bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling CO2 and N2O emissions from a tropical semi-arid parkland cultivated with groundnut and millet
Authors: Agbohessou Yélognissè , Ba Seydina , Ferchaud Fabien , Léonard Joël , Sow Sidy , Bouvery Fredéric , Duthoit Maxime , Delon Claire , Vezy Rémi , Falconnier Gatien N. , Mougin Eric , Ngom Daouda , Taugourdeau Simon , Roupsard Olivier
Published: March 2024

Agriculture contributes to climate changes through land use changes and greenhouse gas emissions. Models can provide crucial insights into the extent of this contribution; however, their effectiveness relies on proper evaluation within the application context. Moreover, crop models that can simulate greenhouse gas emissions have not been extensively tested for the semi-arid tropics. We calibrated and used the STICS soil-crop model to explore the skills of the model to reproduce observed variations in greenhouse gas emissions for a millet-groundnut rotation in an agro-silvo-pastoral parkland dominated by Faidherbia albida trees located in central Senegal. Model simulations were compared with observations of soil temperature, soil water content, N2O and CO2 emissions, aboveground and belowground biomass of millet and groundnut, collected between 2018 and 2022. CO2 emissions were simulated with a two-step approach. Initially, STICS simulated crop leaf area index and biomass (aboveground and belowground), and soil heterotrophic respiration. These variables were then integrated into an independent autotrophic respiration module, and summed with STICS simulated' heterotrophic respiration. In general, the STICS model tends to underestimate the observed minimum soil water content (wilting point) during the dry season and overestimate the observed soil water content after the wet season. However, the temporal dynamics of the soil temperature in the upper layer (0-30 cm) are generally well-represented by the model throughout the simulation period. Simulated N2O emissions were generally consistent in terms of magnitude compared to on-site measurements, although the model currently does not account for N2O absorption by the soil (i.e. negative fluxes). For instance, the simulated peak reached 0.041 kg N ha-1 d-1, while the observed peak was 0.048 kg N ha-1 d-1. The simulated average annual N2O emissions for the period 2018 to 2022 amounted to 0.368 kg N ha-1 yr-1. Simulated CO2 emissions were also comparable to on-site measurements (2021: EF = 0.63, BIAS = -0.75 kg C ha-1 d-1, and RMSE = 15.01 kg C ha-1 d-1; 2022: EF = 0.56, BIAS = -3.25 kg C ha-1 d-1, and RMSE = 5.01 kg C ha-1 d-1). These results indicate that the STICS model can be used to explore the impact of land use and crop management changes on greenhouse gas emissions in a tropical semi-arid context.
Cover crop varieties, tillage dates and irrigation on-demand: their impact on nitrogen and soil water dynamics in Austria’s semi-arid Marchfeld region
Authors: Schmid Andrea , Scheidl Andreas , Eder Alexander
Published: March 2024

Cover crops (CC) have shown promise in reducing nitrogen (N) leaching, but in semi-arid regions, they might compete with subsequent field culture for water availability. In Austria's Marchfeld region, which is intensively used for agriculture, nitrate levels in groundwater exceed threshold values due to N surplus and limited dilution of seepage water caused by low annual precipitation. Early sown CC with sufficient emergence and N uptake might reduce such groundwater contamination. Further, later tillage dates keep the N stored in the organic pool and reduce mineralisation during autumn and winter. However, CC induced changes in soil water availability could impact the follow-up crop. This study investigates the impact of cover crop (CC) varieties with different i) seed compositions, ii) tillage dates and iii) on-demand irrigation on N leaching and soil water availability for subsequent field culture.The randomized block trial included a) frosting CC – autumn conversion, b) frosting CC – spring conversion, c) a mixture of winter hardy and frosting CC – spring conversion and d) fallow plots. On-demand irrigation was performed at plots with same varieties to enhance CC emergence and simulate conditions of both wet and dry years. Within each plot soil moisture sensors and suction cups were installed. Some plots were equipped with matrix potential sensors. Monthly soil samples were analysed for plant available N and plant samples were taken twice. Evaporation was evaluated using four mini-lysimeters, one for each CC composition. STOTRASIM, which is a soil water and mass transport model was used to model the amount of seepage water of each plot and was calibrated on matrix potential measurements.In general, the results show that all tested varieties of CC significantly reduce plant available nitrogen during winter compared to fallow. Despite the relatively low levels of leached N, in semi-arid regions even minor amounts pose a risk of groundwater contamination. Soil water content analysis revealed no significant differences between the CC varieties. The yield of the subsequent crop remained unaffected by the different CC. While CC reduced N leaching and did not compete with the subsequent field culture, integrating practical considerations like phyto-sanitation, seedbed preparation, tillage methods, crop rotation and succeeding crop selection into CC practices is crucial to prevent adverse effects on subsequent field culture.
Simulation of larval dispersal between seamounts for regional environmental management plans of deep-sea mining
Authors: Saito Naoki , Yano Shinichiro , Suzuki Atsushi , Kamoshida Hiroko
Published: March 2024

In deep-sea mining, understanding genetic connectivity through larval dispersal can be the basis for regional environmental management plans. This study conducted larval dispersal simulations for seamounts in the Northwest Pacific where potential mineral resources, cobalt-rich crusts, are distributed. A total of 19 seamounts were selected for simulation within a 1000 x 1000 km2 area around seamounts where contracted areas for exploration of cobalt-rich crusts were established by the International Seabed Authority. The pelagic larval duration was assumed to be 97 days, which is the average for deep-sea species (Hilário et al., 2015, Front. Mar. Sci.). Two-dimensional dispersions were calculated at a depth of 900 m just above the seamount summits. Flow velocity data were obtained from the ocean model JCOPE2M. The simulation results showed that seamounts with contracted areas for exploration were divided into separate clusters in the larval dispersal network. Seamounts without contracted areas served as sources or sinks of larvae to seamounts with contracted areas. These results may provide fundamental insights for effective environmental management based on interactions among seamount populations.
Revealing spatial patterns of lateral hydraulic conductivity through sensitivity analysis of wflow_sbm 
Authors: Weerts Albrecht , Ali Awad mohammed , Imhoff ruben , van Verseveld Willem
Published: March 2024

Moving toward high-resolution gridded hydrologic models asks for novel parametrization approaches. The use of transfer functions and advances in scaling and regionalization play an important role to ensure flux matching across scales. However, for some processes no transfer functions are yet available or simplified approaches, such as a fixed vertical-to-horizontal saturated hydraulic conductivity ratio, are being used. To get insight into the spatial variability of the vertical-to-horizontal saturated hydraulic conductivity ratio we performed a sensitivity analysis on one parameter of the wflow_sbm model across England, Wales and Scotland exploiting the CAMELS-GB dataset. The wflow_sbm models were setup using reproducible workflows based on HydroMT (https://deltares.github.io/hydromt/stable/) for each CAMELS-GB basin.  To investigate the sensitivity to rainfall forcing all derived wflow_sbm models were first run using a default ratio of 100 with both EOBS and CEH GEAR rainfall data. The sensitivity analysis was only based on the high quality CEH GEAR rainfall dataset. In the sensitivity analysis, the vertical-to-horizontal saturated hydraulic conductivity ratio was varied over a large range from 1 – 10,000 and results were assessed using the non-parameteric KGE (which focuses more on recession/baseflow performance). Even with a fixed uniform vertical-to-horizontal saturated hydraulic conductivity ratio results show a big impact of the precipitation forcing on the model results.  The uncertainty analysis shows that wflow_sbm model results have a high sensitivity to the vertical-to-horizontal saturated hydraulic conductivity ratio. For the optimal ratios, we obtain high KGE values (median=0.84). In addition, when plotting the optimal ratios across the GB clear patterns emerge that seem to coincide with geological features. The resulting optimized lateral saturated hydraulic conductivity values seem realistic when compared with literature values. When compared to Grid2Grid model results the wflow_sbm model shows similar performance for most stations. However, for parts in the south of the England where the geology consists of chalk, the performance of Wflow_sbm is poor, but this is likely caused by the used soil depth map when constructing the models which limits the soil depth often to 30-60cm while it is known that the chalk below the soil is also hydrologically active. 
Modeling the interaction between wildfire behaviour and bark beetle outbreak from LiDAR data: new perspective for Italian forests
Authors: Mauri Luca , Lingua Emanuele
Published: March 2024

Among the main issues affecting European forests, forest fires, windstorm and bark beetles outbreaks nowadays represent the most relevant one. In this regard, local stakeholders are  actually facing with critical circumstances both concerning the implementation of efficient silvicultural management of forest stands affected by such problematics. The storm Vaia occurred in 2018 in northeastern Italy created an unexpected scenario for Italian Alps. Following the windthrow produced by the storm, bark beetles proliferated from the downed logs, therefore moving to the neighbour standing forest and modifying the characteristics and the availability of forest fuel. In this context, the development of remote sensing techniques such as Light Detection and Ranging  (LiDAR) and Unmanned Aerial Vehicle (UAV)-based data acquisition, together with wildfire behaviour models, allow researchers to perform detailed estimation of forest fuels, necessary to simulate fire behaviour over disturbed forested areas over time. The prediction of key factors related to wildfire risk (e.g., fire type, rate of spread, flames lengths) is useful in estimating fire behaviour also in those areas affected by bark beetles proliferation. In this connection, new methods able to overcome notable limitations in forest fire simulations is nowadays needed. In particular, the interaction between bark beetles outbreaks and wildland fire dynamics were investigated focusing on a forested catchment (Veneto region, Italy) recently affected by the VAIA storm and hence involved in a widespread outbreak of bark beetle (Ips typographus). Extensive field data collection and the FlamMap fire behaviour model were coupled with high-resolution LiDAR and UAV-based analysis, to compare wildfire behaviour before and after beetle outbreak. Results could enrich the amount of information available for local administration of the Alpine region, in order to find effective interventions and management options for the areas affected by similar natural disturbances over time. 
Migration of tire rubber crumbs through variably saturated laboratory-scale sand columns
Authors: Sharif Shafkat , Foppen Jan Willem , Planes Marc Teixidó
Published: March 2024

Tire wear rubber particles (TWRP) fall under the umbrella of microplastics and are responsible for synthetic particulate pollution in the urban environment. Urban stormwater runoff carries these particles towards receiving water bodies (e.g., aquifers, rivers, or sea). In particular, studies on their migration behaviour to the subsurface through stormwater infrastructures are still elusive.The current study investigated the vertical migration of end-of-life truck and track tire rubber particles (TPs) in synthetic stormwater (SSW) with 5 mg C/l dissolved organic carbon through laboratory-based infiltration sand columns. Thereto, 200 mg of the particles, with a size range of 63 – 180 µm, were placed inside the column at a depth of 3 cm. Subsequently, 6 litres of SSW were flushed intermittently through the columns in varying wetting, drying, and saturation cycles simulating heavy precipitation patterns. Effluents were collected after each cycle and retained particles within the column were extracted at specific depth intervals to test for Zn concentration (as ZnO is a commonly used additive agent in tire manufacturing) as a proxy for tire particles. We found that 45 – 95% of the truck and track TPs were retained in the seeded depth of 0 – 3 cm varying with different scenarios. Significant migration occurred in the first depth interval layer (3 – 8 cm) of the columns, whereas the other layers received fewer and nearly uniform amounts of TPs. The truck particles showed 24% more penetration for wetting and drying cycles, whereas upon reduction of gap time between two subsequent wetting cycles track TPs penetrated 18% more. Furthermore, longer saturation (24-hour contact time with SSW between cycles) consistently released 2 – 6 times more Zn than shorter duration times. Our results indicated that large rubber particles in the size ranges we studied remain in the topmost part of the soil. In case of moist or wet soils, these particles will act as a source of pollution, which will finally leach into groundwater, thereby polluting aquifers.
Locating unsustainable water supplies for supporting ecological restoration in China's drylands
Authors: Fu Fengyu , Wang Shuai , Wu Xutong
Published: March 2024

China, with vast dryland areas, has undertaken extensive ecological restoration (ER) projects since the late 1970s. While ER is a crucial means against desertification and land degradation, it must be implemented in a water-sustainable manner to avoid exacerbating the carbon–water trade-off, especially in water-limited drylands. However, there is still limited research on accurately identifying water unsustainable ER regions in China's drylands. Here, we developed a water supply–demand indicator, namely, the water self-sufficiency (WSS), defined as the ratio of water availability to precipitation. With the use of remote sensing and multisource synthesis datasets combined with trend analysis and time series detection, we conducted a spatially explicit assessment of the water sustainability risk of ER in China's drylands over the period from 1987 to 2015. The results showed that 17.15% (6.36 Mha) of ER areas face a negative shift in the WSS (indicating a risk of unsustainability), mainly in Inner Mongolia, Shanxi, and Xinjiang provinces, driven by evapotranspiration. Moreover, 29.34% (10.9 Mha) of the total ER areas, whose area is roughly double that of water unsustainable ER areas, exhibit a potential water shortage with a significant WSS decline (-0.014 yr-1), concentrated in Inner Mongolia, Shaanxi, and Gansu provinces. The reliability of our findings was demonstrated through previous studies at the local scale and an analysis of soil moisture changes. Our findings offer precise identification of water unsustainable ER regions at the grid scale, providing more specific spatial guidance for ER implementation and adaptation in China's drylands.
Catchment coevolution and the geomorphic origins of variable source area hydrology
Authors: Litwin David , Tucker Gregory , Barnhart Katherine , Harman Ciaran
Published: March 2024

Aspects of landscape morphology including slope, curvature, and drainage dissection are important controls on runoff generation in upland landscapes. Over long timescales, runoff plays an essential and modifying role in shaping these same features through surface erosion. These feedbacks suggest that modeling long-term landscape evolution while accounting for hydrology could provide insight into hydrological function. Here we examine the hydrological features that emerge when runoff is equilibrated with topography, focusing particularly on the emergence and persistence of saturated areas. We use a new coupled hydro-geomorphic model that captures saturated and unsaturated zone storage and water balance partitioning between surface flow, subsurface flow, and evapotranspiration, but has numerical efficiency sufficient to drive a landscape evolution model over millions of years. Our results reveal the emergence of perennial and ephemeral stream networks, variable source areas, and even non-dendritic drainage networks under certain circumstances. When capacity for water storage and lateral drainage relative to climate are low, lower relief landscapes emerge with greater variability in the extent of saturated areas, while greater relief and less variability in saturated areas emerge as soil storage and lateral drainage capacity increase. Results from a case study suggest that emergent topography and runoff generation patterns reflect this coevolution in some places.
Societal Pathways of Cooperation for Water-related Conflict Mitigation
Authors: Kåresdotter Elisie , Cai Zipan , Pan Haozhi , Kalantari Zahra
Published: March 2024

Over the past decade, water conflicts have risen, and cooperation has declined. Research highlights multiple factors driving this change, with climate change acting as a threat multiplier. Human activities, like dam construction and irrigation, and climate-induced hydro-climatic shifts, including extreme precipitation and prolonged droughts, contribute to the risk of increased water conflicts. To guide interventions and reverse this trend, our focus is on enhancing the understanding of factors that facilitate successful cooperation and mitigate water conflicts effectively. In this study, we investigate cooperation and conflict events worldwide in the last 70 years, together with climatic and socioeconomic factors, such as wealth, export dependency, demographics, water use, and hydro-climate trends. The dataset on cooperation and conflict events used is based on the Transboundary Freshwater Dispute Database and Water Conflict Chronology in combination with more current cooperation events extracted from media news reports. Relationships between investigated factors and cooperation are analyzed by combining panel data analysis and qualitative text content analysis of events. The results provide a deeper understanding of the factors behind why certain events are more successful in achieving conflict mitigation than others. We found that cooperation between countries struggling with water-related challenges can reduce expected conflicts over the next five years. The economic benefits of cooperation show a positive correlation between water-related cooperation and improved wealth (measured by GDP growth), particularly in countries with high export dependency. As such, economic collaboration can be an effective tool for enhancing resilience in high-water stress areas, where collaboration in these areas can contribute to a substantial reduction in future conflicts while simultaneously improving economic prosperity. Engaging in cooperation with other countries can therefore contribute to economic growth and resilience, as well as decreasing conflict risk. Understanding successful conflict mitigation factors can provide helpful insights to global policymakers and leaders in water management to avoid future conflict based on current and projected water availability. Keywords: water conflict; collaboration; conflict mitigation; mixed methods; socioeconomic factors
Global changes in extreme precipitation linked with rapid flood simulation tools
Authors: van den Bout Bastian
Published: March 2024

The consensus of climatic research indicates that the likelihoods of extreme precipitation events are going to change significantly, but specific trends depend on the type of dominant weather system, and regional landscape and climate details. Despite the effort of increasingly accurate and converging global circulation models, the uncertainties in the ensemble of CMIP6 models, and the often course spatial resolution make translation of climate models to actionable information of flood forecasts complex and uncertain. We carried out an analysis of a large ensemble of Global Circulation Models (GCMs) of the CMIP6 ensemble that were downscaled statistically as part of the NASA NEX-GDDP-CMIP6 dataset. The analysis looked at segmented windowed return period analysis using the method of l moments to fit general extreme value distributions to global climate models. With analysis of 1, 3 and 7 day duration, median, 15 and 85 percent quantiles, between 5 and 100 year return period, and global spatial coverage, the results show variations in how precipitation events of various return periods and durational are predicted to change in GCMs, and what the associated uncertainty is for various regions of the world. Intermediate analysis outputs show artifacts in yearly extreme precipitation due to the applied statistical downscaling, but relative factors to be used in precipitation scaling under climate change resolves these. Average increases in precipitation extremes of percent are observed globally (+5.1%), with many local outliers for the SSP585 scenario in 2050 (e.g. regions such as the Himalayan region (+23.4 percent median), the Sahel region(+21.6%) or South-Western Spain (-3.9%)). The other SSP scenarios change the global average factors to +3.75% and +4.32% for SPP245 and SSP370 Respectively. Very low variability in the changes is observed for return periods, indicating that the intensity probability curves shift uniformly in the model output. Precipitation events duration does more significantly alter the analysis outputs, and various areas show differences here that correlate with flash and fluvial flood susceptibility. Finally, we open-source the analysis code and link the output as a built-in dataset in the fastflood.org rapid flood simulation platform. Here, automatically derived extreme precipitation events from era5 datasets can be rescaled under climate change conditions by applying the scaling factors derived in this work.
Coexistence patterns of biocrust-vascular plant in the Loess Plateau
Authors: Ma Yali , Ma Li , Yang Liping , Wang Siqing , Jiang Hongyu , Qi Yuhan , Ye Qianhai , Chen Ning
Published: March 2024

Biological soil crust (biocrust) widely distributes in the Loess Plateau, which is the most typical loess platform worldwide, and a cultural origin of China. Since 1999, the Loess Plateau experienced heavily restorations, costed hundreds of billions Chinese Yuan. Even so, we have no clear idea of how do major biological components – biocrust, grass, and shrub coexist together therein, which can greatly affect restoration practices. To that end, this study combined field survey, reference compiling and remote sensing data to identify coexistence patterns of biocrusts and vascular plants (grass and shrub) on the Loess Plateau. A total of 262 data points had been collected. We found that precipitation, surface temperature and solar radiation were the major drivers in the Loess Plateau, and there were three coexistence patterns, namely high biocrust-vascular mixed state under high annual rainfall and surface temperature of 10-12°C, biocrust-dominated state under low rainfall condition and low biocrust-vascular mixed state under low surface temperature situation. Furthermore, we found that high biocrust-vascular mixed and biocrust-dominated states appeared to be alternative states along annual rainfall gradient. This study discovered coexistence patterns of biocrust-vascular plant in the Loess Plateau for the first time, and can guide future restoration and conservation in the region. This is crucial for achieving sustainable development and ecological safety of north China.
Deformation processes and origin of fluids during Oligocene-Miocene post-orogenic extension in Alpine Corsica
Authors: Masoch Simone , Fondriest Michele , Preto Nereo , Prando Francesca , Di Toro Giulio
Published: March 2024

Alpine Corsica is an accretionary wedge formed during the Alpine orogenesis and exhumed through Oligocene-Miocene lithospheric extension controlled by the eastward migration of Apenninic subduction. Here we integrate field geological surveys with microstructural and carbonate stable isotope (δ18O–δ13C) analyses of fault zone rocks to constrain the evolution of the W-dipping extensional Patrimonio Fault System (PFS). The PFS consists of multiple gouge-bearing fault core strands and splay faults in the footwall damage zone, and exhumed the Schistes Lustrés (e.g., impure quartzites, marbles, calcschists, serpentines) and slices of Hercynian granitoids in the footwall block, accommodating ~6 km of cumulative displacement.We describe a deformation sequence during exhumation consisting of D1 mylonitic shearing, D2 seismogenic faulting and D3 shallow veining events. D1 mylonitic shearing produced a decameter mylonitic zone forming the roots of PFS, coeval with localized brittle-ductile shear zones and quartz ± chlorite vein arrays observed in the footwall metamorphic units. Ductile shearing was accommodated by low-temperature quartz and calcite crystal-plasticity, and pressure-solution mechanisms at greenschist conditions (i.e., 300-400 °C). D2 seismogenic faulting either overprinted or cut the D1 structures. Ancient seismic faulting is attested by occurrence of (i) altered pseudotachylytes and (ii) cockade-bearing fault-veins injecting into the host-rocks and mutually overprinting dolomite-rich veinlet mesh and mirror-like slip surfaces observed in the footwall splay faults. Seismic faulting is also accommodated by dolomite-quartz(-chalcedony) crack-seal veins, which have isotopic compositions similar to those of the carbonate-rich units of the Schistes Lustrés. These structural and geochemical observations indicate that ancient seismicity was cyclically modulated by overpressured fluids which isotopic composition was buffered by the host-rocks. The later D3 shallow (≤ 1 km depth) veining event consists of calcite-bearing veins and concretions filling open fractures, which have distinct isotopic compositions compared to the Schistes Lustrés units, suggesting percolation of meteoric fluids at depths. Based on these observations, we speculate that the D2 faults may represent a fossil analogue of the extensional faults active in the Apennines where seismicity is driven by CO2-rich deep-sourced fluids.
The influence of pyrolysis time, moisture, and plant species on carbon bridgehead fraction of charcoal
Authors: Sivapalan Vinothan , Hockaday William
Published: March 2024

Paleofire reconstructions are a challenging endeavor primarily due to the numerous factors involved in wildfire frequency, behavior, and regimes. These factors include, but are not limited to fuel composition, moisture, soil types, climate/weather conditions, and topographical features. Therefore, development of robust wildfire proxies requires vigorous experimental testing for multiple variables. Here, we explore the influence of pyrolysis time, moisture, and plant species on a novel proxy for fire intensity—carbon bridgehead fraction of charcoal. Experimentally, we have produced charcoals from three native Texas plants: live oak (Quercus sp.), Ashe juniper (Juniperus ashei), and broomsedge bluestem (Andropogon virginicus) under a range of temperature (300-700°C), moisture (0-100% moisture capacity), and time (0-1 hr) conditions in a tube furnace. Samples were analyzed using solid-state C-13 nuclear magnetic resonance (NMR) spectroscopy with two experiments to calculate carbon bridgehead fraction: cross polarization – magic angle spinning (CP-MAS) to quantify total aromatic carbon and dipolar dephasing (DD) to quantify aromatic bridgehead carbon. Results reveal significant differences between vegetation types, with moisture delaying or slowing the rate of carbon bridgehead formation. Relationship between carbon bridgehead fraction and time are less clear and may be influenced by the formation of pyrolysis byproducts (such as pyroligneous acids and free radicals) and/or signal losses in the cross-polarization spectra. To assess the influence of these factors on carbon bridgehead fraction we plan to conduct additional analyses on our experimental charcoals, including electron paramagnetic resonance (EPR) spectroscopy to quantify the free radicals in samples and C elemental analysis to assess carbon observability by NMR. Future work involves ground truthing the proxy to modern wildfires and subsequently applying it to paleorecords.
Underwater explosions recorded at IMS hydroacoustic stations from well-defined experiments
Authors: Oliveira Tiago , Prior Mark , Lin Ying-Tsong , Dall’Osto David
Published: March 2024

This study analyzes signals recorded by the CTBT-IMS hydroacoustic network from well-defined underwater explosions in the Atlantic Ocean, and looks at the relationships between yield, location, and detectability. The events analyzed are detonations of TNT charges and are used here to assess the ability of the CTBT-IMS hydroacoustic network to detect H-phases, which are signals from in-water explosions. The locations of the explosions ranged between the continental shelf, shelf break, and deep waters, and their yields were between 0.8 and 18,000 kg TNT. For high-yield explosions, T-stations (coastal seismometers) and Hydrophone stations effectively detected the explosions. For distant low-yield events, the ability of the network to detect the explosions depends heavily on the location of the source. Distant shallow events on the continental shelf can be more detectable than closer deep-water events. This is because the sound from the former events propagates off the shelf and skips off the shelf edge into the SOFAR channel, while events in deep water, depending on their depth, can have more difficulty coupling into the SOFAR channel. Similarly, explosions near the shelf break can have a favourable SOFAR channel coupling mechanism due to reflections from the shelf into the channel.
Origin, gradient, and recharge processes of perched aquifers of the Monahans and Kermit dune fields, northern Chihuahuan Desert, Texas, USA 
Authors: Fournier Alix , Forman Steven
Published: March 2024

Water is scarce in the northern Chihuahuan Desert, with ~350 mm/yr precipitation, potential evapotranspiration at 1800mm/yr, and rising mean annual temperatures by >2°C since 1960. The main water resources are the Ogallala, Pecos Valley, Dockum, and Edwards-Trinity Plateau aquifers, with depletion rates of ~1 m/yr. Despite the arid climate, the Monahans and Kermit dune fields host perched water tables 1-10 m below the surface, in up to 40 m of aeolian sand spanning the past ca. 2.6 ma, and isolated from the underlying Pecos Valley Aquifer by a Pliocene/Pleistocene fluvial gravel-rich clay. A 3D model based on borehole lithology shows a topographic inversion with a southwest-trending paleo-slope infilled with aeolian sand. The aeolian stratigraphy and basin modeling indicate progressive infilling by aeolian sand with periods of pluvial lake formation and soil development, with groundwater providing dune field stability for vertical accretion and limiting aeolian erosion. Cores of sediments retrieved from the Monahans and Kermit dune fields were sampled for OSL ages and yielded ages up to 500 ka 20 m below the surface of the dunes, with identified deposition periods between 545-470 ka, 300-260 ka, 70-45 ka and post 16 ka. A set of three monitoring wells equipped with data loggers revealed aquifer recharge of 35-40 cm in the Spring and Fall consistent with regional precipitation variability, and a daily recharge cycle of 3-8 mm potentially linked to plant uptake or gravitational forces. Deuterium and 18O isotopic ratios for the dune field aquifers indicate an evaporative enriched water source compared to the Pecos Valley Aquifer, Pecos River, and Chihuahuan Desert precipitation, consistent with local precipitation. Apparent 14C ages 1.3 to 2.2 ka for waters ~30 m deep and at the western edge of the aquifer indicate mixing with Holocene recharge waters in a southwest flowing aquifer. In contrast, the Pecos Valley Aquifer yields 14C ages of ca. 0.9 to 40 ka with the youngest ages near the dune fields, which suggests recharge from these perched aquifers.
Delivering Critical Raw Materials: Ecological, Ethical and Societal Issues
Authors: Herrington Richard , Gordon Sarah
Published: March 2024

Leaders across geographical and political boundaries are united behind a pledge to deliver a net zero carbon world by 2050.  Society’s conundrum is that mining is an essential part of that delivery, yet is an activity regarded by many as unpalatable. Projects that have fallen short on ecological, ethical, or social grounds, serve to confirm to many that mining is currently not an industry to be trusted, rather than being the industry that could and should be empowering significant societal development.Examples of societal failure include the incidents around the 2012 miners’ strike at the Marikana platinum mine in South Africa which escalated into violence and loss of life.  Failure on ethical grounds was most recently highlighted by the settlement of corruption claims in the Democratic Republic of Congo (DRC) where international mining company staff bribed country officials to secure “improper business advantages.”  Ecological failures are all too common and most visible in the failure of tailings storage facilities such as the 2015 Mariana (Brazil), 2019 Brumadinho (Brazil), and 2022 Jagersfontein (South Africa) dam disasters.The challenge for those who explore, extract, and process the raw materials so vital for the energy transition, is to do so whilst delivering on true Sustainability right from the start of any project.  Mining disasters are rarely a surprise.  The proactive management of both threats and opportunities is therefore key to the urgent delivery of materials to secure our net zero future in a responsible manner.  We must ensure that this delivery is achieved by projects with wholly net positive outcomes for the environment and people.
Source analysis of the 2022 Nord Stream and 2023 Balticconnector underwater explosions
Authors: Steinberg Andreas , Gestermann Nicolai , Ceranna Lars , Hartmann Gernot , Lund Björn , Dunham Eric , Hupe Patrick , Voss Peter , Larsen Tine , Dahl-Jensen Trine , Köhler Andreas , Schweitzer Johannes , Pilger Christoph , Plenefisch Thomas , Stammler Klaus , Donner Stefanie , Gaebler Peter , Wiedle Christian
Published: March 2024

On 26 September 2022 two seismic events near the Danish island of Bornholm in the Baltic Sea were detected. The first event with a magnitude Mw 2.3 occurred at 00:03 UTC 40 km east-southeast of Bornholm. The determined location and the origin time of the event are consistent with data of the pressure decrease on one of the Nord Stream 2 pipelines. Another sequence of events occurred 17 hours later at 17:03 UTC around 60 km north-east of Bornholm with a maximum magnitude of Mw 2.7. It consists of three closely successive, but separable, single events. Using relative localisation methods and the gas pressure inside the pipeline recorded at the landing site in Germany, we can assign the epicentres of the three events to the locations of the leaks in the pipelines of Nord Stream 1 and 2.Based on comparable events in the region, which include both tectonic earthquakes and explosions, the explosive character of the investigated Nord Stream events can be verified. Infrasound signals associated with the destruction of the Nord Stream pipelines were recorded at two stations (I26DE in the Bavarian Forest and IKUDE near Kühlungsborn) in Germany. Particularly after the event sequence at 17:03 UTC, distinctive signals were registered whose characteristics indicate an explosive event with subsequent gas leakage at the surface.Our modelling of the sources shows that the measured seismic signals can sufficiently be explained by the instantaneous gas release. Synthetic seismograms for such a source and a subsurface model adapted for the study area show high consistency with the measured signals. Based on the released energy and the characteristics of the recorded waveforms, we conclude that the impulsive gas release from the burst gas pipes constitutes the dominant part of the signal source. The model places an upper limit of approximately 50 kg TNT equivalent on the yield of the chemical explosive component of the events, but we note that smaller yields may also be consistent with the data.We also carried out an analysis of the seismic signals of the event on the Balticconnector pipeline between Finland and Estonia on 8 October 2023 and found that again the instantaneous gas release can sufficiently explain the observed data. This supports a possible mechanical cause of the damage. 
Evaluation of extreme events in global coupled climate models by satellite gravimetry
Authors: Middendorf Klara , Eicker Annette , Jensen Laura , Dobslaw Henryk
Published: March 2024

Under the assumption that a warming climate leads to an intensification of the global water cycle, it can be hypothesized that also the occurrence frequency and severity of extreme events such as droughts or floods will increase in the upcoming decades to centuries. Global coupled climate models, which project the future evolution of various variables of the Earth's climate system are important tools for the analysis of such expected changes. To assess the reliability of the models and to identify possible systematic discrepancies, it is essential to evaluate the model output against observations.In this study, present and future occurrences of extreme events are analysed in water storage time series simulated by coupled global climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) and compared against spatio-temporal changes in water mass derived from GRACE and GRACE-FO. This comparison is based on Extreme Value Theory, as the exact timing of modelled extreme events cannot be assessed by observations due to the stochastic behavior of climate variability in unconstrained model experiments. From estimated extreme value distributions return levels are calculated, a quantity describing the magnitude or frequency of extreme values.  Challenges that have to be overcome in the analysis are the non-stationary data and the relatively short time span of the GRACE observations. The latter issue is addressed by additionally assessing GRACE-based water storage reconstructions available over many decades.This study provides insights into the ability of global climate models to model the occurrence of TWS extremes, namely unusual dry and wet phases. It also examines whether the climate model projections predict an increasing intensity of extreme events.
The 2023 marine heatwave in the North Atlantic and the Mediterranean Sea: ocean response to atmospheric circulation
Authors: Behr Lorine , Xoplaki Elena , Luther Niklas , Tragou Elina , Luterbacher Jürg , Zervakis Vassilis
Published: March 2024

The year 2023 was characterized by record-breaking global surface air and sea surface temperatures (SSTs), the latter reaching a record 21° C in April (excluding the polar regions; Copernicus 2023). As June to October were the warmest on record globally (WMO 2023), extreme and long-lasting marine heatwave (MHW) events were observed, especially in the North Atlantic and the Mediterranean Sea. In general, the occurrence of MHWs in the subtropics and western boundary current regions is predominantly driven by atmospherically induced processes such as the net ocean heat uptake from the atmosphere, associated with a reduction in latent heat loss and increased shortwave radiation (Schlegel et al. 2021; Vogt et al. 2022). The atmospheric circulation with persistent high‑pressure systems and anomalously weak wind speeds associated with increased insolation is the dominant driver of the above processes. We focus on the state of the atmosphere at the surface and in the mid-troposphere during 2023 and identify specific atmospheric patterns and SST anomaly structures. To detect MHWs and calculate their characteristics we use the daily gridded NOAA OI SST version 2.1 dataset (Huang et al. 2021, updated), derived from the AVHRR satellite, in-situ ship and buoy SST data. For the atmospheric component, we used the mean sea level pressure (SLP), the horizontal wind at 10 m, the geopotential height at 500 hPa (zg500) and the 2 m maximum temperature (Tmax) from the ECMWF ERA5 reanalysis (Hersbach et al. 2020, updated). Atmospheric and ocean datasets are provided globally with a high resolution (0.25°). We use daily anomalies with 1983 to 2012 as the reference period (as recommended by Hobday et al. 2018). The evaluation of MHW metrics such as frequency, duration, mean and cumulative intensity in different subregions of the North Atlantic and Mediterranean revealed that the most frequent MHWs were observed in the western Mediterranean (WMED), the longest MHWs in the central northeast Atlantic and the cumulatively most intense MHWs in the northwest Atlantic and central northeast Atlantic. The most intense MHWs are found in the WMED and off Newfoundland. During summer we detect asynchronous, above normal SLP, zg500 and Tmax over the northwest Atlantic, the WMED and the Black Sea, representing a type of blocking condition. A weakened Azores High, associated with reduced wind speed, mixing and upwelling, allows SSTs to rise substantially in the central northeast Atlantic during summer (Copernicus 2023). The first Empirical Orthogonal Function shows an antiphase dipole of SST and zg500 anomalies (explained variances of 43.9 % and 34.3 %, respectively) between the Mediterranean and West of the British Isles as well as monopol SST and zg500 anomalies (explained variances of 57.7 % and 41.9 %, respectively) over the northwestern Atlantic and the Labrador Sea.
Growth rate of deep convective system cloud shields: satellite observations and km-scale radiative convective equilibrium simulations
Authors: Roca Remy , Fiolleau Thomas , Elsaesser Gregory
Published: March 2024

Deep convection gives rise to large upper level clouds that strongly interact with radiation and are important to the climate energy budget. From an object-oriented perspective, these individual deep cloud systems are characterized by a well depicted cloud shield life cycle, starting with small cloud extents that grow at varying rates before decaying and vanishing. A simple formulation of the growth rate of the cloud shield has been proposed that links together the growth rate on the convective part of the cloud, the mass flux of both the convective and stratiform parts of the cluster and a simple removal sink term (Elsaesser et al., 2022). In this presentation we first show using a suite of satellite observations (infrared from geostationary satellites, GPM radar, etc.) that the functional form of the proposed equation is well suited to quantify the shield growth rate. We then focus on RCE simulations, with deep cloud system objects post processed, to explore the relative role of each term of the growth rate budget. Three different models are used in the same RCEMIP-like configurations. The results show that the budget equation works very well for each model, although the time constants require model-dependent adjustments. We will further show in Vienna the commonalities and the specificities of each model.
Downward migration of Cs-137 in soils reduce root uptake of Japanese cedar in Fukushima
Authors: Takahashi Junko , Iguchi Satoshi , Sasaki Takuya , Onda Yuichi
Published: March 2024

IntroductionRadiocesium (Cs-137) deposited on forests was intercepted by the canopy, then migrated to the litter layer and eventually to the soil layer, where some of it has been absorbed by roots and circulated through the forest ecosystem for a long time. In other words, the amount of Cs-137 uptake by roots will control the long-term dynamics in the forest ecosystem in the future, temporal changes in Cs-137 in tree roots have rarely been reported. In this study, we investigated the Cs-137 concentration and inventory in the soil and very fine (VF) roots (< 0.5 mm) of Japanese cedar from 2011 to 2020.MethodsAn approximately 3 m x 3 m plot was established in a cedar forest (initial deposition 440 kBq m-2) in the Yamakiya district of Kawamata Town, Fukushima Prefecture. Litter and soil samples were collected twice a year during 2011-2012 and once a year after 2013 using a scraper plate at 0.5 cm intervals for 0-5 cm, 1 cm intervals for 5-10 cm, and 5 cm intervals for 10-20 cm. Root samples were collected by further separating only the roots with tweezers from soil samples in 2012, 2015, 2017, and 2020, and washed by ultrasonic homogenizer to remove soil particles on the root surface. The roots measured were absorptive VF roots of 0.5 mm or less of the current year's growth.Results and discussionsThe Cs-137 concentration in the litter layer was still decreasing exponentially more than 12 years after the accident, its inventory was about 0.2-0.5% of the deposited amount. The depth distribution of Cs-137 concentration in the mineral soil layers was fitted with an exponential equation until 2019, but after 2020, the peak concentration shifted slightly downward and was fitted with a hyperbolic function. The Cs-137 inventory in the soil increased over time due to the migration from the forest canopy and litter layers, whereas that in the VF roots decreased in 2020. Especially, the Cs-137 inventory in the VF roots in the 0–2 cm of soil reached 89% in 2012; however, it decreased with time to approximately 43% in 2020. This decrease in the Cs-137 concentration in the VF roots at 0–2 cm was caused by the decrease in Cs-137 concentration in the litter layers. Although the Cs-137 concentration in the VF roots below 2 cm increased with increasing Cs-137 concentration in the soil, the downward migration of Cs-137 within the soil can reduce the amount of Cs-137 absorbed by roots because the VF root biomass decreases exponentially with depth. In other words, Cs-137 can be removed from the long-term active cycles of forest ecosystems as they migrate deeper into the soil without physical decontamination. This natural downward migration process can be regarded as a “self-cleaning” of the forest ecosystem, resulting in a decrease in the air dose rate and the amount of Cs-137 absorbed by roots.