bluuebunny/crossref_metadata_2025 huggingface dataset:
The hydrometeorological ingredients needed to fill dry Saharan lakes
Authors: Armon Moshe , Rieder Joëlle C. , Dente Elad , Aemisegger Franziska
Published: March 2024

The Sahara desert was potentially much wetter and vegetated in the past during the warm African Humid Period. Although debated, this climatic shift is a possible scenario in a future warmer climate. The most prominent reported evidence for past green periods in the Sahara is the presence of paleo-lakes. Even today, Saharan desert lakes get filled from time to time. However, very little is known about these events due to the lack of available in-situ observations. In addition, the hydrometeorological conditions associated with these events have never been investigated in a dedicated climatological approach. This study proposes to fill this knowledge gap by investigating the meteorology of lake-filling episodes (LFEs) of Sebkha el Melah – a commonly dry lake in the northwestern Sahara. Heavy precipitation events (HPEs) and LFEs are identified using a combination of precipitation observations and lake volume estimates derived from remote sensing satellite imagery. Weather reanalysis data is used together with three-dimensional trajectory calculations to investigate the moisture sources and characteristics of weather systems that lead to HPEs and to assess the conditions necessary for producing LFEs. Results show that hundreds of HPEs occurred between 2000 and 2021, but only 6 LFEs eventuate. The runoff coefficient, i.e. the ratio between the increase in lake water volume during LFEs and precipitation volume during the HPEs that triggered the lake-filling, ranges five orders of magnitude and is much smaller than the figures often cited in the literature regarding this arid area. We find that LFEs are generated most frequently in autumn by the most intense HPEs, for which the key ingredients are (i) the formation of surface extratropical cyclones to the west of the Atlantic Sahara coastline in interplay with upper-level troughs and lows, (ii) moisture convergence from the tropics and the extratropical North Atlantic, (iii) a premoistening of the region upstream of the catchment over the Sahara through a recycling-domino-process, (iv) coupled or sequential lifting processes (e.g., orographic lifting and large-scale forcing), and (v) the stationarity of synoptic systems. Based on the insights gained into Saharan LFEs in the present-day climate, future studies will be able to better assess the mechanisms involved in the greening of the Sahara in the past and also in a warmer future.
Predicting Vp/Vs in North America with a Machine Learning Approach
Authors: Gao Xingxing , Chen Yunfeng , Zhang Zhou , Zhao Wenyu
Published: March 2024

Vp/Vs (or the Poisson's ratio) provides critical information to constrain the bulk crustal composition, stress state, and tectonic evolution. The crustal Vp/Vs beneath the seismic station can be effectively determined by the receiver function H-κ stacking technique. However, complex crustal structures often cause large uncertainty in Vp/Vs measurements. Additionally, Vp/Vs observations are sparse in many regions of the world due to the uneven distribution of seismic stations. While interpolation methods have been widely applied to obtain a continuous distribution of Vp/Vs, these results are not accurate enough and may be strongly biased by the interpolation artifacts. Therefore, reliable mapping of the Vp/Vs variation in the crust remains a major challenge in seismological study.We present a machine learning approach to estimate the Vp/Vs using multiple geophysical datasets. This approach assumes that the Vp/Vs is related to the physical and chemical properties of the crust. Specifically, we implement a Gradient Boosted Regression Tree algorithm (XGBoost) to develop an optimal prediction model for North America. To train the model, we use Vp/Vs as the target values and a compilation of geophysical observations as the predictor variables. These measurements are composed of two types of data: (1) continuous data, such as crustal velocities and gravity anomalies; (2) categorical data (tectonic type). We use 80% of the measurements to train the model, and the remaining 20% to validate the model. We first examine the reliability of this method by predicting Vp/Vs for the United States, where extensive geophysical data are available. Overall, the model achieves a high R2 value of 0.88 in all measured results versus prediction results, indicating robust prediction results at most locations. In the second, a more challenging test, we predict Vp/Vs for Canada where measurements are sparse and uneven, and the amount of data is only 14% of that in the United States. The results show an R2 value of 0.87 between the measured and predicted values. Feature importance analysis indicates that crustal shear wave velocity and tectonic type contribute most significantly to reducing the loss function. The prediction results show that bulk Vp/Vs varies between 1.70 and 1.90 across Canada, with a mean value of 1.82.  The cratonic regions generally exhibit high (>1.80) Vp/Vs with a relatively small (
Geometrical characteristics of buried fault damage zones in the Bohai Basin, eastern China
Authors: Yang Nianfa , Liao Zonghu
Published: March 2024

Characterizing the structures of buried faults is inherently challenging due to a lack of data. However, the seismic survey has demonstrated the potential to reveal geometrical features of faults in the subsurface. In this study, we utilized three-dimensional seismic data and its associated attributes of variance, edge detection, and azimuth for investigating the distribution and structural characteristics of the buried faults in the Bohai Basin, eastern China. The results indicate: (1) there are two 7-km NNE strike-slip carbonate faults (F1, F2, in the Figure) dominated in this region, with fault sub-systems of horst and graben, stepped combinations, and "Y"-shaped; (2) F1 fault is approximately 6.5km with a fault damage zone of about 0.75km in width, and F2 fault is about 7.5km with a fault damage zone of 1.0km in width; (3) The width of fault damage zones increases from south to north, with increasing fault displacement. The maximum fault displacements of F1 and F2 are estimated at 420m and 700m, respectively. We argue that fault displacement leads to the growth of fault damage zones, which potentially controls the evolution of fault architecture. The geometrical information from the subsurface may provide crucial insights for understanding the fault mechanisms and associated earthquakes.Figure 1. (A) Seismic attribute map of edge detection and time structure showing the two carbonate faults (F1, F2); (B) Measured fault displacement and damage zone width along the fault striking direction of F1 and (C) F2.
Phenomenology of organic aerosols light absorption in europe based on in situ surface observations 
Authors: Rovira Jordi , Chen Gang , Yus-Díez Jesús , Močnik Grisa , Pandolfi Marco
Published: March 2024

Both chamber and field experiments have shown that a fraction of organic aerosols (OA), called brown carbon (BrC), can efficiently absorb UV-VIS radiation with important effects on radiation balance. However, the optical properties of BrC, and its climate effects, remain poorly understood because a variety of chemical compositions are involved and their fractions vary with source and formation process. We present a phenomenology of OA light absorption in Europe using Aethalometer (AE) data. AE data were used to calculate the black carbon (BC) and BrC contribution to the total measured absorption in the UV-VIS spectral range (babs,BC(l), babsBrC(l)). Fig. 1 shows the BrC absorption at 370 nm and shows that the BrC absorption was on average higher in urban than in rural sites.Figure 1. Map of BrC absorption in rural and urban sites.At 18 out of 41 sites, simultaneous ACSM (Aerosol Chemical Speciation Monitor) data were available allowing reporting the mass absorption cross-section (MAC), the imaginary refractive index (k), the k Angström Exponent (w) of OA particles and OA sources. We compared the experimental data the with Saleh’s classification, that groups BrC in four optical classes, namely very weakly (VW-BrC), weakly (W-BrC), moderately (M-BrC) and strongly (S-BrC) absorbing BrC. Preliminary results show that both MAC and k of POA sources were higher compared to SOA sources and that BBOA (biomass burning OA) followed by CCOA (coal combustion OA) and HOA (hydrocarbon-like OA) dominated the absorption by BrC.  Data reported indicate a relationship between w and k with higher w associated to less absorbing OA particles.With this work we provide a robust experimental framework that can be used to better constrain the climate effect of OA particles represented in climate models. In our results we found that most of the measured ambient OA particles present from W to M absorption properties. Variations in OA k and w depend on the relative contribution of POA compared to SOA as also reflected by the higher k observed in winter compared to summer. Our results also demonstrate a strong variation of OA optical properties in Europe thus further confirming the complexity of OA absorption properties.This work was supported by the FOCI Project (G.A. 101056783) and ARRS P1-0385. Action Cost COLOSSAL. We thank the COLOSSAL Team for providing OA sources and AE33 data.Chen et al (2022). Env. Int. 166, 107325.Nakao et al (2013). Atm. Env. 68, 273-277.Canagaratna et al (2015). Atmos. Chem. Phys. 15, 253-272.Saleh et al (2020). Curr. Pollution Rep. 6, 90–104.
Intercomparison of MAX-DOAS, FTIR and direct-sun DOAS HCHO retrievals in Xianghe (China)
Authors: Pinardi Gaia , Van Roozendael Michel , Friedrich Martina M. , Langerock Bavo , Vigouroux Corinne , De Smedt Isabelle , Hendrick François , Wang Ting , Wang Pucai , Zhou Minqiang
Published: March 2024

MAX-DOAS, direct-sun DOAS and FTIR measurements are increasingly used as fiducial reference for the validation of HCHO satellite observations. Understanding their strengths and limitations, and assessing their consistency is therefore crucial to produce robust and consolidated validation results. So far, only a few studies have explored the complementarity between MAX-DOAS and FTIR HCHO measurements.In the present study, we take benefit of MAX-DOAS and FTIR instruments being simultaneously operated at the Xianghe station (39.75° N, 116.96° E, approximately 55 km southeast of Beijing) to compare HCHO vertical columns retrieved from both instruments during one full year in a site under the influence of strong VOC emissions from biogenic and anthropogenic origins. In addition to its standard MAX-DOAS geometry, the IAP/BIRA instrument also provides regular direct-sun measurements suitable for comparison with FTIR solar absorption data. HCHO total columns from FTIR and direct-sun DOAS measurements are found to be in excellent agreement demonstrating the high level of consistency of spectroscopic parameters in the UV and infrared spectral ranges.We also investigate results obtained using different MAX-DOAS algorithms (namely bePRO, MMF and MAPA), assessing the agreement reached with respect to reference FTIR and direct-sun data. Various retrieval assumptions (e.g., a-priori profiles, covariance matrices, …) that can be tuned in the FRM4DOAS centralized-facility are tested. The study takes into account both MAXDOAS and FTIR sensitivities and a-priori profile information, and also links the obtained results to reference model data.
Analyzing Grain Size Distribution and Depositional Traits at the Ganga River Bend near Varanasi, India
Authors: Pandey Abhishek , Behera Pradyumna Kumar , Deshpande Vishal
Published: March 2024

Sediment transport within an alluvial channel significantly hinges on the distribution of grain size of the sediment particles. This distribution inherently influences the morphological dynamics of a river system by altering its cross-sectional area and morphological pattern. In this context, statistical matrices like mean, standard deviation, skewness, and kurtosis serve as pivotal indicators, which are used to characterize the grain size and the requisite energy conditions governing the transportation and deposition of the river sediments. The present investigation specifically targets the preliminary assessment of the depositional traits of river sediments. This involves two primary steps: (1) computing the grain size distribution of sand particles, (2) scrutinizing the correlation between grain size and shear stress in the Ganga River at the bend near the city of Varanas, India. To achieve the objectives, samples were meticulously collected from 20 distinct sites with each site containing 3 observation points for sampling. Approximately 2000 grams of samples were collected from each collection site. Subsequently, the soil samples underwent thorough analysis to unveil their statistical parameters linked to the grain size. The finding reveals that a mean grain size ranging approximately from 1.185 to 1.313 is indicative of medium-grained sand composition. Additionally, other important parameters such as: standard deviation, skewness, and kurtosis were obtained within the range of approximately 1.232 to 1.349, ~ 1.232 to 1.349, ~ 0.2 to 0.7, and ~ 0.096 to 1.236, respectively. These values collectively suggest a fine skewed distribution and a platykurtic nature of collected samples.The comprehensive analysis of these parameters and their intricate relationships provide essential insights into the depositional characteristics of the sand. Examination using CM diagram unveiled that at a specific study location, sand deposition predominantly occurs due to suspension and rolling mechanisms. In the CM diagram, 'C' stands for the coarser one percentile value, and 'M' stands for the median value of sediment samples on a log-probability scale.  Moreover, the plot containing bed shear stress against critical shear stress indicates that the deposition of sand particles is prevalent across a significant portion of the study area. Expanding the analysis to indicate specially/spatially? explicit information on sediment transport capacity by employing geospatial tools such as sediment transport index (STI), revealed noteworthy insights. It was deduced that the study area exhibits minimal erosion while showcasing considerable depositional characteristics at various locations.Keywords: Sediment transport, grain size distribution, river morphology, statistical parameters, depositional characteristics, bed shear stress, sediment transport index (STI).
Using observations of surface fracture to address ill-posed ice softness estimation over Pine Island Glacier
Authors: Surawy-Stepney Trystan , Cornford Stephen L. , Hogg Anna E.
Published: March 2024

Many numerical models used to simulate ice streams require the specification of control fields representing the slipperiness of the ice/bed interface and local deviations in the assumed rheological properties of the ice. These poorly constrained components of the system are often found by solving an inverse problem given observations of model state variables - typically ice flow speed. However, these inverse problems are generally ill-posed, resulting in degenerate or error-dominated solutions. The clearest way to improve this is to take advantage of additional prior information regarding the control fields. In this study, we investigate two ways of using maps of surface fracture, derived from Sentinel-1 satellite imagery, to provide prior information to the inverse problem. We first consider a prior that assumes values of effective viscosity significantly different from Glen's flow law are, for the most part, due to observable fractures. Using Pine Island Glacier as a case study, we investigate the solutions and conditioning of this data-informed inverse problem and compare with a typical heuristic regularisation technique. We find that the inclusion of fracture data results in softness fields that resemble fracture features on floating ice. On grounded ice, despite the prevalence of surface crevassing, the softness fields look no more plausible when fracture data is included - suggesting that the presence of surface fracture is not the largest contribution to our uncertainty in the ice rheology. We go on to investigate the use of timeseries of fracture maps to constrain the evolution of the softness field on ice shelves through time, making the assumption that changes to ice rheology occurring on annual timescales are dominated by the fracturing of ice. We show that this method can result in softness fields that visually mimic fracture patterns on floating ice without significantly affecting the quality of the misfit. Such softness fields could be used to constrain evolution equations in isotropic damage models.
Effects of variations in density and effective viscosity of the mantle lithosphere on the distribution of intraplate earthquakes in western and central Europe 
Authors: Bott Judith , Scheck-Wenderoth Magdalena , Kumar Ajay , Cacace Mauro , Noe Sebastian , Faleide Jan Inge
Published: March 2024

The distribution of seismicity in intracontinental western and central Europe is not well understood despite evidence for tectonic forces and glacial isostatic adjustments to partially affect local stress and strain relationships. Our region of interest, located between the northern Alpine Deformation Front and the southwestern margin of Fennoscandia, is well differentiated into seismically quiet domains (e.g., most of Ireland, the southern North Sea and the Paris Basin region) and elongated zones of increased seismicity, such as across mainland Britain and the European Cenozoic Rift System. Some inherited zones of crustal weakness have been suggested to control the observed clustering of active deformation, but the majority of earthquakes in the region cannot unequivocally be mapped to specific crustal discontinuities. To investigate potential effects of upper mantle heterogeneities on the lateral distribution of earthquakes across stable western and central Europe, we have derived thermal field variations from a continent-scale tomographic shear-wave velocity model by using a Gibbs's free energy minimization approach. This way we find that seismicity in this intraplate region is largely limited to areas that exhibit a temperature-controlled low-density layer in the uppermost lithospheric mantle and preferentially clustered above large lateral gradients in upper mantle effective viscosity. We propose that the spatial correlations between mantle low-density bodies and crustal seismicity reflect gravitational instabilities due to buoyancy forces within the mantle lithosphere. In addition, lateral contrasts in temperature and related effective viscosity seem to foster localized deformation within the shallow mantle which imposes differential loading of the overlying crust and earthquake clustering.
Hydrothermal fluid circulation at La Soufrière de Guadeloupe inferred from soil CO2 degassing, thermal flux, and self-potential
Authors: Klein Amelie , Jessop David E. , Donnadieu Franck , Pierre Joanny , Moretti Roberto
Published: March 2024

Quantifying subsurface fluid circulation and the associated heat and gas fluxes provides crucial clues for interpreting the evolution of volcanic unrest in volcanoes with active hydrothermal systems. To better constrain the distribution of current hydrothermal activity on La Soufrière de Guadeloupe, we conducted repeated mapping of diffuse ground CO2 degassing, ground temperature, and self-potential on the dome summit in 2022-2023.We produced maps by interpolating these data, which allowed us to identify areas of fluid recharge into the hydrothermal system and the areas of ascending hydrothermal flows. We were also able to quantify the convective and conductive ground heat fluxes and the area affected by ground heating.Our measurements allowed us, for the first time, to quantify the ground CO2 flux of the dome, estimate the condensation depth of ascending fluids, and relate it to soil permeability. We found diffuse ground CO2 degassing corresponds to about half of the CO2 emissions from the summit fumaroles.Further, we performed continuous self-potential measurements at the summit to analyse the temporal variability of underground fluid fluxes. The combination of these measurements and comparison with high-resolution thermal images taken in recent years allows us to track the spatial and temporal evolution of the shallow hydrothermal fluid circulation. Moreover, we were able to constrain the controlling factors of the observed changes in the surface manifestations in the NE sector of the summit, where a fumarole field has been developing since 2012. Our results imply that monitoring soil degassing and ground temperature gradients can enhance understanding of the sealing state of the dome, which is crucial for assessing potential hazards linked to fluid pressurisation.
Fast and cost efficient analysis of organic molecular tracer compounds in PM for source apportionment studies
Authors: van Drooge Barend L , Jaén Clara , Bedia Carmen
Published: March 2024

A fast and cost-efficient off-line methodology was developed to analyze organic molecular tracer compounds in atmospheric particulate matter collected on quartz filter after high- or low-volume sampling in outdoor ambient air. The method allows the processing of 20 samples/h, and another hour per sample for analyze by GC-MS of more than 30 tracer compounds that are related to air pollution and major emission sources, such as biomass burning, plastics, personal care products, food cooking, soil dust, traffic, and secondary organic aerosol formation processes. These compounds can be used independently for source apportionment analysis, or by analyzed in combination with data from air quality, meteorology, or toxicity.Overall, the developed methodology provides fast acquisition of data; saving time (85%) and consumables (99% solvents) in the analysis respect to conventional methods, which is very relevant for long term air pollution monitoring and large sample sets. Moreover, only a very small fraction of the whole HiVol-filter sample (
Sulfur disproportionation in sub-arc COHS slab fluids drives mantle wedge oxidation
Authors: Maffeis Andrea , Frezzotti Maria Luce , Connolly James Alexander Denis , Castelli Daniele , Ferrando Simona
Published: March 2024

Sulfur degassed at volcanic arcs calls for dissolved S6+ released by subduction-zone fluids, oxidising (in association with C) the sub-arc mantle, but sulfur speciation in subduction fluids at subarc depths remains unclear. We apply electrolytic fluid thermodynamics to model the dissolution behaviour of pyrite in meta-carbonate sediments as a function of P, T and rock redox state up to 4.3 GPa and 730°C. At subarc depth and at the redox conditions of the fayalite-magnetite-quartz oxygen buffer, pyrite dissolution releases oxidised S in fluids by disproportionation into sulfate, bisulfite, and sulfide species. These findings indicate that oxidised, sulfur-rich COHS fluids form within subducting slabs at depths greater than 100 km independent from slab redox state and that sulfur can be more effective than the concomitantly dissolved carbon at oxidising the mantle wedge, especially when carbonates are stable in the mantle. Further open system modelling shows that such fluids are capable of oxidising the sub-arc mantle within a few million years.
Dynamic morphology of clathrate hydrates in porous media
Authors: Xu Zelin , Konno Yoshihiro
Published: March 2024

Natural gas hydrates represent a significant and widely distributed potential energy source globally. Furthermore, hydrates are also considered a possible carbon capture and storage method in the permafrost and deep ocean sea areas. Hydrate morphology is critical in determining the sediments' flow properties and production/storage efficiency. However, the dynamic morphology remains unclear, especially in the microscale. This study was performed by MH21-S and funded by the Ministry of Economy, Trade and Industry, and we used our self-invented micromodels (micron level) for hydrate formation in an air bath of 1 °C for several months. Meanwhile, the state-of-the-art high-resolution microscope was used to detect the dynamic morphology of hydrate formation and dissociation. The result showed that the hydrate growth mechanism could be divided into four stages due to different driving forces: hydrate fingering formation, Ostwald ripening phenomenon, hydrate contraction, and heterogeneous hydrate dissociation processes. In the first stage, the hydrate fingering formation process consistently occurs from the inlet to the outlet area, and the fingering process stops after several days. In the second stage, the Ostwald ripening phenomenon was detected in the microscale for the first time. Smaller hydrate particles first dissolved and then redeposited onto larger hydrate particles, which is a spontaneous process. In the third stage, the surface area of hydrates tends to reduce to reach a more stable phase, resulting in the hydrate contraction. Finally, manual temperature increases induce heterogeneous hydrate dissociation. Our study aims to enhance the understanding of hydrate behaviors in sediments over an extended period.
Long-term agricultural drought monitoring in the Central America Dry Corridor using Vegetation Health Index
Authors: Qiu Junliang , Tarolli Paolo
Published: March 2024

The Central American Dry Corridor (CADC) spans Guatemala, Honduras, El Salvador, Costa Rica, and Nicaragua. Over half of the population in this region is engaged in agricultural activities, with more than 73% of the rural population living in poverty, and 7.1 million people experiencing severe food insecurity. The increasingly frequent droughts exacerbate the challenges faced by agricultural production in this area. Long-term series of agricultural drought mapping can assist agricultural planners in minimizing the impact of drought on production. Based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) spanning from 2001 to 2021, this study will utilize the Vegetation Health Index to map agricultural drought in CADC at monthly, seasonal, and interannual scales. Multi-temporal agricultural drought mapping will reveal the spatiotemporal distribution patterns of agricultural drought in CADC over the past 20 years. Additionally, the study will employ the Mann-Kendall test and Sens' slope estimator to simulate the changing trends of agricultural drought, aiming to identify regions where agricultural drought is worsening.
HSS/CIR Driven Positive Ionospheric Storm at Mid-latitudes: Insights from Millstone Hill Radar and GNSS TEC measurements
Authors: Prasannakumara Pillai Geethakumari Gopika , Aikio Anita , Cai Lei , Vanhamäki Heikki , Virtanen Ilkka , Coster Anthea J. , Marchaudon Aurellie , Blelly Pierre-Louis , Maute Astrid , Ellahouny Nada , Norberg Johannes , Oyama Shin , Grandin Maxime
Published: March 2024

During the declining phase of the solar cycle, geomagnetic storms, primarily driven by high-speed solar wind streams (HSSs) and associated co-rotation interaction regions (CIRs), become prominent. One of the major effects of these storms are the F region electron density perturbations, usually referred to as ionospheric storms. This study focuses on a positive ionospheric storm, characterized by an increase in electron density at mid-latitudes (40°- 60° MLAT) and observed during a moderate yet prolonged HSS/CIR-driven geomagnetic storm with a SYM-H minimum of -65 nT. The storm commenced on 14 March 2016 at 17:20 UT with a strong storm sudden commencement (SSC) and lasted until 21 March. This study uses global navigation satellite system (GNSS) total electron content (TEC) data for a global perspective of electron density variations and Millstone Hill incoherent scatter radar (52° MLAT, MLT=UT-4.6) data to provide local measurements of plasma parameters during the positive storm.In the global analysis of the TEC variations during the storm, a 6-h long strong positive ionospheric storm (TEC increase up to 50 %) at the mid-latitudes was observed in the day and dusk sectors, whereas a depletion in TEC (negative storm) prevailed at the high latitudes. The positive ionospheric storm initiated during the SSC and subsequently intensified with the onset of the main phase. The local electron density data from the Millstone Hill incoherent scatter radar showed an enhancement throughout the local evening MLTs. An uplift in the peak height together with an increased line-of-sight upward ion velocity was observed simultaneously as the traveling ionospheric disturbances (TIDs) reached Millstone Hill from the north-east direction with a phase velocity of 760 m/s. When the plasma is uplifted to greater altitudes in the F region, the recombination rate becomes slower and electron density may be enhanced. The TIDs were plausibly triggered by the Joule heating at high latitudes during the main phase of the geomagnetic storm. After the initial uplift, the peak height of electron density at Millstone Hill descended but electron densities were further enhanced. We will discuss the possible mechanisms including transportation of oxygen-rich air from high to mid latitudes when interpreting the measurements.
Optimization-based driver detection and prediction of seasonal heat extremes
Authors: McAdam Ronan , Peláez Rodríguez César , Hansen Felicitas , Pérez Aracil Jorge , Squintu Antonello , Cavicchia Leone , Zorita Eduardo , Saldez-Sanz Sancho , Scoccimarro Enrico
Published: March 2024

As a consequence of limited reliability of dynamical forecast systems, particularly over Europe, efforts in recent years have turned to exploiting the power of Machine Learning methods to extract information on drivers of extreme temperature from observations and reanalysis. Meanwhile, the diverse impacts of extreme heat have driven development of new indicators which take into account nightime temperatures and humidity. In the H2020 CLimate INTelligence (CLINT) project, a feature selection framework is being developed to find the combination of drivers which provides optimal seasonal forecast skill of European summer heatwave indicators. Here, we present the methodology, its application to a range of heatwave indicators and forecast skill compared to existing dynamical systems. First, a range of (reduced-dimensionality) drivers are defined, including k-means clusters of variables known to impact European summer (e.g. precipitation, sea ice content), and more complex indices like the NAO and weather regimes. Then, these drivers are used to train machine learning based prediction models, of varying complexity, to predict seasonal indicators of heatwave occurrence and intensity. A crucial and novel step in our framework is the use of the Coral Reef Optimisation algorithm, used to select the variables and their corresponding lag times and time periods which provide optimal forecast skill. To maximise training data, both ERA5 reanalysis and a 2000-year paleo-simulation are used; the representation of heatwaves and atmospheric conditions are validated with respect to ERA5. We present comparisons of forecast skill to the dynamical Copernicus Climate Change Service seasonal forecasts systems. The differences in timing, predictability and drivers of daytime and nighttime heatwaves across Europe are highlighted. Lastly, we discuss how the framework can easily be adapted to other extremes and timescales.
Attribution of European Heatwaves to Global Warming Using Spectrally Nudged Storylines
Authors: Leon Dalena , Feser Frauke , Van Garderen Linda
Published: March 2024

This study employs Spectrally Nudged Storylines to attribute heatwaves to anthropogenic global warming. Utilizing high-resolution global (ECHAM) and regional (CCLM) climate models, we aim to discern the influence of anthropogenic climate change on the characteristics of European heatwaves observed in the last decade. Differently to the statistical approach that uses large ensembles/datasets to study large amount of similar events and attribute their occurrence to climate change, the storylines simulate a specific extreme event under different thermodynamical conditions by constraining the large scale dynamics of the system. Thus, directly attributing the change in characteristics of the extreme event to the changes in the thermodynamics, based on the prescribed sea surface temperature and greenhouse gases emission levels. In such way, three storylines are built: a Factual storyline that resembles the climate state as we know it, a Counter Factual storyline that is fixed to the past century representing a world without climate change, and a Plus 2°C storyline that shows how these extreme events change in a world where the global mean temperature is 2°C higher than in pre-industrial times. By the use of these three storylines, we can tell to what extent global warming has provoked heatwaves to be as extreme in a world as we know it, and what can we expect them to be in a warmer future climate.
High-fidelity modeling of landslide dam overtopping failure using SPH-DEM method 
Authors: Su Zhengyang , Wang Shun , Li Dianqing
Published: March 2024

Corresponding author: Shun Wang       E-mail: shun.wang@whu.edu.cnAbstract: Overtopping failure of landslide dams is a complex process that involves strong soil-water coupling and structural failure. Physically based numerical models are needed for breach mechanism as well as failure process and flood prediction. In this study, we establish an SPH-DEM dam-break model that considers the combined effect of seepage and overflow. The key feature of the proposed high-fidelity dam-break model is that both solid and fluid phases are solved simultaneously in two different sets of Lagrangian particles using their own governing equations. In the numerical framework, the water phase is modeled as weakly-compressible Newtonian fluid using the SPH method, and the soil phase is modeled using the DEM method. The interactions between these two phases including drag force, buoyancy and adhesion. The capillary force generated by the meniscus between two soil particles is solved to characterize the saturated and unsaturated processes of soil. The model is validated by three benchmarks including the simulations of seepage through an earth dam, a small-scale dam-break test and the whole progress of dam profile erosion. In a small-scale dam break test, the calculation error of overtopping peak flow is 3.5%. Simulation results predicted by the SPH-DEM dam-break model show good agreements with the finite element method and experimental results. Furthermore, the high-fidelity dam-break model is able to simulate many other soil-water coupling processes, such as reservoir water infiltration, dam slope erosion and collapse, breach development, and dam failure. In the future, the proposed SPH-DEM soil-water coupling framework could be applied to the modeling of geohazard chain triggered by rainfall-induced landslides, blocking river and dam outburst flood.Keywords: landslide dam; overtopping modeling; SPH-DEM; soil-water coupling
A decade of interdisciplinary research on the dynamics of surface processes and landscape change at the Bonneville Salt Flats, Utah, USA
Authors: Bowen Brenda
Published: March 2024

The Bonneville Salt Flats, a landscape characterized by a perennial halite crust and seasonal flooding in western Utah, USA, provides a natural laboratory for advancing understanding of the processes that create and change dynamic saline environments. A decade of interdisciplinary research on the Bonneville Salt Flats has resulted in a new understanding of the salt's history, the functioning of the salt crust ecosystem, and the role that humans play in shaping this landscape. Sedimentological analyses of cores collected across the salt has changed our understanding of the history of the landscape, including evidence of extensive erosion after Pleistocene Lake Bonneville, the surprisingly young age of the oldest salt (~5.4 cal ka BP), and historical and ongoing crust halite dissolution. 16S rRNA gene and metagenomic analysis of the salt crust reveals a complex and robust microbial and archaeal ecosystem within the salt, hosting a wide range of metabolic pathways that actively cycle C, N, and S through the landscape. A long-term environmental observation station established at the center of the salt crust provides a robust new record of landscape processes, weather data, and eddy covariance flux measurements that have helped to constrain the energy and water budgets and highlight the sensitivity of ecosystem-scale surface conductance in the absence of vegetation to atmospheric drying. Arial and spaceborne remote sensing data show the impacts of over a century of human activities on landscape composition and texture, including groundwater extraction for potash mining, intensive surface modification, and land use associated with high-speed vehicle racing on the salt. Brine extraction and attempted mitigation have resulted in salinity and salt crust extent decreases over the last several decades, potentially limiting future landscape uses. The intricate interconnection of the human-natural system has enabled the exploration of variations in mental models influencing decision-making, attribution of blame, and the feasibility of adaptive management in dynamic landscapes serving diverse and conflicting needs. Integration of science with art has expanded the nature of the inquiry and led to new ways of thinking about human connections to a seemingly barren, but truly alive, place. All of these new insights into saline landscapes and the role that human land use and climate change play in altering processes are significant to understand as water delivered to closed basin saline lakes globally is in decline, potentially leading to an expansion of exposed salt-encrusted landscapes.
Spatial variability in C-N-P concentrations during the fragmentation of an intermittent stream in a temperate agricultural catchment
Authors: Casanova Andrés , Dupas Rémi , Jaffrezic Anne , Fovet Ophélie
Published: March 2024

Intermittent rivers and ephemeral streams (IRES) are watercourses that stop flowing at some point during the year. IRES are found in all climates and biomes and their occurrence is predicted to increase with climate change and increasing demand for freshwater. Knowledge of biogeochemical cycles in IRES is mainly based on research in the Mediterranean region. The region of Brittany in western France, characterised by a temperate oceanic climate and intensive agriculture, offers research opportunities to understand C-N-P dynamics in temperate IRES with high nutrient loadings.In this work, we analyse the spatial variability of C-N-P concentrations in the intermittent stream network of the Kervidy-Naizin catchment (7 km²) during the different phases of intermittency. We hypothesise that the spatial variability of C-N-P concentrations increases during the stream fragmentation, as the formation of isolated pools leads to different physico-chemical conditions due to variable solar radiation, temperature, and nutrient availability. To investigate this, we conducted repeated synoptic sampling campaigns at a high spatial resolution (every 100 to 200 m) along the stream network during the spring-summer of 2023. We sampled forty sites and analysed, among others, DOC, DIN and TP and physico-chemical parameters (conductivity, redox potential, temperature and pH) during four field campaigns spanning from stream recession to the rewetting phase after the summer dry period.The results showed an increasing spatial variability of concentrations with stream fragmentation, with spatial coefficients of variation increasing from 27% to 49% for DOC, from 15% to 64% for DIN and from 44% to 74% for TP. During the stream fragmentation, mean DOC concentrations increased from 2.43 to 4.76 mg.L-1, mean DIN concentrations decreased from 15.1 to 8.47 mg.L-1 and mean TP concentrations increased from 0.023 to 0.071 mg.L-1. Spatial patterns of concentrations observed during the flowing phase tended to be disrupted by the stream fragmentation, with isolated pools exhibiting extremely high or low concentration values. We interpret these changes in spatial patterns as a consequence of redox processes and nutrient assimilation.
Early Mesozoic magma-induced mid-crustal flow and high-temperature metamorphism in the Yunkai massif, South China
Authors: Liu Jiashuo , Wang Bo , Cochelin Bryan , Lu Shenghua , Shu Liangshu , Gumiaux Charles , Chen Yan , Raimbourg Hugues , Faure Michel , Ni Xinghua
Published: March 2024

Early Mesozoic evolution and geodynamic processes of the South China Block remain controversial and its rheology is not well understood. The granites and migmatites exposed in the Yunkai massif preserve important records of middle crust mechanical behavior during Indosinian orogeny. They show a significant strength decreasing of the crust during this period, further affecting the rheological behavior of the entire lithosphere in South China. In order to better understand the Early Mesozoic evolution and geodynamic processes of the South China Block, we conducted detailed studies on structural geology, multi-minerals geochronology and P-T estimate on Mesozoic migmatites and granitoids in the Yunkai massif. Three tectonic/metamorphic events are identified. The main one corresponds to the development of a regional NE-SW extension. It constitutes a dome-like structure with amphibolite-facies metamorphism during 243–237 Ma (D1), followed by a rapid cooling to ~300 °C within ~20 Ma. Conventional mineral thermobarometers constrain the D1 metamorphism at 665–692 °C and 6.1–6.2 kbar, indicating an upper amphibolite – granulite facies metamorphism. Based on the phase equilibrium modelling, the grossular component (XGrs=0.12–0.13) in the garnet core, Ti content (XTi=0.15–0.17) of biotite and An value (An=0.84–0.86) of plagioclase in the matrix define a peak P–T condition at 780–810 °C and 6.8–7.0 kbar within the stability field of the observed assemblage, indicating a mid-crustal high-temperature metamorphism. Combined with the field structural relationships, geochemical similarity and inherited zircons, the protoliths of the D1 amphibolite-facies metamorphism are of Silurian (
Unveiling the Kinematics of the 2022 Düzce Earthquake (Mw 5.9) and Its Impact on Regional Tectonics
Authors: Farımaz İlay , Özarpacı Seda , Özdemir Alpay , Ayruk Efe Turan , Astudillo Simon Orrego , Eskiköy Figen , Kıray Havva Neslihan , Zabcı Cengiz , Ergintav Semih , Doğan Uğur
Published: March 2024

In 1999, The North Anatolian Fault (NAF) generated two destructive earthquakes, namely, the Mw 7.4 Izmit earthquake and the Mw 7.1 Düzce earthquake, in the western part of Türkiye and broke more than 180 km of NAF. After 22 years of silence, at the overlapping section of these ruptures,  the region produced two earthquakes: one with a magnitude of 5 and another, a year later, with a magnitude of 5.9. In this study, we aim to examine the role of these recent earthquakes in terms of slip deficit between two ruptures.Our primary focus is on the Düzce earthquake (Mw 5.9) that occurred on 23 November 2022.  Here we use a novel method to reconstruct the coseismic deformation field by  enhancing the signal-to-noise ratio (SNR) from ~3 years of Interferometric Synthetic Aperture Radar (InSAR) Sentinel-1 TOPS data spanning the earthquake. We estimate a coseismic surface displacement of ~2 cm for this event.Furthermore, data from the stations belonging to the Turkish National GNSS Network and data from eight new cGPS sites that we have established in the area have been processed to observe coseismic and postseismic displacement. Postseismic deformations are estimated for one month interval after the earthquake, maximum postseismic deformation is observed on the site named AKSU: 18.6 ± 2.18 mm at east and -1.5 ± 2.28 mm at north direction.A joint inversion model was developed using the aforementioned geodetic and seismological data to estimate the region's final state and was linked to the potential slip deficit of previous major earthquakes in 1999.
Sedimentary and provenance constraints on Carboniferous multiple-stage paleogeographic and tectonic transitions in the East Kunlun-Qaidam
Authors: Qi Yukun , Sun Jiaopeng
Published: March 2024

The Carboniferous tectonic settings of the East Kunlun-Qaidam region, which is located at the present-day northern part of the Tibetan Plateau, are of a great significance for understanding the tectonic evolution of the Paleo-Tethyan Ocean. There is a debate concerning Carboniferous source-to-sink relation and topographic background of the East Kunlun-Qaidam, associated with contrasting views on tectonic processes of the Paleo-Tethyan South Kunlun Ocean during Carboniferous. Some previous studies proposed that the East Kunlun-Qaidam was located in a passive continental margin that tilted southward to the South Kunlun Ocean, the construction of which was related to the continuous oceanic crust spreading. In contrast, other research results indicate that, in response to the subduction of the South Kunlun Ocean lithosphere, the East Kunlun-Qaidam was positioned in the north-dipping back-arc region inboard the East Kunlun Andean-type magmatic arc. To resolve this debate, we investigated the well-exposed Carboniferous sedimentary successions in the Qimantagh, Dulan, and the northern Qaidam in the East Kunlun-Qaidam region. A set of new provenance data were obtained and complied, including paleocurrents, sandstone petrologic composition, and detrital zircon U-Pb chronology. These results have shown that the main peaks of detrital zircon ages are concentrated at ca. 350–250 Ma. The existence of Carboniferous-age detrital zircons, in combination with northward-directed paleocurrents, constrains magmatic activity of the East Kunlun magmatic arc during this period and further implies the subduction of the South Kunlun Ocean lithosphere. Combined with sedimentary evidence such as paleocurrents, the East Kunlun-Qaidam area, as a whole, was a northward-tilting back-arc extension basin during the Carboniferous. The sources mainly came from the south, and the Paleo-Tethys South Kunlun Ocean was in the subduction stage at that period. The obvious spatial differences in the provenance of the Carboniferous reflect complicated source-sink systems that existed in this paleogeographic pattern. Furthermore, percentage of zircons with Precambrian ages significantly varies through time, indicating changing in provenances along with a rapid uplift and exhumation of the basement. The dominance of detrital zircons with ages of ca. 2500–1700 Ma suggests additional sediment dispersal from the basement of East Kunlun and Qaidam, as well as the remnants of the Northern Qaidam Orogenic Belt during the early stage.