bluuebunny/crossref_metadata_2025 huggingface dataset:
Making an informed use of observations and climate models to advance understanding of past and future sea ice changes
Authors: Massonnet François
Published: March 2020

Polar Regions are viewed by many as "observational deserts", as in-situ measurements there are indeed scarce relative to other regions. The increasing availability of satellite observations is salutary but does not entirely solve the problem due to persistent uncertainties in the derived products. Climate models have been instrumental in completing the big picture. However, models are themselves subject to errors, some of which are systematic. How to take advantage of the respective strengths of observations and models, while minimizing their respective weaknesses? To illustrate this point, I will discuss how recent advances in data assimilation, model evaluation, and numerical modeling have enabled major progress in tackling important questions in polar research, such as: What are the causes of the recent Antarctic sea ice variability? What might the future of Arctic sea ice look like? How to improve the skill of seasonal sea ice predictions? How should the existing observational network be improved at high latitudes? What are the priorities in terms of sea ice modeling for climate change studies? By running through these cases, I will provide evidence for the emerging hypothesis that "the whole is greater than the sum of its parts": treating observations and climate models as two noisy instances of the same, but unknown truth, gives insights that would not be possible if each source was used separately.
Climate extremes and ecosystem resilience in a future world
Authors: Bahn Michael
Published: March 2020

The ability of ecosystems to resist and recover from climate extremes is of fundamental societal importance given the critical role of ecosystems in supplying ecosystem services such as food and fiber production, or water and climate regulation. To date there is a lack of understanding of how the projected increases in the frequency and intensity of climate extremes will affect ecosystems in a future world. Will the legacy of past extreme climatic events alter ecosystem responses to subsequent extreme events? What are the thresholds of severity altering ecosystem recovery from extreme events or causing irreversible shifts in ecosystem functioning? How do ecosystems respond to climate extremes in the context of multiple co-occurring environmental changes, including climate warming, elevated atmospheric CO2 concentrations, and interacting other climate extremes (i.e. ‚compound events‘)? In what ways do biodiversity and the composition of species and their traits affect ecosystem resilience? How do land management and land-use changes alter ecosystem responses to climate extremes? In this talk I will show some recent insights on these questions and will illustrate how observations can be placed in a framework permitting a comparable quantification of resilience across different ecosystems, ecosystem functions and services. Finally, I will discuss implications for enhancing the adapaptive capacity of social-ecological systems to absorb climate extremes.
Sharp changes in lake-levels preconditioning seismogenic mass failures in the Dead Sea
Authors: Lu Yin , Agnon Amotz , Marco Shmuel , Bookman Revital , Waldmann Nicolas , Wetzler Nadav , Alsop Ian , Moernaut Jasper , Strasser Michael , Hubert-Ferrari Aurélia
Published: March 2020

Subaqueous mass failures that comprise slides, slumps and debris flows are a major process that transport sediments from the continental shelf and upper slope to the deep basins (both oceans and lacustrine settings). They are often viewed together with other natural hazards such as earthquakes, and can have serious socioeconomic consequences. It is increasingly important to understand the relationship between mass failures and climate-driven factors such as changes in water-level. Despite extensive marine investigations on this topic world-wide, the relationship between changes in water-level and mass failures is still highly disputed. This is due largely to the significant uncertainties in age dating and different potential triggers and preconditioning factors of mass failure events from different geological settings. Here, we present a 70 kyr-long record of mass failure from the Dead Sea Basin center (ICDP Core 5017-1). This sedimentary sequence has been dated in high accuracy (±0.6 kyr) and has similar responses to climate forcing. Moreover, the mass failure record is interpreted to be controlled by a single trigger mechanism (i.e. seismicity).
Based on the recent detailed study on the sedimentological signature of seismic shaking in the Dead Sea center, these seismogenic mass failures (seismites) account only for a part of the whole seismites catalog, suggesting that mass failure follows only part of seismic shaking irrespective of intensities of the shaking. This is evidenced by the common absence of mass failures following the in situ developed and preserved seismites (e.g., the in situ folded layer and intraclast breccias layer) which represent different intensities of seismic shaking. This feature implies that some non-seismic factor(s) must have preconditioned for the seismogenic mass failures in the Dead Sea center.
Our observations reveal decoupling between change in sedimentation rates and occurrence probability of these seismogenic mass failures, thus suggesting that a change in sedimentation rate is not the preconditioning factor for the failure events. While 79% of seismogenic mass failure events occurred during lake-level rise/drop in contrast to 21% events occurred in the quiescent intervals between. Our dataset implies that seismogenic mass failures can occur at any lake-level state, but are more likely to occur during lake-level rise/drop due to the instability of the basin margins. In addition, the seismogenic mass failures occurred more frequently during glacials (characterized by highstand and high-amplitude lake-level changes) than during interglacials, as a result of the morphologic characteristics of the lake margin slopes and different lithologies (e.g. halite) influences which are both connected to the glacial-interglacial lake-level changes.
Review of flood and ice forecasting systems and methodologies in the Danube River countries
Authors: Sraj Mojca , Kobold Mira , Petan Sašo , Bezak Nejc , Brilly Mitja
Published: March 2020

The Danube River basin is the most international river basin in the world with many large tributaries having catchments in 19 countries. Since frequency of floods in the Danube River basin increased in the last decades, the need for a more effective and harmonized regional and cross-border cooperation in the field of flood and ice forecasting arises. The need for enhanced cooperation in flood protection was officially recognized in various international and interregional policy documents, therefore DAREFFORT project was initiated under the Interreg Danube Transnational Programme to identify the state of the art of flood and ice forecasting techniques and raise awareness among the countries about the basic problems of flood and ice forecasting (e.g. the lack of a unified data exchange at the catchment level) and to help implement the Danube Flood Risk Management Plan in line with the Flood Risk Directive.

The main aim of the DAREFFORT project is to give a comprehensive overview about the complex national flood and ice forecasting systems and to eliminate the shortcomings of the existing forecasting practices as well as to improve the exchange and availability of hydrological and meteorological data between the participating countries with establishment of the Danube Hydrological Information System (Danube HIS). In order to achieve this goal, national reports on the status quo of the Danube regional flood and ice forecasting system and methodologies as well as a detailed questionnaire were prepared by all project partner countries. Information about the countries’ hydrological and meteorological data availability, recording methods and coverage with the monitoring networks, codings and national database system, data flow, forecasting time intervals and accuracy, response times, cross-border issues and data dissemination etc. was covered in the questionnaire. The evaluation of 12 national reports and results of questionnaires showed a comprehensive overview of flood and ice forecasting systems and methodologies in the Danube River basin.

The gathered information about national flood and ice forecasting practices and the acquired knowledge through the project implementation process will result into an international policy proposal for a harmonized data exchange protocol, including the sufficient quantity, quality, and format of the data exchange.
Remote Sensing for Convective System Tracking and Associated Sea Surface Wind Pattern Detection
Authors: La Tran Vu , Messager Christophe , Sahl Rémi , Honnorat Marc
Published: March 2020

Convective Systems (CS) are dangerous weather events since they are associated with intense precipitation (up to 50 mm/hr) and strong surface winds (exceeding 20 m/s), for instance over the sea surface. Furthermore, they happen suddenly and evolve quickly, and thereby their effects on the sea surface are difficult to track and predict. Thanks to the geostationary meteorological satellites of METEOSAT (Europe), GOES (USA), and Himawari (Japan), the CS detection and tracking can be performed in most of the world with a 5-15-minute observation time sampling and about 2.8-km spatial resolution (up to about 1-km for the new–generation satellites). Indeed, the instruments onboard these satellites perform the CS detection based on the identification of deep convective clouds. The deeper the convective clouds, the lower the brightness temperature is. The highest (coldest) clouds have the lowest brightness temperature (200 K–205 K).

While the CS detection has been significantly improved for recent years thanks to the infrared images, the investigation of strong winds (or wind gusts) produced by the CS downdrafts hitting the sea surface did not progress a lot. It is mainly due to the lack of in-situ data and (especially) high-resolution remote sensing images. Some studies proposed the use of ASCAT scatterometers for the detection of surface wind patterns associated with the CS. However, the ASCAT only identified the mesoscale patterns (100–300 km) and failed to detect the convective-scale gust fronts (5–20 km), due to their large spatial resolution (12.5–25 km wind grid). To be able to observe both small- and large-scale surface wind patterns, Synthetic Aperture Radar (SAR) images are used in this study thanks to their high spatial resolution, wide swath, and availability in most weather conditions. Indeed, the obtained results in (La et al., 2018, 2020) illustrate that Sentinel-1 (C-band SAR) may detect surface wind patterns in shapes of a mesoscale squall line and sub-mesoscale convection cells. The associated wind intensity with the patterns exceeds 10–25 m/s.

To strengthen the assumption that the detected wind patterns on SAR images are produced by the CS downdrafts hitting the sea surface, we use the corresponding METEOSAT images for the detection of deep convective clouds (200 K–205 K brightness temperature). The comparisons between Sentinel-1 and METEOSAT images illustrate that surface wind patterns and deep convective clouds have a matching in spatial location (and sometimes in shape). In particular, the coldest spots of deep convective clouds correspond to the one with high wind intensity (15–25 m/s) of the patterns. This result thus permits to highlight a strong relationship between the detected wind patterns on the sea surface and the CS aloft.
Direct injection of water vapor into the lower stratosphere through extreme convection: A case study for the summer 2019 in the mid latitudes
Authors: Khordakova Dina , Rolf Christian , Krämer Martina , Riese Martin
Published: March 2020

Water vapor is one of the strongest greenhouse gases of the atmosphere. Its driving role in the upper troposphere / lower stratosphere region (UTLS) for the radiation budget was shown by e.g. Riese et al., (2012). Despite its low abundance of 4 - 6 ppmv in the stratosphere, even small changes in its mixing ratio can leed to a positive feedback to global warming. To better understand changes and variability of water vapor in the lower stratosphere, we focus here on exchange processes from the moist troposphere to the dry stratosphere in the mid latitudes. These processes are caused by extreme vertical convection, which is expected to increase in intensity and frequency with progressive global climate change.

Within the MOSES (Modular Observation Solutions for Earth Systems) campaign in the summer of 2019, two extreme vertical convection events could be captured with balloon borne humidity sensors over the eastern part of Germany. The comparison of measurements before and after both events reveal distinct water vapor enhancements in the lower stratosphere and show that even in mid-latitudes over shooting convection can impact the water vapor mixing ratio in the UTLS. The measurements are compared with the Microwave Limb Sounder (MLS) data as well as ECMWF reanalysis data.

We will show a deeper analysis of both events by using visible and infrared weather satellite images in combination with meteorological fields of ECMWF. Backward trajectories of the air masses with the enriched water vapor mixing ratios calculated with the CLAMS model and combined with the satellite images can confirm the convective origin. Additionally, we show the further development of this distinct water vapor filaments within the lower stratosphere in order to trace the transport and mixing process, based on an analysis of forward trajectories.
Set-up and performance evaluation of a seismic rock fall observatory in the Alps
Authors: Schöpa Anne , Hovius Niels , Turowski Jens
Published: March 2020

Rock falls are important agents of erosion shaping the topography of bedrock slopes. Despite the considerable attention rock falls get when causing damage we still lack detailed information about the triggers, lag times, seasonal and elevation-dependent rock fall occurrence. This is due to the difficulty in observing rockfalls directly as the mobilisation of rock masses occurs rapidly, infrequently and distributed at a priori unknown locations. To identify seasonal and elevation-dependent rock fall activities and characteristics and their environmental drivers and triggers in an alpine setting, we have operated a monitoring network to detect and classify rock falls in the Reintal valley, German Alps, since 2014. The Reintal is an Alpine valley in the Wetterstein massif close to the Zugspitze, Germany’s highest mountain. The Reintal observatory produces nearly continuous datasets of seismic, meteorological and camera data. To our knowledge, these datasets are one of a few that permit a systematic study of rockfall patterns and their controls over a period of several years in an alpine setting.

In this contribution, we present the layout of the observatory and the instrumental network. Six seismometers record the motion of the ground; different types of seismic signals are shown and their sources discussed. This is done in combination with the meteorological data of the two weather stations in the valley and the images of the optical and infrared cameras of the observatory. We evaluate the performance, limitations and capabilities of the observatory. In addition, we discuss how we dealt with challenges such as power consumption of the instruments in the field, data storage and data loss. Our experience with the set-up and maintenance of the observatory can help guide the design and construction of other observatories in mountain environments.
Tectono-magmatic and thermal evolution of the SE China margin-NW Palawan breakup
Authors: Mohn Geoffroy , Nirrengarten Michael , Schito Andrea , Kusznir Nick , Corrado Sveva , Bowden Stephen , Pubellier Manuel , Sapin François , Larsen Hans-Christian
Published: March 2020

Continent Ocean Transitions (COTs) record the processes leading to continental breakup and localized oceanic accretion initiation. The recent IODP Expeditions 367-368 and 368X at the SE China margins combined with high quality multi-channel seismic profiles provide a unique dataset to explore the tectono-magmatic and thermal evolution from final rifting to early seafloor spreading. To investigate these issues, we developed a multi-disciplinary approach combining reflection seismic interpretations with geophysical quantitative analysis calibrated thanks to drilling results, from which we measured and modelled the thermal maturity in pre-/syn- to post-rift sediments.

Drilling results show that the transition from the most thinned continental crust to new, largely igneous crust is narrow (~20 km). During final rifting, decompression melting forming Mid-Ocean Ridge type magmatism emplaced within thinned continental crust as deep intrusions and shallow extrusive rocks concomitant with continued deformation by extensional faults. The initial igneous crust of the conjugate margins is asymmetric in width and morphology. The wider and faulted newly accreted domain on the SE China side indicates that magmatic accretion was associated with tectonic faulting during the formation of initial oceanic lithosphere, a feature not observed on the conjugate Palawan side. We suggest that deformation and magmatism were not symmetrically distributed between the conjugate margins during the initiation of seafloor spreading but evolved asymmetrically prior to the spreading ridge stabilising.

Organic matter from post-rift sediments has low thermal maturities due to limited burial and the absence of late post-rift magmatism. In contrast, pre to syn-rift sediments show significant variability in thermal maturities across the COT. Localised high thermal maturities for the pre- to syn-rift sediments requires that significant additional heat be imparted at shallow depths during breakup, likely related to magmatic intrusion or subsurface expressions of volcanism. The heterogeneous variation in thermal maturity observed across the COT reflects localised thermal perturbations caused by magmatic additions.
The effect of root exudates on soil nitrogen availability - an evaluation using microdialysis
Authors: Buckley Scott , Brackin Richard , Näsholm Torgny , Schmidt Susanne , Jämtgård Sandra
Published: March 2020

Plant root exudates are believed to increase root capture of nutrients (including nitrogen) by encouraging development of a rhizosphere root community, and providing them with an energy source to facilitate degradation of litter and soil organic matter. However, observing the consequences of root exudation on nutrient cycling and microbial activity is challenging with current methods, given the small scales involved. We investigated the effect of root exudation on nitrogen (N) availability by simulating root exudation with microdialysis. This novel technique enables continuous release of synthetic solutions of root exudates via diffusion in situ in soil by using a root-sized permeable membrane. Importantly, it also allows for simultaneously monitoring the effects on inorganic N fluxes. To emulate growth of a root tip through a specific soil region, sucrose was released for seven days before substituting sucrose with water for a further 7 days. We investigated boreal forest soils with and without litter amendments (ground pea shoots) to attain different C/N ratios and we used two rates of exudation by retrodialysing with either 0.5 or 5 mM sucrose solution. We observed that pea litter promoted significant N immobilisation, along with greater rates of sucrose release from microdialysis probes - peaking at 90.7 ± 8 µg sucrose m-2 s-1 using the 5 mM sucrose solution after three days. This suggests that greater root exudation may be driven by microbial demand for both C and N, with no short-term nutritional benefit for plant roots, even after exudation has ceased within a specific soil region. Glucose and fructose fluxes (breakdown products of sucrose) were also greatest in the litter treatment, indicating enzyme activity was promoted by the availability of both sucrose and litter. CO2 respiration measurements indicated significant differences between litter and control soils, but there was no detectable effect of sucrose exudation, suggesting that the small amounts of C supplied and the limited area influenced by the diffusion of sucrose had little impact on overall microcosm respiration. We conclude that short-term C exudation presented no immediate benefit for plant nutrition in our experiment. Future studies can benefit from using microdialysis to investigate the influence of more complex root exudate solutions, as well as the mechanistic roles of transpiration-induced mass flow on plant N availability in the rhizosphere.
The uncertainty in Antarctic sea-level rise projections due to ice dynamics
Authors: Blasco Javier , Tabone Ilaria , Moreno Daniel , Alvarez-Solas Jorge , Robinson Alexander , Montoya Marisa
Published: March 2020

Projections of the Antarctic Ice Sheet (AIS) contribution to future global sea-level rise are highly uncertain, partly due to the potential threat of a collapse of the marine sectors of the AIS. However, whether the inherent instability of such sectors is already underway or is still far away from being triggered remains elusive. One reason for ambiguity in results relies on the uncertainty of basal conditions. Whereas high basal friction can potentially prevent a collapse of the marine zones of the AIS, low basal friction can promote such a process. In addition, future sea-level projections from the AIS are generally run from an equilibrated present-day (PD) state tuned to observational data. However, this procedure neglects the thermal memory of the ice sheet. Furthermore, there is no apparent reason for ruling out that the PD may be subject to a natural drift since the onset of the last deglaciation (~20 kyr BP). Here we study the uncertainty in sea-level projections by investigating the response of the AIS to different RCP scenarios for four different basal-dragging laws. For this purpose we use a three-dimensional ice-sheet-shelf model that is spun up from a deglaciation. Model parameters of all friction laws have been optimized to simulate a realistic PD. In addition, we study the response of the AIS to a sudden CO2 drop to investigate the potential irreversibility of the ice sheet depending on the RCP scenario and friction law.
Testing the first-order SOC decay hypothesis over multiple sites through Bayesian uncertainty representation
Authors: Menichetti Lorenzo , Ågren Göran , Barré PIerre , Moyano Fernando , Kätterer Thomas
Published: March 2020

The conventional soil organic matter (SOM) decay paradigm considers SOM quality as the dominant decay limitation, and it is modelled with simple first-order decay kinetics. This view and modelling approach is criticized for being too simplistic and unreliable for predictive purposes. It is still under debate if first-order models can correctly capture the variability in temporal SOM decay observed between different environments. The hypothesis needs to be tested statistically, but this implies the use of a dynamic model with multiple degrees of freedom to describe the observations. Since we want to test the general validity of the SOC decay theory the test must also include multiple sites, and rises the problem of how to describe the unavoidable local variability. This defines a multivariate space where the hypothesis must be tested which, considering also the known problem of an equifinality “by design” in biogeochemical models, generate difficulties.

To address this issue, we calibrated a first-order model (Q) on six long-term bare fallow field experiments across Europe within a Bayesian framework assuming some general and some local parameters. Following conventional SOM decay theory, we assumed that parameters directly describing SOC decay (rate of SOM quality change and decomposer metabolism) are thermodynamically constrained, therefore valid for all sites. Initial litter input quality and edaphic interactions (both local by definition) and microbial efficiency (possibly affected by nutrient stoichiometry) were instead assumed to be site-specific. Initial litter input quality explained most observed kinetics variability, and the model predicted a convergence toward a common kinetics over time, while site-specific variables played no detectable role. All these characteristics could be represented with posterior probability distributions and their comparison provided the hypothesis testing.

According to our analysis the decay of decades-old SOM seemed mostly influenced by OM chemistry and was well described by first order kinetics and a single set of general kinetics parameters.
Vegetation history of Western Russia (Upper Dnieper, Smolensk region): Climate and human impact on landscape in last two millennia
Authors: Lavrenov Nikita , Ershova Ekaterina , Zhuravkova Margarita , Krenke Nikolay
Published: March 2020

Climate and vegetation history of Upper Dnieper region (Western Russia) is investigated poorly while archaeological studies provide evidences of human activities during last 3 millennia. Our study presents vegetation reconstruction based on pollen analysis of sediments extracted from two sites in Smolensk region. The first site is located in Katynka river bassin and pollen analysis of extracted buried soil, alluvium and peat sediments demonstrates vegetation dynamics in archaeologically rich area over 5 millennia. The second site is located in 50 km from to the west from Smolensk and in 15 km to east from the Russian-Belarus state border. The analysis of extracted peat sediments presents regional history of vegetation. The aim of our study is to compare data obtained from both sites and to estimate climate and human influence on vegetation during last two millennia when activities associated with agriculture changed Dnieper valley landscape significantly.

The first results of pollen analysis data of the first site allow to register significant human impact on vegetation 2.0-0.8 ka BP. Before that period pollen of indigenous forest trees dominates in spectra while since 2.0 ka BP pollen compassion changes dramatically and pollen of Betula and Pinus is in majority in so-called “Gnezdovo soil” lay. Medieval lays of sapropel contains mostly pollen of Pinus with admixture of Betula and Alnus. Taxonomic diversity and presence of meadow herbs, weeds and cultivated taxa pollen increases significantly (up to 30%). Dynamics of pollen composition in specimens from the second site allows us to register slow processes of indigenous vegetation recovery over last 3 centuries approximately. Modern analogue technique applied on pollen data and analysis of historical data makes possible to separate impacts of climate and human on vegetation of the past and to reconstruct the climate of last two millennia.

The study was funded by RFBR, project number 19-34-90172.
Historical droughts in the Qing dynasty (1644-1911) of China and the role of human interventions
Authors: Lin Kuan-Hui Elaine , Wang Pao K. , Pai Pi-Ling , Lin Yu-Shiuan
Published: March 2020

This study presents a new epistemology to analyze drought chronology through a clear-cut methodology for reconstructing past drought series as well as series for other associated ecological and societal variables. Instead of building grading system based on mixed criteria, this method can facilitate transparency in the reconstruction process and can enable statistical examinations of all variables when building the series. The data used is from the REACHES database, however other archival documentary and index data from independent sources are also applied to understand drought narratives and to cross check and validate the analysis derived from the REACHES. From time series analysis, six severe drought periods are identified in the Qing dynasty, and then spatial analysis is performed to demonstrate spatial distribution of drought and other variables in the six periods as well as social network analysis to reveal connections between drought and other ecological and societal variables. Research results clearly illustrate the role of human intervention to influence the impacts of drought on societal consequences. Particularly, the correlation between drought and socioeconomic is not strong; crop failure and famine are important intermediate factors, meanwhile ecological factor such as locust and disaster relief measures are all imperative to intervene between crop production and famine. Implications of the study on drought impact are provided as well as the significance of historical climate reconstruction studies.
Heteroaggregation of micro-polystyrene in the presence of amorphous iron hydroxide (ferrihydrite)
Authors: Schmidtmann Johanna , Papastavrou Georg , Helfricht Nicolas , Peiffer Stefan
Published: March 2020

Plastic pollution in the marine and terrestrial environments is ubiquitous and a widespread problem. While the occurrence of plastics and microplastics, as well as their effects on marine and freshwater organisms, have already been investigated in numerous studies, so far only little attention has been paid to the fate, transport, and transformation processes of microplastics in the environment. In this work, the aggregation behavior of polystyrene (PS) microplastics in the presence of ferrihydrite, a natural inorganic colloid, was studied using zeta potential and hydrodynamic diameter measurements, as well as scanning electron microscope (SEM) techniques, considering the influence of pH and ionic strength. An increase of pH led to a more negative surface charge of PS. Furthermore, increasing concentrations of NaCl and CaCl2 showed that mono- and divalent cations influence the zeta potential in a different way. Divalent ions compress the electric double layer more efficiently compared to monovalent ions, which resulted in a decrease of repulsive forces. Studies on the heteroaggregation between PS and ferrihydrite showed that the highest aggregation took place at neutral pH values. Aggregate sizes in samples with neutral pH increased significantly compared to more acidic and alkaline pH values. Furthermore, the results indicated that at neutral pH values, ferrihydrite completely covers the PS surface. SEM images and hydrodynamic diameter measurements revealed that the heteroaggregation between PS and ferrihydrite increased with ionic strength. Our results demonstrate that the fate of microplastic particles in aquatic systems can be strongly influenced by natural colloidal water constituents, such as iron hydroxides.
Towards a scale-independent fractional snow-covered area parameterization for complex terrain
Authors: Helbig Nora , Bühler Yves , Eberhard Lucie , Deschamps-Berger César , Gascoin Simon , Dumont Marie , Deems Jeffrey , Jonas Tobias
Published: March 2020

Whenever there is snow on the ground, there will be large spatial variability in snow depth. The spatial distribution of snow is significantly influenced by topography due to wind, precipitation, shortwave and longwave radiation, and even snow avalanches relocate the accumulated snow. Fractional snow-covered area (fSCA) is an important model parameter characterizing the fraction of the ground surface that is covered by snow and is crucial for various model applications such as weather forecasts, climate simulations and hydrological modeling.

We recently suggested an empirical fSCA parameterization based on two spatial snow depth data sets acquired at peak of winter in Switzerland and Spain, which yielded best performance for spatial scales larger than 1000 m. However, this parameterization was not validated on independent snow depth data. To evaluate and improve our fSCA parameterization, in particular with regards to other spatial scales and snow climates (or geographic regions), we used spatial snow depth data sets form a wide range of mountain ranges in USA, Switzerland and France acquired by 5 different measuring methods. Pooling all snow depth data sets suggests that a scale-dependent parameter should be introduced to improve the fSCA parameterization, in particular for sub-kilometer spatial scales. Extending our empirical fSCA parameterization to a broader range of scales and snow climates is an important step towards accounting for spatio-temporal variability in snow depth in multiple snow model applications.
Voluminous crustal degassing and immiscible sulfide genesis caused by magma-shale interaction in Large Igneous Provinces
Authors: Deegan Frances , Bédard Jean , Troll Valentin , Dewing Keith , Geiger Harri , Grasby Steve , Misiti Valeria , Freda Carmela
Published: March 2020

Large Igneous Province (LIP) activity is hypothesized to impact global volatile cycles causing climate changes and environmental crises deleterious to the biosphere. Recent work suggests that the potential of LIPs to impact climate is magnified where they intrude organic-rich (i.e. shale-bearing) sedimentary basins. However, the chemical and degassing dynamics of magma-shale interaction are not well understood. Here we present the first experimental simulations of disequilibrium interaction between LIP magma and carbonaceous shale during upper crustal sill intrusions in the Canadian High Arctic LIP (HALIP), the latter of which were co-eval with oceanic anoxic event 1a. Experiments show that magma-shale interaction results in intense syn-magmatic degassing and simultaneous precipitation of sulfide droplets at the ablation interface. Magma-shale interaction on a basin-scale can thus generate substantial amounts of climate-active H-C-S volatiles, while the presence of strongly reducing volatiles may also increase the likelihood of magma to segregate a sulfide melt. These findings have fundamental consequences for our understanding of both large-scale Earth outgassing and metal prospectivity in sediment-hosted LIPs.
Time-lapse tomographic images of the Irpinia Fault System (Southern Italy) reveal Vp/Vs ratio changes that correlate with micro-seismicity production and evolution
Authors: De Landro Grazia , Esposito Raffaella , Ortensia Amoroso , Zollo Aldo
Published: March 2020

This study focuses on the the active fault system that caused the 1980 M_S 6.9 Irpinia earthquake (Irpinia fault zone (IFZ)) that is presently interested by a continuous and frequent micro-earthquake activity occurring within the volume in the volume enclosed by two antithetic faults. It is therefore important to improve the knowledge of the IFZ dynamics, with reference to potential future occurrence of moderate to large earthquakes, especially in terms of earthquake triggering mechanisms. Several previous works evaluated the spatial distribution of elastic/anelastic fault-embedded medium properties and related rock physical micro-parameters in connection with the seismicity rate. These studies showed a spatial correlation between high Vp/Vs, low seismic attenuation in rock volumes where most of seismicity occurs, suggesting that fluid-driven pore-pressure changes may plays a key role in controlling the seismicity production at the IFZ.
Here we reconstruct accurate 4D seismic velocity images of the volume embedding IFZ which allows to detect and track space-time changes of medium elastic properties possibly induced by fluid pore pressure migration and investigate the related seismicity production.
We analyzed the arrival time phase catalogue of about ten years (2005-2016) of Mw < 3.1 events recorded by the ISNet (Irpinia Seismic Network) and INGV network. We divided the catalog in 5 not-overlapping epochs by selecting in each of them , approximately the same number of events and an uniform volume coverage, in order to ensure that the 3D P and S velocity models could be equally well resolved for each epoch. By comparing the Vp, Vs and Vp/Vs images at each epoch in the equally resolved volume, we are able to detect medium velocity changes. Some regions, in the first 6 km of depth of NE part, do not show velocity changes with time, which is interpreted as the main effect of unperturbed lithology mainly controlling the average seismic velocity. In other regions, in the central part of the model at about 8-10 km depth, we clearly detect velocity changes causing an up to 10% Vp/Vs variation between different epochs. Based on the rock physical modelling, we associate the time-varying Vp/Vs and the observed amplitude of variation to fluid-driven changes in rock physical properties related to their spatial migration or pore-pressure induced changes. The regions where large Vp/Vs changes occur appear correlated with the largest seismicity production volumes, suggesting a direct link between the physical processes associated with fluid mobility and/or pore pressure migration and earthquake generation at the IFZ.
Properties and fate of microplastics entering drinking water treatment plants
Authors: Novotna Katerina , Cermakova Lenka , Pivokonska Lenka , Pivokonsky Martin
Published: March 2020

Microplastics (MPs) are being detected in aquatic environments worldwide, including seawaters and freshwaters. Moreover, some scarce studies have also reported the presence of MPs in potable water, both in water from public water supply and in bottled water. Despite any potential adverse effects on human health are not known yet, the occurrence of MPs in drinking water raises considerable attention. Drinking water treatment plants (DWTPs) pose a barrier for MPs to pass from raw water to treated water intended for human consumption; thus, the fate of MPs entering DWTPs is of a great interest. In order to encapsulate current knowledge in this regard, and so as to identify research needs in this filed, more than 100 studies were reviewed to provide concise conclusions. Focus was laid on: (i) summarizing available information on MP abundance and character in water resources and in drinking water; (ii) combining research results on MP contents at the inflow and outflow of DWTPs and on MP removal by distinct treatment technologies; (iii) comparing MPs to other common pollutants, the removal of which is commonly addressed at DWTPs; and (iv) providing an insight into the fate of MPs at waste water treatment plants (WWTPs), that act as a barrier for transition of MPs from waste to the nature, thus, have an “opposite” position than DWTPs. Additionally, the topic of (v) fate of MPs in DWTP and WWTP sludge was also put forward. This review brings together valuable information regarding the MP occurrence, character, and fate in freshwater aquatic environments in relation to the MP appearance at water treatment facilities, i.e. DWTPs and WWTPs, that may act as both sink and source of this emerging pollutant. Thus, the “cycle” of MPs between natural water bodies and “water in use by humans” is proposed.
The Equatorial Atlantic Laboratory: sediment routing systems and lithosphere deformation
Authors: Rouby Delphine , Chardon Dominique , Ye Jing , Bajolet Flora , Loparev Artiom , Dall'Asta Massimo
Published: March 2020

We summarize the results of a 7 years study of the sediment routing systems of the West African Craton transporting its erosional products to the Central and Equatorial Atlantic passive margins at geological time scale. We used paleogeograhic maps to define the geodynamics framework of this routing system with in particular the propagation of the Equatorial Atlantic oblique rift separating the West African and Amazonian Cratons. We used sub-surface data to evaluate the evolution of lithosphere necking distribution along the conjugated African and South American margins of the rift system. We estimated the long-term denudation pattern at continental scale from low temperature thermochronology measures of samples from 3 transects perpendicular to the Atlantic margin. We used the exceptional preservation of geomorphologic markers to reconstruct the drainage system of the craton since 45 Ma, and estimate the associated denudation and exports of terrigeneous sediments to the Atlantic margin. Finally, we estimated the accumulation history in the passive margin basins and compare them with the estimated denudation histories from thermal histories and geomorphologic markers. We show that the modes of preservation of sedimentary export in the passive margin basins are highly variable in time (immediate post roft versus late post-rift) and space (transform/oblique versus divergent margin segments). We show that the present day drainage of the West African Craton as been stable since 30 Ma when it underwent a major reorganization driven by the growth of the relief associated with the Hoggar mantle plume. We show that accumulation in the passive margin basins fall within the same order of magnitude than denudation on the craton at the scale of the Meso-Cenozoic. This allows us to argue to the relevance of using the stratigraphic architecture of passive margin basins to estimate the denudation history of their continental domains.
Relative dispersion in the Nordic Seas - new insights ten years later
Authors: Koszalka Inga Monika , LaCasce Joseph
Published: March 2020

The POLEWARD experiment in the Nordic Seas (2007-2009) involved deployment of 150 drifters in the eastern Nordic Seas and has been the first large drifter pair experiment in the ocean (and one of the very few conducted up to date). The experiment yielded nearly 100 drifter pairs with initial separations 2km or less, which allowed us to elucidate several aspects of the relative dispersion (a proxy for tracer spreading and transport) at a basin scale, to quantify the role of mesoscale eddies in surface transport, and to further develop the relevant theoretical and analytical methods through a series of publications. Ten years ago however there were no modeling tools available to carry out a similar numerical Lagrangian study in this region resolving relevant scales of variability.

In this presentation, we will present an update on the relative dispersion of surface drifter pairs in the Nordic Seas, with over 400 pairs available. We will then compare the observed statistics to these derived from Lagrangian simulations (OpenDrift scheme) forced by output from a very high resolution regional ocean model (Regional Ocean Modeling System). The comparison is very favorable pointing to the ability of the ocean model to represent surface eddy stirring processes. We will also show analysis of the regional dispersion regimes using both drifter observations and model simulations, and consider the effect of including vertical motion in the Lagrangian simulations, which impacts their horizontal dispersion. We will also present statistics of the temperature differences on drifters pairs. These are underestimated by the model on daily time scales and deformation scales, which has implications for the model ability to simulate tracer processes on these scales. 

 
On the physical origin of enhanced turbulent-dispersion of 'heavy particles' in suspended-load
Authors: chauchat julien , Revil-Baudard Thibaud , Cheng Zhen , Hurther David , Hsu Tian-Jian
Published: March 2020

In the state-of-the-art for suspended-load modeling it is commonly assumed that the concentration profile results from a balance between a settling flux, in which the settling velocity is considered as equal to its value for a single settling particle in quiescent water, and an upward turbulent flux modeled using a Fickian gradient diffusion approximation. While this model provides a general framework, comparison with experiments reveals that the concentration diffusivity is not equal to the eddy viscosity and a turbulent Schmidt number needs to be introduced. Based on Coleman (1970,1981) data, van Rijn (1984) proposed an empirical model which suggests that the Schmidt number is a decreasing function of Ws/u*. This result is intriguing as it suggests that the turbulent dispersion of sediment concentration is enhanced when the particle’s settling velocity increases relative to the bed friction velocity. Van Rijn suggested that this is due to centrifugal forces that tends to throw inertial particles out of the turbulent vortices leading to an enhanced particle dispersion compared to momentum. In the present contribution, we use high-resolution experimental data and turbulence resolving two-phase flow simulations that directly resolve the turbulent momentum and particle fluxes and the flow turbulence to investigate the different terms appearing on the mass balance mentioned above.  Both the experimental and the numerical results show that the actual turbulent Schmidt number based on the resolved sediment flux is higher than unity meaning that turbulent dispersion efficiency of « heavy particles » is reduced. This contradicts van Rijn’s prediction model of the Schmidt number. One plausible explanation is that the settling velocity of particles is reduced in highly turbulent flows. Using the experimental and numerical results, the actual settling velocity in the turbulent flow is retrieved from the mass balance at steady state. It is found that it is significantly retarded compared with the value in quiescent water (10 to 40%). This result is in good agreement with the one obtained in recent experiments performed in a turbulent grid at KIT (Germany) using the same particles (Akutina et al., 2020). The authors found a settling retardation of 16% for the same turbulent intensities as in the present experiments. The results presented herein completely change the paradigm for turbulent suspension load modeling and open new perspectives on the development of new, physical process-based, parametrizations required for large-scale models. This, of course, will require to extend the proposed methodology to a wider range of flow and sediment conditions.
In-situ basal melt rate distribution of the floating tongue of 79°N Glacier, Greenland
Authors: Zeising Ole , Steinhage Daniel , Neckel Niklas , Christmann Julia , Helm Veit , Dörr Nils , Humbert Angelika
Published: March 2020

The 79°N Glacier (79NG) in northeast Greenland, one of the last glaciers in Greenland with a floating ice tongue, plays a crucial role for buttressing the North-East Greenland Ice Stream (NEGIS). Remote-sensing studies indicate high basal melt rates (> 50 m/a) near the grounding line but these methods are limited by the hinge zone, where the floating ice is not in hydrostatic equilibrium. As part of the Greenland Ice Sheet Ocean Interaction (GROCE) project, we have performed a dense grid of repeated measurements with a phase-sensitive radio echo sounder (pRES) accompanied with autonomous pRES (ApRES) stations to estimate basal melt rates focusing on the hinge zone of 79NG. For analysing the pRES measurements, we additionally used ice thickness information derived from AWI’s ultra-wideband radar (UWB) revealing steep channels at the base. The estimated basal melt rates downstream the hinge zone are approximately the same as satellite-derived melt rates. In the hinge zone we found by far larger basal melt rates exceeding 100 m/a next to basal channels.