bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution Mapping of Terrestrial Evapotranspiration using ECOSTRESS: Insights into Surface Energy Balance Modeling
Authors: Hu Tian , Mallick Kanishka , Hitzelberger Patrik , Didry Yoanne , Szantoi Zoltan , Boulet Gilles , Olioso Albert , Roujean Jean-Louis , Gamet Philippe , Hook Simon
Published: March 2024

ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) has been providing high spatio-temporal thermal infrared (TIR) observations (~70 m, 1-5 days) since August 2018. Land surface temperature (LST) retrieval obtained from TIR observations indicates the thermal status of the surface as a consequence of the land-atmosphere exchange of energy and water. It carries the imprint of vegetation water use and stress, thus serving as a pivotal lower boundary condition for retrieving evapotranspiration (ET). Taking advantage of the ECOSTRESS observations, the European ECOSTRESS Hub (EEH) funded by the European Space Agency (ESA) retrieves high-resolution ET for terrestrial ecosystems.In EEH Phase 1 (2020-2022), instantaneous ET data between 2018 and 2021 were generated from three models with different structures and parameterization schemes over Europe and Africa, including the Surface Energy Balance System (SEBS) and Two Source Energy Balance (TSEB) parametric models, as well as the analytical Surface Temperature Initiated Closure (STIC) model. The evaluation by comparing against ground measurements at 19 eddy covariance sites for 6 different biomes over Europe showed that the physically based STIC model had relatively better consistency and higher accuracy across varying aridity and diverse biomes. Also, an advantage of STIC was found as compared to the official ECOSTRESS ET product obtained using the PT-JPL model, especially over arid and semiarid regions due to the weak LST control in PT-JPL.Taking advantage of the recalibrated ECOSTRESS Collection 2 data, EEH Phase 2 (2023-2025) analyses the impacts of LST estimates from different algorithms on ET retrieval and related biophysical conductances over different biomes. It is found that ET estimates of STIC driven by LST retrieved from the two most commonly used algorithms (i.e., split window, SW, and temperature and emissivity separation, TES) have comparable accuracies. The sensitivity of ET to LST over savannas is almost three times of those over biomes over lower aridity. Surface-canopy conductance is more sensitive to surface temperature as compared to aerodynamic conductance.Overall, the EEH is promising to provide quality assured ET estimates for monitoring terrestrial ecosystem water use and stress. Furthermore, it will facilitate the preparation for the next generation high-resolution thermal missions by investigating surface energy balance modeling, including TRISHNA (CNES/ISRO), SBG (NASA), and LSTM (ESA).
Geochemistry of core sediments from the southeast coast of Bangladesh: Implications for provenance and chemical weathering intensity
Authors: Hossain H. M. Zakir , Hossain Anas Al , Islam Md. Aminul , Liu Zhifei , Yu Mingyang , Zheng Ce
Published: March 2024

Geochemical analyses of major oxides, trace, and rare-earth elements (REE) were examined on the ~70 m core sediments collected from the southeast coast of Bangladesh to determine sediment provenance, maturity, and chemical weathering conditions. The sediment samples contained high SiO2 (62-91 wt.%) and low Al2O3 (~5-17 wt.%) contents and showed a marked negative correlation (r = -0.99) with strong linear trends, indicating that SiO2 was mainly controlled by the quartz content rather than aluminosilicates. Substantial depletion of major labile elements (Na2O, CaO, K2O, Ba, and Sr) compared to the upper continental crust (UCC) indicates the destruction of feldspar during chemical weathering in the source area. The chondrite-normalized REE patterns show LREE enrichment (LaN/YbN, 7.61-14.35), nearly flat HREE (GdN/YbN, 1.33-2.25), and marked Eu anomalies (Eu/Eu*, ~0.58-1.40), suggesting an influx of sediments from felsic provenance. Numerous provenance discrimination diagrams and elemental ratios (Th/Sc, La/Sc, Zr/Sc, Cr/Th, Th/Co, Eu/Eu*, and GdN/YbN) show that the core sediments were derived from felsic source rocks mostly granodiorites, rhyolites, and granites. The REE patterns and parameters are very similar throughout the sequence studied, indicating that the overall source composition in the basin remained unchanged. The Index of Compositional Variability (ICV) values of the sediments varied from 0.79 to 1.83, which indicates immature to moderate compositional maturity. The Chemical Index of Alteration (CIA, ~67 to 81), Chemical Index of Weathering (CIW, ~69 to 91), and Plagioclase Index of Alteration (PIA, ~71 to 92) parameters suggest moderate to high chemical weathering intensity in the source area, which was favored and accelerated by the warm and humid climatic conditions. The elemental ratios (V/Cr, Ni/Co, Cu/Zn, and V/V+Ni) suggested oxic to sub-oxic depositional environment for the accumulation of sediments in the studied Bengal coast. However, the variation of weathering patterns and proxies in the core sediments could be influenced by the strength of South Asian monsoon circulation over the Himalaya-Tibetan Plateau.
Stratospheric impact on subseasonal forecast uncertainty in the Northern extratropics 
Authors: Spaeth Jonas , Rupp Philip , Garny Hella , Birner Thomas
Published: March 2024

Extreme events of the stratospheric polar vortex can modulate subsequent surface weather at subseaonal to seasonal (S2S) timescales. Moreover, they are considered to form windows of opportunity for tropospheric forecasting. This study aims to improve understanding of how the canonical surface response of polar vortex events translates into modulated surface predictability. First, we confirm that in the ECMWF extended-range prediction model, the mean signal of weak (strong) polar vortex events projects onto a negative (positive) phase of the North Atlantic Oscillation. The associated equatorward (poleward) shift of the eddy-driven jet then enhances or suppresses synoptic variability in specific regions. By constructing a leadtime, seasonal and model version-dependent climatology of forecast ensemble spread, we link these regions to anomalous forecast uncertainty. For example, sudden stratospheric warmings (SSWs) are followed by a southerly jet shift, which translates into suppressed Rossby wave breaking over Northern Europe, resulting in anomalously high forecast confidence in that region.In general, both signatures in the mean and spread can contribute to predictability. However, when forecasts are compared to reanalyses, they manifest differently in different skill scores, such as the Root-Mean-Squared Error or the Continuously Ranked Probability Skill Score. We therefore discuss how separate consideration of anomalies in the ensemble mean and ensemble spread may aid to interpret predictability following polar vortex events.Finally, we apply the diagnostics also to tropical teleconnections. We find indications that windows of forecast opportunity might be dominated by stratospheric polar vortex variability over the Atlantic and by ENSO variability over the Pacific.
AI-driven insights into soil health and soil degradation in Europe in the face of climate and anthropogenic challenges
Authors: H. Afshar Mehdi , Hassani Amirhossein , Aminzadeh Milad , Borrelli Pasquale , Panagos Panos , Robinson David A. , Shokri Nima
Published: March 2024

A healthy soil supports life on Earth through maintaining ecosystems that provide food, feed and fibre whilst supporting Earth system functions such as waste recycling, climate, flood, and water regulation. The intensification of anthropogenic activities and climate challenges pose serious threats to soil health (Hassani et al., 2021), exacerbating the processes of soil degradation that are putting at risk soil management, biodiversity, and food security.This study thus aims at enhancing our understanding of the state and changes of soils by combining machine learning methods with a comprehensive series of climate and environmental variables. We employ machine learning methods to analyze the relationships between soil health indicators and a wide range of climatic parameters, and chemical, physical, and biological soil attributes in Europe. Capitalizing on the LUCAS (Land Use/Cover Area frame statistical Survey) topsoil database (2009-2018) and digital soil mapping techniques, our preliminary results highlight the regions across Europe showing consistent decline in soil nutrients and carbon content, signaling potential risks of soil degradation. The proposed framework enables us to understand, document and respond to soil changes in ecosystems under different land management and climate scenarios. This contributes to devising necessary action plans for sustainable soil management and preservation.This research is part of the project AI4SoilHealth (Accelerating collection and use of soil health information using AI technology to support the Soil Deal for Europe and EU Soil Observatory) funded Horizon Europe (Grant No. 101086179). ReferenceHassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. Commun., 12, 6663. https://doi.org/10.1038/s41467-021-26907-3.
Dayside ionospheric conductivities and horizontal currents derived from MAVEN/ROSE data
Authors: Majeed Tariq , Bougher Stephen
Published: March 2024

A complex magnetic topology at Mars gives rise to diverging magnetic field cusps and closed magnetic loops with local magnetic conditions similar to those found above Earth’s polar region. Several such cusps are identified from MAVEN/Radio Occultation Science Experiment (ROSE) electron density profiles mostly observed during the period July 2016 to December 2020 in the southern high latitudes, where the crustal magnetic field is nearly vertical and open to the access of solar wind plasma through magnetic reconnection with the interplanetary magnetic field.  This reconnection can allow solar wind electrons to penetrate the Martian upper atmosphere, causing ionization and heating, which leads to inflate the topside plasma distribution to high altitude and increase the topside electron density scale heights. We use our 1-D chemical diffusive model from an altitude of 100 km to 400 km to interpret the twenty ROSE electron density profiles with the vertical plasma transport simulated by vertical ion velocities and by imposing an outward flux boundary condition.  The output of this model and available crustal magnetic field information at Mars are used to estimate the vertical distribution of ionospheric conductivities.  We find that the ionosphere is highly conductive in the Martian dynamo region between 100 and 220 km altitude where plasma –neutral collisions permit electric currents perpendicular to the crustal magnetic field.  The magnitudes of Pedersen and Hall conductivities are estimated to be ~0.60 – 0.85 S/m, respectively, near the Martian ionospheric peak of the observed electron density profiles included in this study. The electrons in this region are constrained to gyrate along magnetic field lines while ions are dragged by neutrals and move along the direction of applied force. In the absence of the electric field, the horizontal current in the Martian dynamo is generated by the differential motion of ions and electrons. The results of the present study will allow us to quantify the flow of atmospheric electric currents which can be analyzed for a deeper understanding of the Martian ionospheric electrodynamics. The model results will be presented in comparison with existing estimates of the Martian conductivities and ionospheric currents.   
Development of hydro geophysical techniques to characterize water fluxes in the vadose zone of karstified and porous heterogeneous aquifers
Authors: Thadathummal Sathyan Harmya , Hastreiter Nele , Dietrich Peter , Sauter Martin , Engelhardt Irina
Published: March 2024

This research aims to develop in-situ and non-invasive hydrogeophysical techniques to monitor water fluxes within the unsaturated zone. While porous media are more continuous in their flow pattern, no suitable technique so far exists at the field scale for karstifed vadose zones. Motivated by the existing uncertainty in understanding vadose zone water flux patterns at a larger scale our study aims to develop a new technique to invert tracer signals, such as heat, into a 3D flow field with the vadose zone.
Up to now, there are only very few studies published that use 3D mechanistic flow models to analyse 3D high- resolution heat as a tracer for water fluxes in the unsaturated zone. Natural daily temperature fluctuations influence soil water temperature down to 1 meter below the surface, while natural seasonal variations extend to depths of 15 to 20 meters. Beyond this depth, in the 'neutral zone,' temperature responses are influenced by rock thermal conductivity and regional heat flux density.
We investigate two test sites: one in a porous medium and the other in a karstified aquifer. Our investigations allow us to compare under similar climate water fluxes of a porous with a karstified medium and to assess their higher vulnerability to drought periods. Utilizing Distributed Temperature Sensing (DTS) for continuous monitoring of soil water temperature profiles, we installed the DTS equipment in several boreholes and analyse temperature fluctuations over time using HYDRUS-3D.
Distributed Temperature Sensing (DTS) technology will be installed within boreholes positioned in the vadose zone, with each borehole interconnected by a fiber optic cable. The DTS system enables continuous and precise monitoring of groundwater temperature profiles. Over an extensive period of six months, the study will collect comprehensive datasets capturing natural temperature signals within the vadose zone.
The successful installation of the fiber optic cable within the boreholes poses another significant challenge. The cable must be carefully deployed to minimize the risk of breakage or damage during installation. Specialized techniques and equipment may be required to handle the cable delicately, ensuring its integrity throughout the entire length.
In summary, addressing challenges related to optical fiber reliability, cable installation integrity, and precise warm water injection is critical for the success of the experiment. Implementing proactive monitoring, rigorous installation practices, and contingency plans will contribute to overcoming these challenges and obtaining robust and reliable results from the research study.
Continuous motion conditions of turbidity current in Xiaolangdi reservoirs, China
Authors: Yang Fei , Wang Qiang , Wang Yuangjian , Jiang Enhui
Published: March 2024

Turbidity currents venting is most efficient method for Xiaolangdi reservoir under normal water level when tackling sediment-laden floods to reduce sedimentation. The concept of continuous motion conditions of turbidity current was introduced as the requirements for the main part of turbidity current reach the dam site. Dynamics of turbidity currents in Xiaolangdi reservoir were investigated using the layer-averaged equations of motion. Water-sediment exchange with bed and above have been concealed for simplicity, by which the mechanism that drives continuous motion is subjected to the gravitational force. Two major control parameters, the relative longitudinal bed slope and the relative length of turbidity current, are proposed regarding topography and hydrodynamics. The ratio of the average riverbed longitudinal gradient J from the plunging point to the dam site to the critical gradient Jc of the turbidity current, J/Jc, represents the relative longitudinal bed slope. The ratio of the product of the equilibrium velocity u and duration T of the turbidity current to the radial distance L from the plunging point to dam site, uT/L, represents the relative length of turbidity current. Therefore, a discrimination diagram for continuous motion conditions of turbidity current was determined based on J/Jc and uT/L, successfully differentiated whether turbidity currents can reach the Xiaolangdi dam site.
Ensemble forecast post-processing based on neural networks and normalizing flows
Authors: Mlakar Peter , Merše Janko , Faganeli Pucer Jana
Published: March 2024

Ensemble weather forecast post-processing can generate more reliable probabilistic weather forecasts compared to the raw ensemble. Often, the post-processing method models the future weather probability distribution in terms of a pre-specified distribution family, which can limit their expressive power. To combat these issues, we propose a novel, neural network-based approach, which produces forecasts for multiple lead times jointly, using a single model to post-process forecasts at each station of interest. We use normalizing flows as parametric models to relax the distributional assumption, offering additional modeling flexibility.We evaluate our method for the task of temperature post-processing on the EUPPBench benchmark dataset. We show that our approach exhibits state-of-the-art performance on the benchmark, improving upon other well-performing entries. Additionally, we analyze the performance of different parametric distribution models in conjunction with our parameter regression neural network, to better understand the contribution of normalizing flows in the post-processing context. Finally, we provide a possible explanation as to why our method performs well, exploring per-lead time input importance.
Quantifying the oxidative potential of aerosols in low-income urban areas in South Africa
Authors: van Zyl Pieter G. , Segakweng Constance K. , Liousse Catherine , Gnamien Sylvian , Gardrat Eric , Beukes Johan P. , Jaars Kerneels , Dumat Camille , Guinot Benjamin , Josipovic Miroslav , Language Brigitte , Burger Roelof P. , Piketh Stuart J. , Xiong Tiantian
Published: March 2024

Health impacts associated with exposure to atmospheric aerosols are of global concern and are not completely understood. In addition, health studies are, especially, complicated in developing countries such as South Africa. Oxidative potential (OP), defined as a measure of the capacity of aerosols to oxidise target molecules, has been proposed as a viable alternative relevant biological metric to better quantify toxicological responses related to atmospheric aerosol exposure in health studies. The dithiothreitol (DTT) assay is the most commonly used method to determine OP of aerosols, which was used in this study to quantify the OP of outdoor and indoor atmospheric particulates collected at three low-income settlements in South Africa. This technique is easy-to-operate, low-cost, effective and reproducible. The DTT methodology had to be modified according to previous applications, which required choosing a suitable extraction procedure and -setup. The redox activity of size-resolved sampled aerosols was evaluated and related to their chemical composition with correlation analysis. The seasonal variations of DTT redox activity were established by normalizing in terms of aerosol mass and sampled volume for indoor and outdoor particulate samples. Higher redox activity was determined for the smallest aerosols (aerodynamic diameter
Historical volcanic eruptions slowed down rapid decline in Arctic sea ice linked to global warming
Authors: Wang Xinyue
Published: March 2024

Arctic sea ice has experienced a differential decline in speed due to the same anthropogenic greenhouse gas forcing, as evidenced by rapid decline after the end of the last century. Our convergent observations, last-millennium reanalysis, and model analyses have revealed that large tropical volcanic eruptions can lead to a decadal increase in Arctic sea ice, and the 1982 and 1991 large volcanic eruptions slowed down the decline of Arctic sea ice during the last century. The models, selected based on the observed sensitivity of Arctic sea ice to volcanic eruptions, suggest that the earliest ice-free summer year in the Arctic will be around 2040 in high-emission sceneria of SSP585. These findings emphasized the crucial need to incorporate volcanic influences when projecting future Arctic changes amid global warming.
A model for predicting permeability of geotextile envelope after combined clogging in arid areas
Authors: Qin Shuai , Guo Chenyao , Wu Jingwei
Published: March 2024

The clogging problem of geotextile envelopes in subsurface drainage pipes in arid areas can lead to a reduction of the drainage capacity in the drainage system. The current research on combined clogging is mostly in the stage of phenomenological observations or indoor experiments, and quantitative methods are lacking. In this study, a model for predicting permeability of geotextile envelope was developed using pore distribution theory of geotextile envelope. Then, a stepwise coupled combined clogging model was proposed based on the evolution characteristics of physical and chemical clogging. The coupled model was verified by field sampling, and the measured results of the three sites were within the range of the predicted values. Then, the main factors affecting the combined clogging model of the geotextile envelope were analyzed, and the clogging evolution was predicted. The results showed that the combined clogging model was sensitive to the physical clogging coefficient β1 during the first 30 days and more sensitive to the calcium carbonate saturation index (SI) after 30 days of drainage. When β1 was equal to 0.3, a saturation index greater than 1.0, which corresponds to drainage mineralization exceeding 3.0 g/L, indicated a high risk of clogging in Xinjiang.
Progressive decline in topsoil nitrogen pool upon decadal warming in a permafrost ecosystem
Authors: Wei Bin , Yang Yuanhe
Published: March 2024

Nitrogen (N) plays an important role in mediating many aspects of permafrost carbon cycle, such as plant productivity, soil organic matter decomposition and the production of greenhouse gases. In contrast to the well-recognized effects of climate warming on soil organic carbon stocks and vulnerability, the fates and pools of soil N has received little attention in permafrost ecosystems.Here, based on a decadal warming experiment in a permafrost ecosystem on the Tibetan Plateau, we assessed changes in soil N stocks over a 10-year time-scale, and in situ measured the majority of N-cycling processes involving biological N fixation and soil N transformation, and the preferential plant uptake of different N forms, and above- and belowground litter decomposition and N release, and N leaching losses as well as high-resolution nitrous oxide (N2O) flux during the growing season.Our results showed that experimental warming progressively reduced topsoil N stocks but had no effect in the deeper soils on a 10-year time-scale. The observed decline in topsoil N pools could be due to the fact that decadal warming enhanced plant N uptake and intensified N leaching and gaseous losses. Specifically, warming treatment had a negligible effect on ecosystem biological N fixation rate, but increased the above- and belowground plant N pools. Meanwhile, simulated warming accelerated belowground litter N release and soil N transformation rate, and enhanced plant uptake of organic N. However, warming intensified the topsoil inorganic N leaching losses and N2O flux during the growing season.These findings highlight that progressive N limitation could occur in permafrost ecosystems under continuous climate warming due to the re-allocation of N pool from soils to plants and the losses of N through leaching and gases flux, which would make the future trajectory of permafrost carbon cycle and its feedback to climate warming more complex than previously thought.
Tectonic setting and its effect on organic matter enrichment of the lower Cambrian shales in the Sichuan Basin (SW China)
Authors: Tang Jun , Wang Jian , Wu Guanghui
Published: March 2024

AbstractThe lower Cambrian shale, a significant source rock, has been witness to substantial tectonic and environmental shifts on Earth. However, the correlation between early Cambrian tectonic history and organic matter enrichment (OME) remains elusive. The Sichuan Basin in the northwestern Yangtze Block hosts the largest Precambrian-Cambrian gas field in China. The primary source rocks contributing to this reservoir are mainly the lower Cambrian shales. The organic matter enrichment of the lower Cambrian shale is commonly ascribed to paleoproductivity, redox conditions, localized hydrothermal activity, upwelling currents, and terrigenous inputs. However, organic matter enrichment varies across the Yangtze Block due to different influencing factors. Particularly, little information has been employed to elucidate the tectonic impact on OME in the lower Cambrian shales within the Sichuan Basin. This study presents detrital zircon U-Pb ages and geochemical data obtained from late lower Cambrian shales in the Sichuan Basin, SW China. The black shales exhibited similar chondrite-normalized REE patterns. They display a slightly right-dipping trend in LREE, a gentle slope in HREE, and a significant Eu anomaly in some samples. Additionally, trace elements generally exhibited a slightly right-leaning pattern, with distinct depletions observed in Nb, Ta, Sr, and Ti. These suggest a complex provenance and origin of the Cambrian shales. The maximum deposition ages of YB-10, NHX-22, and O1H-4 samples were 541Ma, 580Ma, and 523Ma, respectively. These samples were analyzed in cumulative scale maps (crystallization and deposition ages), and it was found that the samples all fell into the collision environment. The detrital zircon U-Pb ages signify a novel magmatic activity in a continental arc setting from the Ediacaran to the early Cambrian, acting as a major sedimentary provenance. It suggests that a weakening retreating subduction-related weak extensional basin rather than a passive marginal or foreland basin of the early Cambrian Sichuan Basin, which had led to diminished extensional and broad trough-platform shales. The compiled geochemical data indicate that OME during the early Cambrian was strongly linked to high primary productivity, redox conditions, and detrital input. However, the influence of these factors on organic matter enrichment varied spatiotemporally, likely due to the unstable and variable tectonic-sedimentary environment associated with the retreating subduction event. This case study illuminates the effects of retreating subduction on the differential organic matter enrichment in the platform shales.Keywords: Cambrian; shale; retreating subduction; organic matter enrichment; tectonic effect; Sichuan Basin
A portable reflected-sunlight spectrometer for measuring atmospheric CO2 and CH4: Accounting for aerosols
Authors: Löw Benedikt A. , Kleinschek Ralph , Enders Vincent , Sander Stanley P. , Pongetti Thomas J. , Schmitt Tobias D. , Hase Frank , Butz André
Published: March 2024

Mapping the greenhouse gases carbon dioxide (CO2) and methane (CH4) above source regions, such as urban areas, can deliver insights into the distribution and dynamics of local emission patterns. To this end, we conduct ground-based measurements in the reflected-sun geometry, where a NIR spectrometer in an elevated position points downward at shallow viewing angles and observes reflected sunlight from a target area. From the spectra, we infer CO2 and CH4 concentrations integrated along a long (>10 km) horizontal path. Measurements in this viewing geometry are particularly sensitive to concentrations in the planetary boundary layer.We deployed our portable reflected-sun prototype instrument (termed EM27/SCA) [1] during one month in April/May 2022 on Mt. Wilson above the Los Angeles basin to perform side-by-side measurements with the stationary CLARS-FTS [2]. We find a relative precision of 0.36%–0.55% for CO2 and CH4 slant column densities and good consistency with simultaneous CLARS-FTS measurements. However, we also identify the necessity to account for radiation scattered into the ray path when performing the quantitative analysis of recorded spectra.Here, we present the instrument performance as well as our approach to account for atmospheric scattering effects. Our retrieval algorithm is based on the RemoTeC radiative transfer and retrieval algorithm, previously employed for solar backscatter satellite measurements. We showcase its performance by simultaneously inferring aerosol optical thickness, CO2 and CH4 from EM27/SCA observations. References:[1] Löw, B. A., et al.: A portable reflected-sunlight spectrometer for CO2 and CH4, Atmos. Meas. Tech., 16, 5125–5144, https://doi.org/10.5194/amt-16-5125-2023, 2023.[2] Fu, D., et al.: Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site, Atmos. Meas. Tech., 7, 713–729, https://doi.org/10.5194/amt-7-713-2014, 2014.
Reducing boundary effects during True Triaxial loading of rocks
Authors: Stanton-Yonge Ashley , Mitchell Thomas , Meredith Philip , Browning John , Healy David
Published: March 2024

Even though stresses in the crust are triaxial (𝜎1>𝜎2>𝜎3) the overwhelming majority of rock deformation experiments are conducted under axisymmetric (or conventional triaxial) loading (𝜎1>𝜎2=𝜎3). This configuration disregards the effect of 𝜎2 on the physical and deformation properties of rocks, thus complicating and degrading the extrapolation of results to natural crustal conditions. A True Triaxial loading configuration is necessary to overcome this simplification, however, these improvements in addressing real crustal conditions come at a cost, which is the challenging boundary conditions that arise from having six loading rams rather than just two. Two main loading boundary effects can severely impact the stress distribution and failure mechanism of samples deformed in a True Triaxial Apparatus (TTA): 1) the end friction effect caused by the stiffness contrast between the rock sample and the metal loading platens, and 2) the unstressed sample edges resulting from the requirement that loading platens must necessarily be slightly smaller than the rock specimen. Managing and reducing these boundary effects is fundamental for obtaining accurate and representative data from true triaxial experiments, and for the further development of these apparatuses.A novel TTA developed in the UCL Rock & Ice Physics Laboratory was designed to subject cubic or cuboid rock samples to truly triaxial stresses through the independent control of six loading rams. The apparatus is equipped with a confining and pore pressure system that allows for the deformation of saturated samples whilst simultaneously measuring permeability along the three axes. A suite of Finite Element Method (FEM) models was implemented to evaluate the parameters that minimize loading boundary effects in UCL’s TTA for a 50 mm edge-length cubic sample of sandstone. Our results indicate that using aluminum loading platens (𝐸𝑠𝑎𝑚𝑝𝑙𝑒/𝐸𝑝𝑙𝑎𝑡𝑒𝑛=0.47) reduces the end friction effect by a factor of two compared to using steel platens (𝐸𝑠𝑎𝑚𝑝𝑙𝑒/𝐸𝑝𝑙𝑎𝑡𝑒𝑛=0.17). In addition, we find that elevated confining pressure significantly reduces the stress concentration produced by unstressed edges. Specifically, a confining pressure of 10 MPa eliminates tensile stresses at the sample corners. These results are currently being implemented into the experimental protocol and execution in UCL’s TTA in order to ensure that we obtain reliable true triaxial data. However, these observations are generic and could therefore contribute to improved development and operation of true triaxial loading systems generally.
Advancing Streamflow Modelling: Bias Removal in Physically-Based Models with the Long Short-Term Memory Networks (LSTM) Algorithm
Authors: Mohammed Safa , Nasr Ahmed
Published: March 2024

Traditional hydrological models have long served as the standard for predicting streamflow across temporal and spatial domains. However, a persistent challenge in modelling lies in mitigating bias inherent in streamflow estimation due to both random and systemic errors in the employed model. Removal of this bias is pivotal for effective water resources management and resilience against extreme events, especially amidst evolving climate conditions. An innovative solution to address this challenge involves the integration of hydrological models with deep learning methods, known as hybridisation. Long Short-Term Memory networks (LSTM), have emerged as a promising and efficient approach to enhancing streamflow estimation. This study focuses on coupling LSTM with a physically distributed model, Wflow_sbm, to serve as a post-processor aimed at reducing modelling errors. The coupled Wflow_sbm-LSTM model was applied to the Boyne catchment in Ireland, utilising a dataset spanning two decades, divided into training, validation, and testing sets to ensure robust model evaluation. Predictive performance was rigorously assessed using metrics like Modified Kling-Gupta Efficiency (MKGE) and Nash-Sutcliffe Efficiency (NSE), with observed streamflow discharges as the target variable. Results demonstrated that the coupled model outperformed the best-calibrated Wflow_sbm model in the study catchment based on the performance measures. The enhanced prediction of extreme events by the coupled Wflow_sbm-LSTM model strengthens the case for its integration into an operational river flow forecasting framework. Significantly, Wflow is endorsed by the National Flood Forecast Warning Service (NFFWS) in Ireland as a recommended model for streamflow simulations, specifically designed for fluvial flood forecasting. Consequently, our proposed Wflow_sbm-LSTM coupled model presents a compelling opportunity for integration into the NFFWS. With demonstrated potential to achieve precise streamflow estimations, this integration holds promise for significantly enhancing the accuracy and effectiveness of flood predictions in Ireland.
Future glacier mass loss in the Tien Shan strongly impacts summer water availability 
Authors: Van Tricht Lander , Zekollari Harry , Huss Matthias , Vanderkelen Inne , van Tiel Marit , Compagno Loris , Huybrechts Philippe , Farinotti Daniel
Published: March 2024

Glaciers in the Tien Shan act as natural reservoirs, storing freshwater in the form of snow and ice and releasing it during dry periods. This water source serves various purposes and is particularly crucial during dry periods, where it serves agriculture, hydropower, industry, and human consumption. Here, we use GloGEMflow to simulate the future evolution of all glaciers in the Tien Shan under CMIP6 SSP climate scenarios. In all climate scenarios, our results reveal an exceptionally pronounced retreat of the glaciers, surpassing the projected glacier loss for most regions of the world. By 2040, we project a loss of 30% of the glacier mass from 2020, which increases to 60% by 2100 under low emission scenarios (SSP1-1.9, SSP1-2.6) up to 90% under moderate to high emission scenarios (SSP3-7.0 and SSP5-8.5). This drastic retreat is driven by the unique climate of the Tien Shan, with most precipitation occurring during spring and early summer. Rising temperatures not only accelerate glacier melt but also reduce snow accumulation. Regardless of the scenario, we project that peak water from the glacier runoff will occur before 2050. By 2100, total annual glacier runoff decreases by 35% compared to the 2015-2020 mean level. The annual glacier runoff peak shifts from summer, when water demand is highest, to spring, presenting challenges for both agricultural and industrial sectors. We also examine and combine the simulated glacial runoff with information on water availability and demand from the ISIMIP framework. This helps to grasp and evaluate how important glacial meltwater is in the Tien Shan region. Our research provides essential insights for creating adaptive policies to handle water resources effectively at both local and regional level.
The diurnal variation of the difference between surface skin temperature and in-situ 2 m air temperature of forests in China
Authors: Xu Ru , Li Yan , Davin Édouard
Published: March 2024

Forests play an important role in regulating land-atmosphere interactions, e.g., the temperature difference (δT) between land surface and air. However, previous studies have primarily focused on analyzing spatial characteristics of δT at global or regional scales, with limited research on its diurnal variations especially using observational data. In this research, we investigated the diurnal changes of δT, using air temperature from large numbers of meteorological stations and surface temperature data from ERA5-Land, for forested areas in China. Results revealed that the diurnal variations in δT (2.18°C) were greater than the observation across seasons (0.8°C), highlighting the importance of considering diurnal scale in understanding δT dynamics. The hourly δT exhibited strong positive correlations with Bowen ratio albeit with a 2-3 hour time lag. Obvious relations also detected between δT and precipitation at daytime, while nighttime relationships remained uncertain when considering the influence of elevation. Simulations from Community Earth System Model (CESM) agree well with the δT-precipitation relations during the daytime, but it overemphasizes the role of elevation in controlling hydrothermal process. We remain hopeful for further enhancement of relevant physical processes in CESM can improve its ability in simulating such interactions.
 Heat transfer modeling in karst environments to study the impact of climate change on the future of decorated caves
Authors: Artigue Clément , Mugler Claude
Published: March 2024

The effects of global warming have already been recorded in many decorated caves located in karst systems, and some prehistoric paintings are already deteriorating. Modeling the microclimate of caves under various climate change scenarios will enable to adapt the conservation strategy for rock art heritage.The first step in this modeling approach is to simulate heat transfer from the surface to the cave through the soil/epikarst/karst system. The rock characteristics in the model are calibrated using sensor data taken at various depths in the soil and in the karst over a few years, and in the cave thanks to long-term monitoring. To provide long-term climate forcing, a transfer function is established between meteorological data measured at a height of 2 meters by Météo France and the temperature measured at the ground surface.Then, this heat transfer model is fed with projections from regional climate downscaling models. This modeling approach, which integrates both current data and climate projections, will be a significant step towards the effective management and conservation of decorated caves, which are not only geological wonders but also hold critical historical and archaeological significance.
Lithology-constrained phosphorus (P) releasement
Authors: Ouyang Shenghui
Published: March 2024

Phosphorus (P), as an indispensable nutrient element in Earth’s biological system, exerts a pivotal role on the burial of organic carbon over million-year time scales. By producing oxygen and consuming carbon dioxide, organic carbon burial may have paved the path for multicellular organisms by reforming the anoxic atmosphere to an oxic one. Organic carbon burial, on long time scales, is ultimately limited by continental P influx released by chemical weathering of P-bearing minerals. As crystalline rocks characterized by prominent discrepancy in P-bearing mineral composition undergoing various dominant weathering forces on surficial environment, P availability for organic carbon burial could be controlled by lithology. To decipher the conundrum of P releasement, a catchment scale case study was conducted, encompassing a series of lithologies following the crystalline rock order. Preliminary data suggests that the P release efficiency is lithology-constrained, indicating an enhanced P releasement in felsic catchment. The result gives us a hint that felsic crust would export more P to the ocean and promote the organic carbon burial, the lithology-constrained P releasement also enlightens us a new perspective to understand the coevolution among crust, atmosphere and life.
Enhancing Agricultural Drought Assessment through the Standardized Irrigation Water Deficit Index
Authors: Wang Shijia , Zhang Yongqiang , Tian Jing
Published: March 2024

Irrigation plays a crucial role in bolstering crop productivity and ameliorating the adverse impacts of drought. Despite its significance, existing studies have not extensively incorporated irrigation into agricultural drought indicators. In this study, we introduce a novel agricultural drought index, the Standardized Irrigation Water Deficit Index (SIWDI) that is quantified using meteorological, phenological, and runoff inputs. To test its robustness, we calculated the irrigation water deficit for three major crops across various time scales in the Yangtze River Basin over the past 23 years. Our analysis reveals that the irrigation water deficit in this region follows a norminvgauss probability distribution. Drawing a mathematical parallel to the Standardized Precipitation Evapotranspiration Index (SPEI), the SIWDI is compared to the SPEI across the Yangtze River Basin. Results underscore the SIWDI’s notable advantage in evaluating drought conditions in agriculturally concentrated regions, alleviating the impact of non-growing season droughts by incorporating crop growth processes and spatial distribution. This innovative index provides monitoring outcomes closely aligned with actual conditions, empowering farmers to respond more effectively to the looming threat of drought.
Characterising dust particles in the RECAP ice core with a multi-method approach to investigate abrupt climate changes
Authors: Stoll Nicolas , Larkman Piers , Clases David , Gonzalez de Vega Raquel , Di Stefano Elena , Delmonte Barbara , Barbante Carlo , Bohleber Pascal
Published: March 2024

Ice cores can supply high-resolution insights into abrupt changes within the climate system. The RECAP ice core from the Renland ice cap, East Greenland, contains a substantial variety in dust particle size throughout its record, reaching back to the Eemian. Changes in dust particle sizes have been shown to reflect smaller ice cap extent during interglacial periods. Thus, local dust sources are only periodically available and can be characterised by large dust particles. For abrupt changes during the last glacial period, it is necessary to disentangle the potential imprint of dust sources and the role of snow accumulation. To better understand dust chemistry and size changes at high resolution, we apply several analytical methods in an ongoing investigation: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) 2D imaging, coulter counter (CC), time-of-flight single particle analysis (SP ICP-TOFMS), and Low- Background Instrumental Neutron Activation Analysis (LB-INAA). We show that high-resolution (10-40 µm) 2D chemical images, focusing on Na, Al, Mg, and Fe, reveal the clustering of particles in the microstructure and a species-dependent preferred localisation. Subsequent measurements, taken where possible on the same samples provide new insoluble particle size and concentration data (CC) and further in-depth elemental characterisation of the dust particles (LB-INAA). Furthermore, first results from SP analyses display their potential for ice core research regarding largely unexplored areas, such as the characterisation of rare earth elements of dust deposited in Greenland. The expertise and insight on high-resolution dust chemistry and size gained during this multi-method approach on ice with partly highly thinned annual layers will eventually be crucial for interpreting the dust signal stored in future Antarctic ice cores reaching back up to 1.5 Myr.
Modelling the northern peatland methane fluxes with a process-based model
Authors: Wu Mousong , Duan Wenzuo , Noumonvi Koffi , Ratcliffe Joshua , Nilsson Mats , Peichl Matthias , Jansson Per-Erik
Published: March 2024

Northern peatlands are significant carbon reservoirs, serving as long-term atmospheric carbon dioxide sinks and sources of methane and nitrogen dioxide. However, methane processes interacting with environmental changes in Northern peatlands, remain unclear. Therefore, the need for better simulation of key processes of methane in peatlands is still urgent. In this study we used the process-based CoupModel combining the long-term in-situ measurements to successfully constrain the energy, water and carbon fluxes modeling in a boreal peatland (CH4, r2=0.62). We noticed that plant transportation is the most dominant pathway for methane emissions from this peatland (57.87% of total CH4 emission), followed by surface diffusion (31.06%) and ebullition (11.07%). The relationship between CH4 fluxes and water table depth is non-linear, and the dominant CH4 emission pathway varies as the water table regime changes. Our study provided new insights into the emission mechanisms of methane in boreal minerotrophic mire and contributed to a better understanding of boreal peatlands for both modelling and observation communities.
Penetrative strain of the Aragüés fault-propagating folds in the Southern Pyrenees revealed by magnetic fabric analysis
Authors: Schöfisch Thorben , Koyi Hemin , Teixell Antonio , Almqvist Bjarne
Published: March 2024

The Aragüés thrust system, in the Southern Pyrenees, is a superb and well-exposed sequence of thrust imbricates to study the deformation and development of fault-propagating folds. The mechanisms of folding and thrusting, including the importance of material contrast during the development of the thrust sequence, are well-studied in this area. However, insights into the distribution and magnitude of penetrative strain remain unknown. Therefore, analysis of anisotropy of magnetic susceptibility (AMS) is used to reveal penetrative deformation within the sedimentary rocks of the Aragüés thrust system. Rock samples from 66 locations are collected across the Aragüés thrust imbricates with a focus on the layered limestone unit. A total of 489 cylinders were retrieved from the oriented hand samples and their AMS signal was measured. Thermomagnetic and magnetic remanence measurements show that the magnetic susceptibility of the samples is dominated by paramagnetic minerals and the magnetic lineation (axis of maximum susceptibility) is mainly parallel to subparallel to bedding. However, the more strongly magnetic samples (kmean: 3-5 x 10-4SI) show a magnetic lineation parallel to the general NNE-SSW shortening direction at the back- and forelimbs of fault-propagation folds. In contrast, the samples with a lower magnetic susceptibility (kmean: 1-3 x 10-4 SI), which are also closer to fold hinges, reveal a magnetic lineation perpendicular to the main shortening direction. We interpret the differences in fabric alignment and magnetic susceptibility to mineral composition and structural evolution. For example, the magnetic lineation parallel to the shortening direction is a consequence of flexural slip and flow along bedding surfaces or incompetent beds of the layered limestone units in the fold limbs. Additionally, a relationship between the magnetic lineation and the development of cleavage and stylolites within the limbs can be identified, but is not consistent. The magnetic lineation at the fold hinge is perpendicular to the main shortening direction and needs further investigation for strain accommodation prior to folding, an effect of buckling and/or development as intersection lineation. These first interpretations of the magnetic fabric provide additional insights into the deformation of the Aragüés thrust system and the development of fault-propagating folds. Moreover, the AMS data adds new information on penetrative strain in this region of the Southern Pyrenees and reveals a general tectonic overprint on grain-scale within sedimentary rocks during deformation.