bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution inclination records from Sites U1418 and U1419 in the Gulf of Alaska (IODP Expedition 341)
Authors: Velle Julie Heggdal , Walczak Maureen , Reilly Brendan , St-Onge Guillaume , Stoner Joseph , Fallon Stewart , Mix Alan , Belanger Christina , Forwick Matthias
Published: March 2022

International Ocean Drilling Program (IODP) Expedition 341 in the Gulf of Alaska recovered a 112-meter-long sedimentary record from the continental slope at Site U1419. At this site, an exceptionally expanded late Pleistocene sequence (sedimentation rates >100 cm/kyr) combined with a high-resolution radiocarbon chronology (Walczak et al., 2020), provide an opportunity to study Paleomagnetic Secular Variations (PSV) on centennial to millennial timescales over the past ~43,000 years.
Natural and laboratory-induced magnetic remanence were measured on u-channels using the stepwise AF demagnetization procedure. In addition to continuous magnetic susceptibility measurements, hysteresis parameters were obtained on 95 discrete samples, and IRM acquisition curves on 9 discrete samples to obtain additional information on the magnetic mineralogy of the sediment. Due to the influence of lithology, magnetic mineralogy, depositional and post-depositional processes, Site U1419 is not suitable for paleointensity studies. However, with removal of intervals influenced by the environmental signal and/or coring deformation, the high sedimentation rates at this site have helped to preserve a reliable record of inclination. Because of signal to noise issues, inclination as measured after the 20 mT AF demagnetization step provides the most accurate estimate. This is demonstrated by comparing the U1419 inclination to a stack of the shipboard inclination at Site U1418 on a new age model developed from 19 radiocarbon dates on U1418 and 18 magnetic susceptibility-based tie-points to site survey core EW0408-87JC (Praetorius et al., 2015). This independently replicated inclination record verifies centennial to millennial scale variations in the Gulf of Alaska that can now be compared with other northeast Pacific and western North American records to begin deciphering geomagnetic variability and provide a new stratigraphic correlation tool for 15 and 30 cal kyr BP interval in this region.
Assessment of the water balance of a Dinaric karst polje (Planinsko Polje, Slovenia)
Authors: Mayaud Cyril , Kogovšek Blaž , Gabrovšek Franci , Blatnik Matej , Petrič Metka , Ravbar Nataša
Published: March 2022

Poljes are flat closed depressions in karst terrains that are prone to regular flooding. The strongest floods can be several meters high and persist for months, making significant damages in infrastructures. To predict how climate change might affect the occurrence, amplitude and duration of the flood, a better understanding of the flooding dynamics is necessary. Among others, the computation of the water balance is a prerequisite. This method allows assessing when the polje will begin to flood, and gives information on the maximum water level potentially reached. However, this technique encounters the difficulty that a notable part of the inflow entering in poljes is generally ungauged, while it is challenging to quantify the outflow. This is because numerous springs and ponors activate only temporary with the rise of the water level. Moreover, many poljes are generally poorly monitored due to financial reasons. This work aims to see whether these drawbacks can be overcome. To this end, a typical Dinaric polje recharged by a combination of allogenic inflow and a rise of the regional groundwater level is equipped with a network of several measuring stations installed over its surface and in the nearby water-active caves. Combining an accurate Lidar of the surface with recorded water levels and inflow of the main two springs made possible to evaluate the polje flooding dynamics and to characterize its water balance. The method is able to quantify the polje total inflow, while an estimation of the outflow is presented. Then, the main ungauged signals affecting flooding are identified and separated. These values are used as input and calibration data in a numerical model aiming to reproduce the flood dynamics of the polje and its surrounding aquifer. Modelling results validate both water balance and conceptual hydrogeological model, and justify the significance of installing a network of several hydrological stations to monitor the poljes. The method can be applied to other poljes flooding in a complex way of superimposed input and output signals.
Spectral mixture analysis to quantity winter wheat (Triticum aestivum L.) damage caused by hailstorms 
Authors: Furlanetto Jacopo , Longo Matteo , Nicoli Lorenzo , Caceffo Daniele , Persichetti Antonio , Morari Francesco , Dal Ferro Nicola
Published: March 2022

Extreme weather events such as hailstorms represent a threat to crops, causing both economic and food supply losses. Hailstorm intensity is likely to increase in the future pushing more farmers to purchase crop insurances to prevent related economic losses. Currently, insurers mostly rely on field inspectors for crop damage assessments, which can build up limitations such as: (i) partial subjectivity in damage estimations; (ii) inaccuracies in wide-area assessments; (iii) difficulties in accounting for damage spatial variability. Sensors mounted on UAVs (Unmanned Aerial Vehicles) and satellites can fulfill these requirements when coupled with advanced spectral analysis techniques, such as spectral mixture analysis (SMA). In this experiment we applied SMA on UAV hyperspectral images to quantify dead-and-alive organs during the growth of winter wheat (Triticum aestivum L.) and estimate yield loss due to hail damage. The experiment was conducted on a 17-ha field located in the surroundings of Venice (NE Italy). The experiment involved four simulated hail treatments (null, low, medium and high damage) at three plant growing stages (flowering, milky and over-ripe). Treatments were in triplicate for a total of 30 plots, nine sized 60x60 m and 18, 20x20 m. Damages were inflicted using a prototype specifically designed at the University of Padova, consisting of a rotating pole with whips attached and positioned on the back of a tractor. Damage intensity was adjusted with the aid of insurance field inspectors. A UAV M600 Pro (DJI, Shenzhen, China) was equipped with a nanohyperspec (400-1000 nm) camera (Headwall, Boston, USA). Pixel ground resolution was about 0.04 m. UAV surveys were performed after each damage, leaving a period of 7-10 days to the crop for developing a detectable morphologic and physiologic response (e.g., leaf drying, development of necrosis). At each flight, crop samples were collected, and pure spectral signatures of dead and alive stems, leaves and spikes were analyzed using an ASD Fieldspec 4 (Malvern Panalytical Ltd, Malvern, UK) in proximal sensing configuration. SMA algorithm was run on UAV imagery by selecting endmembers composed of intact green plant organs, bare soil and dead spikes, thus allowing for differentiation between damaged and undamaged vegetation. Results showed that increasing yield loss due to hail damage intensity was associated with an increasing number of dead spikes. Proximal-sensed hyperspectral signatures highly differentiated between undamaged and damaged vegetation, especially in the red-edge and chlorophyll absorption (~ 680 nm) regions. In this context, the SMA technique was promising for disentangling dead spikes from alive organs, aiding the area-damaged classification and allowing hyperspectral imagery for a direct estimate of yield losses.
Geodetic imaging of the magma ascent process during the 2021 Cumbre Vieja (La Palma, Canary Islands) eruption
Authors: Przeor Monika , Barrancos José , Castaldo Raffaele , D’Auria Luca , Pepe Antonio , Pepe Susi , Sagiya Takeshi , Solaro Giuseppe , Tizzani Pietro
Published: March 2022

On the 11th of September of 2021, a seismic sequence began on La Palma (Canary Islands), followed by a rapid and significant ground deformation reaching more than 10 cm in the vertical component of the permanent GNSS station ARID (Aridane) operated by the Instituto Volcanológico de Canarias (INVOLCAN). The pre-eruptive episode lasted only nine days and was characterized by an intense deformation in the western part of the island and intense seismicity with the upward migration of hypocenters. After the onset of the eruption, which occurred on the 19th of September of 2021, the deformation increased a few cm more, reaching a maximum on the 22nd of September and subsequently showing a nearly steady deflation trend in the following months.

We obtained a Sentinel-1 DInSAR dataset along both ascending and descending orbits, starting from the 27th of February of 2021 and the 13th of January of 2021, respectively. We selected the study area at the radial distance of 13 km from the eruption point (Latitude: 28.612; Longitude: -17.866) to realize an inverse model of the geometry of the causative sources of the observed ground deformation. While the ascending orbit that passed on the 18th of September indicated mainly a dike intrusion in the shallow depth, the descending orbit from the 20th of September seemed to indicate a deformation caused by at least two sources: the pre-eruptive intrusion and the nearly-vertical eruptive dike. The deeper source spatially coincides with the location of most of the pre-eruptive volcano-tectonic hypocenters.

Finally, based on the preliminary inverse model of the DInSAR dataset, we applied the geodetic imaging of D’Auria et al., (2015) to retrieve the time-varying spatial distribution of volumetric ground deformation sources. The final results show the kinematics of the upward dike propagation and magma ascent.

 

References

D’Auria, L., Pepe, S., Castaldo, R., Giudicepietro, F., Macedonio, G., Ricciolino, P., ... & Zinno, I. (2015). Magma injection beneath the urban area of Naples: a new mechanism for the 2012–2013 volcanic unrest at Campi Flegrei caldera. Scientific reports, 5(1), 1-11.
Evaluation of air stagnation periods using regional climate models over Europe
Authors: Van Schaeybroeck Bert , Van Nieuwenhuyse Joren , Caluwaerts Steven , De Deyn Jonathan , Delcloo Andy , De Troch Rozemien , Hamdi Rafiq , Termonia Piet
Published: March 2022

Due to its high population density and strong industrialisation, Europe is subject to a high degree of air pollution. Reliable information on current and future air quality (AQ) is therefore necessary to develop policies. This information can be based on regional climate models (RCMs) such as used in CORDEX where weather-related uncertainties are estimated using RCM ensemble. Air polution peaks often occur during stagnant atmospheric conditions. We validate EURO-CORDEX RCMs to reproduce stagnant periods characterized by the Horton atmospheric stability index. We first prove the index's relation with both average and extreme air pollutant concentrations. The spatio-temporal features of air stagnant periods over continental Europe are then compared with reanalysis data from ERA5 for 25 RCM models. Overall a satisfactorily agreement is found for the stagnant periods despite a systematically underestimated frequency and stagnation duration. This bias is tracked back to the behavior of a large group of models over orographically complex regions. We show how bias correction can be used to improve the average, the variability and the duration of stagnation periods. 
Impacts of approach bedforms on live-bed scour at rock weirs
Authors: Zhang Wen , Wang Lu , Liu Xingnian , Nie Ruihua
Published: March 2022

Rock weirs are river restoration structures used for grade control, raising upstream water level and restoring river habitat. This paper presents an experimental study of local scour at rocks weirs under live-bed scour condition. The effects of approaching bedform, flow intensity, weir height and void ratio on the scour depth at rock weirs are analyzed and discussed. Under clear-water scour condition, scour occurs only at the downstream of rock weirs; the equilibrium scour depth increases with increased flow intensity and weir height, but decreases with increased void ratio. Under live-bed scour condition, scour occurs both upstream and downstream of rock weirs. The equilibrium upstream scour depth increases first and then decreases with increased flow intensity, decreases with increased weir height, and has a complex relationship with increased void ratio. The equilibrium downstream scour depth decreases first and then increases with flow intensity, increases with increased weir height, and decreases with increased void ratio.
Aircraft-Based Measurements of Biomass Burning Emissions of Malaysia Oil Palm Cultivation
Authors: Krysztofiak Gisele , Xue Chaoyang , Catoire Valéry , Schlager Hans , Eckhardt Sabine , Pfeilsticker Klaus
Published: March 2022

During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) campaign in Nov. and Dec. 2011, polluted air masses were observed in the marine and terrestrial boundary layer (0 – ~2 km) and in the free troposphere (~2 – 12 km) over Borneo/Malaysia. The measurements include CO, CO2, CH4, N2O, NO2, and SO2 as primary pollutants, O3 and HCHO as secondary pollutants, and meteorological parameters. This set of trace gases combined with a Lagrangian particle dispersion model (e.g., FLEXPART) and emission inventories are used to fingerprint different sources (e.g., biomass burning) of local and regional air pollution.

The long-term trend and seasonal variation of biomass burning emissions in this region are first presented and discussed based on the FINN inventory the FLEXPART simulation. Results highlighted the recurrent influence of palm plantation fires near the Miri airport, allowing regular sampling of this fire at different age plumes. The study of the emission ratio compared to CO2 or CO can be used as a measure of combustion efficiency to help define the type of biomass burning. Additionally, the age of plume sampled by the aircraft measurement is determined by FLEXPART and compared with the ΔO3/ΔCO ratio measured in this study and bibliographic database in order to study the ozone production during the transport of biomass burning plumes and implement such database with palm fire data.
Nutrient inputs to sahelian soil by atmospheric dust deposition 
Authors: Marecar Rizewana , Marticorena Beatrice , Bergametti Gilles , Galy-Lacaux Corinne , Losno Rémi , Rajot Jean Louis , Chevaillier Servanne , Feron Anais , Triquet Sylvain , Dias-Alves Maria
Published: March 2022

Dust emission affects soil fertility through nutrient loss in source regions while dust deposition can represent a significant nutrient input for remote ecosystems. If the Sahel is a well-known dust source region, it is also a region where large amounts of dust from the Sahara desert are deposited.                                                         

To quantify the input of nutrients that mineral dust deposition represents for Sahelian soils and to identify the sources responsible for these deposits, a dedicated instrumental setup was deployed during two years in two Sahelian sites of the INDAAF Network : Bambey (Senegal) and Banizoumbou (Niger). The insoluble and the soluble fraction of the atmospheric deposits have been collected separately and analysed. In parallel,  the elemental composition and carbon content of PM10 were determined. A special attention was given to the most important nutrients for the soil fertility in this region (P and N) and on the organic C. Other elements (Fe, Al, K, Ca, ...) were also analysed in order to identify the sources of the deposited particles.                                                

For most of the analysed elements, the elemental compositions of PM10 and dust deposit are consistent and the dust samples composition reveals a seasonal change. During the dry season, the dust composition is similar in Niger and Senegal. During the wet season, mineral dust in Niger exhibits a typical signature of sahelian soils (i.e., enriched in Fe and depleted in Ca) while in Senegal dust composition suggests a regional source enriched in Ca. The analysis of the soluble and insoluble fraction of dust deposition allows to estimate the total annual amount of P, N and C deposited on Sahelian soil.
The 3D Dynamics of Solar Flare Magnetic Reconnection 
Authors: Antiochos Spiro , Dahlin Joel , DeVore Richard
Published: March 2022

Solar eruptive events (SEE) consisting of a massive filament eruption, intense X-class flare, and a fast CME are the most powerful manifestations of explosive energy release in our solar system and the primary drivers of highly destructive space weather at Earth and in interplanetary space. These giant events, which have global scale of solar radii, allow us to study in great detail fundamental space plasma processes such as magnetic reconnection that are important to many cosmic phenomena. Both 2.5D and 3D numerical simulations have shown that the fast energy release is due to reconnection in a large-scale current sheet that forms in the corona, but the 3D dynamics of the reconnection are far from understood.  The greatest challenge to understanding SEEs is their extreme rate of energy release, and for some events, the amazing efficiency at converting magnetic energy into high-energy particle energy. We present new ultra-high-resolution 3D simulations of flare reconnection using the adaptive-mesh-refinement code ARMS. We find that the reconnection dynamics are dominated by 3D magnetic islands, and show that the islands should have clear observational signatures, especially in the so-called flare ribbons that are commonly observed in the chromosphere. We discuss the central role of the islands for understanding the multiscale coupling at the heart of reconnection, the fast energy release rate, and the high efficiency of particle acceleration.

 

This work was supported by the NASA Living With a Star Program and by the NASA DRIVE Center Program.

 
Large-scale variation in seismic anisotropy in the crust and upper mantle beneath Anatolia, Turkey
Authors: Legendre Cedric , Zhao Li , Tseng Tai-Lin
Published: March 2022

Seismic anisotropy beneath Anatolia is complex, with several layers of different anisotropy. 
The average anisotropy is well constrained by shear-wave splitting measurements [Kaviani et al., 2009], suggesting very strong anisotropy (over 1.5s delay time). However, the vertical layering of anisotropy and the contribution of each layer is still an open question. 

We construct anisotropic phase-velocity maps of fundamental-mode Rayleigh waves for the Anatolia region using records from several regional seismic stations, using both earthquake and ambient noise data. 
The collision between the Arabia and Eurasia plates leads to the westward extrusion (and EW anisotropy) of the Anatolian crust, consistent with the seismic anisotropy patterns we found in the crust (1%, EW fast axis) and with previous studies [Mutlu et al., 2011; Legendre et al., 2020].
The Aegean/Anatolian subduction system with slab tearing and breakoff induces a complex flow pattern and anisotropy in the upper mantle [van Hinsbergen et al., 2010; Kaviani et al., 2018].
This is in agreement with the anisotropy we image in the lithosphere (1%, N020E and N100E fast axes) and asthenosphere (1%, N120E). However, the anisotropy in these layers display limited amplitudes.
At deeper depth, remnant Bitlis and Tethyan slabs are lying flat above the 660-km discontinuity [Berk Biryol et al., 2011]. 

The uniform pattern of anisotropy from shear-wave splitting observations can not be explained solely by a single anisotropic layer, and is not consistent with the anisotropy observed in the crustl lithospheric and asthenospheric mantle. This suggests that main contribution of the anisotropy likely originates from a deep source around the mantle transition zone [Legendre et al., 2021].
Heat content and temperature trends in the Mediterranean Sea as derived by Argo float data (2005 – 2020)
Authors: Kubin Elisabeth , Menna Milena , Mauri Elena , Notarstefano Giulio , Poulain Pierre-Marie
Published: March 2022

The Mediterranean Sea is very sensitive to climatic changes due to its semi-enclosed nature and is defined as one of the hotspots in future climate change projections. In this study we use Argo float data to describe spatial variabilities and trends in Ocean Heat Content (OHC) within the entire Mediterranean Sea and for specified sub-basins (e.g. Western and Eastern Mediterranean, Gulf of Lion, South Adriatic). The amount of the OHC, spatially averaged in bins of 1 °x1 ° over the period 2001-2020, increases from west to east in the Mediterranean Sea.
Time series of temperature and OHC from 2005 to 2020, estimated in the upper and intermediate layers (5-700 m) and deeper layer (700-2000 m), reveal significant warming trends and an increase of OHC: the upper 700 m of the Mediterranean Sea show a warming trend of 0.041±0.012 °Cyr-1, corresponding to a yearly increase in OHC of 3.59±1.02 Wm-2. The upper 700 m of the Western Mediterranean Sea are warming fastest with an increase in temperature at a rate of 0.070±0.015 °Cyr-1, corresponding to a yearly increase in OHC of 5.72±1.28 Wm-2.

Mixing and convection events transport and disperse the temperature and OHC changes: significant warming trends are evident in the deeper layers (700-2000 m) of the two deep convection sites in the Mediterranean Sea (Gulf of Lion, South Adriatic), with an exceptionally strong warming trend in the South Adriatic from 2013 to 2020 of  0.058±0.005 °Cyr-1, corresponding to a yearly increase in OHC of 9.43±0.85 Wm-2. 

The warming of different water masses will show its feedback on ocean dynamics and the atmosphere (air-sea fluxes) in the next years, decades or even centuries when these warming waters spread or re-emerge. This will stress ecosystems and accelerate the extinction of several marine species. This study contributes to a better understanding of climate change in the Mediterranean region and should be another wake-up call for policy makers and society.
A modular and scalable workflow for data-driven modelling of shallow landslide susceptibility
Authors: Edrich Ann-Kathrin , Yildiz Anil , Roscher Ribana , Kowalski Julia
Published: March 2022

The spatial impact of a single shallow landslide is small compared to a deep-seated, impactful failure and hence its damage potential localized and limited. Yet, their higher frequency of occurrence and spatio-temporal correlation in response to external triggering events such as strong precipitation, nevertheless result in dramatic risks for population, infrastructure and environment. It is therefore essential to continuously investigate and analyze the spatial hazard that shallow landslides pose. Its visualisation through regularly-updated, dynamic hazard maps can be used by decision and policy makers. Even though a number of data-driven approaches for shallow landslide hazard mapping exist, a generic workflow has not yet been described. Therefore, we introduce a scalable and modular machine learning-based workflow for shallow landslide hazard prediction in this study. The scientific test case for the development of the workflow investigates the rainfall-triggered shallow landslide hazard in Switzerland. A benchmark dataset was compiled based on a historic landslide database as presence data, as well as a pseudo-random choice of absence locations, to train the data-driven model. Features included in this dataset comprise at the current stage 14 parameters from topography, soil type, land cover and hydrology. This work also focuses on the investigation of a suitable approach to choose absence locations and the influence of this choice on the predicted hazard as their influence is not comprehensively studied. We aim at enabling time-dependent and dynamic hazard mapping by incorporating time-dependent precipitation data into the training dataset with static features. Inclusion of temporal trigger factors, i.e. rainfall, enables a regularly-updated landslide hazard map based on the precipitation forecast. Our approach includes the investigation of a suitable precipitation metric for the occurrence of shallow landslides at the absence locations based on the statistical evaluation of the precipitation behavior at the presence locations. In this presentation, we will describe the modular workflow as well as the benchmark dataset and show preliminary results including above mentioned approaches to handle absence locations and time-dependent data.
Effect of phase angle on estimation of Earth reflectance
Authors: Marshak Alexander , Delgado Bonal Alfonso , Knyazikhin Yuri
Published: March 2022

The Deep Space Climate Observatory (DSCOVR) was launched in February 2015 to a Sun-Earth Lagrange-1 (L1) orbit, approximately 1.5 million kilometers from Earth towards the Sun.  It observes the full, sunlit disk of Earth from a unique vantage point with the two instruments: the Earth Polychromatic Imaging Camera (EPIC) and the NIST (National Institute of Standards and Technology) Advanced Radiometer (NISTAR).  The Earth-observing geometry of the EPIC instrument is characterized by a phase angle between 4° and 12°.  After March 2020 the range of phase angles for DSCOVR EPIC and NISTAR has been substantially decreased towards backscattering reaching 1.95 degrees in December 2020.  This provides a unique opportunity to study correlation between Earth reflectance and phase angle.  The dependence of reflection on scattering angle (180o – phase angle) is shown separately for ocean and land areas, for cloudy and clear pixels, while cloudy pixels are also separated to liquid and ice clouds.  A strong increase of reflectance towards back-scattering direction observed for all wavelengths.  The spectral signature of the dependence indicates the strongest increase at near IR (780 nm) where contribution from vegetation dominates.  Surface Bidirectional Reflectance Factor (BRF) acquired by EPIC and Terra MISR sensors over the Amazon basin is used to demonstrate the bi-directional effects of solar zenith and scattering angles on variation of reflected radiation from rainforest.  NISTAR observations also demonstrate an increase with scattering angle for all bands but the strongest one is for B-band radiance (0.2–4 μm).
The role of the SE China passive margin for the formation of Taiwan orogen
Authors: Rodrigues de Vargas Mateus , Mohn Geoffroy , Tugend Julie
Published: March 2022

Taiwan orogen records a singular geological context where different stages of convergence are preserved. From south to north, the Taiwan region records the transition from oceanic and continental subduction of the SE China passive margin to its collision with the Luzon Magmatic Arc.

This study aims to define the thermal, compositional, and structural inheritance of the Chinese SE passive margin onto the processes of continental subduction and early collision. We combined geological and geophysical data (e.g., crustal thickness, seismicity, gravimetry, and magnetic anomaly maps) to propose a structural rift domain map of the SE China margin and its inversion. Open access seismic data is currently being interpreted to identify key tectonostratigraphic sequences, showing the crustal architecture and the tectonic-sedimentary evolution of the region. By building these offshore-onshore transects, we aim to capture the along-strike variations of the trench morphology. Initial results suggest a northward thickening of the accretionary prism in relation to the change from oceanic to continental subduction.

This work is part of an ongoing Ph.D. thesis in which the analysis of the results will not only focus on establishing new first-order tectonic models for the early collision but also on better constraining the control of former rifted margin on the locus of the deformation in this tectonically active zone.
Global Assessment of Compound Risk of High Temperature and Low Streamflow
Authors: An Rihui , Liu Pan , He Xiaogang
Published: March 2022

In river flowing areas, the co-occurrence of high temperature and low streamflow may cause compound hydrologic hot-dry events (CHHDEs). When thermal and hydrological extremes interact, the impact can be worse than when they occur individually. Evidence shows that CHHDEs have severe socio-economic effects, such as increasing pollutant concentration, endangering aquatic species, and reducing power generation. Despite the importance, large-scale risk quantification of CHHDEs remains rarely studied due to the lack of enough simulated data at the global scale.

Therefore, the objectives of this study are threefold: (1) developing the first global hydrologic hot-dry event dataset from 1901 to 2014 (containing four attributes: duration, intensity, severity, and magnitude) based on a state-of-the-art physically-based Tightly Coupled framework for Hydrology of Open water Interactions in River–lake network (TCHOIR) model, which dynamically simulates thermal and hydrological regimes; (2) developing a robust statistical framework to conduct attribution analysis to identify drivers of compound risk (distinguishing high temperature-driven, low streamflow-driven, and dependence-driven); (3) quantifying the impact of river order and hydrologic belt on compound risk to pinpoint CHHDEs hotspots.

CHHDEs have multi-sectoral impacts, including water availability, food security, and energy production. The compound risk analysis provides crucial insights to maintain regional resilience and guide adaptation strategies.
Is longer or warmer melt season a more important driver of ice dynamics.
Authors: de Fleurian Basile , Davy Richard , Langebroek Petra M.
Published: March 2022

In recent years, temperatures over the Greenland ice sheet have been rising, leading to an increase in surface melt. This increase however can not be reduced to a simple number. Throughout the recent years we have seen some extreme melt seasons with melt extending over the whole surface of the ice sheet (2012) or melt seasons of lower amplitudes but with a longer duration (2010). The effect of those variations on the subglacial system and hence on ice dynamic are poorly understood and are still mainly deduced from studies based on mountain glaciers.

Here we apply the Ice-sheet and Sea-level System Model (ISSM) to a synthetic glacier with a geometry similar to a Greenland ice sheet land terminating glacier. The forcing is designed such that it allows to investigate different characteristics of the melt season such as its length or intensity. Subglacial hydrology and ice dynamics are coupled within ISSM allowing to study the response of the system in terms of subglacial water pressure and the final impact on ice dynamics. Of particular interest is the evolution of the distribution of the efficient and inefficient component of the subglacial drainage system which directly impacts the water pressure evolution at the base of the glacier. We note that the initiation of the melt season and the intensity of the melt at this period is a crucial parameter when studying the dynamic response of the glacier to different melt season characteristics.

From those results, we can infer a more precise evolution of the dynamics of land terminating glaciers that are heavily driven by their subglacial drainage system. We also highlight which changes in the melt season pattern would be the most damageable for glacier stability in the future.
Evapotranspiration process under typical herb cover after wildfire
Authors: Liu Kemin , Wang Lunjiang
Published: March 2022

Soil moisture is a key factor limiting vegetation succession in karst ecosystem. Wildfire changes soil physical and chemical properties, which likely affect evapotranspiration of post-wildfire plant recovery. However, merely studies have been performed to elucidate the evapotranspiration processes and the controlling factors. In this experiment, two typical herbaceous plants (Compositae Artemisia and Gramineae Saccharum) in karst areas were selected for pot experiment. The treatment without plant was used as the control. Combustions were laboratorially carried out with different severity (light, moderate, and high) to simulate different intensities of wildfire disturbance. During the experiments, the mass change in each pot was measured to obtain evapotranspiration under different weather conditions. We also collected meteorological data (total radiation, water vapor pressure, air temperature, relative humidity, atmospheric pressure, soil heat flux, soil temperature, etc.), biomass, and soil properties. Our study showed the impact of wildfire on evapotranspiration. We also compared the differences in evapotranspiration of different herb covers. We detected that weather conditions (e.g., duration of continual drought) also had important influences on the evapotranspiration during post-wildfire restoration. The study provides more insight into characteristics of soil water movement after wildfire in karst areas and evaluating the availability of soil moisture after wildfires. 
Prediction of hourly runoff in the Savitri River basin in India: Use of a local approximation approach
Authors: Saji Namitha , Jothiprakash Vinayakam , Sivakumar Bellie
Published: March 2022

In this study, the concept of nonlinear dynamics is used to predict runoff in the Savitri River basin, Maharashtra, India. Hourly runoff from four stations in the basin, namely Kangule, Bhave, Birwadi, and Kokkare, are studied. The nonlinear prediction method with a local approximation approach is employed, and one-hour-ahead runoff predictions are made. The method uses (1) reconstruction of the single-dimensional runoff series in a multi-dimensional phase space; (2) determination of the Euclidean distances between the reconstructed vectors; and (3) prediction using a nearest-neighbor local approximation approach, with consideration of different number of neighbours. For each of the four streamflow stations, data observed during the period 2000–2009 are used for phase space reconstruction, and predictions are made for the year 2010. Three statistical evaluation measures, correlation coefficient (CC), Nash-Sutcliffe efficiency (NSE), and normalized root mean square error (NRMSE), are used to determine the performance of the method. The prediction results for the four stations indicate very good accuracy, with the CC values ranging between 0.980 and 998, the NSE values between 0.961 and 0.995, and the NRMSE values between 0.010 to 0.014. The optimal embedding dimensions (i.e. the dimensions yielding the best predictions) for the Kangule, Bhave, Birwadi, and Kokkare are 9, 13, 6, and 9, respectively. These dimensions suggest that the complexity of the dynamics of hourly runoff in the Savitri River basin is medium-to-high dimensional. The outcomes from the present study are certainly encouraging to further enhance the application of nonlinear dynamic concepts for studying the runoff dynamics in the Savitri River basin.

Keywords: Runoff prediction, Nonlinear dynamics, Chaos, Phase space reconstruction, Local approximation prediction, Savitri River basin
Combined Use Of 3H/3He Apparent Age And On‐Site Helium Analysis To Identify Groundwater Flow Dynamics And Transport Of PCE
Authors: Moeck Christian , Popp Andrea , Brennwald Matthias , Kipfer Rolf , Schirmer Mario
Published: March 2022

3H and tritiogenic 3He concentrations and their interpretation as  3H/3He apparent water ages have been proven to offer crucial insights on groundwater flow and transport processes. However, the analysis is expensive as well as labor‐ and time‐intensive. Recent developments of portable field‐operated gas equilibrium membrane inlet mass spectrometer (GE‐MIMS) systems provide however, a unique opportunity to measure relatively fast dissolved gas concentrations, such as 4He, in groundwater systems with a high resolution at relatively low costs but they are not capable of providing an apparent age. However, 4He accumulation rates are often obtained from 3H/3He ages and it has been shown that non-atmospheric 4He concentrations determined in the laboratory (e.g., by static (noble gas) mass spectrometry) and by field-based (GE-MIMS) methods closely agree. This agreement allowed to quantify the local (radiogenic) 4He accumulation, e.g., we were able to establishing an inter‐relationship between 3H/3He apparent groundwater ages and the non-atmospheric 4He excess (e.g., calibrating the 4He excess in terms of residence time).

We demonstrate that the 4He excess concentrations derived from the GE‐MIMS system serve as adequate proxy for the experimentally demanding laboratory based analyses. The combined use of 3H/3He lab‐ based ages and calibrated  4He ages opens new opportunities for site characterization due to the measurements facilitated by the GE‐MIMS.

For our urban and contaminated study site, we combine groundwater ages with hydrochemical data, water isotopes (δ18O and δ2H), and perchloroethylene (PCE) concentrations (1) to identify spatial inter‐aquifer mixing between artificially infiltrated surface water and groundwater originating from regional flow paths and (2) to explain the spatial differences in PCE contamination. Moreover, for some wells, we identify fault‐induced aquifer connectivity as a preferential flow path for the transport of older groundwater, leading to elevated PCE concentrations.
Climatic imprint in the mechanical properties of ice sheets and its effect on ice flow. Observations from South Pole and EPICA Dome C ice cores
Authors: Martin Carlos , Conway Howard , Koutnik Michelle , Mulvaney Robert , Drews Reinhard , Ershadi M. Reza , Ritz Catherine
Published: March 2022

The climatic conditions over ice sheets at the time of snow deposition imprint distinctive crystallographic properties to the resulting ice. As it gets buried, its macroscopic structure evolves due to vertical compression and horizontal extension but retains traces of the climatic imprint that generate distinctive mechanical, thermal and optical properties. Because climate alternates between glacial periods, that are colder and dustier, and interglacial periods, the ice sheets are composed from layers with alternating mechanical properties. Here we compare ice core dust content, crystal orientation fabrics, borehole temperature and englacial vertical velocity, measured with phase-sensitive radar (ApRES), at South Pole and EPICA Dome C ice cores. Similarly to previous observations, we show that ice deposited during glacial periods develops stronger crystal orientation fabrics. In addition, we show that ice deposited during glacial periods ice is harder to vertically compress and horizontally extend but softer to shear. These variations in mechanical properties are ignored in ice-flow modelling but they could be critical to interpret ice core records. Also, we show that the changes in crystal orientation fabrics due to transitions from interglacial to glacial conditions can be detected by radar. This information can be used to constrain age-depth in future ice-core locations. Finally, we give our perspective on how radar-detected crystal orientation fabric and englacial vertical velocity can be used to investigate the mechanical properties of ice, its rheology, that are the core of every ice flow model.
Treatment of Density Variations in Ice-Flow Models using the Shallow Ice Stream Approximation
Authors: Schelpe Camilla , Gudmundsson Hilmar
Published: March 2022

In most models of large-scale ice-sheet dynamics, horizontal density variations within the ice are largely ignored. Ice-sheets typically comprise a core of meteoric ice, and an overlying layer of lower-density firn of variable thickness. This gives rise to spatial variation in the average density of the ice at each point on the surface, which in principle will modify the glacial dynamics.  A common approach to handle density-variation in the ice is to adjust the thickness of the glacier to the equivalent height of constant-density meteoric ice. We refer to this as the density-to-thickness (D2T) adjustment method. While this approximation preserves the total mass of the ice-column at each spatial coordinate, it introduces additional unwanted terms in the momentum equations, and misses other correction terms. 

In this study, we investigate the D2T adjustment approximation in detail, and consider a number of alternative formulations to handle the density variation in the ice-sheet, based around the modified field equations that we derive in the presence of a variable density field. The alternative formulations include: a static density distribution in which accumulation and compactfication of the firn layer counteracts the advection of the density field so that the time-evolution of the density field can be ignored; or alternatively a time-evolving density distribution with advects with the ice-flow, such that the material derivative of the density field is zero. 

These different formulations are studied in detail within the framework of perturbation analysis. We derive transfer functions for the induced perturbations in both the glacial thickness and velocity, in response to a small perturbation in the density field. We study the frequency profile of the response and its temporal evolution. This helps us gain a deeper understanding of the different formulations, and their impact on glacial dynamics. Within the numerical ice-flow model Úa, we compare the D2T adjustment method to an approach which explicitly includes the density variations, applied to numerical simulations of the Western Antarctic region containing Pine Island and Thwaites Glaciers.
Effects of long-term soil warming on soil organic and inorganic nitrogen cycling in a temperate forest soil as assessed by measurements of natural 15N abundances of soil N pools
Authors: Wanek Wolfgang , Bachmann Michaela , Inselsbacher Erich , Heinzle Jakob , Tian Ye , Kwatcho-Kengdo Steve , Shi Chupei , Borken Werner , Schindlbacher Andreas
Published: March 2022

The capacity of forest soils and trees to sequester C is closely linked to soil nitrogen (N) bioavailability, a major control of microbial and plant growth and functioning. Recent meta-analyses indicated that both, soil organic C and N cycling, intensify with climate/soil warming, though little studies investigated this in long-term (decadal) warming experiments. Changes in N cycling processes have been addressed by measuring total and labile N pools, net and gross N process rates, and changes in extracellular enzyme activities. An alternative approach, integrating over longer time intervals, is to study the natural 15N abundances of different soil and plant N pools. In this study we quantified the natural 15N abundances (d15N values) of coarse and fine litter, fine roots, soil organic N, extractable organic N, microbial biomass N, ammonium and nitrate at the long-term soil warming experimental site in Achenkirch (Tyrol, Austria). This site is one of the few climate manipulation experiments in forests operating for more than 14 years and has provided unique insights into the effects of global warming on forest ecosystem processes. We analyzed ecosystem compartments across three seasons (May, August, October 2019), to investigate the consistency of warming effects on soil N cycle processes. Moreover, we developed an isotope fractionation model to decipher the isotope fractionations of the studied soil N processes and the fractions transformed by them, i.e. for depolymerization, microbial uptake, N mineralization, nitrification and soil N losses. Overall, the consistent increase in fine root δ15N in warmed soils indicated a general opening of the soil N cycle (greater N losses), which was mirrored in increased ammonium d15N values, the latter implying increased fractions of ammonium being oxidized to nitrate. Higher fractions of ammonium being nitrified makes labile N more amenable to N losses, either by leaching of nitrate or by denitrification losses. Since nitrification and denitrification exhibit strong isotope fractionation effects against 15N, the lost N is concomitantly 15N depleted, while residual substrates remaining in the ecosystem become 15N enriched, thereby explaining the 15N enrichment with increasing N cycling and N loss rates in warmed soils. 
Vegetation history of the Eastern Mediterranean–Black Sea–Caspian-Corridor during the last 12500 years
Authors: Cruz-Silva Esmeralda , P. Harrison Sandy , Prentice Colin , Marinova Elena
Published: March 2022

The Eastern Mediterranean-Black Sea Caspian Corridor (EMBSeCBIO) region (33°–49°N, 20°–60°E ), is characterized by strong temperature and precipitation gradients and topographic heterogeneity, resulting in the clear patterns in biome distribution within a relatively limited geographic space. The complexity of this area is a challenge for reconstructing the dynamics of the vegetation throughout the Holocene. In this study, we apply a recently developed method to reconstruct past vegetation changes. The method uses a large dataset of modern pollen samples assigned to biomes based on potential natural vegetation cover data to characterize biomes according to the means and standard deviations of the abundances of each taxon. We use this characterization to calculate an index of dissimilarity between any given pollen sample and each biome, and thus evaluate the probability that a pollen sample belongs to a particular biome. The method also allows us to identify non-analogue vegetation types, when the scores for fossil samples are outside the range of modern scores. The vegetation reconstructions were used to produce point-to-area interpolated maps for 300 years windows. We identify periods of relative ecological stability for mapping, and also periods of rapid environmental change, by analysing high resolution (=<200 years) fossil records using a breakpoint regression approach. For quantifying ecological change, we used ordination analysis to characterize the major gradient of compositional variation in pollen records. Preliminary results indicate the presence of non-analogue vegetation at several sites during the late glacial. They document a rapid expansion of forest and semi-open forest vegetation after the late glacial period in the Black Sea region, the Balkans, the Aegean and the Carpathians, but the persistence of open vegetation types in the mountains of south-eastern Anatolia (Zagros Mountains). The reconstructions indicate the maximum expansion of temperate forest at ~6000 calibrated years BP, where it reaches the south-eastern part of Anatolia and the mountains at the south of the Aegean Peninsula. A replacement of forest vegetation by open or semi-open vegetation types occurred in the Aegean Peninsula from ~7 to 5 ky. The middle to late-Holocene transition from forest vegetation to more open vegetation types was observed across the central Aegean area, Anatolia and the Caucasus.
Increasing footprint of climate warming on flash droughts occurrence in Europe
Authors: Shah Jignesh , Hari Vittal , Rakovec Oldrich , Markonis Yannis , Samaniego Luis , Mishra Vimal , Hanel Martin , Hinz Christoph , Kumar Rohini
Published: March 2022

Flash droughts cause a rapid depletion of soil moisture, which severely affect vegetation growth and agricultural production. Notwithstanding the growing importance of flash droughts under the warming climate, drivers of flash droughts across the Europe are not well understood. Here we estimate the changes in flash droughts characteristics across Europe using the latest release of ERA5 reanalysis for 1950-2019 period. We find a substantial increase in the frequency and spatial extent of flash droughts across Europe (with 76\% of the total area) during the growing season in the recent decades. Increased occurrence of flash drought is largely attributed to frequent occurrence of warmer and drier compound extremes, with a sharp gradient of changes being noticed in Mediterranean and Central European regions. Compound extremes causing the flash drought events across Europe are pre-dominantly driven by the recent climate warming. With unabated greenhouse gas emissions and current pace of climate warming, Europe is likely to face an increased occurrence of flash droughts, requiring prompt response for effective drought adaptation and management strategies.