the Late Danian Event (LDE, starting of the generic diversification of rotaliids), Paleocene Eocene Termal Maximum (PETM, faunal turnover followed by abrupt decrease in both generic and specific diversity), Early Eocene Climatic Optimum (EECO, increase in number of K-strategists under widespread oligotrophic conditions) and Middle Eocene Climatic Optimum (MECO, ultimate drop in diversity and competition with other larger foraminifers).

This study was funded by the Italian Ministry of Education and Research (MIUR), funds PRIN 2017: project “Biota resilience to global change: biomineralization of planktic and benthic calcifiers in the past, present and future” (prot. 2017RX9XXY).
Direct radiative effects of smoke aerosol during the extreme 2019/2020 Australian wildfire season
Authors: Heinold Bernd , Baars Holger , Christensen Matthew , Kubin Anne , Ohneiser Kevin , Schepanski Kerstin , Schrödner Roland , Senf Fabian , Tegen Ina
Published: March 2021

Record wildfires affected Australia from December 2019 to early 2020. Massive plumes of fire pollutants were lifted into the upper troposphere and even into the stratosphere by pyro-convection triggered by the intense heat of the fires. Subsequently the smoke aerosol was transported over thousands of kilometres eastwards at above 20 km altitude as Lidar observations in South America and satellite imagery show. Space and ground-based remote sensing of aerosol optical thickness indicate a temporary substantial increase in aerosol loading over large parts of the Southern Hemisphere, which offset the usual hemispheric contrast in aerosol. In addition to the massive impact on air quality at Australia’s east coast, this had important effects on the hemisphere-wide radiation budget.

We investigate the dispersal of the fire smoke aerosol and its radiative effects with the global aerosol-climate model ECHAM6.3-HAM2.3. Biomass burning emissions are prescribed by daily satellite-based estimates from the Global Fire Assimilation System (GFAS). As the horizontal model resolution is too coarse to explicitly resolve convection, the injection height of Australian fire smoke is set to heights between 5 and 15 km and varied in terms of sensitivity studies. The model results for late 2019 and early 2020 are evaluated with ground and satellite remote sensing measurements, as well as contrasted with smoke results for years with low Australian wildfire emissions. The sensitivity results show how the fire injection heights affect the evolution of the smoke plume but also what role radiatively induced self-lifting plays. According to the model, the 2019/20 Australian wildfires considerably perturbed the radiation budget of the Southern Hemisphere. Due to large transport heights relative to clouds and a long lifetime of smoke particles in the stratosphere, the solar irradiance at ground averaged from January to March 2020 decreased by more than 1 W m-2 for the Southern Hemisphere, which corresponds roughly to the short-term cooling caused by a large volcanic eruption, while the elevated smoke layers experienced significant absorptive heating.

Considering the recent series of extreme wildfires globally and their probably further increasing occurance in a changing climate,  these results indicate a need for larger attention to pyro-convection in global climate modelling.
Ionospheric plasma irregularities inside the mid-latitude trough by using Swarm observations
Authors: Liu Yiwen , Xiong Chao , Wan Xin
Published: March 2021

The mid-latitude ionospheric trough (MIT) is a well-known feature in the topside ionosphere and plasmasphere. In this report, we investigated the plasma irregularities inside the MIT region based on the high-resolution (2 Hz) measurements of electron density and temperature from the Swarm satellite. We developed a method to automatically identify the mid-latitude trough from Swarm in-situ density measurements, and the small-scale irregularities inside MIT region can also be well determined by considering appropriate thresholds of both the relative (∆Ne/Ne) and absolute (∆Ne) density fluctuations. Further statistics has been performed based-on the multi-years database of identified MITs and irregularities from Swarm. Finally, we provided for the first time the seasonal and magnetic local time distributions of irregularities within the MIT region, and the involved plasma instabilities that cause the irregularities at the MIT region have been discussed.
Dynamic rainfall mapping using multi-radar multi-gauge observations in changing synoptic environments
Authors: Gou Yabin , Chen Haonan
Published: March 2021

It is well known that the performance of radar-derived quantitative precipitation estimates greatly relies on the physical model of the raindrop size distribution (DSD) and the relation between the physical model and radar parameters. However, incorporating changing precipitation microphysics to dynamically adjust the radar reflectivity (Z) and rain rate (R) relations can be challenging for real-time applications. In this study, two adaptive radar rainfall approaches are developed based on the radar-gauge feedback mechanism using 16 S-band Doppler weather radars and 4579 surface rain gauges deployed over the Eastern JiangHuai River Basin (EJRB) in China. Although the Z–R relations in both approaches are dynamically adjusted within a single precipitation system, one is using a single global optimal (SGO) Z–R relation, whereas the other is using different Z–R relations for different storm cells identified by a storm cell identification and tracking (SCIT) algorithm. Four precipitation events featured by different rainfall microphysical characteristics are investigated to demonstrate the performances of these two rainfall mapping methodologies. In addition, the short-term vertical profile of reflectivity (VPR) clusters are extensively analyzed to resolve the storm-scale characteristics of different storm cells. The verification results based on independent gauge observations show that both rainfall estimation approaches with dynamic Z–R relations perform much better than fixed Z–R relations. The adaptive approach incorporating the SCIT algorithm and real-time gauge measurements performs best since it can better capture the spatial variability and temporal evolution of precipitation.
A new mechanism for generating a bolus within a double layer following Scott Russell
Authors: Fourdrinoy Johan , Dambrine Julien , Petcu Madalina , Pierre Morgan , Rousseaux Germain
Published: March 2021

While seeking to revisit an old experiment of John Scott Russell, we discovered a new mechanism for generating a non-shoaling bolus (an ovoid coherent mass of recirculating mixed fluids immerged in a surrounding medium/a of different density/ies) propagating along a pycnocline. In a study about dead-water (Fourdrinoy et al. 2020), a wave resistance phenomenon induced by internal waves formation at the interface between waters of different densities, we modified the setup used by Scott Russell. The Scottish engineer studied the formation and propagation of dispersive waves when an object is removed from a laterally confined open channel with a shallow layer of water. The “vacuum” created by the mass removal generates a linear dispersive free surface deformation with a front of negative polarity followed by a wave train. If we extend this configuration to a two-layers stratification, we can observe a linear dispersive wave with negative polarity à la Scott Russell, propagating along the interface. In addition, the removal of the object generates under certain conditions a bolus which induces a mixing zone and a gradient transition layer. We will present this new method of boluses creation, as well as an experimental characterization with space-time diagrams thanks to a subpixel detection procedure.

The dual nature of the dead-water phenomenology: Nansen versus Ekman wave-making drags.
Johan Fourdrinoy, Julien Dambrine, Madalina Petcu, Morgan Pierre and Germain Rousseaux.
Proceedings of the National Academy of Sciences, Volume 117, Issue 29, p. 16739-16742, July 2020.
Missing evidence for landscape transience induced by tectonic forcing since the Late Quaternary in the steep marginal escarpments of the Korean Peninsula
Authors: Byun Jongmin
Published: March 2021

Steep and narrow escarpments develop along the eastern margin of the Korean Peninsula. They are compartments of a passive continental margin and thus have been considered tectonically stable. In contrast to the traditional notion, geomorphic markers indicative of the enhanced tectonic uplift since the Late Quaternary (i.e., coastal terraces at several different altitudes) have been observed along the eastern coastal areas of the peninsula. Therefore, the steep escarpments in the eastern margin are assumed to be tectonically reactivated. However, the spatial magnitude and timing of the reactivation and how the escarpments have responded to the reactivation have not been well studied. Knickzone is a typical geomorphic marker, which has long been utilized for deciphering the history and distribution of tectonics. Here, we examined the knickzones of the marginal escarpments, where transient knickzones are likely to be observed, in order to understand the spatial pattern of the Late Quaternary reactivation and its effects on the evolution of the marginal escarpments. We used SRTM 1 arc-second DEMs, satellite images with fine resolution, and geological maps to identify and classify knickzones. We also conducted field surveys for the verification of the identified knickzones. As a result of the knickzone analysis, 46 knickzones were identified in the study catchments. Their mean length and gradient are 461 m and 0.19 m/m, respectively. Most knickzones are at relatively high altitudes (i.e., median elevation 532 m) and thus are placed far from the coast. According to the classification of the identified knickzones, they are formed mainly due to varying rock types (11) or changes in lithologic features of the same rock type (e.g., weathering degree of rocks) (31). Few of them are associated with the accumulation of coarse sediments at a channel junction (3) and meander neck cut-off (1). This result implies that all identified knickzones in the study catchments are stationary rather than transient. Consequently, it postulates that the Late Quaternary tectonic forcing was insufficient to generate any transient knickzone. Otherwise, potential transient knickzones due to the reactivation might have disappeared rapidly during their upstream migration, which seems highly relevant to the high concavity of the stream profiles in the drainage basins of the escarpments. Additionally, the result suggests that transient knickzone is not a good indicator for interpreting the responses of the marginal escarpments to the reactivation during the Late Quaternary.
Impacts of climate and land use changes on the erosion processes in a Mediterranean agricultural catchment (Northern Morocco)
Authors: Briak Hamza , Moussadek Rachid , Aboumaria Khadija , Kebede Fassil , Mrabet Rachid
Published: March 2021

Recent studies on vulnerability to climate and land use change show a trend towards increased aridity accelerating soil erosion which is the primary factor to be considered by decision makers in the environmental field. Furthermore, to reduce the soil erosion intensity, it is required to clarify the sources zones of sediment yield where soil conservation works have to focus on. The model selected for this work is the Soil and Water Assessment Tool (SWAT) which is one of many models widely used to assess soil erosion risk and simulate conservation measures efficiency. In fact, the objective of this work is to evaluate the effects of different agricultural Best Management Practices (BMPs) on sediments using SWAT model in the Kalaya river basin located in the North of Morocco in order to recommend the most appropriate one. The model was calibrated and validated using observed data of flow and sediment concentration; the performance of the model was evaluated using statistical methods and the total soil erosion rate was estimated by this model in the study area. However, we concentrated on the representation of three interesting and most usable practices by the SWAT model: contouring, strip-cropping and terracing. The general parameters of the model have been modified to reflect the implementation of four different BMPs. The modification of these parameters was based on previous research and modeling efforts conducted in watersheds. Resulting sediment yield were compared with the result of simulation of the baseline scenario (existing conditions). In fact, effective measures to reduce sediment losses at the watershed level are organized according to their effectiveness, and these are terracing (28% reduction and the value is 15t/ha/y) followed by strip-cropping (9% reduction and the value is 5t/ha/y). On the other hand, measurements performed by the contouring are inappropriate for the study area because they have contributed to increasing the soil erosion (more than 31% of losses and the value is 17t/ha/y more than existing conditions). The mean annual values of sediment yields obtained for scenarios with and without BMPs were compared to assess the effectiveness of BMPs. Among all other practices, terracing was the most effective BMPs for reducing sediments which is perfectly recommended in the Mediterranean regions in general to avoid the risk of damage during intense rainfall. These results indicates that the use of terracing on agricultural land can potentially make improvements marked the control and limitation of soil erosion, and it also affords useful information for involved stakeholders in water and soil conservation activities for targeted management.
Role of initial condition and parametric uncertainty in a severe hailstorm forecast
Authors: Kuntze Patrick , Miltenberger Annette , Hoose Corinna , Kunz Michael
Published: March 2021

Forecasting high impact weather events is a major challenge for numerical weather prediction. Initial condition uncertainty plays a major role but so potentially do uncertainties arising from the representation of physical processes, e.g. cloud microphysics. In this project, we investigate the impact of these uncertainties for the forecast of cloud properties, precipitation and hail of a selected severe convective storm over South-Eastern Germany.
To investigate the joint impact of initial condition and parametric uncertainty a large ensemble including perturbed initial conditions and systematic variations in several cloud microphysical parameters is conducted with the ICON model (at 1 km grid-spacing). The comparison of the baseline, unperturbed simulation to satellite, radiosonde, and radar data shows that the model reproduces the key features of the storm and its evolution. In particular also substantial hail precipitation at the surface is predicted. Here, we will present first results including the simulation set-up, the evaluation of the baseline simulation, and the variability of hail forecasts from the ensemble simulation.
In a later stage of the project we aim to assess the relative contribution of the introduced model variations to changes in the microphysical evolution of the storm and to the fore- cast uncertainty in larger-scale meteorological conditions.
Seven years of monthly low-degree gravity field models from Swarm GPS data
Authors: de Teixeira da Encarnacao Joao , Arnold Daniel , Bezdek Ales , Dahle Christoph , Guo Junyi , van den IJssel Jose , Jaeggi Adrian , Klokocnik Jaroslav , Krauss Sandro , Mayer‐Guerr Torsten , Meyer Ulrich , Sebera Josef , Shum CK , Visser Pieter , Zhang Yu
Published: March 2021

The Swarm satellite constellation provides GPS data with sufficient accuracy to observe the large-scale mass transport processes occurring at the Earth’s surface since 2013. We illustrate the signal content of the time series of monthly gravity field models. The models are published on quarterly basis and are the result of a combination of the individual models produced by different gravity field estimation approaches, by the Astronomical Institute of the University of Bern, the Astronomical Institute of the Czech Academy of Sciences, the Institute of Geodesy of the Graz University of Technology and the School of Earth Sciences of the Ohio State University. We combine the models at the solution level, using weights derived from a Variance Component Estimation, under the framework of the International Combination Service for Time-variable Gravity Fields (COST-G).

 

We estimate the monthly quality of the models by comparing with GRACE and GRACE-FO products and illustrate the improvement of the combined model as compared to the individual models. We present the high signal-to-noise ratio of this uninterrupted time series of models, smoothed to 750km radius, over large hydrological basins. Finally, we compare the behavior of degree 2 and 3 coefficients with GRACE/GRACE-FO and SLR.
Sediment transfer in the Rhône River Basin, Switzerland: the role of localized severe Alpine storm events on triggering turbidity currents in Lake Geneva
Authors: Mettra François , Blanckaert Koen , Lemmin Ulrich , Barry David Andrew
Published: March 2021

In Lake Geneva, a deep peri-Alpine lake in Switzerland, the sublacustrine Rhône River delta presents a deep canyon, the Rhône Canyon. Previous studies and recent observations show that low-velocity underflows and high-velocity turbidity currents pass frequently in the Rhône Canyon. The former carry little sediment, are long-lasting, slow moving and typically occur in winter when the lake is destratified, whereas the latter are sediment-rich, short-lived and occasionally generate high velocities. In the present study, we revisit three different event types that can trigger turbidity currents in the Rhône Canyon: large-scale floods of the Rhône River, sublacustrine slides on the Rhône delta and short high concentration sediment transport events induced by localized severe storms in the Rhône watershed (~5500 km2). Simultaneous observations of hyperconcentrated sediment-laden floods or debris flows in small sub-catchments (as small as 4 km2), suspended sediment concentration at the Rhône river mouth, and velocity profiles in the Rhône canyon demonstrate how localized storm events trigger turbidity currents in the canyon. Evidence that these turbidity currents can continue into the deep hypolimnion of Lake Geneva is provided. Preliminary estimations of the frequency of turbidity currents relative to their type of triggering and their contribution to the total sediment load discharged into Lake Geneva are discussed.
Irregular stick-slip and the role of cohesion in an ice friction experiment
Authors: Korkolis Evangelos , Gimbert Florent , Weiss Jérôme , Renard François
Published: March 2021

Understanding the evolution of fault strength over multiple interseismic periods is crucial to quantifying seismic hazard. According to Coulomb’s failure criterion, restrengthening, or healing, may result from an increase in friction and/or in cohesion. Classic sliding experiments on rocks and fault gouges are not able to resolve the contribution of cohesion to the healing of frictional interfaces. Here, we present a zero nominal normal stress friction experiment capable of large displacements that exhibits similar complexity as the deforming lithosphere (intermittent, aperiodic deformation; Gutenberg-Richter-type scaling of event sizes). This Couette-type apparatus is designed to shear millimeter-thick layers of columnar ice, grown in-situ in a meter scale circular water tank. When the system is driven at low sliding velocities, the ice plate fractures and sliding occurs along a complex, non-prescribed frictional interface. Water beneath the ice can percolate through the sliding interface and freeze, increasing its strength. A torque gauge and an array of acoustic emission transducers are used to measure the shear strength of the frictional interface and to monitor acoustic activity. Previous work, using constant values of sliding velocity, showed that deformation occurs via a combination of slow and fast slip events, and that the “seismic” part consists of two populations of acoustic emission (AE) events: standalone and correlated, with different Gutenberg-Richter b-values. The asymmetric shape of the shear stress (torque) fluctuations was attributed to cohesion-dominated strength recovery. We are currently using a new, high speed sampling system to investigate the relationship between the stress fluctuations and the concurrent AE activity in constant as well as variable sliding velocity experiments. This work aims to evaluate the effect of time-dependent processes on systems that deform intermittently.
Biological processes in modelling soil functions – a balancing act between too complex and too simple
Authors: König Sara , Weller Ulrich , Reitz Thomas , Betancur-Corredor Bibiana , Lang Birgit , Vogel Hans-Jörg , Wollschläger Ute
Published: March 2021

Mechanistic simulation models are an essential tool for predicting soil functions such as nutrient cycling, water filtering and storage, productivity and carbon storage as well as the complex interactions between these functions. Most soil functions are driven or affected by soil organisms. Yet, biological processes are often neglected in soil function models or implicitly described by rate parameters. This can be explained by the high complexity of the soil ecosystem with its dynamic and heterogeneous environment, and by the range of temporal and spatial scales these processes are taking place at. On the other hand, the technical capabilities to explore microbial activity and communities in soil has greatly improved, resulting in new possibilities to understand soil microbial processes on various scales.

However, to integrate such biological processes in soil modelling, we need to find the right level of detail. Here, we present a systemic soil model approach to simulate the impact of different management options and changing climate on soil functions integrating biological activity on the profile scale. We use stoichiometric considerations to simulate microbial processes involved in different soil functions without explicitly describing community dynamics or functional groups. With this approach we are able to mechanistically describe microbial activity and its impact on the turnover of organic matter and nutrient cycling as driven by agricultural soil management.

Further, we discuss general challenges and ongoing developments to additionally consider, e.g., microbe-fauna-interactions or microbial feedback with soil structure dynamics.
A scale-independent cost-effective design of Nature-Based Solutions within a multifractal framework
Authors: Qiu Yangzi , Schertzer Daniel , Tchiguirinskaia Ioulia , Monier Laurent , Willinger Bernard , Tisserand Bruno
Published: March 2021

In the last decades, Nature-Based Solutions (NBS) have become widely considered as a sustainable development strategy for the development of urban environments. Many previous studies only focused on the hydrological performances of NBS, whose economic impacts were not considered. Some studies considered both hydrological performances and economic costs to design cost-effective NBS scenarios, but only at a single catchment scale. Thus, a comprehensive investigation of NBS in terms of both hydrological performances and Life cycle costs (LCC) within the Universal Multifractal (UM) framework is significant for improving the multi-scale resilience of cities. In this study, the hydrological response of a 5.2 km2 semi-urban watershed is investigated under various NBS scenarios and highly spatially variable rainfall events. First, the heterogeneous spatial NBS distribution in each scenario is quantified using their fractal dimension. Then, the hydrological responses are assessed with the help of the fully-distributed and physically-based model (Multi-Hydro) with a spatial resolution of 10 m. To evaluate the cost-effectiveness of NBS scenarios across scales, the statistical scale-independent “maximum probable singularity” γs, as defined in the UM framework, is combined with the economic indicator (LCC) to obtain the scale-independent cost-effectiveness (scale-independent CE) indicator for designing cost-effective NBS scenarios. The effective maximum singularity γmax of each simulation is combined with LCC at different scales to obtain a scale-dependent cost-effectiveness (scale-dependent CE) indicator to be compared with the scale-independent CE. Results show that CEs obtained by both methods are strongly correlated, especially over the small-scale range. Therefore, the scale-independent CE based on UM framework is considered as an appropriate indicator to design NBS implementation at different scales.

Overall, this study presents a new approach for designing cost-effective NBS scenarios. This approach is based on the UM framework and enables to quantify the NBS scenario cost-effectiveness across a range of scales with the help of a scale-independent CE indicator. This approach can be efficiently applied to urban planning across various scales.
Predicting the Antarctic sea level contribution to sea level rise with emulation
Authors: Turner Fiona , Edwards Tamsin ,   ISMIP6 team and others
Published: March 2021

The Antarctic ice sheet has the potential to be a major contributor to future global sea level rise, but this has been difficult to predict, in part due to the combination of expected ice mass loss and snowfall accumulation. A great deal of uncertainty arises from the large variation of atmospheric and oceanic changes across climate models, and sensitivity to ocean changes across ice sheet models, but these uncertainties cannot be fully sampled because the models are too computationally expensive.

Here we make projections of Antarctica’s contribution to global sea level rise based on the simulations of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). Using a Gaussian process emulator, a statistical approximation of expensive computer models, we estimate probability distributions by sampling uncertainties in future climate and ice sheet sensitivity to ocean warming far more thoroughly than the original ISMIP6 ensemble could. We find a sea level contribution of 4 cm (5th-95th percentile range -5 to 14 cm) sea level equivalent by 2100 under current emissions policies, increasing to 21 cm (5th-95th percentile range 7 to 43 cm) if we use the subset of climate models, ice sheet models and ice sheet/ocean sensitivity values that lead to the highest sea level contributions.

We then compare the output from this emulator to a linear mixed model emulator, which  incorporates a random effect to represent the variation arising from different ice sheet models. We do this for all three Antarctic regions (West and East Antarctica, and the Peninsula) under two greenhouse emissions scenarios (SSP1-26 and SSP5-85). Both methods produce similar probability distributions of sea level contribution in 2100, demonstrating that differences in statistical models are not dominating the results.