bluuebunny/crossref_metadata_2025 huggingface dataset:
Post-Disturbance Recovery Shifts in Boreal Evergreen Landscapes: Impacts on Carbon Dynamics and Land Surface Properties.
Authors: Layritz Lucia S. , Gregor Konstantin , Krause Andy , Kruse Stefan , Meyer Ben , Pugh Tom A. M. , Boettiger Carl , Rammig Anja
Published: March 2024

In the evergreen boreal forest, field studies show that vegetation does not always regenerate to its previous state after disturbance but instead transitions to systems dominated by deciduous trees or non-forest vegetation. Gaining a better understanding of drivers and impacts of post-disturbance recovery is thus crucial to accurately project future vegetation dynamics and associated impacts on the carbon, water, and energy balance of the region. We here perform simulations with the dynamic vegetation model LPJ-GUESS to investigate (1) if observations of post-disturbance recovery dynamics can be reproduced in the model, (2) which environmental factors control such shifts, and (3) how these in turn influence land surface properties such as albedo and evapotranspiration. We find that post-disturbance recovery trajectories can be clustered into distinct response patterns of recovery and shifts to alternative plant types. These shifts occur even in places where multiple plant types can in theory establish in the model and thus emerge due to shifts in competitive advantage mediated by warming and soil properties. We further find that shifts from forested to non-forested ecosystems have strong impacts on land-surface properties while shifts between different forest types are less impactful. We conclude that LPJ-GUESS is capable of reproducing observed disturbance-induced changes in vegetation dynamics following disturbances. Post-disturbance recovery is a key process driving accelerated vegetation change under climate change, further stressing the importance of accurately representing disturbance impact and recovery processes in land surface and coupled modeling.
Thermal runaway as driving mechanism of deep earthquakes – Constraints from numerical modeling
Authors: Spang Arne , Thielmann Marcel , Kiss Daniel
Published: March 2024

Deep-focus earthquakes occur at depths of 300-700 km below the surface where brittle failure is unlikely due to the large lithostatic pressure. Instead, they require a ductile localization mechanism that can significantly reduce rock strength and create highly localized shear zones. The feedback loop of shear heating, temperature-dependent viscosity and localization is called thermal runaway and has been linked to deep-focus earthquakes.We present one- and two-dimensional (1D and 2D) numerical, thermomechanical models that investigate the occurrence, nucleation and temporal evolution of thermal runaway in a simple shear setting. The models are characterized by a visco-elastic rheology where viscous creep is accommodated with a composite rheology of diffusion and dislocation creep as well as low-temperature plasticity. We utilize the pseudo-transient iterative method in combination with a viscosity regularization and adaptive time stepping to solve this nonlinear system of equations and avoid resolution dependencies.Varying eight input parameters, we observe two distinct types of behavior. After elastic loading, models either release stress over hundreds to thousands of years, accompanied by low slip velocities and moderate temperature increase, or they release stress within seconds to minutes while slip velocity and temperature increase drastically – Thermal runaway occurs. With nondimensional scaling analysis, we unite the eight different input parameters into two nondimensional numbers that allow inferring the behavior. The ratio tr/td describes the competition between heat generation by viscous dissipation and heat loss due to thermal diffusion whereas the ratio Uel/Uth compares the elastic and thermal energy density before stress relaxation.2D experiments show that thermal runaway allows highly localized ductile ruptures to nucleate at small heterogeneities and propagate like brittle fractures. The ruptures accelerate during propagation and reach the highest velocities when two tips link up. Rupture trajectories are usually parallel to the direction of background deformation but bend in the vicinity of other ruptures to allow for a link up. The results demonstrate that thermal runaway can create highly localized, propagating shear zones that reach slip velocities in line with slow earthquakes at upper mantle and transition zone conditions.
AI based assessment of flash flood damages to company
Authors: Singh Apoorva , Sairam Nivedita , Shahi Kasra Rafiezadeh , Buch Anna , Dhanya Chandrika Thulaseedharan , Kreibich Heidi
Published: March 2024

Flash floods like the flood in 2021 in the west of Germany result in particularly large numbers of fatalities and heavy asset damages. Among the several flood-exposed sectors, companies are severely affected by floods and constitute a significant component of overall flood damages. However, understanding and modeling the underlying processes influencing flash flood losses for companies is specifically challenging due to (1) heterogeneity in terms of sectors, building size and type, number of employees, and equipment, and (2) scarcity of company-specific flood loss data. In comparison to fluvial floods, the influence of flood characteristics and hydro-dynamic processes on damage is different in the case of flash floods.  To tackle this challenge, multi-variate probabilistic flash flood loss models are developed based on feature selection using empirical data from detailed surveys conducted with companies after the flash floods of 2002, 2016, and 2021 in Germany. The machine learning ensemble-based approach of feature selection revealed the significance of the following hazard variables (water depth, flow velocity, contamination), exposure variables (sector, number of employees, size of premise), and vulnerability variables (implementation of precautionary measures, early warning time, flood experience) in determining flood losses. The Bayesian Networks-based flood loss models developed in this study provide probability distributions of estimated losses and as such inherently quantify uncertainties.
Application of Transfer Learning techniques in one day ahead PV production prediction
Authors: Lóderer Marek , Sandanus Michal , Pavlík Peter , Rozinajová Viera
Published: March 2024

Nowadays photovoltaic panels are becoming more affordable, efficient, and popular due to their low carbon footprint. PV panels can be installed in many places providing green energy to the local grid reducing energy cost and transmission losses. Since the PV production is highly dependent on the weather conditions, it is extremely important to estimate expected output in advance in order to maintain energy balance in the grid and provide enough time to schedule load distribution. The PV production output can be calculated by various statistical and machine learning prediction methods. In general, the more data available, the more precise predictions can be produced. This poses a problem for recently installed PV panels for which not enough data has been collected or the collected data are incomplete. A possible solution to the problem can be the application of an approach called Transfer Learning which has the inherent ability to effectively deal with missing or insufficient amounts of data. Basically, Transfer Learning is a machine learning approach which offers the capability of transferring knowledge acquired from the source domain (in our case a PV panel with a large amount of historical data) to different target domains (PV panels with very little collected historical data) to resolve related problems (provide reliable PV production predictions). In our study, we investigate the application, benefits and drawbacks of Transfer Learning for one day ahead PV production prediction. The model used in the study is based on complex neural network architecture, feature engineering and data selection. Moreover, we focus on the exploration of multiple approaches of adjusting weights in the target model retraining process which affect the minimum amount of training data required, final prediction accuracy and model’s overall robustness. Our models use historical meteorological forecasts from Deutscher Wetterdienst (DWD) and photovoltaic measurements from the project PVOutput which collects data from installed solar systems across the globe. Evaluation is performed on more than 100 installed PV panels in Central Europe.
Change in flow field next to riprap sloping structure caused by variability of scoured bathymetry
Authors: Gilja Gordon , Harasti Antonija , Delija Dea , Mejašić Iva , Valyrakis Manousos
Published: March 2024

One approach to scour protection for bridge piers is constructing riprap sloping structure around the pier. To maintain its designated function, riprap must remain stable throughout the service life of the bridge, often exceeding 100 years and thus being vulnerable to more extreme hydrological events driven by climate change. The riprap sloping structure increases the size of the recirculation zone and turbulence downstream compared to a single pier. This paper presents the results of a detailed investigation of flow field dynamics over the scoured riverbed downstream of the riprap sloping structure. The research combines flume experiments with a physical model and numerical simulations using FLOW-3D software calibrated with experimental data measured with an acoustic Doppler velocimetry profiler, Vectrino ADVP. Investigating the complexities of the flow field resulting from the presence of riprap and interactions between the flow and scour development is essential for enhancing the design and performance of riprap structures in various hydraulic conditions. The results show that the change in scour geometry over time influences the flow direction in the zone downstream of the pier. References[1]    Gilja, G.; Fliszar, R.; Harasti, A.; Valyrakis, M. Calibration and Verification of Operation Parameters for an Array of Vectrino Profilers Configured for Turbulent Flow Field Measurement around Bridge Piers—Part I. Fluids 2022, 7, 315. https://doi.org/10.3390/fluids7100315[2]    Gilja, G.; Fliszar, R.; Harasti, A.; Valyrakis, M. Calibration and Verification of Operation Parameters for an Array of Vectrino Profilers Configured for Turbulent Flow Field Measurement around Bridge Piers—Part II. Fluids 2023, 8, 199. https://doi.org/10.3390/fluids8070199 AcknowledgmentsThis work has been supported in part by the Croatian Science Foundation under the project R3PEAT (UIP-2019-04-4046)
Unraveling the Forcings behind West Antarctic Summer Melt: CMIP6 Perspectives on Remote Climate Drivers
Authors: Fang Yingfei , Screen James , Yang Song , Hu Xiaoming , Lin Shuheng
Published: March 2024

The circulation pattern conducive to summer surface melt over the Ross Ice Shelf in West Antarctica is intricately linked to sea surface temperature anomalies in the tropical central-eastern Pacific associated with El Niño, along with atmospheric heating anomalies over western Australia. Our study utilizes 61 models within the Coupled Model Intercomparison Project (CMIP6) and reveals their ability to effectively simulate these primary drivers that influence the circulation pattern over West Antarctica.El Niño emerges as a crucial force shaping atmospheric circulation anomalies over the Ross Sea, inducing two distinct wave trains toward West Antarctica—one originating from the central Pacific and the other from the Maritime Continent. Furthermore, irrespective of El Niño, anomalous atmospheric heating over western Australia emerges as another significant forcing, initiating a Rossby wave train that extends from subtropical Australia to the Ross Sea.This comprehensive assessment advances our understanding of the remote forcings steering climate variability in West Antarctica during the austral summer. Moreover, it instills confidence in the predictability of future climate changes in this region.
Effect of sample preparation on the FTIR DRIFT spectra in the case of soils with different organic material content
Authors: Szalai Zoltán , Karlik Mate , Jakab Gergely , Vancsik Anna , Hatvani István Gábor , Cseresznyés Dóra , Király Csilla
Published: March 2024

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (FTIR DRIFT) is a widely used method for investigating soil organic materials. The existing literature suggests variations in sample preparation techniques for soil analysis. Notably, the powdering and drying method may influence the presence of organic materials, clay minerals, and carbonates. These minerals are occasionally found as coatings on different mineral surfaces and sometimes as part of the matrix within soil aggregates. This study examined four topsoils of distinct types from Hungary: Arenosol, Leptosol, Gleysol, and Phaeozem (WRB2022). The samples were pulverized both to < 250 µm and < 63 µmAnd also various procedures for drying were used: 1-hour drying sessions at 50 °C, 100 °C, 150 °C, 200 °C, and 250 °C, as well as overnight drying at 50 °C, 100 °C, and 150 °C. Additionally, samples were measured without undergoing extra drying at room temperature. This study aimed to focus on significant organic material bands.Pulverization has a more pronounced effect on FTIR DRIFT spectra in soils with aggregates, furthermore, when the original soils contain a higher proportion of sand fraction. The drying method affects the measured absorbance values at the highlighted wavenumbers with an underlined influence on the aliphatic components range. Support of the National Research, Development, and Innovation Office (Hungary) under contract K142865, and Eötvös Loránd Research Network SA41/2021 are gratefully acknowledged.
Mercury speciation in soils through thermo-desorption technique as a rapid screening tool for risk assessment procedure at mercury-contaminated sites
Authors: Floreani Federico , Pavoni Elena , Petranich Elisa , Antonini Paolo , Mauri Mara , Covelli Stefano
Published: March 2024

A key aspect for the evaluation of environmental and health risk associated with mercury (Hg) contamination is the assessment of its speciation, which can influence the mobility and bioavailability of this element in the environment. The evaluation of Hg speciation in soils and sediments of contaminated sites is commonly based on selective sequential extraction (SSE) methods, which, however, have certain disadvantages: they do not allow for a specific removal of Hg species, are generally time-consuming and characterised by a low reproducibility. An easy-to-use alternative to SSE may be represented by thermo-desorption (TD) technique, where different Hg species can be identified according to their specific release temperature during a gradual heating. The aim of this study was to evaluate the potential application of TD for the risk assessment associated with Hg occurrence in alluvial soils at some sites in the Friuli-Venezia Giulia Region (NE Italy) affected by past Hg inputs related to mining and, to a lesser extent, industrial activities. At each site, surface and deep soil samples (n≥12) were collected and analysed for total Hg concentration and Hg speciation through TD. Speciation analyses were performed by means of a Hg atomic absorption spectrometer (Lumex RA915M) coupled with a pyrolysis attachment (PYRO-915+). This setup allows for a continuous monitoring of Hg released during the sample heating. Calculations of risk associated to Hg volatilisation, leaching, and ingestion were performed using the relative amount of non-cinnabar (non-α-HgS) compounds determined through TD, considered as potentially mobile. Results were then compared with those obtained through the application of a SSE method commonly used for the assessment of Hg speciation in the investigated area. Almost all samples analysed through TD showed the occurrence of non-mobile red cinnabar (α-HgS), confirming the remarkable legacy of the mining source. Generally, although a slightly higher abundance of potentially mobile Hg forms was obtained through TD than SSE, the calculated risk resulted “acceptable” (hazard index < 1) using data from both techniques. Besides, it must be stressed that calculation performed through TD data are based on a larger number of samples, thus providing a greater representativeness of the mobility of the Hg species and associated risk in the investigated area. Considering also the good reproducibility of data obtained through TD and its celerity and accuracy in Hg species discrimination, the proposed approach could be considered as a valid and relatively low expensive tool for risk assessment at Hg contaminated sites. This is especially true for sites such as former Hg mining areas characterised by the occurrence of α-HgS, easily discriminable through TD.
The Laki Eruption – studying Weather and Climate during the Little Ice Age with Paleo-Reanalysis
Authors: Franke Jörg , Friedman Andrew , Imfeld Noemi , Brönnimann Stefan
Published: March 2024

The assimilation of early instrumental, documentary, and proxy data into model simulations allows the study of multivariate climate variability from monthly to centennial time scales. The strength of our paleo-reanalysis ModE-RA (Modern Era Reanalysis) lies specifically in the period of the Little Ice Age because the number of assimilated values per year increases from hundreds in the 17th century to thousands in the 18th century to tens of thousands in the 19th century. In addition, recent efforts of weather reconstruction based on early instrumental data even allow for European reconstructions at daily time scales back into the 18th century.Here, we present a case study of the global climate and European weather anomalies following the Laki eruption in 1783. Most reports have been limited to the European domain and described an unexpectedly warm summer of 1783 and extremely cold winters in the three following years. Our weather reconstruction and ModE-RA support recent model simulations which suggested atmospheric blocking to be the cause of the unexpected warm anomalies in Europe. However, the entire summer of 1783 was not hot, but only a relatively short period in June and July. On the northern hemisphere scale, we find an aerosol-induced cooling. African and Indian Monsoon rainfall is reduced due to a weaker land-sea temperature gradient in line with the response to strong tropical eruptions and an interhemispheric temperature contrast in line with the response to strong extratropical eruptions. In contrast to recent simulations of the Laki eruption, ModE-RA shows a clear boreal winter warming at high latitudes, slightly dampening the hemispheric-scale cooling signal. In the future, monthly paleo-reanalysis or even daily weather reconstructions could be used to drive models of Little Ice Age glacier dynamics.
South Atlantic Convergence Zone impacts on climate and vegetation changes over the last 16,000 years in Central Brazil based on a speleothem multi-proxy record
Authors: Della Libera Marcela Eduarda , Scholz Denis , Vonhof Hubert , Stumpf Cintia , Weber Michael , Cauhy Julio , Cruz Francisco William , Stríkis Nicolás , Novello Valdir Felipe
Published: March 2024

The South American Monsoon System (SAMS) plays an important role in the hydroclimate variability and rainfall patterns across South America. Stemming from its convective core in the southwestern Amazon basin, the South Atlantic Convergence Zone (SACZ) is a southeastward convection band, being a critical component of SAMS responsible for large-scale moisture transport, particularly over Central Brazil. Previous paleoclimate studies suggest that SACZ has changed over time, usually associated with changes in the SAMS, and there are current debates regarding the nature of SACZ, shifts in position, size, and intensity, and their potential impacts on vegetation changes. Therefore, this study addresses these debates for the last 16,000 years based on a novel multi-proxy paleorecord of δ18O, δ13C, and Sr isotope ratios (87Sr/86Sr) from a stalagmite collected in São Mateus Cave at the northeast limits of SACZ in central Brazil. This site is therefore under the regime of SACZ, with a climate characterized as tropical semi-humid with a rainy summer season and a dry winter.The inclusion of Sr isotope data enhances our interpretation of past local climate variability since changes in 87Sr/86Sr can provide valuable information about the water residence in the epikarst and changes in soil composition. Furthermore, as São Mateus Cave lies within the Cerrado biome, it offers a unique insight into the past climate and environmental changes in central Brazil due to its distinct floral compositions influenced by factors such as location, soil, rainfall distribution, and fire frequency. Comparisons with other paleoclimate data from SACZ-influenced sites are made to access climate and vegetation changes in different locations within this convective band, particularly over larger time scales, such as the transition from the Late-Pleistocene to the Holocene and longer trends. We demonstrate that even though there is a common change in the regional δ18O signal connected with SACZ variations, differences in vegetation and local moisture between northern and southern SACZ limits are evident albeit being in the same biome. This multi-proxy approach, combining traditional stalagmite proxies with high-resolution LA-MC-ICP-MS Sr isotope analysis, offers a better understanding of SACZ changes and their implications for Central Brazil's climate and environment. 
Past, Present, and Future Impacts of Climate Change and Variability on Flood Hazards in Sub-Saharan Africa
Authors: Ekolu Job , Dieppois Bastien , Tramblay Yves , Eden Jonathan , Sidibe Moussa , Villarini Gabriele , Moulds Simon , Slater Louise , Grimaldi Stefania , Salamon Peter , Camberlin Pierre , Pohl Benjamin , Mahé Gil , van de Wiel Marco
Published: March 2024

Sub-Saharan Africa (SSA) is strongly affected by flood hazards, which endanger human lives and disrupt economic stability. It is therefore critical to further understand the potential impact of climate change and variability on historical and future flood hazards in SSA. To do so, we first reconstructed a complete 65-yearlong daily streamflow, presenting over 600 stations distributed throughout SSA. Using this new dataset, we found that historical trends in flood frequency, duration, and intensity were strongly modulated by decadal to multidecadal variability. We then identified internal modes of climate variability in the Pacific and Indian Oceans as primary drivers of decadal variations in flood occurrence in southern and eastern Africa. Meanwhile, decadal sea-surface temperature anomalies (SSTa) over the eastern Mediterranean region and the North Atlantic were primarily driving decadal trends in floods occurring over western and central Africa. Using 12 climate model large ensembles from the Coupled Model Intercomparison Project Phases 5 and 6 (CMIP5 and 6), we also found such decadal variations in SSTa in the Mediterranean Atlantic, Pacific, and Indian oceans could modulate the occurrence of flood hazards by up to 50% in SSA during the 21st century. Finally, combining bias-corrected CMIP6 data and the open-source hydrological model LISFLOOD, we examine the potential impact of climate change on future trends affecting the intensity, frequency, and duration of floods in West Africa. This study therefore enabled us to compare for the first time the relative importance of climate change and climate variability on future changes affecting flood hazards in SSA.
Dynamical mapping of SWOT: performances from real observations
Authors: Ubelmann Clement , Le Guillou Florian , Ballarotta Maxime , Cosme Emmanuel , Metref Sammy , Rio Marie-Hélène
Published: March 2024

The Surface Water and Ocean Topography (SWOT) mission offers two-dimensional measurements of Sea Surface Height (SSH), capturing scales of a few tens of kilometers and enabling the study of previously unobserved short mesoscale dynamical structures. However, the mission faces technical challenges in maximizing scientific benefits, particularly during the science phase with its 21-day repeat orbit, which limits observations of small-scale structure evolution over time.To address the challenge of high spatial and low temporal samplings, we propose an original dynamic interpolation scheme that we call 4Dvar-QG. This innovative method combines a weakly constrained, reduced-order, 4-dimensional variational scheme with a quasi-geostrophic model. The weak constraint of the quasi-geostrophic model on the inversion procedure ensures that the estimated maps closely match the observations while preserving the space-time continuity of the reconstructed structures.The 4Dvar-QG method is applied in the North Atlantic Ocean on a constellation of real conventional altimeters and SWOT, during both the SWOT’s fast sampling and science phases. Performance evaluations are conducted through Observing System Experiments, utilizing independent data (such as altimetric and drifter data) as ground truth and comparing results to operational products like the Multiscale Interpolation Ocean Science Topography product (MIOST). The 4Dvar-QG method significantly improves the mapping of short energetic structures, reducing the root mean square error by up to 50% and increasing the effective resolutions by up to 30% compared to MIOST, while maintaining good reconstruction of large-scale and/or low energetic structures. 
Interplay between rifting-induced extension and surface loading effects illustrated by lateral magma propagation at Nyiragongo volcano
Authors: Pinel Virginie , Mériaux Catherine
Published: March 2024

The lateral magma propagation is a common feature of rift zones, with vertical dykes flowing parallel to the rift direction and opening against the minimum compressive stress. Depending on the competition between vertical and lateral magma migration, these dykes may either feed an eruption or not. In this context, the topography which includes the edifice load acts against the rise of the magma and favor lateral migration radially away from the edifice central area, thus feeding peripheral vents. Here, we use the case of Nyiragongo volcano, a volcanic edifice located in the western branch of the East African Rift and culminating at 3,470 meter above sea level to study such combined effect of rifting-induced extension and topographic loading on both the orientation of vertical dykes and on the balance between lateral versus vertical magma propagation within the propagation plane. Using analytical and numerical models taking into account the effect of topography and the local West-East extension stress field, we show that the path of a dike coming from the volcanic edifice is first influenced by the load of the volcano, leading to a radial propagation while beyond 5 km, the extensional stress field dominates leading to a North-South propagation towards Lake Kivu. These results are consistent with the path of the magma deduced from geophysical observations for the last two eruptive events of the Nyiragongo volcano (2002 and 2021). Furthermore, the downward slope toward Lake Kivu and, to a lesser extent, the slight increase in southward rift extension both favour lateral magma propagation, but reduced magma buoyancy at shallow depths is required to explain the lateral propagation over more than 20 km, where the magma remains trapped beneath the lake.
Cloud radiative feedback on the Venus climate simulated by a General-Circulation Model
Authors: Shao Wencheng , Mendonca Joao , Dai Longkang
Published: March 2024

Venus has regained great interest from planetary scientists in recent years because of the multiple upcoming Venus missions (e.g., EnVision, DAVINCI+ and VERITAS). Studying Venus is crucial for understanding the evolution of terrestrial planets as well as projecting the Earth’s future. One important component of the Venus climate system, the sulfuric acid clouds, has exhibited spatial and temporal variabilities. These variabilities are closely connected with the interactions between dynamics, photochemistry, radiative transfer and cloud physics. Current modeling studies of the Venus atmosphere have shed light on the underlying physics of the cloud variabilities. However, none of them has resolved the cloud radiative feedback. As an essential step to fully understanding the complex interactions, we develop a state-of-the-art General-Circulation Model (GCM), with cloud condensation/evaporation and radiative feedback processes included. In this talk, I will quantify the radiative forcing caused by the acidic clouds and provide indications of how the radiative forcing can influence the Venus climate evolution.
Resolving the interannual to multi-decadal variability in ocean heat content, a simulation study of current and future satellite gravity missions
Authors: Schlaak Marius , Pail Roland , Blazquez Alejandro , Meyssignac Benoit , Lemoine Jean-Michel
Published: March 2024

Ocean Heat Content (OHC) is an essential indicator of Earth’s climate state. Climate change is driven by the disequilibrium of Earth’s radiation budget. This abundant energy in the system is the Earth Energy Imbalance (EEI), which is challenging to measure globally. About 90% of EEI is accumulated in the oceans, resulting in an increase in ocean heat content. Therefore, OHC is a suitable proxy for EEI and can be measured globally using a combination of geodetic satellite techniques. By combining satellite altimetry and satellite gravimetry, it is possible to measure the change in global ocean heat content over the mission’s lifetime. While the altimeter record covers several decades, satellite gravity missions have been observing global mass transports for two decades. To steadily estimate the system’s long-term behavior, an extended observation period of the satellite systems is needed. The upcoming satellite gravity mission Grace-C, planned to be launched in 2028 by NASA, is meant to ensure continuity and extension of the data record. At the beginning of the 2030s, an additional inclined pair will be launched by ESA to form together with GRACE-C the Mass change And Geosciences International Constellation (MAGIC), for which higher spatial and temporal resolutions are expected.This contribution presents the results of multi-decadal closed-loop simulations of current and future satellite gravity observations. It shows the benefit of an increased duration of the observation and an improved observational system while comparing processing strategies for long-term trends in ocean mass changes. The observed climate signal is based on projections of mass change signals of oceans, ice sheets, and glaciers derived from CMIP6 climate projection under a shared socio-economic pathway scenario without drastic reduction of Greenhouse gases emissions (SSP5-8.5). A particular focus here is on the accuracy of long-term ocean trends. The direct estimation of long-term trends benefits from an increasing observation period and allows improved spatial resolution compared to trends estimated from monthly temporal gravity fields. The global ocean heat content is estimated from the steric sea-level change which is derived by subtracting the observed ocean mass change from the overall sea level change. The resulting long-term trends in ocean heat content are then compared to initial inputs to the simulation to illustrate the difference in performance between current and future satellite gravity constellations.
Effects of artificial root-pores on maize roots growth in compacted soil using X-ray computed tomography
Authors: Gao Weida , Liu Lingling , Qin shijie
Published: March 2024

Compaction is one of the main types of soil degradation worldwide. The macropores left by ex-plant roots were expected to provide channels to root to penetrate hard soil layers. However, there are few studies to quantitate the relationship between the elongation of maize roots and the root pores, due to complex morphological characteristics of the real root pore systems. In this study, we tried to build an artificial pore with sheath to simulate the effects of root pores on maize root growth in the compacted soil by X-ray CT. Our results indicated that the method for simulating root pores worked well. The sheath width of artificial root-pore was about 2.69 mm. Moreover, sheath of pores had higher organic carbon content and abundance of actinobacteria compared with bulk soil. Compared with artificial macropores, the presence of artificial root-pores diminished the border effects of the pot wall and increased the growth angle of node1 roots and the maximum growth depth of maize roots. However, there were no significant differences in terms of roots spatial distribution (in soil matrix, macropore sheath, macropore), and the ways (crossing or colonizing) of utilization by maize roots to macropores between the treatments with artificial macropores and artificial root-pores. This study provides a new insight into the interactions between root pore, root-pore sheath and maize roots.
Groundwater influence on the frequency of heatwaves: A global perspective
Authors: Vogelbacher Anastasia , Aminzadeh Milad , Afshar Mehdi H. , Shokri Nima
Published: March 2024

Groundwater plays a crucial role in land-atmosphere interactions through its effect on soil moisture, evaporation and thus surface heat fluxes (1). Variation of rainfall patterns in a changing climate and the increase in water demands are expected to influence groundwater dynamics that affect soil moisture-air temperature feedback processes and subsequently the occurrence of heatwaves. The decline in groundwater levels with intensified abstraction could hinder its buffer capacities to impede soil desiccation and onset of heatwaves. The current understanding of the relationship between shallow groundwater tables and heatwave events is often limited to regional studies or specific land covers, with a very few endeavors seeking to characterize global-scale trends and responses. We thus aim to globally investigate the relation between groundwater levels and heatwave events considering different land cover types and environmental variables by conducting a wide-ranging statistical analysis. Our approach involved leveraging a comprehensive dataset, allowing us to distinguish potential links between groundwater tables and the frequency of heatwaves over a range of geographical and climatological parameters. The findings from our investigation provide valuable insights into the relationship between groundwater dynamics and heatwave frequency within the broader context of the interactions between soil moisture and air temperature. This information will aid in devising effective action plan to mitigate the adverse effects of climate change.  Reference:(1) Maxwell, R., Kollet, S. Interdependence of groundwater dynamics and land-energy feedbacks under climate change. Nature Geosci1, 665–669 (2008). https://doi.org/10.1038/ngeo315 
Water potential dynamics in a precipitation pulse experiment: comparing direct and remote sensing metrics at the leaf scale
Authors: Guo Jessica , Smith William , Scott Russell , Biederman Joel
Published: March 2024

Plant water potential is a dynamic and fundamental driver of carbon and water fluxes, yet observations over time remain sparse. In a Sonoran Desert grassland, we utilized a precipitation manipulation experiment to a) evaluate the temporal trajectory of plant water potential following different precipitation pulse sizes and b) relate plant water potential to remote sensing proxies at the leaf scale. Beginning in 2020, natural summer rainfall was excluded and replaced with consistent irrigation divided among three watering treatments, which received identical seasonal totals delivered in return intervals of 3.5, 7, and 21 days (P3.5, P7, and P21, respectively), with correspondingly varied event magnitudes, between July and September. In 2023, we measured predawn and midday leaf water potential (ΨPD and ΨMD) as well as leaf-level hyperspectral on Digitaria californica, a native perennial bunchgrass, characterizing pulse events on Aug 14 (all treatments) and Aug 21 (second pulses for P3.5 & P7 only). Two spectra per leaf were measured, corrected for known breakpoints, and averaged prior to calculating NDVI, NDWI, and PRI.Prior to the Aug 14 pulse irrigation, ΨPD was above -2 MPa in P7 while P3.5 and P21 both exhibited ΨPD around -2.5 MPa. While ΨPD peaked on day 1 following irrigation in all treatments, the amount of time spent in the well-watered range differed greatly. ΨPD dropped after day 1 in P3.5, after day 2 in P7, and after day 12 in P21, consistent with the varying pulse magnitudes. Uniquely in P21, pulse irrigation increased soil water content at 25 cm, indicating the availability of deeper soil moisture to D. californica with fewer/larger precipitation events. When comparing the replicated pulse events in the frequent/smaller treatments, the water potential response to Aug 14 and Aug 21 pulses differed greatly in P3.5 but not in P7. While soil water contents were similar across pulses, ΨPD in P3.5 started above -1 MPa during the Aug 21 pulse and did not exhibit a peaked response, coinciding with lower cumulative VPD. Reduced atmospheric demand may significantly moderate water potential responses to small precipitation events. Finally, across treatments and time-of-day, leaf water potential was most closely correlated with greenness indices of NDVI and PRI (R2 = 0.166 and 0.183, respectively), while only loosely correlated with the water content index NDWI (R2 = 0.018). Next, we intend to develop our own indices that can better capture the temporal response of leaf water potential to precipitation dynamics. 
Downscaling Soil Moisture with Simple Machine Learning Ensembles
Authors: Poehls Jeran , Alonso Lazaro , Koirala Sujan , Carvalhais Nuno , Reichstein Markus
Published: March 2024

Soil moisture is a key factor that influences the productivity and energy balance of ecosystems and biomes. Global soil moisture measurements have coarse native resolutions of 36km and infrequent revisits of around three days. However, these limitations are not present for many variables connected to soil moisture such as land surface temperature and evapotranspiration. For this reason many previous studies have aimed to discern the relationships between these higher resolution variables and soil moisture to produce downscaled soil moisture products.In this study, we test four ensembles of simple machine learning models for this downscaling task. These ensembles use a dataset of over 1,000 sites across the US to predict soil moisture at sub-km scales. We find that all ensembles, particularly one with a very simple structure, can outperform SMAP on  a cross-fold analysis of the 1,000+ sites. This ensemble has an average ubRMSE of 0.058 vs SMAPs 0.065 and an average R of 0.639 vs SMAPs 0.562. However, not all ensembles are beneficial, with some architectures performing better with different training weights than with ensemble averaging. Additionally, we find that although general improvements over SMAP are observed, there appears to be difficulty in consistently doing so in cropland regions with high clay and low sand content.Key Points:Ensembles of simple ML architectures can downscale SWC predictions to sub 1km resolutions
Simpler architectures can outperform these ensembles and may be further enhanced with an improved weighting scheme during training
Training the models on temporally padded data provides more benefits than drawbacks in terms of overall performance.
The top performing ensemble is unreliable on croplands with higher than average clay and lower than average sand content.
The density and viscosity of a bilithologic plume-fed asthenosphere
Authors: Shao Jia , Morgan Jason
Published: March 2024

Pyroxenites are generated by the subduction of sediments and oceanic basalts into the deep mantle. These rocks, together with the larger volume fraction of their surrounding mantle peridotites make up a lithologically heterogeneous two-component mantle, sometimes called a ‘marble-cake’ or ‘plum-pudding’ mantle. Geochemical and petrological observations have shown that pyroxenites play a significant role in the genesis of oceanic island basalts (OIB). However, the consequences of preferential pyroxenite melting on bulk mantle properties have yet to be systematically explored. For example, how does the plume melting process modify a plum-pudding mantle’s bulk density and viscosity? This question could be very important, in particular if the asthenosphere is formed by material from upwelling, melting plumes.To explore the above questions, we use the thermodynamic software Perple_X to determine densities for different degrees of depleted (i.e. partially melted) peridotites and pyroxenites. We then include these relations into a one-dimensional numerical simulation code for the upwelling and pressure-release melting of a potentially wet multi-component mantle. We investigate the density changes associated with the melting of this idealized mantle’s pyroxenites and peridodites, and also the viscosity change by assuming that the reference viscosity of pyroxenite is 10-100 times that of dry peridotite at similar P-T conditions, since the peridotite’s olivines are the weakest large volume-fraction minerals in the upper mantle. We have explored the effects of mantle temperature, initial water contents, initial fractions of pyroxenites and peridotite, peridotite solidi, and the thickness of the overlying lithosphere which will affect the depth-interval of upwelling and melting. Preliminary results show that significant density and viscosity changes should take place during plume upwelling and melting. ~30% partial melting of pyroxenite would lead to a net bulk density reduction of 0.3%, comparable to the thermal buoyancy associated with a ~100° temperature increase. As long as the surrounding peridotites do not melt, the mixture’s aggregate viscosity will remain that of wet peridotitic mantle; after the peridotites have melted a percent or so, the aggregate viscosity will increase 10-100-fold to that of dry peridotite. This could lead to the formation of a 10-100x asthenospheric viscosity restitic hotspot swell root. Eventual peridotitic melting will reduce the density of the more depleted peridotites relative to fertile peridotite as originally noted by Oxburgh and Parmentier (1977), but to a lesser degree than the density reduction associated with the preferential removal of pyroxenites by their partial melting. A dynamical consequence is that the asthenosphere is likely to be strongly stratified by density, with its most pyroxenite-depleted materials likely to rise to form a layer along the base of the overlying oceanic lithosphere. 
SedCas_Volcano: a novel approach to modelling decadal evolution of lahar hazard in response to episodic volcanic eruptions
Authors: Christie James , Bennett Georgie
Published: March 2024

Lahars are a common and potentially long-lived hazard in river basins affected by explosive volcanic eruptions. They result from the hydrological disturbance of surrounding landscapes, driven by the destruction of vegetation and deposition of pyroclastic material. These modifications typically result in heightened rainfall runoff responses, via reduced interception and infiltration, leading to increased water and sediment flux, manifesting as lahars. With time, landscapes recover via removal of sediment, establishment and stabilisation of channels, and the redevelopment of vegetation. This recovery subsequently reduces the runoff response to rainfall and in turn limits the potential magnitude and frequency of lahars. Numerical modelling is an important approach for assessing the hazard posed by lahars. Most modelling approaches related to lahars consider the remobilisation susceptibility of pyroclastic deposits under particular conditions, or the runout/inundation potential of individual or probabilistic ensembles of flows. To date, very limited research has sought to address the longer-term (years to decade) evolution of lahar activity in affected catchments as they respond to and recover from disturbance. Here we present and discuss SedCas_Volcano, a simple model designed to simulate the longer-term evolution of lahar incidence in a catchment on the island of Montserrat that has been repeatedly disturbed by episodic volcanic activity since 1995. Using this simple and computationally inexpensive numerical framework, we account for variability in sediment supply, vegetation cover, and rainfall. Here we will discuss the merits of this model and identify possible next steps for continued model development.
Influence of pre-existing faults on damage distribution in carbonate fault zones: the case study of the Roccapreturo Fault, central Apennines
Authors: Mercuri Marco , Agosta Fabrizio , Fondriest Michele , Smeraglia Luca , Billi Andrea , Tavani Stefano , Carminati Eugenio
Published: March 2024

Understanding the origin and distribution of damage within carbonate-hosted fault zones is crucial, yet it remains a complex challenge, which hampers the overall assessment of their mechanical and hydraulic structure. In carbonate-hosted fault zones, shattered to intensely brecciated non-cohesive rocks have been reported. Although their origin has been related to the propagation of multiple seismic ruptures, great uncertainties persist regarding their interpretation and distribution.The NW-SE striking, approximately 15 km long Roccapreturo Fault, in the central Apennines of Italy, is an intriguing case study where non-cohesive fault rock domains occur within its footwall damage zone. These domains elongate in a NE-SW direction for ~200 meters from the main slip surface.We employed a multiscale approach to better understand the distribution and origin of the non-cohesive fault rocks. The fault geometry and throw distribution along the main fault segments were characterized through fault-perpendicular geological cross-sections. Virtual outcrop models of key exposures, located in and around an abandoned quarry, were constructed using Structure from Motion-Multiview Stereo photogrammetry. These models utilized photos taken with a Mavic Mini 2 drone. The interpretation of virtual outcrop models, combined with classical fieldwork, allowed us to map the damage and minor fault strands.The Roccapreturo Fault displaces Cretaceous rocks originally deposited in various depositional environments. Along its strike, from NW to SE, the fault intersects rocks from internal or restricted carbonate platform, margin, and proximal slope to basin depositional environments. Notably, non-cohesive fault rocks are exposed between the margin and proximal slope rocks. This area coincides with the maximum throw of the fault, which is ca. 600 meters, and with the intersection with a system of pre-existing NE-SW-striking steeply dipping faults.At the outcrop scale, faults exhibit two preferred orientations, parallel and perpendicular to the main slip surfaces of the Roccapreturo Fault, respectively. The former ones show predominant dip-slip kinematics, while the latter ones show both dip-slip and strike-slip kinematics.We interpret the distribution of non-cohesive fault rocks along the Roccapreturo Fault as influenced by its intersection with the NE-SW fault system, where most of the slip accumulated. Accordingly, the pre-existing NE-SW faults accommodated transtensional slip during latest extensional deformation and coeval rock exhumation from depth. The transition of the Cretaceous depositional environments, which was accommodated by the NE-SW-striking faults, therefore highlights the pivotal role of pre-existing anisotropies in dictating the distribution of damage, particularly of non-cohesive fault rocks, in carbonate hosted faults.