bluuebunny/crossref_metadata_2025 huggingface dataset:
Cretaceous paleomagnetic directions in different volcanics in Chukotka (NE Russia)
Authors: Lebedev Ivan , Bobrovnikova Elizaveta , Moiseev Artem , Tatiana Bagdasarian
Published: March 2021

The Cretaceous Okhotsk-Chukotka volcanic belt (OChVB) is one of the largest provinces of continental marginal magmatism with length more than 3000 km along the Pacific edge of Asia. In the field studies of 2019 and 2020 we sampled 21 sections in the northern part of the OChVB and 3 sections from basement of OChVB. These sections are represented by basalts and andesites; their tuffs, ignibrites and other volcanic rocks are much less common. The age of these volcanics is estimated based on U-Pb and Ar-Ar published data and our new Ar-Ar dates.

Based on the obtained data, a new paleomagnetic pole for the Chukotka part of the OChVB was calculated. The latitude of this paleomagnetic pole differs from the expected one when compared with that calculated for Chukotka from published data from Besse and Courtillot, 2003; Torsvik et al., 2012. These results are inconsistent with most of the existing geological data. Only a few works admit younger displacements in the southern part of the Verkhoyansk fold belt or in modern diffuse boundary of the Eurasian and North American plates. Moreover, we compare our OChVB pole with results from basaltic complexes from the basement, which has been likely remagnetized when OChVB was formed.

Acknowledgements: study of cretaceous volcanics is supported by RSF grant № 19-47-04110 and jurassic by RSF grant №18-77-10073.
Advances in 3D characterisation for correlative microscopy in geosciences
Authors: Taylor Rich
Published: March 2021

The proliferation of modern techniques available for petrologists has resulted in an explosion of detailed information on mineral compositions and processes over the last decade. One area of research that is undergoing dramatic advances is the non-destructive interrogation of samples in three dimensions through X-ray microscopy (XRM). Techniques such as ZEISS Versa and Ultra XRM can be performed at a variety of scales and resolutions, resulting in micro-to-nano scale information on geological samples. Such techniques can be correlated with each other i.e. expanding nanoscale resolution to a large sample or internal calibration of X-ray intensity to identify mineral assemblages, or even correlation with other techniques such as electron microscopy (EM). X-ray techniques are also particularly adaptable to digital resolution enhancements through software processes such as machine learning algorithms.

Collecting 3D information for petrological investigations can often require ground truthing of mineralogical and compositional interpretations. The more developed the 3D microscopy becomes, the more we are increasingly interested in features that are deeply buried within our samples. This means the corresponding techniques for excavating a region of interest also need to advance in both speed and accuracy.

The ZEISS Crossbeam-Laser (XBL) system provides a unique capability of rapidly excavating to a point of interest within a 3D sample volume. The XBL is already seeing use in material sciences, with a standard XB chamber with focussed Ion Beam (FIB) and Electron Microscopy (EM), and a correlated femtosecond laser chamber for rapid material removal. Sample data collected through XRM can be correlated to the XBL stage so that any internal features located by XRM have their coordinates automatically available in three dimensions. The femtosecond laser can excavate to a region of interest (RoI) within the sample within seconds or minutes, dramatically reducing preparation time compared to standard FIB/PFIB. The laser cut surface can be used for analysis techniques such as energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD), even prior to final polishing with the focussed ion beam (FIB).

Here we show the XRM-XBL workflow in high grade metamorphic rocks for identifying minerals in context for geochronology and micro-to-nano scale textures.
Adaptation and Application of the large LAERTES-EU RCM Ensemble for Hydrological Modeling
Authors: Ehmele Florian , Kautz Lisa-Ann , Feldmann Hendrik , He Yi , Kadlec Martin , Kelemen Fanny Dora , Lentink Hilke Simone , Ludwig Patrick , Manful Desmond , Pinto Joaquim Ginete
Published: March 2021

Enduring and extensive heavy precipitation associated with widespread river floods are among the main natural hazards affecting Central Europe. Since such events are characterized by long return periods, it is difficult to adequately quantify their frequency and intensity solely based on the available observations of precipitation. Furthermore, long-term observations are rare, not homogeneous in space and time, and thus not suitable to run hydrological models (HMs). To overcome this issue, we make use of the recently introduced LAERTES-EU (LArge Ensemble of Regional climaTe modEl Simulations for EUrope) data set, which is an ensemble of regional climate model simulations providing 12.000 simulated years. LAERTES-EU is adapted and applied for the use in an HM to calculate discharges for large river catchments in Central Europe, where the Rhine catchment serves as the pilot area for calibration and validation. Quantile mapping with a fixed density function is used to correct the bias in model precipitation. The results show clear improvements in the representation of both precipitation (e.g., annual cycle and intensity distributions) and simulated discharges by the HM after the bias correction. Furthermore, the large size of LAERTES-EU improves the statistical representativeness also for high return values of precipitation and discharges. While for the Rhine catchment a clear added value is identified, the results are more mixed for other catchments (e.g., the Upper Danube).
On the consolidation behaviour of double-porosity geomaterials
Authors: Choo Jinhyun
Published: March 2021

Many natural and engineered geomaterials have double-porosity structure where two dominant pore systems coexist. Examples include structured soils where the two pore systems are inter-aggregate pores and intra-aggregate pores, and fissured rocks where the two pore systems are fissures and matrix pores. Although such double-porosity materials are frequently observed in geosciences and geoengineering applications, it remains mostly unclear how fluid flow and solid deformation interact differently in single- and double-porosity materials. The presentation explores this question through numerical simulation of consolidation – a paradigmatic problem in poromechanics – based on a recently developed modelling framework for fluid-infiltrated, inelastic materials with double porosity. Built on a combination of continuum principles of thermodynamics and standard plasticity theory, the framework can capture deformation, flow, and their coupling that occur individually in each pore system. Simulation results using this framework suggest that double-porosity structure gives rise to a two-staged consolidation behaviour, where the second stage appears similar to secondary compression in clays. It is also found that the simulated two-staged behaviour bears a striking semblance to experimentally observed consolidation processes in shales. These findings suggest that double-porosity structure may exert dominant control over the long-term hydro-mechanical behaviour of geomaterials.
Backtracking oil slicks by using an iterative algorithm with a forward trajectory model. Implementation and verification.
Authors: Valainis Aigars , Bethers Uldis
Published: March 2021

Our goal was to investigate the performance of the in-house mathematical drift model using the oil spills according to the Marine Search and Rescue Service (MRCC) Riga data for the Eastern part of Baltic Sea 

There have been 15 cases in the Latvian territorial waters in 2016 when satellite imagery has identified potential marine pollution on the sea surface. Two additional reports of potential marine pollution have been received from ships. Satellite imagery from CleanSeaNet has identified 16 possible cases in the Latvian territorial waters in 2017, and further 19 possible cases in 2018.

We consider the following three cases of possible oil (and other pollutants) spills:

1) Possible oil spill in 2016.01.26 north of the harbor of Ventspils in Irbe strait.

2) Possible oil spill from ballast waters in 2017.05.14.

3) Possible pollutant (vegetable oil) spill in 2018.07.25.

Investigation of MRCC Riga sea pollution cases has revealed the following constraints and requirements for the FiMar oil drift model. First, the detected pollutant slicks are of size above 5 km2 and already of complex structure. This follows from the CleanSeaNet service detection capabilities and spill occurrence pattern; for example, dumping of ballast waters happens during the night, with spill being detected with the sunrise. Second, the pollutant slicks have a short lifespan and unknown chemical composition. Therefore, future development should focus on backtracking from a large target to a single most probable location in time-space.

The condition of nearly divergence-free flow is usually met in large-scale flows, but nonlinear changes in the properties of the oil are impossible to handle simply by reversing the direction of the wind field and the current field.

Method inspired by (Breivik, Bekkvik, Wettre and Ommundsen, 2011, BAKTRAK: Backtracking drifting objects using an iterative algorithm with a forward trajectory model.) was introduced into FiMar software and verified. This amends traditional reverse-time backtracking where a trajectory model is initialized and run in the forward direction, whereupon the individual ensemble particles that come within an acceptable time-space distance of the observation are used to initialize a new forward run. Unsuccessful particle trajectories thereafter are discarded. This procedure is then iterated until an acceptable number of trajectories end up within the target area (defined as a time-space radius around the location of the observation) is reached and time-space distribution of possible initial locations for the drifting object/ pollutant slick has been established.

The study was funded by Latvian Academy of Sciences, project lzp-2018/1-0162 DRIMO – Drift Modelling for pollution reduction and safety in the Baltic Sea, 2018-2021. 
Southern control of interhemispheric synergy on marine carbon sequestration during glacial cycles   
Authors: Du Jinlong , Zhang Xu , Ye Ying , Völker Christoph , Tian Jun
Published: March 2021

The mechanisms of atmospheric CO2 draw-down by ~90 ppm during glacial cycles have been one of the most contentious questions in the past several decades. Processes in the Southern Ocean (SO) have been suggested to be at the heart, while the North Atlantic (NA) is recently proposed to be critical during glacial periods as well. However, in a full course of glacial cycles, the individual and synergic roles of these two regions remain enigmatic. Using a state-of-the-art biogeochemical model (MITgcm-REcoM2) associated with an interactive CO2 module, we examined the impact of the onset of individual mechanisms and combinations of them on atmospheric CO2. Here we show that SO controls carbon sequestration in both hemispheres. In sensitivity runs with respect to mechanisms happening during glacial inceptions, cooling in SO contributes to a larger portion of CO2 draw-down than cooling in NA, by shortening the surface water exposure time, while the early sea ice expansion tends to weaken the carbon uptake. The efficiency of surface carbon storage in the North Atlantic depends on the volume of Antarctic bottom water and reaches its maximum when the glacial stratification is well developed during glacial maxima.  SO cooling and sea ice expansion strongly promote the formation of AABW and the full development of the glacial stratification. Furthermore, increased dust deposition during the glacial maxima raises the contribution of the Southern Ocean in the global biological carbon pump, leading to a higher efficiency of the biological carbon pump. And the maximal expanded sea ice suppresses local carbon leakage.

 

 

 
Impact of climate change on groundwater : a global assessment with the CNRM climate models
Authors: Costantini Maya , Decharme Bertrand , Colin Jeanne
Published: March 2021

Groundwaters found in aquifers play an important role in the hydrological cycle and are essential for human activities and for natural ecosystems. They account for approximately one third of the human fresh water withdrawals and sustain ecosystems by supplying soil moisture during dry periods. Climate change will impact every components of the climate system and aquifers are no exception. Precipitation is the main driver of groundwater recharge and relatively shallow aquifers respond rather quickly to changes in the precipitation rates. Thus, climate change should have an impact on water table depths and could lead to water scarcity and food insecurity in some regions. Therefore, knowing the response of the aquifers to climate change is important to improve the development of mitigation and adaptation plans in water management. 

Here, the response of unconfined shallow aquifers to climate change is assessed at the global scale using the global climate model developed in our institute (CNRM) : CNRM-CM6 and CNRM-ESM2. We analyse simulations conducted for the Coupled Model Intercomparison Project 6 (CMIP6) following four pathways of greenhouse gas concentrations until 2100. The CNRM models are the only global climate models representing the physicals processes involving aquifers. Results show that aquifers should replenish at the global scale on average, which is consistent with the projected global intensification of precipitation. However, the evolution of water table depths is not uniform and presents large regional disparities. Additionally to climate change, anthropogenic impacts like intensive groundwater withdrawals for agricultural, domestic and industrial purposes should exacerbate the depletion in some aquifers basins. In order to identify these regions, the evolution of the water table depths is compared with the population density. This analysis highlights the widening risk of water stress in some already aquifer-dependant regions.
Comparison sea ice data for Baltic Sea region based on modelling simulations and remote sensing measurements. 
Authors: Jakacki Jaromir , Muzyka Maciej , Konik Marta , Przyborska Anna , Stramska Małgorzata
Published: March 2021

A comprehensive analysis of the results of remote measurements of the Baltic Sea ice cover has been performed. For this purpose, two modelling integrations were made. Two modelling simulations have been compared with two satellite data sets. As a modelling tool Community Ice Code (CICE) was implemented for Baltic Sea region. It was forced by two independent atmospheric data sets.  In the first simulation, the eBalticGrid system was the source of the atmospheric data, which has been operating in operational mode for almost five years. The second simulation used data from the SatBałtyk system. The satellite data differed in the method of evaluating the quality of the results - in some cases, the result was supervised by ice experts, and in the other, the quality was assessed automatically.  Comparisons with model we have performed using the daily ice concentration and ice thickness maps over the Baltic Sea. Datasets are produced by the Finnish Meteorological Institute (FMI) and disseminated through the central dissemination unit: Copernicus Marine Environment Monitoring Service (CMEMS, http://marine.copernicus.eu/services-portfolio/ access-to-products/). The analysis showed an unnatural increase in the average ice thickness obtained from satellite data at the end of the ice season, for selected regions. The possibility of water appearance on the surface of the analyzed cells was assumed as the source of the potential error, which has a significant impact on the optical properties of the surface. It was proposed to eliminate cells containing a specific surface wetting fraction. However, the results do not allow this approach to be considered correct and therefore the work needs to be continued.
Late Miocene to present-day tectonostratigraphy of the northern central Algerian Basin: Evidence of a contractional salt system from reprocessed seismic data
Authors: Blondel Simon , Camerlenghi Angelo , Del Ben Anna , Bellucci Massimo
Published: March 2021

This study presents the interpretation of reprocessed seismic data covering the southwestern Balearic promontory and the central Algerian basin. The new depth processing of 2D seismic lines dataset allows for the first time a good resolution on salt structures in the deep basin. Most of the salt structures result from active diapirism. In the deep basin, sedimentary loads and regional shortening are proposed to be the dominant driving forces, showing an overall contractional salt system. The north Algerian margin tectonic reactivation could have provoked a regional shortening of the salt structures and overburden. Identified unconformities suggest that this process probably started shortly after salt deposition and is still active nowadays. It is expressed by salt sheets, pinched diapirs and a décollement level. The African convergence and the narrowness of the western Algerian basin could be the explanation of an overall greater salt deformation intensity compared to the eastern Algerian basin. This demonstrates how in tectonic and sedimentary components appear to be dominant in salt deformation in the central Algerian basin compared to gravitational gliding, only localized in the proximal parts of the margin.
Spatiotemporal evolution of deep seismicity beneath the central Himalayas
Authors: Michailos Konstantinos , Carpenter N. Seth , Hetényi György
Published: March 2021

The Himalayan orogen, formed by the continental collision between the Indian and Eurasian plates, is a unique geological structure that has been extensively studied over the past few decades. These previous studies highlighted the occurrence of earthquakes in the orogen's roots beneath the central Himalayas. However, the characterization of these deep earthquakes remains limited. Here, we compiled a detailed, long-duration catalog, which we use to investigate the spatiotemporal characteristics of seismicity beneath the Himalayan orogen. 

To create this catalog, we collected all available continuous seismic data acquired during the last two decades in the central Himalayas region (i.e., 2001-2005). We applied a systematic, semi-automatic processing routine to obtain absolute earthquake locations using a 1-D velocity model. Using high-quality picks, ~8,000 preliminary earthquake locations have been determined, at least 1,000 of which have hypocentral depths >50 km. We plan to refine the preliminary locations and calculate local magnitudes for the intermediate-depth lithospheric earthquakes. Using this refined catalog, we will analyze the spatiotemporal evolution pattern and properties of the Himalayan deep seismicity. This analysis is expected to provide us with insights into the processes and mechanisms that control seismogenesis beneath the orogen. For example, is seismicity driven by earthquake stress transfer (mainshock-aftershock sequences), or is it caused by external processes like fluids or aseismic slip, or both?
Effects of labile carbon on anaerobic decomposition processes in permafrost wetlands
Authors: Marushchak Maija E. , Nykänen Hannu , Pumpanen Jukka , Sannel A. Britta K. , Ström Lena , White Joel , Biasi Christina
Published: March 2021

Climate warming and permafrost thaw are exposing the large carbon (C) pools of northern wetlands to enhanced decomposition, potentially increasing the release of the greenhouse gases carbon dioxide (CO2) and methane (CH4). Permafrost thaw is usually associated with changes in hydrology and vegetation: Ground collapse leads to the formation of new, productive thermokarst wetlands, and active layer deepening allows plant roots to penetrate to deeper soil layers. These processes promote interaction between old permafrost carbon and recent plant-derived carbon, but the effect of this interaction on anaerobic decomposition processes is poorly known.

Here, we report the preliminary results of a 1+-year-long soil incubation experiment where we investigated the role of fresh organics on anaerobic decomposition in arctic wetlands. We sampled mineral subsoil of Greenlandic wetland sites and the active layer and permafrost peat in a Swedish palsa mire, and incubated them with and without repeated amendments of 13C enriched glucose and cellulose. We determined the rate and isotopic composition of CO2 and CH4 with an isotopic laser, and estimated the contribution of soil organic matter decomposition vs. added carbon to the total C gas release. These results represent new understanding on how plant-derived organics change the magnitude and composition of C gas, thus affecting the climatic feedbacks from permafrost wetland C pool.
Household final energy footprints in Nepal, Vietnam and Zambia: composition, inequality and links to well-being
Authors: Baltruszewicz Marta , Steinberger Julia , Ivanova Diana , Brand-Correa Lina , Paavola Jouni , Owen Anne
Published: March 2021

The link between energy use, social and environmental well-being is at the root of critical synergies between clean and affordable energy (SDG7) and other SDGs. Household-level quantitative energy analyses enable better understanding regarding interconnections between the level and composition of energy use, and SDG achievement. This study examines the household-level energy footprints in Nepal, Vietnam, and Zambia. We calculate the footprints using multi-regional input-output (MRIO) with energy extensions based on International Energy Agency (IEA) data. We propose an original perspective on the links between household final energy use and well-being, measured through access to safe water, health, education, sustenance, and modern fuels. In all three countries, households with high well-being show much lower housing energy use, due to a transition from inefficient
biomass-based traditional fuels to efficient modern fuels, such as gas and electricity. We find that households achieving wellbeing have 60-80% lower energy footprint of residential fuel use compared to average across the countries. We observe that collective provisioning systems in form of access to health centres, public transport, markets, and garbage disposal and characteristics linked to having solid shelter, access to sanitation, and minimum floor area are more important for the attainment of wellbeing than changes in income or total energy consumption. This is an important finding,  contradicting the narrative that basic wellbeing outcomes require increased income and individual consumption of energy. Substantial synergies exist between the achievement of well-being at a low level of energy use and other SDGs linked to poverty reduction (encompassed in SDG1), health (SDG3), sanitation (SDG6), gender equality (SDG5), climate action and reduced deforestation (SDG 13 and SDG15) and inequalities (SDG10). 
A grid-based b-value approximation through Southern and Northern Norway: preliminary results 
Authors: Estay Rodrigo , Pavez Claudia
Published: March 2021

The Gutenberg – Richter’s b-value is commonly used to analyze the frequency-magnitude distribution of earthquakes, describing the proportion of small and large seismic events as the first estimation of seismic hazard. Additionally, the b-value has been used as a stress meter, giving some insights into the stress regime in different regions around the world. In this research, a grid-based spatial distribution for the b – value was estimated in three different areas of Norway: northern (74°-81° N/ 12°-26° E), southern (57°-64°N/3°-12° E), and the ridge zones of Mohns and Knipovich. For this, we used a complete catalog from the years 2000 to 2019, which was obtained from the Norwegian National Seismic Network online database. The magnitude of completeness was estimated separately for each zone both in time and space, covering a total area of ~425,000 km2. Our results show a regional variation of the mean b-value for northern (bnorth = 0.79) and southern (bsouth = 1.03) Norway, and the Ridge (bridge = 0.73), which can be interpreted in terms of the predominant stress regime in the different zones. So far, a few calculations regarding the b-value were previously done in Norway to analyze local intraplate sequences. Then, according to our knowledge, this research corresponds to the first estimation of a regional spatial variation of the b – value in the country.
Simulating spatially coherent widespread flood events for risk modelling in the UK
Authors: Griffin Adam , Stewart Lisa , Kay Alison , Bell Vicky , Sayers Paul , Carr Sam
Published: March 2021

Within risk modelling, event ‘footprints’ are used to demonstrate how an extreme event impacts different locations at a similar time. Currently, estimates of future impacts from extreme events are derived by applying climate change allowances to at-site flood frequency estimates based on observations from the current period. These modified flow frequency estimates are then used to calculate flood risk and associated losses using a variety of means.

The present work brings together these two strands to develop spatially resolved projections of changes in river flow and, together with new analyses of the spatial coherence, to generate a wider collection of plausible events to improve risk modelling of the rarest events. This wide collection of extreme flood events provides the foundational input for an event-based assessment of risk.

The research extends proven methods to generate extreme, widespread flood events directly based on outputs from a 1km grid-based hydrological model driven by UKCP18 datasets. These modelled events provide coherent and highly credible descriptions of changes in flow based on spatially coherent climate change information. In addition to the small number of widespread extreme events generated directly from the gridded hydrological model, copula-based methods have been extended and applied on a regional and even national scale at a 1km resolution over the GB river network. These extensions to the Heffernan-Tawn model and Empirical Copula models are being used to generate a collection of plausible extreme based on the climate of 1980-2010 and on climate projections for 2050-2080. The collection of events is then used to compare the characteristics and variability of widespread events across different climate ensemble members and compare between present and future estimates.
The Effect of Surface Sublimation on the Snow Isotope Signal
Authors: Wahl Sonja , Zuhr Alexandra , Hörhold Maria , Faber Anne-Katrine , Steen-Larsen Hans Christian
Published: March 2021

Post-depositional processes affect the stable water isotope signal of surface snow between precipitation events. Combined vapor-snow exchange processes and isotope diffusion influence the top layer of snow as well as buried layers below. This implies, that ice core isotope climate proxy records can not be interpreted as a precipitation weighted temperature signal alone.

Here we present to what extend surface sublimation can explain in-situ observed changes of the stable water isotope signal in the snow.
We use direct observations of the isotopic composition of the sublimation flux together with surface snow samples taken in the North-East of the Greenland Ice Sheet accumulation zone throughout the summer months of 2019 to demonstrate sublimation impacts.
We show that, contrary to the understanding of effectless layer-by-layer removal of snow, sublimation involves fractionation and therefore influences the isotopic composition of the snow. Complementary measurements of humidity as well as isotope fluxes constrain the local vapor snow exchange and allow for the quantification of post-depositional influences while the snow is exposed to the atmosphere.
This improved process understanding of the formation of the climate signal found in snow is important for merging climate modeling and ice core proxies. 
Anti-herbivore silicon defences in a model grass are greatest under Miocene levels of atmospheric CO2
Authors: Biru Fikadu , Islam Tarikul , Cibils-Steward Ximena , Cazzonelli Christopher , Elbaum Rivka , Johnson Scott
Published: March 2021

Silicon (Si) has important role in mitigating diverse biotic and abiotic stresses, mainly via silicification of plant tissues. However, environmental changes such as reduced atmospheric CO2 concentrations may affect grass Si concentration which, in turn, can alter herbivore performance. Recently, we demonstrated that pre-industrial atmospheric CO2 increased Si accumulation in a grass, however, how Si is deposited and whether this affects insect herbivores performance is unknown. We, therefore, investigated how pre-industrial (reduced) (rCO2, 200 ppm), ambient (aCO2, 410 ppm) and elevated (eCO2, 640 ppm) CO2 concentrations and Si-treatments (Si+ or Si-) affect Si accumulation in the model grass, Brachypodium distachyon and its subsequent effects on the performance of the global insect, Helicoverpa armigera. rCO2 caused Si concentrations to increase by 29% and 36% compared to aCO2 and eCO2, respectively. Furthermore, increased Si accumulation under rCO2 decreased herbivore relative growth rate (RGR) by 120% relative to eCO2, whereas rCO2 caused herbivore RGR to decrease by 26% compared to eCO2. Moreover, Si supplementation increased the density of trichomes, silica and prickle cells, and these changes in leaf surface morphology reduced larval feeding performance. The observed negative correlation between macrohair density, silica cell density, prickle cell density and herbivore RGR supports this. To our knowledge, this is the first study to demonstrate that increased Si accumulation under pre-industrial CO2 environment reduced the performance of this generalist insect herbivore performance. Contrastingly, we found  reduced Si accumulation under higher CO2, which suggests  that some grasses might become more susceptible to insect herbivore under the projected climate change scenarios.
Turbulence and intermittency of electron density fluctuations in the inner heliosphere: Solar Orbiter first data.
Authors: Sorriso-Valvo Luca , Carbone Francesco , Yuri Khotyaintsev Yuri , Graham Daniel , Steinvall Konrad , Telloni Daniele ,   The Solar Orbiter RPW and MAG Teams
Published: March 2021

The recently released spacecraft potential measured by the RPW instrument onboard Solar Orbiter has been used to estimate the solar wind electron density in the inner heliosphere. Selected intervals have been extracted to study and quantify the properties of turbulence. Empirical Mode Decomposition was used to obtain the generalized marginal Hilbert spectrum, equivalent to the structure functions analysis, additionally reducing issues typical of nonstationary time series. Results show the presence of a well defined inertial range with Kolmogorov scaling. However, the turbulence shows intermittency only in part of the samples, while other intervals have homogeneous scale-dependent fluctuations. These are observed predominantly during intervals of ion-frequency wave activity. Comparisons with compressible magnetic field intermittency (from the MAG instrument) and with an estimate of the solar wind velocity (using electric and magnetic field) are also provided to provide general context and help determine the cause for the absence of intermittency.
Erodibility of loess depending on its weathering: field experiments
Authors: Vojtisek Jan , Bruthans Jiri
Published: March 2021

Piping is an erosion process in which cracks and macropores extend into channels with a diameter of cm or more. The study of loess erosion is important because loess covers about ten percent of the continents surface and is susceptible to piping, formation of gullies and intense erosion of agricultural soil. Study was done in Střeleč quarry (Czech Republic), where a several meters thick loess cover occurs in the upper part, sometimes with cracks and macropores. Rill erosion and piping conduits are formed in the loess cover and this makes it an ideal place for field experiments and observations. The erosion rate of the loess by water trickle at quarry face, erosion of the drill hole and erosion under the impact of the droplets were studied. The erosion rate of the rills was measured using long screws screwed directly into the rill. Rapid erosion occurred within first tens of centimeters from original ground surface in the zone where the loess structure was disintegrated by frost or wetting-drying cycles. Below this zone, the erosion rate was much lower, and it ceased with time as rill deepened. Small piping conduits developed rapidly by pouring water into small desiccation cracks on the loess surface. On the other hand, the dril hole did not expand into piping conduit in deeper zone of loess. Moisture content of small loess blocks have strong impact on final degree of erosion. While dry blocks began to disintegrate relatively quickly into incoherent material, the pre-wetted samples did not disintegrated and more or less kept their initial shape. This shows that slaking is responsible for disintegration of small dry blocks on loess surface. While the surface zone of the loess is highly erodible by flowing water, probably due to the loss of its original structure, the loess in the deeper zone is far less erodible in the quarry and even pre-formed conduit (dril hole) do not develop into larger conduit.

 

Many thanks to the management of Střeleč Quarry for enabling of the field documentation and experiments. The research was supported by Charles University Grant Agency (GAUK #1292119).
Impact of Climate Change on Combined Flood and Drought events in India
Authors: Chetan Kumar Salvadi , Gupta Vivek , Jain Manoj Kumar
Published: March 2021

The drought and floods are a natural phenomenon of ecosystems. Many studies found that the frequency and intensity of individual events of floods and drought are increasing in recent decades due to climate change. However, it is still unclear whether the frequency of combined flood-drought events is increasing in the same year or not under the climate change scenario. To identify drought and flood characteristics, we used the Standardized Weighted Average of Precipitation (SWAP), and copula bivariate distribution concept to estimate the joint probabilities of combined flood-drought events of the same year. We utilized gridded rainfall data from the India Meteorological Department at 0.25 degree for the present study. We estimated drought, flood and combined flood-drought events for the base period (1901-1930) and the current period (1991-2018). The analysis demonstrates that about 51.97% of the total grid points show an increasing monthly SWAP values trend in the summer monsoon season. However, in winter, only 15.55% of the total grid points show an increase in the trend of monthly SWAP values. The univariate flood and drought analysis revealed that 83.98%, 83.98% and 81.90% of total grids show a significant percentage change of drought at 5, 10 and 25-year return periods, respectively when the current period is compared with the base period. Still, only, 27.88%, 16.32% and 13.82% of the total grids show a significant change in the flood 5-year, 10-year and 25-year return periods, respectively. We also found that combined flood-drought events' frequency increases in 39.21%, 36.49% and 20.71% of total grid points corresponding to 5, 10 and 25-year return period values, respectively. This study concluded that less intensity drought, flood, and combined flood-drought events are increasing in more grid points. The study outcomes will help the decision-makers to make efficient decision to overcome the impacts of the hydroclimatic extremes.
Radiocarbon patterns of dissolved and particulate organic carbon in the Yenisei River and its major tributaries
Authors: Polosukhina Daria , Prokushkin Anatoly , Steinhof Axel
Published: March 2021

There is the significant progress in recent decades in the quantification of terrigenous carbon release to the rivers of the Arctic Ocean basin and characterization of its chemical properties, origin and age (e.g. Amon et al., 2012, Holmes et al., 2012). As warming accelerates the thawing permafrost may potentially increase the release the ancient carbon (Wild et al., 2019, Estop-Aragonés et al., 2020). However, more detailed analysis is still needed particularly in regard of the age of carbon exported from the diverse landscapes of large Arctic rivers and its transformation during the transport to the Arctic ocean.

In this study we analyzed D14C in dissolved organic carbon (DOC) and particulate organic carbon (POC) of the Yenisei River main channel and its major tributaries between 56oN and 68oN at freshet, summer and fall seasons. D14C was measured in Max Planck Institute for Biogeochemistry (Germany) by the accelerator mass spectrometry (AMS) system based on a 3MV Tandetron accelerator as described earlier (Steinhof et al., 2017).

 The oldest DOC in the Yenisei main stem was detected right after the Krasnoyarsk dam (56oN) and varied during a year without clear seasonal pattern in the range of the fraction of modern C (fMC) from 0.868 to 1.028. At freshet the fMC increased down stream up to 1.12 at 60oN and then remained relatively stable between 61o and 67.4oN (1.097±0.014). The major tributaries released DOC with fMC ranging from 1.0869 (Angara, 58oN) to 1.1046 (Kurejka (66.5oN), demonstrating more modern C with latitude. During the summer-fall season the Yenisei main channel and main Eastern tributaries contained older DOC (fMC = 0.968-1.054 and 0.949-1.045, respectively).

The POC of the Yenisei River was sufficiently older (fMC = 0.83-0.92) than DOC at all seasons and showed similar latitudinal pattern, i.e. the youngest POC was detected near 60-61oN (fMC > 0.90). The D14C-POC values in analyzed tributaries were increasing with latitude at freshet (R2 = 0.53) and summer lowflow (R2 = 0.33), except the largest Eastern tributaries, demonstrating the slight opposite pattern. On the other hand, increasingly more ancient POC was releasing by permafrost-dominated Eastern tributaries with increasing basin size. In opposite, D14C-POC of Western tributaries showed increased input of more recently fixed carbon. Our findings provided new data on the formation of terrigenic carbon fluxes to the Arctic Ocean from one of the largest river basins in the Arctic. This study was supported by RFBR grants #18-05-60203-Arktika. The radiocarbon analyses were kindly supported by Max-Plank Institute for biogeochemistry (ZOTTO project).
Role of asperities on the transition from seismic to aseismic slip using an experimental fault slip system
Authors: Shu Weiwei , Lengliné Olivier , Schmittbuhl Jean
Published: March 2021

Faults are common geological structures distributed at various depths within the Earth with different behaviors: from seismic to aseismic. The frictional stability of faults is linked to the properties of asperities that make the contact between fault surfaces. Investigating the interaction between asperities and its link with the frictional stability of faults aims at a better understanding of the intrinsic relationships between the observations of earthquake swarms and the slow local aseismic transient. Here we propose an experimental approach, which allows a customized interface sliding slowly under a well-controlled normal load, to study this problem. This interface consists of asperities modeled by poly-methyl-methacrylate (PMMA) balls in a softer, polymer base representing the parts of the fault that are easily deformed, facing a transparent flat PMMA plate. We employ a high-resolution camera for in-situ optical monitoring of the local deformation of the interface while loaded. We also attach acoustic sensors to capture the dynamics events attesting to local dynamic ruptures. We connect our observations with a mechanical model derived from a high-precision topography of the customized interface. We investigate the effects of various internal parameters of natural fault systems, including the density of asperities, their rigidity or the contrast of rigidity compared to the base, on the evolution of the frictional stability under variable normal load and of the behavior of the population of asperities at the transition between seismic and aseismic slip. Our results, bring new observations on the mechanics of swarm and fault transient.
Efficient Pathway Identification from Geospatial Trajectories
Authors: Trahms Carola , Handmann Patricia , Rath Willi , Renz Matthias , Visbeck Martin
Published: March 2021

In the earth-physics community Lagrangian trajectories are used within multiple contexts – analyzing the spreading of pollutants in the air or studying the connectivity between two ocean regions of interest. Huge amounts of data are generated reporting the geo position and other variables e.g. temperature, depth or salinity for particles spreading in the ocean. As state-of-the-art, these experiments are analyzed and visualized by binning the particle positions to pre-defined rectangular boxes. For each box a particle density is computed which then yields a probability map to visualize major pathways. Identifying the main pathways directly still remains a challenge when huge amounts of particles and variables are involved.

We propose a novel method that focuses on linking the net fluctuation of particles between adaptable hexagonal grid cells. For very small areas the rectangular boxing does not imply big differences in area or shape, though when gridding larger areas it introduces rather large distortions. Using hexagons instead provides multiple advantages, such as constant distances between the centers of neighboring boxes or more possibilities of movement due to 6 edges instead of 4 with a lower number of neighbors at the same time (6 instead of 9). The net fluctuation can be viewed as transition strength between the cells.Through this network perspective, the density of the transition strength can be visualized clearly. The main pathways are the transitions with the highest net fluctuation. Thus, simple statistical filtering can be used to reveal the main pathways. The combination of network analysis and adaptable hexagonal grid cells yields a surprisingly time and resource efficient way to identify main pathways.
Characterization of the model error in ICON-D2-EPS using a flow-dependent partial SDE
Authors: Sprengel Martin , Gebhardt Christoph
Published: March 2021

The growing share of renewable energy in power generation increases the impact of the weather on the stability of the power grid.
Especially prior to severe weather events, not only high-quality weather forecasts but also information about forecast uncertainties is needed by the transmission system operators (TSOs) to prepare stability provisions. 
To this end, in the research project gridcast the German Meteorological Service (DWD) aims at an improved representation of the inherent model error in its recently introduced convection-permitting ensemble prediction system ICON-D2-EPS.

We describe the model error using the following stochastic ansatz: The tendency equations for a set of relevant variables for power prediction like temperature, and zonal and meridional winds are extended by an additive tendency error approximated by the solution of a partial stochastic differential equation (SDE). This SDE consists – similar to an Ornstein-Uhlenbeck equation – of a damping term and a random field. However, the SDE is augmented with an additional diffusion term that ensures spatial correlations.
Each of the three terms has a strength parameter that is assumed to be a function of (possibly different) flow-dependent predictor variables. Hence the relative importance of the three terms varies in space and time according to the respective weather conditions.
The functional form of the parameters can be approximated from past estimates of the model error based on ICON-D2 ensemble forecasts.

We present theoretical properties of the SDE and motivate its choice as representation of the model error. Furthermore, we investigate a method to determine the parameters of the SDE and apply this method to the operational ICON-D2-EPS at DWD for the model error of relevant forecast variables.
First numerical results along the development of the scheme are presented.
Acceleration of Solar Energetic Particles in CME-Driven Coronal Shocks up to 30 Rs
Authors: Kozarev Kamen , Nedal Mohamed , Miteva Rositsa , Zucca Pietro , Dechev Momchil
Published: March 2021

The lower and middle solar corona up to about 30 solar radii is thought to be an important region for early acceleration and transport of solar energetic particles (SEPs) by coronal mass ejection-driven shock waves. There, these waves propagate into a highly variable dynamic medium with steep gradients and rapidly expanding coronal magnetic fields, which modulates the particle acceleration near the shock/wave surfaces, and the way SEPs spread into the heliosphere. We present a study modeling the acceleration of SEPs in over 50 separate global coronal shock events between 1 and 30 solar radii. As part of the SPREAdFAST framework project, we analyzed the interaction of off-limb coronal bright fronts (CBF) observed with the SDO/AIA EUV telescope with realistic model coronal plasma based on results from synoptic magnetohydrodynamic (MHD) and differential emission measure (DEM) models. We used realistic quiet-time proton spectra observed near Earth to form seed suprathermal populations accelerated in our diffusive shock acceleration model (Kozarev & Schwadron, 2016). We summarize our findings and present implications for nowcasting SEP acceleration and heliospheric connectivity.
Evaluating the clustering of Central European rain-on-snow events with flood-inducing potential
Authors: Kirschner Moritz Johannes , Krug Amelie , David Lun , Ahrens Bodo
Published: March 2021

Rain-on-snow (ROS) floods are responsible for the overwhelming majority of floods affecting multiple major river basins simultaneously in Europe during the last century. These widespread floods have serious negative economical, social and ecological effects, and knowledge about their rate of occurrence is critical for future projections in the face of climate change.

Recent studies have shown that ROS events (with flood-inducing potential) in Europe increase and decrease based on the elevation range considered since 1950 and there appears to be a clustering pattern of flood-poor and flood-rich periods since 1900. Our goal is to analyze if these changes in frequency can be realistically described by a stationary process (or a combination thereof) or if there must be hidden time-dependent driving factors to explain the observed clustering. To test this theory we analyze a simulation for the time period 1901-2010 based on ERA-20C dynamically downscaled using a coupled RCM. We apply a method from scan statistics and confirm the existence of significant periods poor and rich in ROS events with regards to the reference condition of independent and identically distributed random events and present their position in time. The same procedure is applied to the ROS event constituents (rainfall and snowmelt), where we identify such periods in the rainfall, but not in the snowmelt time series. We construct a stochastic ROS model by modelling precipitation and snowmelt via stationary gamma distributions fitted to our data but are unable to reproduce the observed clustering behaviour using the combined signal.

This study confirms that the observed ROS floods in Central Europe are unlikely to be the result of stationary processes which hints at climate drivers for the compound rain-on-snow process in Europe.