bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for long-lived continental intraplate magmatism: A case study from Mongolia
Authors: Papadopoulou Martha , Barry Tiffany L. , Dash Batulzii , Halton Alison M. , Sherlock Sarah C. , Hunt Alison C.
Published: February 2023

The closure of the Mongol-Okhotsk Ocean in Jurassic – Cretaceous times led to the final amalgamation of the interior of Eastern Asia, thus placing Mongolia in an intraplate tectonic setting. Small and widespread volcanic fields of Mesozoic and Cenozoic age are known through Eastern Asia, attributed to both post-collisional and intraplate mechanisms. In Mongolia, intraplate volcanic fields are scattered across the central and eastern parts of the country. Although several models have been proposed to explain the origin of this late Mesozoic – Cenozoic intraplate magmatism in Mongolia, there is still on-going debate about the process(es) that lead to it. Moreover, there are no temporal reconstructions on the extent of post-collisional magmatism in the area preceding intraplate magmatic activity, nor any hypotheses on the timing of the onset of the latter. In this study, we differentiate between post-collisional and intraplate magmatism in Mongolia using a set of geochemical, isotopic, palaeomagnetic and zircon data, and define the onset of intraplate magmatic activity at 107 Ma. Through evaluation of nearly 700 published radiometric data from the various volcanic fields across Mongolia along with newly-obtained age constraints, we reveal a complex temporal and spatial evolution of the magmatism that runs parallel in different volcanic fields through time, and we identify the extent of hiatuses in the magmatic activity. Based on the assessed data we discuss the source of bias in our understanding of the magmatic history of Mongolia and evaluate the various proposed models for the origin of the Mongolian magmatism. Finally, we suggest that asthenospheric upwellings were induced through a delamination event beneath Mongolia in the late Mesozoic. This initiated the intraplate magmatism, the temporal evolution of which is prolonged due to enhanced mantle flow related to northward progression of Tethys and the Indian plate.
Extreme value statistics of erosive rainfall events – a comparative assessment for agricultural production zones in Austria
Authors: Ozcelik Nur Banu , Strohmeier Stefan , Vásquez Cristina , Stumpp Christine , Klik Andreas , Strauß Peter , Pistotnik Georg , Yin Shuiqing , Dostal Tomas , Laaha Gregor
Published: February 2023

In our ACRP funded project EROS-A we aim at a comprehensive analysis of the erosive energy of rainfall, estimated soil loss, and reported damage using statistical and process-based methods. In this particular study, we evaluate the return periods of erosive rainfall events at 26 meteorological stations in Austria. The main focus is on daily cumulative rainfall and the maximum 30-min rainfall intensity (I30) as these were identified as key parameters for rainfall erosivity assessment. The extreme value series were obtained using both the Annual Maxima Series (AMS) and Peak Over Threshold (POT) approach, in order to assess which of the methods will be most accurate. The assumptions of stationarity and independence of the extreme value series were carefully checked using statistical trend and independence tests and no significant deviations were found.Generalized extreme value (GEV) and generalized Pareto (GPD) probability distributions were fitted using L-moment and maximum likelihood procedures. The GEV distribution is suited for AMS or block maxima data, whereas the GPD is suited for the POT series. For the obtained GEV and GPD models we examined extreme events with return periods of 2, 5, 10, 25, 50, and 100 years. We found that threshold selection is crucial for the POT, with diagnostic tools (such as mean residual life plots) not being fully decisive. Finally sensitivity analysis was performed where convergence of the fitted GPD to the GEV (AMS approach) helped determining robust thresholds for the GPD. The results show that the POT approach for daily cumulative precipitation is the most accurate in 69% of the cases and the AMS approach in 8% of the cases (different return periods and stations), while they have similar performance in 23% of the cases. Similar results are obtained for I30, were the success rates are 80% for the POT, 8% for the AMS and 12% for similar performance. In the next step, we will extend frequency analysis to a regional context, in order to map extreme rainfall erosivity across main agricultural production zones in Austria.
Erosion patterns in the European Alps from zircon fission-track tracer thermochronology
Authors: Glotzbach Christoph , Falkowski Sarah
Published: February 2023

Applications of tracer thermochronology exploit a known or assumed surface thermochronometric age map (based on either interpolated observed or modelled bedrock ages) to determine the provenance of detrital grains within fluvial or glacial catchments. The goal is to interpret the erosion pattern and processes within the sampled catchment. So far, most studies focused on modern sediments and glacial deposits.We extend this approach to several time slices (between 28 and 12 Ma) of well-dated stratigraphic sections of pro- and retro-foreland basins of the European Alps. Foreland basin deposits represent a rich archive of erosional processes that were controlled by tectonics, climate, and lithology. However, importantly, before we reconstruct and interpret past erosion patterns and exhumation from detrital zircon fission-track (ZFT) age distributions and modelled bedrock ZFT ages back in time, we produce a frame of reference of today's situation. We do this by investigating signals from modern river samples and the present-day erosion pattern and mineral fertility in the Alps.Here, we focus on 26 modern river samples (21 previous samples from the Western and Central Alps, and 5 new samples from the Eastern Alps) and discuss observed and predicted (based on possible erosion scenarios) ZFT age distributions, as well as potential pitfalls of the method (such as poor bedrock control in some areas of the Alps). We also show preliminary results from stratigraphic sections.
The role of the ocean circulation in melting the glaciers in Iceland
Authors: Jónsson Steingrímur
Published: February 2023

Iceland enjoys a much warmer climate than the average for its latitude. A major reason for this is the warm ocean currents in the Atlantic south of Iceland. There is a large heat flux from the ocean to the atmosphere and the air temperature therefore depends to a high degree on the ocean temperature. During the last roughly two decades, glaciers in Iceland have generally been retreating as well as having a negative mass balance due to a warmer climate, whereas during three decades prior to that, most of the glaciers in Iceland were advancing. The air temperature in Iceland south of the largest Icelandic glacier, Vatnajökull, showed a rise in temperature of about 1°C from 1995 to the early 2000’s and since then it has mostly remained at this high level. Often this warmer climate is attributed entirely to global warming. However, the temperature in the warm and saline Atlantic water south of Iceland also increased by about 1°C during the same period. This rise in ocean temperature was accompanied by an increase in salinity which indicates that the temperature rise was mostly due to a change in the ocean circulation, resulting in advection of warmer and saltier water to the area. In the period from 1995 to the early 2000’s the ocean heat flux with the Atlantic water across the Greenland-Scotland ridge increased by 21 TW, partly through Denmark Strait towards the continental shelf north of Iceland. The increased heat flux was attributed to a rising temperature as well as increased flow of Atlantic water. Only about 0.5% of this heat flux increase is needed to explain the recent melting of Icelandic glaciers. With a relatively sudden 1°C rise in temperature the glaciers will take decades to reach equilibrium with this new temperature and if the temperature does not decrease, the glaciers will continue to lose mass. There are records of advancing and retreating Icelandic glaciers from 1930 and they show a good correspondence with the Atlantic Multidecadal Oscillation (AMO), that reflects temperature variations in the North Atlantic Ocean.
A new empirical reconstruction of paleoglacier flow lines for the last glacial cycle, spanning high-mountain Asia
Authors: Blomdin Robin , Rogozhina Irina , Heyman Jakob , Castillo-Llarena Andrés , Abderhalden Jogscha , Hillisch Lukas
Published: February 2023

The past 5—10 years have seen a surge in empirically derived geological reconstructions for the high-latitude ice sheets during the last glacial cycle. These reconstructions are often presented in “time slice” formats and are beneficial when constraining numerical ice sheet models and paleoclimate datasets (models and proxy records). However, until now there is no equivalent database for high-mountain Asia (HMA). We, therefore, present the first consistently generated reconstruction of paleoglaciers and ice caps, spanning this vast and rugged region, which includes the Himalayas, Tibetan plateau, Pamir, Karakoram, Tian Shan, and the Altai mountains. This reconstruction is based on an extensive meta-analysis of previously published and expert-derived local reconstructions (n=120), which in turn were based on cosmogenic nuclide (Be-10 and Al-26) exposure age data and different mapping and reconstruction methods. Using landforms and sediment to delineate paleoglaciers in regions of rugged relief is often complicated due to geomorphological processes that overlap, obscure, or completely erase the signatures of former ice margins. Therefore, our reconstruction—the High-mountain Asia Paleoglacier Inventory (HAPI)—focuses on the glacier “flow line”, a simple glacial metric visualizing the trajectory of a hypothetical ice flow vector from the headwall of the catchment to the ice margin limit, constrained downstream by the dated glacial deposit (landform, sediment, or individual erratic clasts). The flow lines describe how long the former glacier was (i.e., glacier length) at a specific point in time and are thus first-order estimates of paleoglacier size. By reconstructing individual glaciers, we can assess their spatial and temporal robustness and compare their timing and relative size changes (compared with the mapped maximum extents), throughout the last glacial cycle, to both high-latitude glacial records and low-latitude monsoon records. Since correlating glacial records across hemispheres or even locally can be a complex task we discuss the foundations for glaciation asynchrony between regions, and across climate transects, by devising time-distance diagrams. Finally, HAPI will be made available for open access through a web interphase featuring downloadable shape file data and will be continuously updated by the authors of the study.
Uncrewed Aircraft Systems (UAS) for in-situ measurements across an air-sea interface
Authors: Baranowski Dariusz
Published: February 2023

Interactions across an air-sea interface are fundamental features of Earth’s climate system with substantial implications for ecosystems. Diurnal variations of local exchange between atmosphere and ocean impacts both environments and rectifies into longer and larger scale through interactions with mesoscale circulation. Therefore, such local processes can influence evolution of weather patterns. At the same time, atmosphere and ocean models struggle with the realistic representation of diurnal variations across an air-sea interface. It is related to gaps in our understating of physical mechanisms behind these interactions which stems from a fact that collocated, reliable measurements within coupled atmosphere and ocean environment, spanning across an air-sea interface are rare.Emergence of the Uncrewed Aircraft Systems (UAS) enables a new opportunity for sampling across air-sea interface. A multirotor UAS equipped with atmosphere and/or ocean measurement capability can be launch from a vessel (e.g. research vessel) and perform measurements in its vicinity, but in flow not obstructed by ship’s structure. In this presentation, observations collected over ocean tropical and subtropical Atlantic, as well as in the coastal zone will be presented. Profiles were collected in both oceanic (temperature profile, top 5m of the ocean) and atmospheric (temperature and humidity, surface to 500m). Therefore, measurements were conducted in the area not only obstructed by vessel’s sole presence but also unreachable by remote sensing techniques. Results demonstrate capability of ocean and atmosphere sensing UAS to measure coupled variability across an air-sea interface.
Microplastics retention in different types of Mangrove forest in Xuan Thuy National Park, Vietnam
Authors: Schneidewind Uwe , Comer-Warner Sophie , Haverson Lee , Kukkola Anna , Nel Holly , Krause Stefan
Published: February 2023

Mangrove forests provide important ecosystem services with regards to carbon storage and nutrient removal in coastal areas. They have also been found to retain emerging contaminants such as microplastics. However, in many parts of the world, mangrove forests are severely affected by deforestation and transformation into areas of intense agriculture/aquaculture. To restore their original ecosystem functions, mangrove forests are increasingly being targeted in small-scale conservation and restoration efforts, which often results in the coexistence of a variety of mangrove forest types with respect to tree age and vegetation density. This might have a severe impact on their retention capacity of fine particulate matter including microplastics (MP).Here, we study Mangrove sediment samples from Xuan Thuy National Park, Vietnam located in the Red River Delta with respect to microplastics. Sediment samples were taken from four types of landcover, i.e., (i) completely deforested area, (ii) 5–7-year-old naturally regenerated forest, (iii) eight-year-old replanted forest, and (iv) 15 year-old naturally regenerated forest. Surface samples and 50 cm-long cores were collected using mini augers and dried at 50°C. Subsamples were used to extract microplastics by means of density separation with ZnCl2 and digestion with Fenton reagent. Extracted MP were stained with Nile Red for florescence microscopy to determine MP concentration and shape. Additionally, microFTIR was used to identify the respective polymer type.Microplastics concentrations (>64 µm) range from 64 to 2141 particles/kg dry weight (n=568) with the vast majority being fragments. Higher concentrations were found in the naturally regrown forests (ii and iv) than in deforested or reforested areas. Although no depth-dependent trends were visible, high concentration spikes in 30 cm depth at sites (ii) and (iii) have been identified. Future analyses will relate particle concentration to sediment grain size distribution and carbon/nutrient data from the same locations.
Quantifying the direct influence of climate change on the rate of spread of wildfires in the Iberian Peninsula
Authors: Senande-Rivera Martín , Insua-Costa Damián , Míguez-Macho Gonzalo
Published: February 2023

Due to its strong connection with meteorological conditions and vegetation structure, fire activity is affected by anthropogenic climate change. As a direct effect, climate regulates fuel moisture, so warmer and drier conditions are linked to higher fuel flammability, increasing fire risk. We use data from ERA5 and different CMIP6 models to build a database of fuel moisture (for both live and dead fuels) under real conditions (factual) and modified conditions without the influence of global warming (counterfactual). We then calculate the rate of spread of some observed wildfires in the Iberian Peninsula from 2001 to 2021, from both factual and counterfactual data. We find that climate change influence is already noticeable and significant. We also identify the areas most vulnerable to the impacts of climate change and the time of the year when these impacts are strongest. 
A Decision Support Tool based on field and Earth observation to support restoration activities in degraded land based on Newlife4drylands Pilot Sites
Authors: Assennato Francesca , Alessi Nicola , Smiraglia Daniela , Riitano Nicola , Labadessa Rocco , Tarantino Cristina
Published: February 2023

Land degradation processes have undergone towards a significant increase in recent decades which is likely to further increase if no actions are taken. The need of adopting practices to contain, mitigate and restore degraded land have been stressed by the new Soil Strategy. In order to guide actions, through a common and effective framework, a cost and time efficient approach is needed. Experiences from six pilot sites in southern European countries, selected within the NL4DL LIFE project, were examined and monitored with both available field data and satellite-acquired data, in order to be replicated, improved and transferred to similar degraded sites. The heterogeneity and complexity of degradation processes resulted from the pilot sites highlighted issues and necessities of harmonization and standardization of ecological/physical indicators, especially those derived from satellite observations, when used as proxies of land degradation.  The aim of the tool is to provide a reference procedure to be applied to monitor restoration activities based on nature-based solutions on degraded lands, once the degradation processes has been identified. Variables considered in the tool include processes of degradation, physical indicators derived from remotely sensed approaches and most common practices of nature-based solutions. Connections between these variables, which form the basis of the relational map of the tool, have been initially collected through the internal knowledge of the project and will be further deepened trough expert-based questionnaires to experts of different disciplines in the field of soil and environmental sciences. The decision-making tool provide a workflow to guide the end users in the field of environmental management and planning, through the identification of land degradation processes, the selection of monitoring indicators viable and the most suitable nature based solution for that particular degraded land. The tool will be used as an input base for an action protocol at local and regional scale for environmental management and planning
A new model for the evolution of oceanic transform faults based on 3D Broadband Seismic observations from São Tomé and Príncipe in the eastern Gulf of Guinea.
Authors: Thomas Myron , Heine Christian , van Itterbeeck Jimmy , Ostanin Ilya , Seregin Andrey , Spaak Michael , Morales Tamara , Oude Essink Tess
Published: February 2023

Oceanic Transform faults are one of manifestations of the three major plate boundaries and a key tectonic feature of oceanic crust. They are broadly considered to accommodate strike-slip displacement along simple vertical faults and to be largely without magmatic addition. We present the first observations from broadband 3D seismic of buried, Cretaceous-aged transform faults in the Gulf of Guinea with complex internal architectures including crustal scale detachments and rotated packages of volcanics within oceanic crust. In the study area, several Oceanic Fracture Zones (OFZ) are described from Top Crust to Moho. OFZ scarps are observed to connect at depth with zones of low angle reflectivity which dip into the OFZ and perpendicular to the spreading orientation. At depth they detach onto the Moho, necking the adjacent crust in the manner of extensional shear zones. Thickly stacked and tilted reflectors, interpreted as extrusive lava flows, are common above the shear zones and infill up to 75% of the crustal thickness within the OFZ. The entire OFZ stratigraphy is overlain and sealed by late-stage lavas that are continuous from the abyssal hills of the trailing spreading ridge. These insights demonstrate complexity previously only predicted in numerical simulations. We propose a model with inside corner extension at a high angle to the spreading orientation along a low angle shear zone that acts as a conduit for decompression related melt and volcanism. Late-stage lavas indicate a second stage of magmatic accretion as dykes propagate through the transform to adjacent crust, as inferred from bathymetric studies. These observations come from a unique 3D seismic dataset and are placed within a kinematic model which combines insights from numerical models. We conclude that these oceanic transforms were non-conservative and not simple strike slip fault zones, contradicting the conventional view.
Constraining regional and global ocean carbon fluxes in RECCAP2
Authors: Hauck Judith , Gruber Nicolas , Ishii Masao , Müller Jens Daniel ,   RECCAP2 ocean chapter leads
Published: February 2023

Keeping global warming in line with the Paris Agreement requires rapid reductions in CO2 emissions. Tracking these reductions demands a thorough bookkeeping of natural and anthropogenic carbon fluxes. The second REgional Carbon Cycle Assessment and Processes (RECCAP2) activity of the Global Carbon Project aims to accurately assess land and ocean CO2 sources and sinks through the efforts of hundreds of scientists around the globe. For the ocean component, regional budgets are developed for the global ocean and five large regions for the period 1980-2018. In addition, four ‘special focus’ themes, namely the biological carbon pump, the seasonal cycle, the coastal ocean and model evaluation are addressed. We use state-of-the-art ocean models and observation-based datasets to provide robust estimates of regional CO2 budgets and constrain their uncertainties. Here, we will provide an overview of RECCAP2 activities, and showcase key results focusing on mean ocean carbon fluxes, and their trends and variability.
The ACA algorithm implemented into the direct BEM approach to reduce its numerical complexity
Authors: Čunderlík Róbert , Bejdák Martin
Published: February 2023

The boundary element method (BEM) as a numerical method can be applied for high-resolution gravity field modelling. To obtain numerical solutions of “cm-level” accuracy, it requires very refined level of the disretization which leads to enormous memory requirements. An implementation of the Hierarchical Matrices (H-matrices) can significantly reduce a numerical complexity of the BEM approach. Here we present an implementation of the Adaptive Cross Approximation (ACA) algorithm into the direct BEM formulation applied for the global gravity field modelling. The ACA algorithm is based on a multilevel matrix-partitioning scheme of the rank-revealing LU decomposition, which uses a low rank of the submatrix belonging to two far groups of points. The algorithm performs a series of decompositions, which results in an approximation of the original submatrix using the product of two sparse matrices with low ranks. This approach can significantly reduce enormous memory requirements. Numerical experiments present efficiency of the ACA algorithm that can achieve a memory saving of 98% for the very refined meshes.
Experimental analysis of seasonal processes in shallow landslide through downscaled observations
Authors: Panzeri Lorenzo , Mondani Michele , Graziotto Andrea , Corti Monica , Papini Monica , Longoni Laura
Published: February 2023

Shallow landslides are phenomena involving small parts of land and are triggered by huge intensity rainfall events of short duration or more moderate but prolonged over time. The area and thickness of such slips are typically reduced, but they are still harmful because there are no warning signs and no information on their possible evolution.Since the middle of the 20th century, heavy precipitation events have been more frequent and intense. In light of the current climate crisis, it is crucial to thoroughly examine the effects of these occurrences in order to establish triggering thresholds in mountain regions.  This work deals with the experimental study of these landslides through the laboratory simulations on a small-scale slope, reproduced at the Gap2 lab of the Lecco Campus.  Different experiments have been performed reproducing the seasonal conditions of the slopes. In particular, extreme rainfall events, soil conditions with different volumetric water content percentages were compared with moderate rainfall events in order to assess the different timing of landslide triggering.To investigate the behaviour of surface landslides under these conditions and to visualise in detail the processes related to water circulation, a multidisciplinary approach was adopted that consist of observations using geological, geophysical and photogrammetric methodologies and instrumentation. These technologies include modified pressure transmitters for the pore water pressure evaluation, GoPro’s cameras, TDR (Time Domain Reflectometry) for the volumetric water content evaluation and a georesistivimeter (IRIS Syscal Pro). In this way hydrogeological processes can be deeply analysed from different perspectives and can highlight peculiarities and assess in detail their evolution leading to collapse.Through the information obtained from geophysics, it is possible to visualise the formation of cracks within the landslide body in advance, also allowing considerations regarding the different water contributions of the simulated rainfall and the initial water content in the soil. The experimental results were then compared with a mathematical model.
How do biocrusts modulate erosion along different climatic conditions?
Authors: Riveras Muñoz Nicolás , Seitz Steffen , Kühn Peter , Seguel Oscar , Scholten Thomas
Published: February 2023

Biological soil crusts (biocrusts) have received increasing attention in recent years, especially in arid regions, where it is the main living cover, due to its active role in a variety of ecological services, for example regulation of nutrient and water cycles, surface stabilization and erosion protection. Nevertheless, biocrusts are present globally but understudied under climatic conditions other than arid, where they also play a role. Our study from the Chilean Coast Range shows that the mechanisms and the subsequent results of the occurrence of biocrust vary in non-arid conditions regarding sediment discharge, surface runoff, and nutrient allocation. Here we show a shift in the surface roughness from smooth to rugose as the water availability increases, resulting in shorter times to start the runoff in humid conditions but a lower total runoff volume. There were also changes in the amount and composition of the sediment discharged during erosion, with a sustained reduction of it in the presence of biocrusts but increasing carbon and nitrogen sediment contents under semiarid climates and a decrease in humid and mediterranean. This place biocrusts as a relevant community along different ecosystems, but with behavior that depends on the local conditions that must be considered.
Numerical modeling of magmatic transport processes, using the pseudo-transient method
Authors: Kiss Dániel , Moulas Evangelos , Kaus Boris , Berlie Nicolas , Riel Nicolas
Published: February 2023

One of the continuing trends in geodynamics is to develop codes that are suitable to model magmatic processes with an increasing level of self-consistency. Developing such models is particularly challenging as most magmatic processes are multiphysics problems, and require coupling between thermal, porous, mechanical and chemical processes. Here we consider reactive flow in a deformable porous medium coupled to thermo-mechanical processes. We present a thermodynamically self-consistent set of governing equations, describing such processes. The governing equations consists of the conservation of mass, momentum, and energy in two phases. One phase represents the solid skeleton, which deforms in a poro-visco-elasto-plastic manner. The second phase represent low viscosity melts, percolating through the solid skeleton, that is described by Darcy’s law. As melt migrates through the rock skeleton we can quantify the chemical evolution of melts due to partial melting and crystallization. The system of equations is solved numerically, using the pseudo transient method, that is well suited to solve highly non-linear problems. We are going to discuss a few key end-member results, such as melt migration along dykes and fractures, along self-localized channels or by magmatic diapirism. We will discuss how the coupling between thermo-mechanical processes and melt migration might affect the chemical evolution of percolating melts.All the codes presented here are written within a modular Julia framework, developed within the MAGMA ERC project, that permits easy future integration of the currently stand-alone software.
Transient Attracting Profiles in the Great Pacific Garbage Patch
Authors: Kunz Luca
Published: February 2023

Anthropogenic impact on the ocean and marine wildlife has never been as pointless as marine debris. Nevertheless, great efforts must be taken to estimate pathways and accumulation zones of marine litter in order to clean the most polluted areas of the sea. The present study intends to introduce a modern hydrodynamical concept to this debate. TRansient Attracting Profiles (TRAPs) act like short-term attractors on the ocean surface and have shown their potential to predict pathways of material transport in previous experiments. Here, I explore the occurrence of these profiles in the North Pacific subtropical gyre, a large-scale convergence zone that is known to entail a major accumulation region for floating debris, the Great Pacific Garbage Patch. There, I compute TRAPs upon daily snapshots of near-surface geostrophic velocity and create an unprecedented large dataset of approximately 4.5 million TRAP objects. With this record, I am able to provide a first characterisation of these structures at the mesoscale. I study their propagation, evaluate their persistency and uncover a driving mechanism behind the formation of TRAPs. Analysing their impact on nearby floating drifters allows me to reveal a signature of hyperbolic transport around these structures. I show that drogued drifters take around 7 days and undrogued ones around 5 days to pass by a TRAP, suggesting that these structures are most likely to organise transport if they are persistent. Throughout the thesis, I present a series of such findings that can be of particular interest to offshore cleanup operators.
Pushing the limits of the Marchenko method
Authors: Wapenaar Kees , Brackenhoff Joeri
Published: February 2023

In recent years, the Marchenko method has proven to be a viable tool to create virtual seismic sources and receivers in the subsurface from reflection measurements at the surface. Applications range from suppressing internal multiples in seismic imaging to forecasting responses to induced seismic sources. One of the attractive aspects of the Marchenko method is that no detailed subsurface model is needed; a smooth background model suffices. All information needed to treat the internal multiples correctly comes from the reflection measurements at the surface. One of the underlying assumptions of the Marchenko method is that the seismic wave field can be decomposed into downgoing and upgoing waves at any position in the subsurface where one wants to create a virtual source or receiver. Although in many situations this implies no significant restrictions, it may hamper the imaging of steeply dipping flanks and it prevents the treatment of refracted and evanescent waves.It can be shown that the Marchenko focusing function (the nucleus of the Marchenko method) can be expressed in terms of the so-called propagator matrix. The propagator matrix, which was introduced in geophysics in the nineteen-sixties for 1D systems and developed further in the nineteen-seventies for laterally varying 3D media, ‘propagates’ a wave field from one depth level to another. It does not rely on up-down decomposition and it accounts for propagating waves at all angles and for evanescent waves. By exploiting the link between the Marchenko focusing function and the propagator matrix, the applicability of the Marchenko method can be expanded. In the presentation we will review the underlying theory and discuss the potential application of the Marchenko method for refracted waves.
Preliminary results of Tolstoj quadrangle (H08) geological mapping
Authors: Giacomini Lorenza , Guzzetta Laura , Galluzzi Valentina , Ferranti Luigi , Palumbo Pasquale
Published: February 2023

Tolstoj quadrangle is located in the equatorial area of Mercury, between 22.5°N and 22.5°S of latitude and 144° and 216°E of latitude. In this work we present the preliminary results of a geological map (1:3M scale). The main basemap used for the mapping is the MDIS (Mercury Dual Imaging System) 166 m/pixel BDR (map-projected Basemap reduced Data Record) monochrome mosaic compiled using NAC (Narrow Angle Camera) and WAC (Wide Angle Camera) 750 nm-images. Moreover, to distinguish spectral characteristics and topography of the surface, MDIS global color mosaics (Denevi et al., 2016) and the MDIS global DEM (Becker et al., 2009), have been taken into account. Then, the quadrangle has been mapped using ArcGIS at an average scale of 1:400k for a final out-put of 1:3M. So far, most of the geological contacts and lineaments of Tolstoj quadrangle have been mapped. The preliminary geological map shows the Caloris basin-related features dominating the Tolstoj quadrangle. The southern half of the basin is located in the upper left corner of quadrangle and interior and exterior smooth plains of the Caloris basin are the most extended volcanic deposits emplaced in the area. Also structural framework is mainly linked with the basin with radial and concentric grabens located in its floor and wrinkle ridges widespread both on the interior and exterior Caloris smooth plains. Further, thrusts have been detected on the quadrangle. They are located outside the Caloris basin but they are absent within its floor. Besides smooth plains, products of effusive volcanism, features related to explosive volcanism are also frequently detected. Interestingly, several volcanic vents have been identified in the inner Caloris smooth plains, aligned with the rim of Caloris basin. They were surrounded by extended pyroclastic deposits appearing in bright yellow in MDIS enhanced global color mosaics. However, vents are not clustered only inside Caloris basin, but other crater floors are affected by this type of features. Finally, few hollow fields have been detected, mainly located within crater floors.Once the mapping activity is accomplished, the geological map will be integrated into the global 1:3M geological map of Mercury (Galluzzi et al., 2021), which is being prepared in support to ESA/JAXA (European Space Agency, Japan Aerospace Agency) BepiColombo mission. Acknowledgements:  We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0 References:Becker K. J., et al. AGU, Fall Meeting, ab-stract#P21A-1189, 2009Denevi et al.:LPS XLVII. Abstract#1264, 2016Galluzzi V. et al.:. Planetary Geologic Mappers 2021, LPI #2610, 202
Spatial flood frequency analysis of ephemeral rivers in Northwest Namibia based on cloud computing of Landsat time series
Authors: Walk Janek , Boemke Bruno , Ullmann Tobias
Published: February 2023

Drylands cover approximately 40% of the Earth’s land surface and are home to over a quarter of the global population. Despite the deficit of surface water, rare but strong precipitation events are the fundamental driver for geomorphic activity in arid regions. A quantification of the frequency and magnitude of episodic river discharge is essential for a robust characterization of flood hazards and, thus, better understanding of the poorly studied hydromorphodynamics in deserts. However, observation data from gauges are sparsely distributed and, if existent, often do not cover a sufficiently long seamless time series or feature extensive gaps. This applies, for instance, to the remote Northwest Namibia, where more than a dozen ephemeral rivers drain the Kunene Highlands towards the Skeleton Coast, yet daily river flow data for a period of several decades is only available from the Hoanib.Hence, we propose a workflow based on the Landsat multispectral satellite imagery archive to detect flood events and their spatial impact since 1984 in a high resolution (30 m) for the entire Kunene Region (~144 km²). To cater for the limitations related to a revisit time of 16 days and potential impracticality of scenes due to cloud cover, we calculated spectral indices allowing for the detection of both inundated areas during flooding (e.g., Normalized Difference Water Index) and effects sustained after flood recession (e.g., Tasseled Cap Wetness to detect increased soil moisture). The large remote sensing dataset is processed via cloud computing using the Google Earth Engine. As a novel approach, we try to implement a frequency analysis directly in the Google Earth Engine environment after attributing the spectral imprints of floods to their magnitudes. For this purpose, a statistical relationship is developed between the daily record of the gauging station at the Hoanib and the spatiotemporal multispectral surface characteristics along the river course and floodplains. By transferring this relationship to the other ephemeral streams, spatially highly resolved recurrence intervals for areas affected by floods of different magnitudes can be derived for the entire Kunene Region.
Near-Sun Alfvenic Slow Solar Wind with Variable Helium Abundance: PSP observation and source tracing
Authors: Wu Ziqi , He Jiansen , Hou Chuanpeng , Peng Jingyu , Duan Die
Published: February 2023

The solar wind, except for the coronal mass ejection events, is traditionally divided into two groups, fast wind and slow wind. However, the origin and releasing mechanism of highly variable slow winds are still a riddle. The slow wind is generally believed to have low Alfvénicity, while the fast wind shows high Alfvénicity. However, Parker Solar Probe shows that highly Alfvénic slow winds take a large proportion of the near-Sun pristine slow winds, suggesting similar sources with the Alfvénic fast winds. Helium abundance (Nα/Np) also bears information about the source region and release mechanism of the slow winds. The typical value of helium abundance in slow winds can be as low as 1% or even lower, while it stays around 4% in fast winds. During its 8th encounter, PSP observed intervals of helium-poor (Nα/Np~0.1%) and helium-normal (Nα/Np~1%) Alfvénic solar winds on two sides of the heliospheric current sheet. We calculate and compare the alpha-particle properties, plasma parameters, collisional age, and magnetic fluctuations in these intervals statistically. In addition, we check the magnetic connection from PSP to the Sun during these intervals with two-step ballistic backmapping. We conclude that the helium-poor winds originate from large quiescent magnetic loops and experience sufficient collisions before and during release. In contrast, helium-normal winds originate from low-latitude coronal holes and experience preferential acceleration and heating due to wave-particle interactions. These results suggest that Alfvénic slow solar winds likely have multiple origins.
Combining water and pesticide data with coupled surface/subsurface hydrological modeling to reduce its uncertainty.
Authors: Lauvernet Claire , Paniconi Claudio , Rouzies Emilie , Gatel Laura , Caisson Antoine
Published: February 2023

In small agricultural catchments over Europe, intensive use of pesticides leads to widespread contamination of rivers and groundwater, largely due to hydraulic transfers of these reactive solutes from plots to rivers. These transfers must be better understood and described in the watershed in order to be able to propose best management practices adapted to the catchment and to reduce its contamination. The physically based model CATHY simulates interactions between surface and subsurface hydrology and reactive solute transport. However, the high sensitivity of pesticide transfers to spatially heterogeneous soil properties induces uncertainty that should be quantified and reduced. In situ data on pesticides in a catchment are usually rare and not continuous in time and space. Likewise, satellite imagery can provide spatial observations of hydrologic variables but not generally of pesticide fluxes and concentrations, and at limited scale and time frequency. The objective of this work is to combine these 3 types of information (model, in situ data, images) and their associated errors with data assimilation methods, in order to reduce pesticide and hydrological variable uncertainties. The sensitivity to spatial density and temporal frequency of the data will be evaluated, as well as the coupled data assimilation efficiency, i.e., the effect of assimilating hydrological data on pesticide-related variables. The methods will be developed using a Python package, and compared/evaluated on twin experiments using virtual data that are however generated over a real vineyard catchment, in Beaujolais, France, in order to ensure realism of the experiments, data, and associated errors.
A Groundwater Flow Modeling Application for the Impact Assessment of Treated Wastewater Reuse by Managed Aquifer Recharge
Authors: Eryilmaz Saylan Cigdem , Elci Alper , Somay Altas Melis
Published: February 2023

The tendency towards more groundwater use is becoming increasingly prevalent in regions where surface water supplies are limited in quantity and quality. However, the over-abstraction of groundwater can lead to serious issues. Therefore, to maintain the supply-demand balance for groundwater, withdrawals from aquifers should not exceed groundwater recharge. In cases where they do, groundwater reserves should be replenished with external water. Returning treated wastewater to the aquifer via managed aquifer recharge structures is a proven strategy that can effectively increase groundwater recharge rates. The objective of this study is to use groundwater flow modeling to assess the impacts of recharging treated wastewater to the aquifer at the sub-basin scale. The study is realized within the scope of the European Union-supported research project TRUST, which is conducted by six Mediterranean countries to mitigate water scarcity under the influence of climate change.A MODFLOW-based groundwater flow model is constructed for the Fetrek Creek sub-basin, which is located in an environmentally stressed semi-urban area in Western Turkiye. The input data for the model consists of information obtained from reviewing and synthesizing borehole logs, groundwater recharge rates from an independent hydrological modeling study, groundwater level time series from 17 monitoring wells, and information from previous geological and hydrogeological studies. The PEST parameter optimization method is used to calibrate the model. First, a baseline scenario representing the current state is investigated using the calibrated flow model. The model is then used to determine the impacts of various managed aquifer recharge application scenarios, thereby reflecting wastewater reuse in the sub-basin. Acknowledgment:This study is funded by the PRIMA program supported by the European Union under grant agreement No: 2024, project TRUST (management of industrial Treated wastewater ReUse as mitigation measures to water Scarcity in climaTe change context in two Mediterranean regions).
Investigating Solar Wind Drivers of Ultrarelativistic Electron Enhancements in the Outer Radiation Belt
Authors: Szabo-Roberts Matyas , Shprits Yuri , Allison Hayley
Published: February 2023

A distinct population of ultrarelativistic electrons has been observed in the outer radiation belt after several geomagnetic storms, and recent modeling results indicate that an existing seed population, and depletions in plasmasphere electron density, are a necessary condition for the appearance of this electron population. In order to similarly deepen our understanding of the solar wind drivers behind the appearance of these electrons with extreme energy, we catalog storms corresponding to ultrarelativistic enhancements by origin, and begin to establish necessary and sufficient solar wind conditions for these enhancement events. To do so, we perform superposed epoch analysis on a 6 year period from 2012 to 2018, using solar wind data from the Omniweb service, as well as electron flux and electron density data products from the Van Allen Probes mission. We also provide an overview of further modeling objectives and open questions for continued investigation of this electron population.
River coastline detection using maximum likelihood classification
Authors: Witek Matylda , Walusiak Grzegorz , Niedzielski Tomasz
Published: February 2023

In frame of the project no. 2020/38/E/ST10/00295 carried out within the Sonata BIS programme, financed by the National Science Centre of Poland, we consider different approaches to delineate the river coastline based only on close-range visible light aerial images (RGB) acquired by unmanned aerial vehicles (UAVs).  Among the scrutinized methods, we use automatic mapping of extent of water bodies  by means of image classification. It was found that the best results of reconstructing inundation extent (even 95%) were obtained using the supervised methods, in particular the maximum likelihood algorithm. The accuracy assessment of this classification, using the confusion matrix visualization, allowed us to notice that the areas incorrectly classified as "water underestimation" (surface where there is real inundation which was not indicated by the classifier) are located mainly on the borders of the water bodies.In most of the analyzed cases, the incorrectly classified "water underestimation" areas form a narrow zone around the inundated areas, which can be interpreted as the water-land interface zone. Therefore, it is possible to delineate, with high probability, the approximate  water-land boundary line. In low-altitude aerial photographs or orthophotomaps with visible fragments of river channels, the designation of such "water underestimation" zone allowed us to delineate the approximate course of the river channel coastline. This approach was tested on several UAV images acquired over the middle Odra River channel in western Poland. We analyzed several images representing various terrain situations: (1) the river channel completely visible, without vegetation, where the visual determination of the reference coastline by the human expert was not difficult, (2) the river channel partially shaded, where significant classifier errors can be expected, (3) the river channel partially covered, for example by vegetation, where the course of the real coastline is uncertain. The obtained results confirm that the proposed approach allows to reconstruct some courses of the coastline for channels with a width of at least 100 m using the "water underestimation" areas.