bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of global change on the protective effect of forests in mountain areas
Authors: Moos Christine , Bottero Alessandra , Stritih Ana , Teich Michaela
Published: February 2023

Forests in mountain regions provide an indispensable ecosystem service by protecting people and infrastructure against natural hazards. Thanks to this Nature-based Solution (NbS), costs of engineered technical protection measures can be reduced or even avoided. Numerous studies have proven the high effectiveness of forests in mitigating the negative impacts of natural hazards. However, open questions remain about the long-term and sustainable provision of protective service by mountain forests, which are expected to be increasingly affected by global change. Natural forest dynamics and disturbances can result in temporary or irreversible loss of protective effects of forests, potentially accelerated by climate change. At the same time, rising temperatures and more frequent and severe droughts will lead to shifts in tree species distribution and forest composition, which may in turn impact their protective effect depending on the type of natural hazard. Furthermore, socio-economic changes, such as land-use change or the expansion of settlements, may affect the protective function of forests. The uncertainties related to these changes pose great challenges for the quantification and sustainable management of this key ecosystem service in mountain areas. To improve our understanding of the various effects global change has on protective forests, we summarized current knowledge based on a quantitative review. We conducted a systematic literature search using predefined terms in different databases. We focused on forests in mountain regions protecting against gravitational hazards (i.e., snow avalanches, landslides, rockfall, torrential floods and debris flow). This resulted in 70 peer-reviewed articles, books or book chapters that we systematically assessed. Most studies focused on anthropogenic forest change (i.e., management, de-/afforestation), followed by natural disturbances, whereas climatically induced changes (e.g., clearly linked to drought or rising temperatures) were less often addressed in the literature. The analyzed studies mainly examined the protection against floods, followed by avalanches, landslides and rockfall. Preliminary results indicate that global change had a predominantly negative impact on the protective effect of forests in mountain areas. In a next step, the types of impacts and potential interacting and compound effects will be analyzed in more detail.
Mapping release and propagation areas of permafrost-related rock slope failures to identify hot spots for hazard assessment; French Alps
Authors: Cathala Maëva , Magnin Florence , Ravanel Ludovic , Luuk Dorren , Zuanon Nicolas , Berger Frédéric , Bourrier Franck , Philip Deline
Published: February 2023

Permafrost-affected rockwalls are increasingly impacted by the effects of climate change and rising air temperature leading to rock slope failures. These events pose a threat for human lives and infrastructure, which underlines the need of better knowledge about their triggering mechanism and propagation.  The aim of this study was to propose a mapping approach of susceptible release areas of rock slope failures and resulting runout distances at a regional scale. This information helps identifying hotspots for subsequent hazard assessment.To do so, we used an inventory of 1389 rock slope failures (volume > 102 m3)recorded in the Mont-Blanc massif from 2007 to 2019 and determined the topographical and permafrost conditions that are most prone to their triggering using a digital terrain model and a permafrost map. These conditions are used in a multi-criteria GIS approach to identify potential unstable slopes at the French Alps scale. Then, the potential release area map is used as input to map the runout of potential events, using a propagation model based on a normalised area dependant energy line principle. The resulting maps of release and propagation areas will be used to point out human assets (mountaineering routes, high mountain infrastructure, tourism areas) and lakes (that can provoke cascading hazards) which could be impacted by rock slope failure hazards.This work is a first step to identify hot spots for a regional hazard assessment where more detailed analyses will be required to evaluate potential risks at a local scale.
Actual evapotranspiration differences between measurements of eddy covariance and lysimeters over grasslands
Authors: Han Qiong , Pütz Thomas , Vereecken Harry , Wang Tiejun , Graf Alexander , Mauder Matthias , Paulus Sinikka , Lee Sung-Ching , El-Madany Tarek , Schneider Katrin , Price Jeremy , Martínez-Villagrasa Daniel , Cuxart Joan , Groh Jannis
Published: February 2023

Accurate measurements of actual evapotranspiration (ETa) play an important role in understanding land surface processes and agricultural management. Two of the most commonly used and established methods for quantifying ETa are eddy covariance (EC) and weighable lysimeters measurements. Previous studies on hourly or daily basis indicated sometimes large differences between the ETa of the two methods (Δly-EC). It is still unclear which factors influence these differences. Here, we examine and compare half-hourly ETa measurements from EC (ETEC) and weighable lysimeters (ETly) at four different sites. The four sites span a climatic gradient from humid conditions at a pre-alpine (Fendt, DE) and a mid-mountain grassland (Rollesbroich, DE) to semi-arid conditions at two sites with a natural grass and shrub (Els Plans, ES) and a tree-grass ecosystem (Majadas de Tiétar, ES). We used a boosted regression tree method to identify environmental drivers of Δly-EC during day and night at the half-hourly resolution.Our results revealed that substantial differences were found with a mean annual Δly-EC of 117 mm, and Δly-EC displayed obvious spatiotemporal variabilities across the sites. Energy balance non-closure of EC was found to be the most important factor contributing to the large annual Δly-EC, especially at Majadas de Tiétar site. With the distinct climatic gradient, Δly-EC was negatively correlated with mean annual wind speed and vapor pressure deficit when they reached a specific level. Monthly ETEC and ETly agreed well with Δly-EC peaking in summer at the sites in Germany, while Δly-EC peaked earlier due to the different climate in Spain. Differences in grass height caused by field management and EC footprint also affected Δly-EC, especially at daily timescales for the pre-alpine and the mid-mountain grassland ecosystem. The relative impacts of different environmental variables to half-hourly ETEC and ETly were almost the same with soil water content (SWC) being more important for nighttime ETly. Meanwhile, we found that the dominant controlling factors of daytime Δly-EC changed with climatic conditions, but nighttime Δly-EC were mainly regulated by SWC. These findings provide a critical evaluation for the roles of climatic and land surface conditions on turbulent flux dynamics from different measurements, which has important implications for ecosystem water and energy balance.
Changes in extreme sea levels along the North Atlantic coasts, over the last century
Authors: Pineau-Guillou Lucia , Lazure Pascal , Wöppelmann Guy , Roustan Jean-Baptiste , Reinert Markus
Published: February 2023

Extreme sea levels are the joint contribution of mean sea level, tide and storm surges. The ClimEx project investigates changes in tide and storm surges over the last century, along the North Atlantic coasts. Concerning the tide, we investigated the long-term changes of the principal tidal component M2, from 1846 to 2018 (Pineau-Guillou et al., 2021). The M2 variations are consistent at all the stations in the North-East Atlantic. The changes started long before the 20th century and are not linear. Regarding the possible causes of the observed changes, the similarity between the North Atlantic Oscillation and M2 variations in the North-East Atlantic suggests a possible influence of the large-scale atmospheric circulation on the tide. A possible underlying mechanism is discussed. Concerning the storm surges, we found a clear shift in the storm surge season at Brest (France), between 1950 and 2000 (Reinert et al., 2021). Extreme storm surge events occurred three weeks earlier (mid-December instead of beginning of January) in the winter 2000 than in the 1950s. Analysis of additional stations in Europe reveals a large-scale process (Roustan et al., 2022). Temporal shifts are positive (later events) in northern Europe, and negative (earlier events) in southern Europe. Such a tendency is similar to the one already reported for European river floods between 1960 and 2010 (Blöschl et al., 2017). References[1] Pineau-Guillou L., Lazure P. and Wöppelmann G. (2021). Large-scale changes of the semidiurnal tide along North Atlantic coasts from 1846 to 2018. Ocean Sci., 17, 17–34. https://doi.org/10.5194/os-17-17-2021[2] Reinert M., Pineau-Guillou L., Raillard N., Chapron B. (2021). Seasonal shift in storm surges at Brest revealed by extreme value analysis. J. Geophys. Res. Oceans, 126, e2021JC017794. https://doi.org/10.1029/2021JC017794[3] Roustan J.-B., Pineau-Guillou L., Chapron B., Raillard N., Reinert M. (2022). Shift of the storm surge season in Europe due to climate variability. Sci. Rep., 12, 8210. https://doi.org/10.1038/s41598-022-12356-5[4] Blöschl G., Hall J., Parajka J., Perdigão R. A. P., Merz B., Arheimer B. et al. (2017). Changing climate shifts timing of European floods. Science, 357(6351), 588–590. https://doi.org/10.1126/science.aan25
The mineralogy of coarse dust aerosols retrieved from its mid−infrared extinction spectra: a laboratory testbed study on dust from worldwide sources
Authors: Di Biagio Claudia , Doussin Jean Francois , Cazaunau Mathieu , Pangui Edouard , Kleiber Paul , Cuesta Juan , Rodenas Mila , Formenti Paola
Published: February 2023

The mineralogy of dust aerosols (i.e. the abundance, relative proportions and state of mixing of the different minerals composing the aerosols, including mainly silicates in the form of clays, quartz, and feldspars, carbonates, sulfates, and iron and titanium oxides) is of key relevance in driving its climatic and environmental effects. Ground–based and airborne observations support the evidence that the dust mineralogy is heterogeneous in the atmosphere, varying from local to global scale due to changes in the mineralogical composition of the emitting source soils and atmospheric processing. However, the capability to get regional and global mapping of airborne dust mineralogy is still missing to date. This gap represents a fundamental limitation for properly developing and validating the representation of dust in Earth System Models and constraining its regional and global climate forcing.Because the different minerals composing the fine and coarse fractions of dust show different spectral absorption signatures, remote sensing spectral and hyperspectral observations can be used to fill this gap by detecting the presence of diverse minerals and reconstructing their relative proportions in the dust aerosols. Based on this idea, recent efforts move into this direction, including the EMIT mission (Earth Surface Mineral Dust Source Investigation) started in 2022.In this study we demonstrate, starting from exemplary data acquired in the CESAM simulation chamber on dust aerosols from global sources (Di Biagio et al., 2017), that the extinction signature of suspended dust aerosols in the 740−1475 cm−1 infrared spectral range (6.8−13.5 µm) can be used to derive dust mineralogy in terms of its infrared−active and coarse−sized minerals: quartz, clays, feldspars and calcite. We show that diverse spectral infrared signatures allow to distinguish dust aerosols from different sources worldwide with variable composition, and that following the changes of the dust extinction spectra with time informs on particles size−selective mineralogy changes during atmospheric transport. Results from the present study confirm the major advance that hyperspectral infrared remote sensing observations, as those by IASI (Infrared Atmospheric Sounding Interferometer) and the IASI−NG (Next Generation) instruments, can provide to dust science. Di Biagio, C., Formenti, P., Balkanski, Y., Caponi, L., Cazaunau, M., Pangui, E., Journet, E., Nowak, S., Caquineau, S., Andreae, M. O., Kandler, K., Saeed, T., Piketh, S., Seibert, D., Williams, E., and Doussin, J.-F.: Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing, Atmos. Chem. Phys., 17, 1901–1929, https://doi.org/10.5194/acp-17-1901-2017, 2017.
Seismic observation at Nirano mud volcanoes, north Italy
Authors: Carfagna Nicolò , Brindisi Albachiara , Paolucci Enrico , Piombo Antonello , Albarello Dario
Published: February 2023

Mud volcanoes are diapirical structures expression of cold overpressured fluidized fine sediments rising from depths of hundreds of meters. When depositional process was fast enough to hamper dehydratation of buried sediments, isolated geological reservoirs are generated marked by elevated fluids pressure also due to gas produced by decompositional processes affecting trapped animals.  Due to the density difference with respect to surrounding rocks and because of the high fluid pressure, those sediments move upwards by following faults or other mechanical discontinuities. In the last decades such Sedimentary Diapirism has increasingly interested scientific community as possible markers of hydrocarbon reservoirs, as responsible for explosive events and their close connection with regional seismotectonic activity. Many studies, in the last years, tried also to find a solid relationship between mud volcanoes and gases emissions, in particular CO2 and CH4, two of the most important greenhouse gases.Among the Italian mud volcanoes, those of Nirano (north Italy), represent a typical example of mud volcanic field, with small and uneventful surface structures. This natural reserve is marked by three main lined up surface structures along the NE-SW direction, close to small pools with less thick clay materials, called “salse”.The structure beneath Nirano mud volcanic field has been investigated by several methodologies, such as geoelectrical, gravimetrical and seismic surveys. In the present work, the study of dynamic behaviour of these structures is focused on aiming at monitoring gas outflow and locating eventual ducts and secondary reservoirs at shallow depth. Specifically, seismic signals possibly associated to gas outflow are investigated by deploying seismic arrays and three directional velocimetric stations.Outcomes of these measurements show that subsonic seismic emissions of these structures present analogies with to those of active volcanoes, possibly due to similar dynamic mechanisms, probably associated to gas bubbling phenomena. Three kinds of seismic activity have been identified: background ambient vibrations, short periodic energy bursts (drumbeats) and high energy paroxysmic phases. All these observed events, compared to that of active volcanoes, present higher frequencies range.The analysis of these signals, in particular of the drumbeats phases, allow the location of the sources. The final locations appear to be local (limited to a few tens of meters away from instruments) and shallow (around 5-10 m from the surface). If these emissions were actually associated to gas bubbling, this kind of outcomes could represent an effective tool for measuring gas outflow and monitoring outgoing mud volcanoes activity.
Speleothem growth and stable carbon isotopes as proxies of last glacial glacier coverage and thermo-dynamical states in the Alps
Authors: Skiba Vanessa , Jouvet Guillaume , Spötl Christoph , Fohlmeister Jens
Published: February 2023

For more than a century, a major focus of Quaternary research has been the investigation of glacier advances and retreats during ice age cycles. The cradle for these studies are the European Alps. In recent years, glacier modelling permitted to produce long-term transient simulations of the European Alps glacier evolution. However, only sparse empirical data, e.g. geological reconstructions of glacier margins in the foreland of the Alps of the Last Glacial Maximum, are available to validate these simulations.Speleothems from the Alps are a widespread palaeoclimate archive. They provide stable carbon isotope records, which can potentially inform about soil and vegetation conditions above a cave site but also about the lack of soil during times of glacier coverage. In addition, speleothem growth in cold, high-elevation cave sites during glacials are a strong indicator of temperatures in the soil-karst-cave system above the freezing point, which is only likely to occur if the cave is covered by a temperate glacier. We here utilise existing speleothem data (growth histories and stable carbon isotopes) from Alpine caves to infer glacier coverage and thermo-dynamical state during the last glacial cycle and to assess the compatibility with modelled reconstructions. We compare data from the last glacial cycle from multiple cave sites located at different elevations (785 to 2319 m a.s.l.) in the Alps with simulations obtained with the Parallel Ice Sheet Model (PISM). We find a general agreement between speleothem-derived soil presence or absence and modelled glacier coverage. However, the speleothem data provide evidence of temperate glacier coverage which is not shown by all of the PISM simulations. Our work demonstrates the value of speleothem-based reconstructions from the Alps as proxies for assessing performance of palaeo-ice flow models.
Ice rise evolution derived from radar investigations at a promontory triple junction, Dronning Maud Land, East Antarctica
Authors: Ershadi M. Reza , Drews Reinhard , Tsibulskaya Veronica , Sun Sainan , Henry Clara , Oraschewski Falk , Koch Inka , Martin Carlos , Tison Jean-Louis , Wauthy Sarah , Bons Paul , Eisen Olaf , Pattyn Frank
Published: February 2023

Promontory ice rises are locally grounded features adjacent to ice shelves that are still connected to the ice sheet. Ice rises are an archive for the atmospheric and ice dynamic history of the respective outflow regions where the presence, absence, or migration of Raymond arches in radar stratigraphy represents a memory of the ice-rise evolution. However, ice rises and their inferred dynamic history are not yet used to constrain large-scale ice flow model spin-ups because matching the arch amplitudes includes many unknown parameters, e.g., those pertaining to ice rheology. In particular, anisotropic ice flow models predict gradients in ice fabric anisotropy on either side of an ice divide. However, this has thus far not been validated with observations.
 
The ground-based phase-sensitive Radio Echo Sounder (pRES) has previously been used to infer ice fabric types for various flow regimes using the co-polarized polarimetric coherence phase as a metric to extract information from the birefringent radar backscatter. Here, we apply this technique using quad-polarimetric radar data along a 5 km transect across a ridge near the triple junction of Hammarryggen Ice Rise at the Princess Ragnhild Coast. A comparison with ice core data collected at the dome shows that the magnitude of ice fabric anisotropy can reliably be reconstructed from the quad-polarimetric data. We use the combined dataset also to infer the spatial variation of ice fabric orientations in the vicinity of the triple junction. The observations are integrated with airborne radar profiles and strain rates based on the shallow ice approximation. We then discuss whether estimated anisotropy from radar polarimetry on ice rises, in general, can be another observational constraint to better ice rises as an archive of ice dynamics.
Quantifying complementary measures of climate-driven sediment dynamics on alluvial fans
Authors: Whittaker Alexander , Brooke Sam , D'Arcy Mitch
Published: February 2023

The effects of environmental change on eroding landscapes and their sedimentary products remains poorly understood. While sediment routing systems at the Earth’s surface can record changes in past environmental boundary conditions, the extent to which landscapes can buffer signals of climate change—of varying magnitude and timescale— is contentious. Mountain catchments and their alluvial fans offer one way to address this question, as they form accessible sediment routing systems in which source and sink are closely coupled and sediment budgets can be closed. Here we consider the extent to which sediment granulometry in stream-flow-dominated alluvial fans records signals of past environmental change. We focus on well-constrained field examples in Death Valley, California, such as the Hanaupah Canyon Fan, which have experienced climate forcing associated with late Pleistocene glacial-interglacial cycles. Using field-derived measures of grain size, we compare three complementary methods that can be used to reconstruct sediment dynamics on alluvial fans. First, we use a self-similarity analysis of sediment calibre to reconstruct sediment mobility on fans over time. Second, we use a downstream-fining model to evaluate the extent to which different depositional units on the fans may record changing sediment fluxes from source catchments. Third, we adopt a palaeohydrological approach to reconstruct unit discharges, bed shear stresses and instantaneous sediment transport capacities for fans, based on field measures of hydraulic geometry and grain size. We evaluate the extent to which these three methods provide consistent results, and we quantify how grain mobility, water and sediment discharge scale with documented variations in the regional climate. Our work demonstrates the potential for using alluvial-fan sedimentology as an archive of information about palaeo-environmental changes, including quantitative measures of past hydroclimate.
Grid-based Ray Theory Amplitude Calculation for Teleseismic Moment Tensor Sources
Authors: Mohr Anne , Friederich Wolfgang
Published: February 2023

Direct numerical modeling of seismic wave propagation at high frequencies remains a computational challenge despite ever-increasing processing capabilities. Ray theory, which is based on a high-frequency solution of the seismic wave equation, provides an alternative to direct numerical modeling for sufficiently smooth velocity models. Here, we present a hybrid 1D-3D approach to model grids of seismic amplitudes of P-phases based on ray theory and dynamic ray tracing. They may serve to construct P-phase synthetic seismograms to be used in high-frequency teleseismic full waveform inversion or the interpretation of scattered and converted waves as done, for example, in receiver function analysis.The modeling domain is split into two parts: 1D bulk earth and a box encompassing a regional study area for which a 3D model is used. 1D dynamic ray tracing and amplitude calculation for a moment tensor source is performed using ray paths calculated with Obspy TauP and the resulting transformation matrices and amplitudes are stored at the box boundaries. In the regional box ray paths from the box boundary to each grid point are calculated using the FM3D software by Rawlinson and Sambridge (2005) and de Kool, Rawlinson and Sambridge (2006). Subsequently, 3D dynamic ray tracing along all calculated rays is initialized from the box boundaries yielding amplitudes at each grid point.The 1D method is tested by comparing amplitude ratios with those calculated using the software Gemini (Friederich and Dalkolmo 1995). The 3D method is tested using a 1D model and comparing amplitudes calculated using the hybrid 1D-3D method with amplitudes calculated using only the 1D method. Additionally, a 3D spherical velocity anomaly is inserted into a 1D background model to test the plausibility of the resulting amplitude grid for this model. The calculated amplitude grid clearly shows the expected focusing effects caused by the anomaly.
Does transient pore-pressure diffusion drive upper-plate aftershocks following megathrust earthquakes?
Authors: Peña Carlos , Heidbach Oliver , Schurr Bernd , Metzger Sabrina , Moreno Marcos , Oncken Onno , Faccenna Claudio
Published: February 2023

Aftershocks are a time-dependent (exponential decay) phenomenon in the aftermath of large earthquakes. In subduction zones, those occurring in the upper plate are of special concern given their potential seismic hazard, as they may produce substantial surface shaking close to highly populated cities. Therefore, the understanding of the mechanisms that drive upper-plate aftershocks is of utmost importance to improving seismic hazard assessment. Transfer of static coseismic stresses has been commonly proposed to explain this; however, they fail to explain their exponential decay over time. This time-dependency is observed in postseismic geodetic measurements, suggesting that the processes that control the postseismic surface deformation also govern or at least are involved in the generation of upper-plate aftershocks. Here, the postseismic surface deformation is dominated by aseismic slip along the fault interface (afterslip), non-linear viscoelastic relaxation in the lower crust and upper mantle, and pore-pressure diffusion in the crust. Despite great research efforts, however, the key driver remains elusive.In this study, we investigate which postseismic mechanism mainly controls the occurrence of aftershocks in the upper plate in subduction zones using the 2014 Mw=8.1 Iquique earthquake, northern Chile, as a study case. We employ a 4D numerical forward model to simulate the transient poroelastic and non-linear viscoelastic relaxation, whose contributions are subtracted from the cumulative Global Navigation Satellite System (GNSS) measurements to then invert for afterslip. Using realistic rock material properties, we first show that this approach explains the surface displacements during the first nine months of postseismic deformation recorded by continuous GNSS. For the same period, we then compute the spatiotemporal Coulomb Failure Stress changes (ΔCFS) that result from individual postseismic processes and compare them with the upper-plate aftershocks using a high-resolution seismicity catalog and focal mechanisms. We show for the first time that the ΔCFS produced by pore-pressure diffusion induced by the mainshock are unambiguously better correlated in space and time with the increase in upper-plate aftershocks than those from afterslip or non-linear viscous relaxation. In addition, pore-pressure diffusion lowers the effective normal stress of the stress tensor more effectively, while its resulting ΔCFS are relatively independent of the fault orientation. The latter would also explain the diversity of faulting styles in the upper plate exhibited by focal mechanisms following the 2014 Iquique earthquake and other subduction zone earthquakes. Our findings provide new insights into the link between pore-pressure diffusion and upper-plate deformation in subduction zones with implications for time-dependent seismic hazard.
Can improved fertilization strategies reduce N2O emissions from winter wheat?
Authors: Skov Nielsen Cecilie , Schrøder Baggesen Nanna , Nair Drishya , Taghizadeh-Toosi Arezoo , Værge Ann Britt
Published: February 2023

Nitrous oxide (N2O) is a strong greenhouse gas, and its atmospheric concentration is rising. Anthropogenic N2O emissions stem mostly from agricultural activities, especially the fertilization of fields. There is an urgent need to reduce the emissions of N2O from agriculture, but so far well documented mitigation options remain scarce.Here we present data from the first year of a series of field trials which aim to test if N2O emissions from Danish winter wheat fields can be reduced by optimizing the fertilization strategy. The field trials were located at three different locations in Denmark with different soil types and climatic conditions. All treatments received 200 kg N/ha except the 0 N treatment (giving the background N2O emissions). The treatments were: (1) ammonium nitrate split in three applications, (2) ammonium nitrate coated with a nitrification inhibitor (3,4-Dimethylpyrazole phosphate, DMPP) split in three applications, (3) ammonium sulfate coated with DMPP split in three applications, (4) liquid fertilizer split in three applications, and (5) ammonium nitrate split in four applications. Nitrous oxide emissions were measured by manual chambers throughout the growing season in 2022 (22 days of measurements).The highest emissions and cumulative emissions were observed in the treatment with liquid fertilizer, and in two of the trials the emissions from the liquid fertilizer treatment were higher than emissions from the treatment with ammonium sulfate coated with DMPP. However, the nitrification inhibitor did not significantly decrease N2O-emissions when compared to the same fertilizer type without inhibitor. In the treatment with ammonium nitrate split in four applications, we did not find significant reductions in N2O emissions. Generally, nitrous oxide emissions from all sites were low (cumulative fluxes of 0.14 – 0.31 kg N2O-N/ha for the growing season) due to a dry spring with a few peaks mainly due to precipitation events. Therefore a preliminary conclusion after the first year of field trials is that in a dry year, with low emissions, the selected fertilization strategies seem to have limited capacity for reducing N2O emissions.
A potential bias using averaged climate projection multi model ensembles when forecasting nitrous oxide emissions from soils under climate change
Authors: Hey Lukas , F. Jungkunst Hermann , H. E. Meurer Katharina
Published: February 2023

Increasing extreme events and drastic shifts in the variability, intensity and frequency of droughts, heavy precipitation and frost are predicted to accompany further climate change. It is most likely that an increasing occurrence of such events will be accompanied by soil feedback of GHG emissions, particularly of nitrous oxide (N2O) known to be an extremely sensitive GHG. The increase in extreme events can lead to an increased occurrence of short-term emission pulses, referred to as ‘hot moments’, which can contribute significantly to the total annual N2O emission balance. To account for this potential feedback to the climate system, biogeochemical models driven by climate projections of multi-model ensembles (CPM) can be used to generate scenarios observing future trends in N2O emission behavior. Most commonly, the CPM average is used as climate input in biogeochemical models. While averaging CPM’s may provide the best overall comparison with real mean climate change, it poses the risk of ‘averaging out’ expected extreme events, thereby biasing soil-atmosphere feedbacks and future N2O emission trends! We follow the hypothesis, that for nitrogen-saturated soils as common in industrialized countries, the annual N2O emissions simulated by the averaged CPM differ from the average annual N2O emissions simulated by the individual CPM’s, as hot moment inducing extreme climate events are averaged as well.For our biogeochemical model simulations, we used weather data from ten selected individual climate-projections based on the multi-model ensemble of the EURO-CORDEX initiative. To focus on the effects of climate and to exclude possible biases, remaining input parameters were unified, i.e., homogeneous soil horizons and a single crop rotation were assumed. In addition, each simulation period was initialised with the same parameters to exclude possible changes in fluxes resulting from soil carbon and nitrogen cycling.First results with CANDY and LDNDC seem to support our hypothesis, showing that annual N2O emissions simulated with the averaged CPM differ clearly from those resulting from the output mean of the individual CPM’s.This emphasises to consider using the averaged output based on individual CPM’s rather than relying solely on averaged CPM’s for predicting future N2O emission trends.
Low frequency eigenmodes of the Earth's fluid core
Authors: Triana Santiago , Rekier Jeremy , Gerick Felix , Dehant Veronique
Published: February 2023

Earth's rotation period varies over many time scales ranging from diurnal to several milennia, in addition to its secular increase due to tidal friction. These variations in the rotation period imply an exchange of angular momentum between the mantle and other fluid layers of the Earth, such as the atmosphere, oceans, and the fluid outer core. In order to disentangle the role of the outer core, a good understanding of its low frequency eigenmodes is necessary. We attempt to build a relatively simple model of the Earth's fluid core including gravitational, viscous, and magnetic coupling with the mantle and the solid inner core. Our goal is to assess whether observed length-of-day variations can be partially attributed to outer core eigenmodes, and if that is the case, to explore the implications related to the outer core-mantle and outer-inner core coupling mechanisms.
Fast forward approximation and multi-task inversion of gravity anomaly based on UNet3+
Authors: Lv Mengzhi , Zhang Yujie
Published: February 2023

Gravity inversion is a process that obtains the spatial structure and physical properties of underground anomalies using surface collected gravity anomaly data. The principle of gravity inversion based on deep learning (DL) is to learn the mapping between gravity anomaly data and geological models by training a neural network with geological models as labels. However, using DL inversion requires generating a large amount of training data for each geological target, resulting in a significant consumption of time and storage space. We propose to use a neural network to approximate the expensive forward computation with a fast evaluation alternative. After training, the network can reproduce gravity anomalies at any observation point. To evaluate the accuracy of the forward model, we use the gravity anomalies predicted by the forward network for inversion network training. In addition, to mitigate the problem of poor generalization of existing DL inversions, we propose to use multi-task learning (MTL). Learning multiple related tasks simultaneously improves the generalization ability of the model, thus improving the performance of the main task. In this paper, a multi-task UNet3+ network is proposed to realize anomaly bodies localization and density reconstruction simultaneously. The test results on the synthetic dataset show that the gravity anomalies predicted by the forward network can be successfully inverted, and the multi-task approach can predict the subsurface geology more accurately than the single-task UNet3+. To further illustrate the effectiveness of the algorithm, we apply the method to the inversion of the San Nicolas deposit in central Mexico, and the inversion results are consistent with known geological information.
Generation and Expansion of the Impact Plasma Cloud after Dust Impacts on Solar Orbiter
Authors: Vaverka Jakub , Pavlů Jiří , Šafránková Jana , Němeček Zdeněk , Ijaz Samia , Kočiščák Samuel , Píša David , Souček Jan , Zaslavsky Arnaud , Owen Christopher J. , Verscharen Daniel
Published: February 2023

Dust grain impacting the spacecraft body can be either partly or totally evaporated and ionized as well as a small part of spacecraft material. A cloud of charged particles (impact cloud) generated by such impact can consequently influence the spacecraft potential and/or measurements of on-board scientific instruments. Electric field antennas are sensitive to these disturbances and typically register signals generated by dust impacts as short transient pulses. This method is commonly used for the detection of dust grains even without dedicated dust detectors. Expanding impact clouds can also influence measurements of other scientific instruments such as magnetometers and particle detectors.The presented study is focused on the understanding of the generation and consequent expansion of impact cloud after dust impacts on Solar Orbiter. The Time Domain Sampler (TDS), a subsystem of the Radio and Plasma Wave (RPW) instrument, is used for the detection of individual dust impacts. Three channels of short electric field waveforms (typically 62.5 ms) provide us with information about the influence of expanding particles on three electric antennas. We have analyzed more than 2000 waveform snapshots with dust impacts in various operation modes (monopole and dipole antenna configurations) of RPW/TDS. Additional information about particles generated by dust impact is provided by the Electron Analyser System (EAS), one of the Solar Wind Analyser (SWA) suite instrument.
Filling Temporal Gaps within and between GRACE and GRACE-FO Terrestrial Water Storage Changes over Indian Sub-Continent using Deep Learning.
Authors: Moudgil Pragay Shourya , Rao G Srinivasa
Published: February 2023

Terrestrial water storage (TWS) anomalies from Gravity Recovery and Climate Experiment (GRACE) and its follow on GRACE-FO satellite missions provide a unique opportunity to measure the impact of different climate extremes and human intervention on water use at regional and continental scales. However, temporal gaps within GRACE and GRACE-FO mission (GRACE: 20 months, between GRACE and GRACE-FO: 11 months and GRACE-FO: 2 months) pose difficulties in analyzing spatiotemporal variations in TWS. In this study, Convolutional Long Short-Term Memory Neural Networks (CNN-LSTM) model was developed to fill these gaps and reconstruct the TWS for the Indian subcontinent (April 2002-July 2022). Various meteorological and climatic variables, such as precipitation, temperature, run-off, evapotranspiration, and vegetation, have been integrated to predict GRACE TWS. The performance of the models was evaluated with the help of Pearson’s correlation coefficient (PR), Nash-Sutcliffe efficiency (NSE), and Normalised Root Mean Square Error (NRMSE). Results indicate that the CNN-LSTM model yielded a mean PR of 0.94 and 0.89, NSE of 0.87 and 0.8, and NRMSE of 0.075 and 0.101 on training and testing, respectively. Overall, the CNN-LSTM achieved good performance except in the northwestern region of India, which showed a relatively poor performance might be due to high anthropogenic activity and arid climatic conditions. Further reconstructed time series were used to study the Spatiotemporal variations of TWS over the Indian Subcontinent.Keywords: GRACE; Deep Learning; TWSA; Indian subcontinent
Runoff controls on stream network branching
Authors: Seybold Hansjoerg , Li Minhui , Kirchner James
Published: February 2023

The geometry of stream networks varies systematically with climate [1,2]. In humid regions diffusive processes seem to dominate the branching geometry of stream networks, resulting in wider branching angles close to 72 degrees, which is the theoretical angle for growth in a diffusive field [1,3]. In arid climates, on the other hand, channel networks display much narrower angles [1,2].Here we show that the narrower angles in arid regions can be related to the higher frequency of extreme runoff events, which are more common in arid landscapes than in humid ones [4]. Erosion due to overland flow leads to incision which is more focused in the direction of regional topographic gradients and thus resulting in narrower branching angles as the influence of diffusive processes becomes weaker and weaker. Our analysis is based on flow frequency distributions derived from USGS gauging stations across the United States [4] and branching angles obtained from the USGS medium resolution National Hydrographic Dataset [1]. Our measurements show, that the tails of the flow frequency distributions become systematically heavier with aridity in the same way as branching angles become narrower.This result suggests that the relative impact of diffusive network growth systematically decreases with increasing aridity as the landscape's Peclet number changes across a landscape with varying climate. References:[1] H. J. Seybold et al., Climate's watermark in the geometry of stream networks, GRL (2017)[2]  A. Getraer & A. C. Maloof, Climate-Driven Variability in Runoff Erosion Encoded in Stream Network Geometry, GRL (2021)[3] O. Devauchelle et al., Ramification of stream networks, PNAS (2012)[4] M. W. Rossi et al., Precipitation and evapotranspiration controls on daily runoff variability in the contiguous United States and Puerto Rico, JGR (2016) 
Hydrogeochemical impacts of pumped hydropower storage in open-pit lignite mines
Authors: Schnepper Tobias , Kühn Michael , Kempka Thomas
Published: February 2023

Large-scale energy storage is becoming more important due to the increase in electricity generation from renewable sources and the related grid balancing requirements. In this context, Pumped Hydropower Storage (PHS) in former open-pit lignite mines can substantially contribute to energy supply safety. Assuming an average storage capacity of 150 MW per open-pit mine, PHS could generate a power output of at least 6 GW in European mines which will be abandoned in the next two decades. Experiences from mine-flooding across Europe demonstrate that hydrogeochemical processes can become a critical environmental and economic factor for the realisation of such projects. Depending on sulphide and oxygen availability, buffer capacities and dilution processes, mine waters with increased acidity as well as elevated sulphate and metal concentrations can pose a threat to adjacent ecosystems, groundwater resources and the installed PHS infrastructure.We present a generic parameter study by means of numerical simulations to predict changes in the mine water composition as a result of PHS operation in different hydrogeochemical settings. Published datasets on hydrogeochemical, hydrogeological and technical conditions with a focus on German mines were applied for model parametrisation. A reaction path model was developed that accounts for initial mine flooding, inflows and outflows as well as pumping and release cycles between the two reservoirs. The simulations were run until chemical equilibrium was achieved in the lower reservoir.Simulation results indicate that the long-term availability of buffer capacities in the reservoir water and adjacent sediments determine the development of acidic or neutral mine waters. Sulphate concentrations are mainly influenced by dilution processes, emphasizing the relevance of considering additional in- and outflows. Depending on these fluxes as well as oxygen availability and initial sulphide concentration in the mine sediments, the time to reach chemical equilibrium in the lower reservoir varies significantly from several weeks to months. Furthermore, the dissolution of sulphides and carbonates as well as the precipitation of iron (oxy)hydroxides may affect the properties of the open-pit slope sediments. Their long-term stability may be altered, based on their initial mineral concentration and hydraulic conductivity.In summary, potential impacts on water quality in the PHS reservoirs have been investigated under different hydrogeochemical settings. We conclude that, under specific boundary conditions such as the availability of sufficient buffer capacities and dilution by controlled inflows and outflows, PHS operation in abandoned open-pit coal mines can be realised from an environmental perspective.
Simulating marine nitrogen and iron biogeochemical feedbacks and drivers of ocean productivity and deoxygenation in the Anthropocene
Authors: Somes Christopher , Landolfi Angela , Oschlies Andreas
Published: February 2023

Nitrogen and iron are the main limiting nutrients on phytoplankton growth in the ocean. Their nutrient budgets contain processes that are sensitive to environmental change including low oxygen thresholds. In this study, we use a global ocean biogeochemical model coupled within an Earth system model of intermediate complexity to quantify anthropogenic controls on marine nitrogen and iron cycling under warming and atmospheric nutrient pollutant scenarios. We performed model sensitivity simulations to isolate the individual and combined effects of marine nitrogen and iron cycle feedbacks on ocean productivity and deoxygenation. Our model simulations demonstrate strong stabilizing feedbacks when considering either the marine nitrogen and iron cycle individually. However, when the full set of marine nitrogen-iron feedbacks were included, enhanced nitrogen and iron source inputs outweighed sinks under anthropogenic scenarios. These marine nitrogen-iron biogeochemical feedbacks were responsible for driving a projected 4% increase in productivity and 27% expansion in the volume of oxygen deficient zones by year 2100 in the model, whereas a sensitivity simulation without these feedbacks resulted in a 9% decrease in productivity and 16% reduction in the volume of ODZs. Our model study suggests that positive amplifying feedbacks between the marine nitrogen and iron cycles may already be playing an important role increasing ocean productivity and deoxygenation in the Anthropocene.
Adaptive land management to fight land degradation in Mediterranean agroforestry pastoral areas
Authors: Ishaq Hafiz Khuzama , Grilli Eleonora , Malrieu Iseult , Mastrocicco Micol , D’Ascoli Rosaria , Busico Gianluigi , Rutigliano Flora Angela , Marzaioli Rossana , Coppola Elio , Pulido Fernando , Silva Filipe , Bijl Marco , Madeira Joao , Castaldi Simona
Published: February 2023

Healthy soils are fundamental to support ecosystem functions and productivity and represent an adaptive fundamental condition to face climatic change extremes, like in Southern Mediterranean often characterized by land degradation, soil erosion and desertification risk. As part of the project LIFE16 CCA/IT/000011 Desert Adapt, since 2018 we have been working on agroforestry pastoral areas of Portugal to test more adaptive strategies, including changes in grazing cycles which can allow a better regeneration of the grass cover, higher protection of the soil and improvement of the overall soil functions that support pasture productivity. We present the first data set of soil monitoring from spring 2022 and we combine the evaluation of soil amelioration with a full integrated management view of the improved grazed system to underline the multiple beneficial environmental effects of soil protection within and beyond the soil system.
Variations of the ionospheric total electron content over Portugal Continental and Azores
Authors: Pereira Joana , Morozova Anna , Barata Teresa , Barlyaeva Tatiana
Published: February 2023

The total electron content (TEC) variations over the Portuguese Mainland (Lisbon) and the Islands (Azores) are studied during the declining phase of the 24th solar cycle (December 2014 – November 2018). The two main goals of this study are (1) to understand main features of the TEC variability during quiet and disturbed days for the Portuguese territory and (2) to find similarities and differences in such features between the Continental (Iberian Peninsula area) and Oceanic (Azores area) parts.Also, two methods to analyse TEC variations are used: TEC variations relative to a “quiet day” variation and the principal component analysis (PCA). Comparison of these methods and suggestions for the use of PCA to study TEC are made.