bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantifying the contribution of wetlands drying to aerosol generation across Iran
Authors: Bayati Majid , Bayat-Afshary Nooshdokht , Danesh-Yazdi Mohammad
Published: March 2021

Wetlands are accounted as important providers of ecosystem services, which yield several functionalities such as the support of biodiversity, flood control, soil stabilization to reduce dust generation, natural treatment of surface waters, groundwater replenishment, climate regulation and economic benefits. Over the past decades, the impacts of anthropogenic manipulations amplified by climatic changes have threatened both the quantity and quality of wetlands, worldwide. A continuous monitoring of wetlands is thus necessary to protect them from further destruction, as well as to devise and assess the success of any rehabilitation plans. The conventional methods of water body monitoring chiefly include field surveying, which is time consuming, costly, and limited in extent. Alternatively, remotely sensed data have facilitated a much less expensive and more extensive monitoring of water bodies over a wide range of spatiotemporal resolutions. In this study, we implemented a learning-based classification framework fed by remote sensing data to evaluate the historical trends of the most important wetlands across Iran using the Google Earth Engine cloud computing platform. To this end, we used Landsat imagery between 2000 and 2020 to extract the water body of wetlands in dry seasons to consider the most critical condition. We also examined different spectral indices to identify the best combination giving the largest classification accuracy for each wetland, separately, based on their distinct conditions of water depth and vegetation cover. We then quantified the contribution of wetlands drying to the generation of dust storms via a frequency-intensity index given the annual number of dusty days and the Aerosol Optical Depth (AOD) provided by MODIS. According to the results, the majority of the studied wetlands show significant descending trends with the average loss of 31% in surface area. The aerosol analysis also witnesses the expansion of dust generation sources around most of the retreated wetlands, particularly in those years when the wetlands areas were smaller than the long-term average. The above observations point out a potential threat for the agricultural activities and highlight serious consequences for the health of nearby urban and rural residents.

Keywords: Wetland, Dust Storm, Remote Sensing, Environmental Monitoring, Ecosystem Protection
Volcanism and tectonics in an island-arc rift environment: proposal to drill at Christiana-Santorini-Kolumbo marine volcanic field, Greece
Authors: Druitt Tim , Huebscher Christian , Kutterolf Steffen , Nomikou Paraskevi , Papanikolaou Dimitris , Karstens Jens , Preine Jonas ,   Participants of the 2017 Athens MagellanPlus workshop
Published: March 2021

IODP proposal VolTecArc aims at deep-sea drilling in and around the Christiana-Santorini-Kolumbo (CSK) marine volcanic field to investigate interactions and feedbacks between tectonics and volcanism and how volcanoes interact with their marine environments. The volcanic field lies in a rift system 100 km long and 45 km wide, oblique to the South Aegean volcanic arc, that is one of the most volcanically and seismically active regions of Europe. The volcanoes include three polygenetic and over 20 monogenetic centers that have jointly produced over a hundred explosive eruptions over the last few hundred thousand years.  The volcanoes pose important hazards to the Eastern Mediterranean region. Unrest at Santorini caldera in 2011-12 raised awareness of eruption threat at an island archipelago visited by 1.5 million tourists per year.

The results of onland volcanological research, eruption dating, multi-beam sea floor mapping, shallow sediment coring and dredge sampling, combined with a high-quality site-survey database of multichannel seismic profiles and a recent seismic tomography experiment, make deep drilling at the CSK volcanic field very timely. Deep drilling will enable characterization and interpretation of depositional packages visible on seismic images, chemical correlation of Santorini-derived volcanic layers in the rift fills with the dated onshore stratigraphy, and provide a tight chronostratigraphic framework for marine successions. Some objectives of drilling are to: (1) document the history of tectonics, subsidence, sedimentation and volcanism in an arc-rift environment, and how volcanism has evolved spatially and temporally since rift initiation; (2) determine how the genesis and compositions of magmas and their associated volatiles have evolved in time and space over the lifetime of the rift; (3) document the dynamics and environmental impacts of arc eruptions and calderas, including eruption frequencies, magnitudes and rates, the mechanisms of caldera collapse, and the origin of caldera unrest events.
Rheology and kinematics of dense granular fault gouges with DEM: shear bands formation and evolution 
Authors: Casas Nathalie , Mollon Guilhem , Daouadji Ali
Published: March 2021

Earthquakes happen with frictional sliding, by releasing all the stresses accumulated in the pre-stressed surrounding medium. The geological third body (i.e. fault gouge), coming from the wear of previous slips, acts on friction stability and plays a key role in this sudden energy release. A large part of slip mechanisms is influenced, if not controlled, by fault gouge characteristics and environment. We aim to link third body properties (geological, mechanical, physical…) to its rheological behavior by testing numerically different types of dense geological third body (% of porosity, % of cohesion, grains shapes…) with distinct contact laws. Different granular samples are generated to simulate a mature fault gouge with mineral cementation between particles. The gouge is then inserted between two rock walls to realize direct shear experiments with Discrete Element Modelling in the software MELODY2D (Mollon, 2016). A dry contact model is considered to investigate mechanisms without fluid (displacement-driven and under constant confining pressure). Researches are based here on a millimeter-scale portion of gouge, considering that the output values could be used in another model at larger scale.

The peak strength can be sharp, short, and intense for dense and highly cohesive cases (angular particles, 15% initial porosity) and relatively low for ultra-dense samples (polygonal particles, 0% initial porosity). The observed regimes also correspond to an evolution of the amount of ductility within the sample. A very dense or highly cohesive sample behaves as a brittle material, whereas a typical cohesionless and porous geological layer tends to behave as a ductile material. The evolution of gouge characteristics truly influences the shape and formation time of Riedel shear bands. A change in contact laws between particles (%cohesion, friction) modifies the entire kinematics of Riedel bands formation. Indeed, with cohesion between particles, Riedel bands are directly linked to the importance of the dilation phase, depending itself on the initial porosity present within the sample (Casas et al., 2020). Then, increasing friction not only changes the principal orientation or Riedel bands but makes them more numerous within the gouge. It also leads to a more sudden post-peak weakening, which is prone to switch the fault behavior from a ductile aseismic response to a brittle seismic slip, depending on the stiffness of the surrounding medium. Global stiffness of the gouge also has an important role to play on Riedel bands formation, and it can be defined as a combination of multiple parameters such as initial porosity, shape and size of particles, numerical stiffness, gouge thickness… The local Breakdown energy, or energy needed to weaken the fault, is also calculated to be connected to Riedel bands formation.
Progress in the formalisation of the Anthropocene GSSP
Authors: Turner Simon ,   AWG-HKW-MPIWG Anthropocene GSSP
Published: March 2021

The Anthropocene Working Group (AWG) has assembled scientific teams to analyse stratigraphic successions, as potential stratotypes, in order to facilitate a formal submission to the Subcommission on Quaternary Stratigraphy. The aim is to seek ratification of the Anthropocene as a geological epoch starting in the mid-twentieth century. Stratigraphic records, including a range of novel materials, geochemical and biological signals spanning the mid-twentieth century interval of unprecedented human activity and industrialisation, are being gathered by international teams of scientists, working on eleven contrasting depositional settings from around the planet. Interwoven with this scientific process to define a Global Boundary Stratotype Section and Point (GSSP), from which a specific year for the onset of the Anthropocene will be established, is a decades long collaborative exploration of the Anthropocene between the AWG, Haus der Kulturen Welt (HKW) and Max Planck Institute for the History of Science (MPIWG).  

While the compilation of stratigraphic data to define a new epoch is as old as the science of geology, the demarcation of one within living history that signifies human activity as a global geological agent is unparalleled. Similarly, there is no precedent of a stratigraphic formalisation process being pivotal to the framing of so much contemporary social, ecological, artistic, historical and political thought. In May 2022 along with the publication of the results and data, an exhibition including a discursive and performative programme will occur at HKW in Berlin as a public forum for the scientific, cultural and socio-political impact of the geochronological research carried out by the international research project on the Anthropocene.

This presentation provides an introduction to the interdisciplinary and collaborative research project between the AWG, HKW and MPIWG. The talk will introduce the prospective sites and stratigraphy of the proposed successions and an update on progress towards the official ratification of the GSSP, as well as collaborative artistic and cultural work embedded in the process.
The transport of microplastic on agriculture soils via soil erosion
Authors: Rehm Raphael , Zeyer Tabea , Fiener Peter
Published: March 2021

Agricultural soils play a key role as sink of microplastic (MP) coming from different sources, especially via the application of sewage sludge, compost, plastic mulch films, and tire ware. However, the effectiveness of this sink might be substantially reduced in areas subjected to water erosion. The aim of this study is to determine the transport behavior of MP during water erosion events on arable land. More specifically it is analyzed if MP is preferentially transported or behaves more conservative as attached to soil minerals and/or encapsulated in soil aggregates. A series of rainfall simulations were performed over 1.5 years on two plots at two test sites representing different intensively used soils (silty loam and loamy sand) in Southern Germany. The plots (4.5 m x 1.6 m) were spiked with microplastic (high density polyethylene) consisting of two different size fractions, fine MP (MPf, 53-100 μm) and coarse MP (MPc, 250-300 μm) incorporated into the topsoil (< 10 cm). The results clearly underline the selective nature of MP erosion leading to an enrichment ratio of MP in the eroded sediments of the loamy sand plot of 3.82 to 7.86, compared to an enrichment ratio from the silty loam plots of 1.41 to 5.29. Interestingly, there was no significant difference in enrichment ratios between MPf and MPc. Over time, an increasing connection between MP and soil particles could be observed. During the first rainfall simulation only 12% (MPc) and 34-49% (MPf) of the eroded plastic particles were connected to mineral particles or soil aggregates, while during the last simulation 1.5 years later about 31-47% (MPc) and 57-67% (MPf) of the eroded particles were bond to the soil matrix. Overall, our results indicate a strong dependency of the erosion transport behavior of MP depending on soil characteristics and time since application, while surprisingly we found little effect of MP size. 
Imaging solar-terrestrial interactions on the global scale: The SMILE mission
Authors: Branduardi-Raymont Graziella , Wang Chi , Escoubet C. Philippe , Sembay Steve , Donovan Eric , Dai Lei , Li Lei , Li Jing , Agnolon David , Raab Walfried , Forsyth Colin , Read Andy , Spanswick Emma L. , Carter Jenny A. , Connor Hyunju , Sun Tianran , Samsonov Andrey , Sibeck David G.
Published: March 2021

A key link in the Sun – Earth connection is the solar wind coupling with the terrestrial magnetosphere. Mass and energy enter geospace via dayside magnetic reconnection; reconnection in the tail leads to release of energy and particle injection deep into the magnetosphere, causing geomagnetic substorms. The end product of these processes is the visual manifestation of variable auroral emissions. These have been observed both from the ground and from space, the latter for relatively short continuous periods of time. In situ measurements by a fleet of solar wind and magnetospheric missions, current and planned, can provide the most detailed observations of the plasma conditions both in the incoming solar wind and magnetospheric plasma. However, we are still unable to quantify the global effects of the drivers of Sun - Earth connections, and to monitor their evolution with time. This information is the key missing link for developing a comprehensive understanding of how the Sun gives rise to and controls the Earth's plasma environment and space weather. We are now able to take a novel approach to global monitoring of geospace: X-ray imaging of the magnetosheath and cusps is made possible by the X-ray emission produced in the process of solar wind charge exchange, first observed at comets, and subsequently found to occur in the vicinity of solar system planets, including the Earth's magnetosphere. This is where SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) comes in.

SMILE is a novel self-standing mission dedicated to observing the solar wind – magnetosphere coupling at Earth via simultaneous X-ray imaging of the magnetosheath and polar cusps (large spatial scales at the magnetopause), UV imaging of global auroral distributions (mesoscale structures in the ionosphere) and in situ solar wind/magnetosheath plasma and magnetic field measurements. SMILE will provide scientific data on solar wind – magnetosphere interaction at the global level while monitoring it continuously for long, uninterrupted periods of time from a highly elliptical northern polar orbit.

SMILE is a collaborative mission between ESA and the Chinese Academy of Sciences that was selected in Nov. 2015, adopted into ESA’s Cosmic Vision Programme in March 2019, and is due for launch at the end of 2024. The novel science that SMILE will deliver, the ongoing technical developments and scientific preparations, and the current status of the mission, will be presented.
The Influence of Anthropogenic Climate Change on (drivers of) Multi-Year Droughts in North-Western Europe
Authors: Batelaan Thomas J. , van der Wiel Karin , Wanders Niko
Published: March 2021

The summer of 2018 in North-Western Europe was exceptionally warm and dry, which negatively impacted many sectors. The drought of 2018 was followed by the dry summer of 2019 and the dry spring of 2020. Such multi-year droughts bring unique challenges to the agricultural sector, water authorities and society, and require different adaptation strategies compared to ‘normal’ single-year droughts. The succession of these dry years raises a question: is it pure coincidence that North-Western Europe experienced such a multi-year drought, or are there physical processes that cause multi-year droughts? Furthermore, in the present era it is obvious to ask whether anthropogenic climate change will amplify multi-year droughts in the region.

We aim to find drivers of multi-year droughts by using ERA5 reanalysis data and  state-of-the-art Large Ensemble simulations from seven climate models. We select multi-year droughts in these datasets based on the Standardised Precipitation and Evapotranspiration Index and compare drought characteristics in the 1991-2020 reference period with multi-year droughts towards the end of the century. The models show a strong increase in multi-year drought risk from present-day to the end of the century. The frequency of multi-year droughts near doubles and the median duration of selected drought events increases from 16 months to 50 months. Model differences are substantial, mostly due to differences in temperature trends, but all models agree on the increase in multi-year drought risk. Internal variability is large, indicating a large ensemble approach is indeed required to study this problem.

Next we discuss geophysical drivers of multi-year droughts. Slow-varying ocean processes (through sea surface temperatures) and land processes (through soil moisture) are investigated as potential sources of meteorological conditions that lead to multi-year droughts. We consider the full Earth system, including ocean-land-atmosphere feedbacks, as potential forcing for these events. Summarizing, we will show that anthropogenic warming has potentially large impacts on the frequency, duration and therewith societal risk of multi-year droughts, warranting detailed studies of this topic.
Active transpression along the Owen oceanic transform fault, India - Somalia plate boundary
Authors: Janin Alexandre , Rodriguez Mathieu , Chamot-Rooke Nicolas , Rabaute Alain , Delescluse Matthias , Dyment Jérôme , Fournier Marc , Huchon Philippe , Olive Jean-Arthur , Vigny Christophe
Published: March 2021

The Owen oceanic transform fault is a 300-km long linear structure connecting the Carlsberg and Sheba spreading centers in the northwest Indian Ocean. It presently forms with the Carlsberg ridge the active plate boundary between India and Somalia. The Owen transform fault accommodates the left-lateral strike-slip motion between India and Somalia at a rate of about 23 mm/yr.  Firstly identified by Tuzo Wilson in the 60s, this oceanic transform remains poorly described. The fault was recently surveyed in the Spring of 2019 during the VARUNA and CARLMAG cruises (https://doi.org/10.17600/18001108, https://doi.org/10.17600/18000872) along its entire length aboard BHO Beautemps-Beaupré, an oceanographic ship operated by the French Naval Hydrographic and Oceanographic Services (SHOM) and the French Navy.

During these missions a set of high-resolution seismic lines (>5000 km) were acquired together with high resolution multibeam bathymetry. The data cover both the active and fossil traces of the transform fault between 9°N and 15°N, at a place where continuous deposition of the distal Indus turbiditic sediments offers a unique high-resolution stratigraphic record of past regional tectonic events.

The new bathymetric mapping reveals two remarkable transpressive ridges on the active fault trace. A precise stratigraphic work using seismic profiles and drilling data of the ODP leg 117 allows the time calibration of the new seismic lines as far south as the Carlsberg ridge.

We show that a major compressive event occurred on the Owen Oceanic Transform Fault recently between 1.5 Ma and 2.4 Ma. Compression is still active today as evidenced by Sub-bottom profiler data (3.5 kHz) and two compressive focal mechanisms found in the historical seismicity records. At the intersection with the Carlsberg ridge, the southern transpressive ridge bends and stands ~1200 m above the seafloor at its apex, suggesting a maximum surrection rate near 800 m/Ma.  These new geophysical dataset combined with previous cruises offers an unprecedented window on the recent evolution of the India-Somalia plate boundary.
Observed snow depth trends in the European Alps 1971 to 2019
Authors: Matiu Michael , Crespi Alice , Bertoldi Giacomo , Carmagnola Carlo Maria , Marty Christoph , Morin Samuel , Schöner Wolfgang , Cat Berro Daniele , Chiogna Gabriele , De Gregorio Ludovica , Kotlarski Sven , Majone Bruno , Resch Gernot , Terzago Silvia , Valt Mauro , Beozzo Walter , Cianfarra Paola , Gouttevin Isabelle , Marcolini Giorgia ,   Rest of the European Alps station snow observations team
Published: March 2021

The European Alps stretch over a range of climate zones, which affect the spatial distribution of snow. Previous analyses of station observations of snow were confined to regional analyses, which complicates comparisons between regions and makes Alpine wide conclusions questionable. Here, we present an Alpine wide analysis of snow depth from six Alpine countries: Austria, France, Germany, Italy, Slovenia, and Switzerland; including altogether more than 2000 stations, of which more than 800 were used for the trend assessment. Using a principal component analysis and k-means clustering, we identified five main modes of variability and five regions, which match the climatic forcing zones: north & high Alpine, northeast, northwest, southeast, and south & high Alpine. Linear trends of monthly mean snow depth between 1971 and 2019 showed decreases in snow depth for most stations for November to May. The average trend among all stations for seasonal (November to May) mean snow depth was -8.4 % per decade, for seasonal maximum snow depth -5.6 % per decade, and for seasonal snow cover duration -5.6 % per decade. However, regional trends differed substantially after accounting for elevation, which challenges the notion of generalizing results from one region to another or to the whole Alps. This study presents an analysis of station snow depth series with the most comprehensive spatial coverage in the European Alps to date.
The impact of wildfires in Ukraine on carbon flux and air quality changes by carbon-containing compounds
Authors: Savenets Mykhailo , Pysarenko Larysa
Published: March 2021

Wildfires remain among the most challenging problems in Ukraine. Each year numerous cases of open burning contribute to huge carbon emissions and turn into forest fires. Using the Global Fire Emissions Database (GFED4), there were studied an average burned fraction in Ukraine, which equals of about 0.2-0.3. 90% of wildfires appeared on agricultural lands. The total contribution to carbon emissions is 0.2-1.0 g·m2·month-1 with the increasing trend of about 1-2 g·m2·month-1 per decade. There are three periods with the highest carbon emissions: April, July-August and September-October. While a summer maximum is corresponding to unfavorable temperature and moisture regimes, the main reason of wildfires in spring and autumn is the agricultural open burning. Based on the Sentinel-5P data, it was found that wildfires significantly change the seasonality of carbon monoxide (CO) variations. If maximal CO content is mainly observed in winter at the end of the heating season, in Ukraine the highest CO values continue to exist in April until the open burning stops and the resulting forest fires are extinguished. Wildfires caused the CO content increase to 4.0–5.0 mol·m-2 which is comparable to the most polluted Ukrainian industrial cities. As a result, air quality deterioration observed at the distances more than 200 km from the burned areas. Using the Enviro-HIRLAM simulations, there were estimated black carbon (BC) distribution, which showed elevated content within the lowest 3-km layer. BC content reaches 600 ppbm near the active fires, 150 ppbm at the distance up to 100 km and 30 ppbm at the distance of about 200-500 km.
Low-Energy Desalination Technologies for Treating Mining Effluents 
Authors: Kolliopoulos Georgios
Published: March 2021

As our societies evolved and the quality of primary resources deteriorated, water use in process circuits has led to the generation of ever-increasing volumes of contaminated effluents. Despite the efforts for water recycling in process circuits, desalination technologies fail to treat solutions of high salinity, due to their focus on dilute solutions, such as seawater. The lack of energy efficient effluent desalination technologies leaves vast volumes of aqueous residues sitting in tailings ponds. This practice often allows oxygen to dissolve in water and oxidize certain elements, which leads to the generation of acid in a sequence of events known as acid mine drainage. Uncontrolled discharges resulting from such mining wastes have detrimental effects on the nearby water quality and aquatic ecosystems as well as on the health of the people of the local communities. In this work, we report on novel freeze desalination processes that can recover clean water from such industrial effluents in the form of ice at significantly lower energy compared to state-of-the-art desalination processes. Therefore, the developed technologies promise to economically and efficiently reduce the water-consumption related environmental footprint of the processing industry, the risks and liabilities associated with tailings ponds, as well as to secure access to safe clean water for nearby communities.
P-TRAP – Reducing diffuse phosphorus input to surface waters
Authors: Behrends Thilo , Walter Sylvia
Published: March 2021

Phosphate (P) as an essential resource for food production is becoming scarce. Its uncontrolled loss from agricultural areas is in conflict with the principles of a circular economy. Enhanced loading of surface waters with P is the main cause for eutrophication and presents a key challenge in meeting the objectives of the EU Water Framework Directive. Understanding and controlling environmental P fluxes therefore is key to target both problems, to develop new methods and approaches to manage environmental P fluxes, and to improve surface water quality.

In March 2019 the EU Marie Sklodowska-Curie Innovative Training Network P-TRAP has been launched. P-TRAP establishes a framework of partners from multiple science and engineering disciplines. Integration of non-academic partners from various stakeholder groups into the P-TRAP consortium paves the way for direct implementation of the acquired knowledge. The project is targeting the diffuse flux of phosphate (P) into surface waters, i.e. the problems of understanding and controlling environmental P fluxes. P-TRAP aims to develop new methods and approaches to trap P in drained agricultural areas and in the sediments of eutrophic lakes. Trapping of P involves the application of iron(Fe)-containing by-products from drinking water treatment. P-TRAP aspires the ideas of a circular economy and aims at recovering the retained P in agricultural systems. Novel microbial technologies will be developed to convert P-loaded Fe-minerals into marketable fertilizers whose suitability will be evaluated. The P-TRAP technologies have in common that they rely on the naturally strong connection between P and Fe and the innovative P-TRAP strategies will be underpinned by process-orientated investigations on the behaviour of P during the transformation of Fe minerals. The latter are key in trapping and recycling of P in agricultural systems and lakes. Here we will present the structure and the planned research of the project, including a first overview of achievements of the first two years. 
Can intercropping stabilize yields in the face of climatic changes?
Authors: Vico Giulia , Weih Martin , Berghuijs Herman NC
Published: March 2021

Intercropping has been proposed as a way to reduce some of the negative consequences of intensive agriculture while maintaining or enhancing crop yields. Not only yields can be increased in intercrops, but they can also be more stable in the face of variable climatic conditions, offering an avenue of climate change adaptation. Nevertheless, exploiting the benefits of intercropping requires determining what the most appropriate members of the plant team are, and matching plant team and management to the local pedoclimatic conditions. Process-based mathematical models can complement field experiments to quantify via numerical simulations the performance of a variety of combinations of plant teams, management, and pedoclimatic conditions. These models are particularly useful when exploring the potential advantages of intercropping under climate change. Here we use the newly developed model M3 (Minimalist Mixture Model; Berghuijs et al, Plant and Soil, 2020) to simulate the biomass and grain yields of pure culture or intercropping systems, as a function of plant traits, management and environmental conditions. Focusing on wheat and faba bean grown in pure culture and intercrop in the Netherlands and Central Sweden, we quantified crop yields and their stability over the period 1951-2100, exploiting modelled climatic data series. We found large interannual variability in yields both on a per unit area and per plant basis, mostly due to the interannual variability in weather conditions. On a per unit area basis, yield differences between crops and cropping systems are consistent under historical and future climatic conditions. However, under future climatic conditions, the yields per plant were lower in faba bean, but not in wheat. Overall, pure cultures benefitted from future climatic conditions, while intercrops appeared to be negatively affected. Moreover, climate change increased yield variability in both crops and cropping systems. Therefore, against expectations, intercropping does not necessarily reduce yield variability with respect to pure culture
Carboniferous granitic plutons of Nordensheld Archipelago (eastern part of the Kara Sea, Russian High Arctic)
Authors: Kurapov Mikhail , Ershova Victoria , Khudoley Andrei , Schneider Gennady
Published: March 2021

Nordensheld Archipelago is a relatively large cluster of islands in the eastern part of the Kara Sea located north of the Taymyr Peninsula. Belonging to the Northern Taimyr tectonic domain of the Taimyr-Severnaya Zemlya fold-and-thrust belt, this area in Late Paleozoic represented southern part of the Kara Terrane.

Samples were collected from outcrops across the Nordensheld Archipelago and shallow offshore wells in the close proximity to the archipelago and from offshore well located in Toll bay (eastern part of the Kara sea). Studied plutons are represented by coarse- to medium-grained biotite, two mica and hornblende-biotite granites. U-Pb dating of the granites yelled ages of ca. 334 and 326 Ma. The granitoids are high- to medium acidic, mainly calc-alkalic to alkali-calcic, ferroan and magnesian, metalumious and peraluminous.

The U-Pb zircon age from the Toll Bay well is the first granite age obtained offshore within eastern part of the Kara Sea. Petrographic and geochemical features of the Nordensheld Archipelago and eastern Kara Sea Visean-Serpukhovian granites indicate their suprasubduction origin. This correlates well with data from Northern Taimyr and provides new evidence for the Uralian Ocean subduction magmatism within Taimyr-Severnaya Zemlya fold-and-thrust belt.

This research was supported by RFBR grant № 19-35-90006, Russian Science Foundation grant № 20-17-00169.
A quick fix for modeling infiltration in water-repellent soils
Authors: Stewart Ryan , Abou Najm Majdi R. , Di Prima Simone , Lassabatere Laurent
Published: March 2021

Water repellency occurs in soils under a wide spectrum of conditions. Soil water repellency can originate from the deposition of resinous materials and exudates from vegetation, vaporization and condensation of organic compounds during fires, or the presence of anthropogenic-derived chemicals like petroleum products, wastewater or other urban contaminants. Its effects on soils range from mild to severe, and it often leads to hydrophobic conditions that can significantly impact the infiltration response with effects extending to the watershed-scale. Those effects are often time-dependent, making it a challenge to simulate infiltration behaviors of water-repellent soils using standard infiltration models. Here, we introduce a single rate-constant parameter (αWR) and propose a simple correction term (1-e-αWRt) to modify models for infiltration rate. This term starts with a value of zero at the beginning of the infiltration experiment (t = 0) and asymptotically approaches 1 as time increases, thus simulating a decreasing effect of soil water repellency through time. The correction term can be added to any infiltration model (one- two- or three-dimensional) and will account for the water repellency effect. Results from 165 infiltration experiments from different ecosystems and wide range of water repellency effects validated the effectiveness of this simple method to characterize water repellency in infiltration models. Tested with the simple two-term infiltration equation developed by Philip, we obtained consistent and substantial error reductions, particularly for more repellent soils. Furthermore, results revealed that soils that were burned during a wildfire had smaller αWR values compared to unburned controls, thus indicating that the magnitude of αWR may have a physical basis.
Identification of dominant hydrological mechanisms using Bayesian inference, multiple statistical hypothesis testing and flexible models
Authors: Prieto Cristina , Kavetski Dmitri , Nataliya Le Vine Nataliya , Álvarez César , Medina Raúl
Published: March 2021

In hydrological modelling, the identification of hydrological model mechanisms best suited for representing individual hydrological (physical) processes is a major research and operational challenge. We present a statistical hypothesis-testing perspective to identify dominant hydrological mechanism. The method combines: (i) Bayesian estimation of posterior probabilities of individual mechanisms from a given ensemble of model structures; (ii) a test statistic that defines a “dominant” mechanism as a mechanism more probable than all its alternatives given observed data; (iii) a flexible modelling framework to generate model structures using combinations of available mechanisms. The uncertainty in the test statistic is approximated via bootstrap from the ensemble of model structures. Synthetic and real data experiments are conducted using 624 model structures from the hydrological modelling system FUSE and data from the Leizarán catchment in northern Spain. The findings show that the mechanism identification method is reliable: it identifies the correct mechanism as dominant in all synthetic trials where an identification is made. As data/model errors increase, statistical power (identifiability) decreases, manifesting as trials where no mechanism is identified as dominant. The real data case study results are broadly consistent with the synthetic analysis, with dominant mechanisms identified for 4 of 7 processes. Insights on which processes are most/least identifiable are also reported. The mechanism identification method is expected to contribute to broader community efforts on improving model identification and process representation in hydrology.
Inferring ice rheology in Antarctic ice shelves from remotely sensed observations
Authors: Millstein Joanna , Minchew Brent
Published: March 2021

Glaciers and ice sheets flow as a consequence of ice rheology. At the temperatures and pressures found on Earth, several creep mechanisms allow glacier ice to flow as a non-Newtonian (shear-thinning) viscous fluid. The semi-empirical constitutive relation known as Glen’s Flow Law is often used to describe ice flow and to provide a simple expression for an effective viscosity that decreases with increasing stress and deformation rate. Glen’s Flow Law is a power-law relation between effective strain rate and deviatoric stress, with two parameters defining the rheology of ice: a rate factor, A, and stress exponent, n. The rate factor depends on features such as temperature and grain size, while the stress exponent is primarily representative of the creep mechanism. Neither A nor n are well constrained in natural ice, and the stress exponent is typically assumed to be n = 3 everywhere. Here, we take advantage of recent improvements in remotely sensed observations of surface velocity and ice shelf thickness to infer the values of A and n in Antarctic ice shelves. We focus on areas of ice shelves that flow in a purely extensional regime, where extensional stresses are proportional to observed ice thickness, drag at the base of the ice is negligible, and extensional strain-rates are calculated from the gradients of observed surface velocity fields. In this manner, we use independent observational data to derive spatially dependent constraints on the rate factor A and stress exponent n in Glen's Flow Law. The robust spatial variability provides insights into the creep mechanisms of ice, thereby capturing rheological properties from satellite observations. Our analysis indicates that n ≈ 4 in most fast-flowing areas in an extensional regime, contrary to the prototypical value of n = 3. This finding implies higher non-linearity in ice flow than typically prescribed, influencing calculations of mass flux and the response of ice sheets to perturbations. Additionally, This result suggests that dislocation creep is the dominant creep mechanism in extensional regimes of Antarctic ice shelves, indicative of tertiary creep. This analysis unites theoretical work and synoptic-scale observations of ice flow, providing insights into the rheology and stress-states of ice shelves in Antarctica.
Pore-scale study of effects of surface roughness on the transport of interfacial reactive tracers during primary drainage process
Authors: Gao Huhao , Tatomir Alexandru , Karadimitriou Nikolaos , Steeb Holger , Sauter Martin
Published: March 2021

Porous media surface roughness strongly influences the transport of solutes during drainage, due to the formation of thick water films (capillary condensation) on the porous media surface. In the case of interfacial-reacted, water-based solutes, these water films increase both the production of the solute, due to the increased number of fluid-fluid interfaces, and the loss of the solute by the retention in the stagnant water films. The retention of the solute in flowing water is described by a mobile mass retention term. This study applies the pore-scale direct simulation with the phase-field method based continuous solute transport (PFM-CST) model on the kinetic interfacial sensitive (KIS) tracer reactive transport during primary drainage in a 2D slit with a wall with variable fractal geometries. The capillary-associated moving interface is found to be larger for rough surfaces than smoother ones. The results confirm that the impact of roughness regarding the film-associated interfacial area can be partly, or totally masked, in a drained slit. It is found that the mobile mass retention term is increased with larger volumes of capillary condensed water films. To conclude, it is also found that the surface roughness factor has a non-monotonic relationship with the overall production rate of solute mass in moving water.
Universal scaling of thin current sheets in space plasma
Authors: Malova Helmi , Zelenyi Lev , Grigorenko Elena , Popov Victor , Dubinin Eduard
Published: March 2021

Thin current sheets (TCSs) with thicknesses about ion Larmor radii can play the key role in space; particularly they can store and then explosively release the accumulated free energy. The dynamics of ions moving along quasi-adiabatic trajectories in TCSs is different from one of magnetized electrons following guiding center drift orbits. Due to this property TCSs can be described in a frame of a hybrid approach. The thickness of the super-thin embedded electron sheet remains uncertain because of the scale-free character of magnetized electron motion. We propose a new analytical approach to describe the multilayer TCS and provide the universal expression describing the embedded electron sheet as a function of the cross-sheet transversal coordinate z characterizing TCS. We demonstrated that the unique property of the electron sheet is the nonlinear character of magnetic field profile:  B(z) ~ z 1/3 which conforms excellently with MAVEN observations in the Martian magnetotail. 

This work was supported by the Russian Science Foundation (grant # 20-42-04418).

 
Tremor Waveform Denoising and Automatic Location with Neural Network Interpretation
Authors: Hulbert Claudia , Jolivet Romain , Gardonio Blandine , Johnson Paul , Ren Christopher , Rouet-Leduc Bertrand
Published: March 2021

Active faults release tectonic stress imposed by plate motion through a spectrum of slip modes, from slow, aseismic slip, to dynamic, seismic events. Slow earthquakes are often associated with tectonic tremor, non-impulsive signals that can easily be buried in seismic noise and go undetected. 

We present a new methodology aimed at improving the detection and location of tremors hidden within seismic noise. After detecting tremors with a classic convolutional neural network, we rely on neural network attribution to extract core tremor signatures. By identifying and extracting tremor characteristics, in particular in the frequency domain, the attribution analysis allows us to uncover structure in the data and denoise input waveforms. In particular, we show that these cleaned signals correspond to a waveform traveling in the Earth's crust and mantle at wavespeeds consistent with local estimates. We then use these cleaned waveforms to locate tremors with standard array-based techniques. 

We apply this method to the Cascadia subduction zone. We analyze a slow slip event that occurred in 2018 below the southern end of the Vancouver Island, Canada, where we identify tremor patches consistent with existing catalogs. Having validated our new methodology in a well-studied area, we further apply it to various tectonic contexts and discuss the implications of tremor occurrences in the scope of exploring the interplay between seismic and aseismic slip.
Last Glacial Maximum Antarctic sea ice linked with global mean ocean temperature: evidence from PMIP3, PMIP4 and MIROC-4m simulations
Authors: Vadsaria Tristan , Sherriff-Tadano Sam , Abe-Ouchi Ayako , Obase Takashi , Chan Wing-Le , Crosta Xavier
Published: March 2021

Southern Ocean sea ice and oceanic fronts are known to play an important role on the climate system, carbon cycles, bottom ocean circulation, and Antarctic ice sheet. However, many models of the previous Past-climate Model Intercomparison Project (PMIP) underestimated sea-ice extent (SIE) for the Last Glacial Maximum (LGM)(Roche et al., 2012; Marzocchi and Jensen, 2017), mainly because of surface bias (Flato et al., 2013) that may have an impact on mean ocean temperature (MOT). Indeed, recent studies further suggest an important link between Southern Ocean sea ice and mean ocean temperature (Ferrari et al., 2014; Bereiter et al., 2018 among others). Misrepresent the Antarctic sea-ice extent could highly impact deep ocean circulation, the heat transport and thus the MOT. In this study, we will stress the relationship between the distribution of Antarctic sea-ice extent and the MOT through the analysis of the PMIP3 and PMIP4 exercise and by using a set of MIROC models. To date, the latest version of MIROC improve its representation of the LGM Antarctic sea-ice extent, affecting the deep circulation and the MOT distribution (Sherriff-Tadano et al., under review).

Our results show that available PMIP4 models have an overall improvement in term of LGM sea-ice extent compared to PMIP3, associated to colder deep and bottom ocean temperature. Focusing on MIROC (4m) models, we show that models accounting for Southern Ocean sea-surface temperature (SST) bias correction reproduce an Antarctic sea-ice extent, 2D-distribution, and seasonal amplitude in good agreement with proxy-based data. Finally, using PMIP-MIROC analyze, we show that it exists a relationship between the maximum SIE and the MOT, modulated by the Antarctic intermediate and bottom waters.
Analysis of mean and eddy energy of the Black Sea circulation derived under account the climatic and real atmospheric forcing
Authors: Dymova Olga , Demyshev Sergey , Alekseev Dmitry
Published: March 2021

The aim of the work is to study the mechanisms of the Black Sea mesoscale variability based on an analysis of Lorenz energy cycles calculated from the density and currents velocity obtained by the results of three numerical experiments. An eddy-resolving z-model with a horizontal resolution of 1.6 km was used. Three experiments were carried out with different atmospheric forcing: 1) - climatic data; 2) - SKIRON data for 2011; 3) – SKIRON data for 2016. The mean current kinetic energy MKE, the eddy kinetic energy EKE, the mean available potential energy MPE, the eddy available potential energy EPE and the rates of energy conversion, generation and dissipation were considered in detail.

For all experiments the generation and dissipation rates of the MKE and EKE are close to each other, so the kinetic energy from wind dissipated inside the sea. A buoyancy work (described by the conversion between the MPE and MKE) increase the MKE. The EKE was increasing due to the energy transport from the mean current into eddies and the transport from the EPE to the EKE for all experiments. It is shown that these two energy fluxes were comparable in the experiment 1, while the ratio between of them has changed almost six times in the experiments 2 and 3. The c(MKE, EKE) prevailed in 2011, but the c(EPE, EKE) dominated in 2016.

The maps analysis of the EKE spatial distribution showed that its maximum in the climatic field was located above a continental slope and in areas of the biggest mesoscale eddies. The mesoscale variability of the climatic circulation was due to the influence of both baroclinic and barotropic instability. The zones of the EKE maximum were located in the abyssal part of the sea in the experiments 2 and 3. EKE was increasing in 2011 mainly due to the inflow from the mean current through barotropic instability. The growth of EKE in 2016 was due to conversion of EPE induced by baroclinic instability.

The difference in the EKE variability by the results of climatic and real forcing experiments is associated with the wind forcing. The contribution of the wind stress work to MKE was decreased for the experiments 2 and 3, so as a result, it was observed weakening in the mean current, intensive stream meandering and generation of mesoscale eddies not only in the coastal zones but also in the abyssal part of the sea. Thus, the Black Sea mesoscale variability is determined by barotropic instability or by the combined contribution of barotropic and baroclinic instability processes under intense wind action. The mesoscale variability is due to baroclinic instability under weak wind action.

The reported study was funded by RFBR and Government of the Sevastopol according to the research project No 18-45-920019 and the state task No. 0555-2021-0004.