bluuebunny/crossref_metadata_2025 huggingface dataset:
The Evolution of Turbulence in the Inner Heliosphere: Insights from the February 2022 Radial Alignment between Parker Solar Probe and Solar Orbiter
Authors: Stawarz Julia E. , Woodham Lloyd , Laker Ronan , Matteini Lorenzo , Horbury Timothy , Woolley Thomas , Bale Stuart , Perrone Denise , Toledo-Redondo Sergio , Sorriso-Valvo Luca , D’Amicis Raffaella , Rivera Yeimy , Paulson Kristoff
Published: February 2023

The solar wind is filled with complex turbulent dynamics that transfer energy from large length scales to progressively smaller scales. This transfer of energy generates a multitude of thin structures, such as current sheets, in the plasma with a preference for forming particularly strong gradients – a property know as intermittency – that are thought to play a role in turbulent dissipation. One of the important problems in the study of solar wind turbulence is understanding how and to what extent the nature of the turbulent dynamics vary as the solar wind expands from the Sun. However, disentangling the dynamical evolution of the turbulence from variations in the properties of different solar wind streams and temporal variations in the source region of a given stream has traditionally been challenging in the solar wind. We make use of a fortuitous alignment between NASA’s Parker Solar Probe and ESA’s Solar Orbiter spacecraft, which occurred at the end of February 2022, to examine how the turbulent fluctuations in the solar wind evolve with radial distance. During this radial alignment the two spacecraft observed the same stream of solar wind plasma, and potentially nearly the same parcel of plasma, at two different radial distances allowing us to separate the evolution with radial distance from the other sources of variability. We explore both the statistical properties of the fluctuations as well as the nature of the most intermittent structures observed by the spacecraft at different length scales in the plasma. The results demonstrate that, while the intermittent fluctuations in the components perpendicular to the radial direction are statistically similar at different radial distances, the intermittency properties in the radial direction can significantly change with distance. Comparisons of the observational results with expanding box simulations of turbulence suggest that some of the key features observed are consistent with the dynamical evolution of spherically polarised Alfvénic fluctuations under the influence of expansion. 
What are the role of mesoscale eddies in air-sea interaction and in sea surface salinity variability in the Tropical Atlantic Ocean?
Authors: Aguedjou Habib Micaël , Chaigneau Alexis , Dadou Isabelle , Morel Yves , Da-Allada Casimir , Baloẗcha Ezinvi
Published: February 2023

The ocean kinetic energy is dominated by mesoscale eddies, which are quasi-circular structures with typical horizontal scales of 10 to 100 km and vertical extension of hundreds meters. the mesoscale eddies play significant roles in the transport and redistribution of water masses with their physical and biogeochemical properties throughout ocean. In this study, we used 8 years of satellite altimetry data, combined with sea surface temperature (SST), sea surface salinity (SSS), latent and sensible heat fluxes (LHF and SHF) and precipitation data, to investigate how mesoscale eddies impact on air-sea heat and fresh water exchange in the tropical Atlantic ocean (TAO). We show that an important fraction of eddies exhibit inverse SST anomalies, and that eddy-induced LHF and SHF anomalies are quasi-linearly proportional to SST anomalies. Moreover, eddies contribute to ~10 – 25 % of the total heat flux variability. However, no direct link has been observed between heat flux and precipitation anomalies over eddies in the TAO. Nevertheless, beneath the Intertropical Convergence Zone (ITCZ), significant correlation were found, suggesting that eddies may modulate both heat and freshwater fluxes in this region. Relative to SSS anomalies within eddies, their variability represents up to 30% of the total variability. In addition, beneath the ITCZ, freshwater fluxes would play an important role in their variability. However, oceanic processes such as horizontal and vertical advection and mixing are suspected to play a key role in the SSS variability at mesoscale beneath the ITCZ. To better understand the role of such processes, numerical modeling studies are needed for future investigations.
SMILE: a mission to image the solar wind-magnetosphere interaction
Authors: Escoubet C.-Philippe , Branduardi-Raymont Graziella , Wang Chi ,   SMILE team
Published: February 2023

The interaction between the solar wind and the Earth's magnetosphere, and the geospace dynamics that result, is one of the key questions in space plasma physics. In situ instruments on a fleet of solar wind and magnetospheric constellation missions now provide the most detailed observations of Sun-Earth connections over multiple scales, from the smallest of a few kilometres up to the largest of a few 10s of Earth radii. However, we are still unable to quantify the global effects of the drivers of such connections, including the conditions that prevail throughout geospace. This information is the key missing link for developing a complete understanding of how the Sun gives rise to and controls Earth's plasma environment and space weather. This is where SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) comes in.SMILE is a novel self-standing mission dedicated to observing the solar wind - magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, soft X-ray imaging of the magnetosheath, magnetopause and polar cusps, and UV imaging of the northern hemisphere auroral oval. Remote sensing of the magnetosheath and cusps with soft X-ray imaging is made possible thanks to solar wind charge exchange (SWCX) X-ray emissions known to occur in the vicinity of the Earth's magnetosphere. SMILE is a joint mission between ESA and the Chinese Academy of Sciences (CAS) due for launch at the beginning of 2025. SMILE science objectives as well as the latest scientific and technical developments jointly undertaken by ESA and CAS and the international instrument teams will be presented.
Conditions for accretion and subduction initiation inside Venus Artemis Coronae
Authors: Davaille Anne
Published: February 2023

According to laboratory experiments and geomorphological observations, it is likely that the very large Artemis coronae is an exemple of plume-induced subduction. As an hot mantle plume  breaks the denser lithosphere and flows above it, it forces it to sink. So the subduction trenches are localized along the rim of the plume and strong roll-back is observed. Predicted roll-back velocities are between 1 and 10 cm/yr for Artemis case. Subduction always occurs along partial circles, which is due to the brittle character of the upper part of the lithosphere. As roll-back subduction proceeds, the coronae expands and an accreting ridge system develops inside the coronae. Laboratory experiments show that the ridge shape is governed primarily by the axial failure parameter  \Pi_F , which depends on the spreading velocity, the mechanical strength of the lithospheric material and the axial elastic lithosphere thickness. Experiments with the largest  \Pi_F  present quite unstable ridge axis with a large lateral sinuosity, transform faults, numerous microplates, and axis jumps. Some of the latter can even cause subduction onset along the abandoned section of the ridge axis. Due to Venus hot surface temperature, this large  \Pi_F regime is the most likely inside Artemis. Magellan data indeed shows a large feature, Britomartis Chasma, that has already  been proposed to be an accretion ridge.  It displays a large sinuosity, comparable to what is predicted by the laboratory experiments. The topography data resolution is not good enough to see transform faults, though. But their presence would explained some of the largest axis offsets. Moreover, the center of Britomartis presents a deep trough, next to a very tall hill. This may be due to core complex formation, but also to the initiation of subduction following an axis jump. Only high-resolution data, such as provided by VERITAS mission, will be able to discriminate between the two options. 
Intense pedogenic development and large carbon contents in soils above the Pleistocene trimline (NW Italian Alps)
Authors: D'Amico Michele , Pintaldi Emanuele , Melacarne Dario , Benech Andrea , Colombo Nicola , Freppaz Michele
Published: February 2023

Most of the Alpine range was influenced by glacier movement or by intense erosive processes during Pleistocene glacial periods, which erased previously existing soils and landforms. Thus, most of the soils in the Alps began developing since at least the end of the Last Glacial Maximum (LGM). However, some surfaces located above the trimline (the upper limit reached by valley and cirque glaciers) still retain “old” morphologies and can be considered paleosurfaces, often covered by fossil or active periglacial features.After having found very well developed Umbrisols hidden inside blockfields at 3030 m a.s.l. on the Stolenberg Plateau, Monte Rosa Massif – NW Italian Alps (Pintaldi et al. 2021a, 2021b, 2022), we explored other relict cryogenic landforms located above the Pleistocene trimline, such as blockfields and blockstreams, observing the soils hidden below the surface stone layers.In most cases, we found extremely well-developed soils, such as Podzols with extremely thick E horizons or Umbrisols with A-Bh horizons up to more than 1-m thick. One of the most important properties was the large organic carbon content, up to 10-13% in soils located inside barren blockstreams and blockfields presently devoid of vegetation, at elevations between 1000 and 2950 m a.s.l..The age of this organic matter is likely very old. For instance, inside the blockfield on the Stolenberg Plateau (3030 m a.s.l.), the organic matter was up to 22 ka old, corresponding to the early retreat glacial phase after the LGM. The age and nature of the organic matter in the other soils is still being analyzed, and it will be able to give important information on past environmental condition in understudied high-elevation areas in the Alps. ReferencesPintaldi E., D’Amico M.E., Colombo N., Colombero C., Sambuelli L., De Regibus C., Franco D., Perotti L., Paro L., Freppaz M. (2021a). Catena. https://doi.org/10.1016/j.catena.2020.105044Pintaldi E., D’Amico M.E., Colombo N., Martinetto E., Said-Pullicino D., Giardino M., Freppaz M. (2021b). https://doi.org/10.1016/j.gloplacha.2021.103676Pintaldi E., Santoro V., D’Amico M.E., Colombo N., Celi L., Freppaz M. (2022). European Journal of Soil Science. https://doi.org/10.1111/ejss.13328
Mapping streams and ditches using Aerial Laser Scanning
Authors: Dos Santos Toledo Busarello Mariana , Ågren Anneli , Lidberg William
Published: February 2023

Streams and ditches are seldom identified on current maps due to their small dimensions and sometimes intermittent nature. Estimates point out that only 9% of all ditches are currently mapped, and the underestimation of natural streams is a global issue. Ditches have been dug in European boreal forests and some parts of North America to drain wetlands and increase forest production, consequently boosting the availability of cultivable land and a national-scale landscape modification. Target 6.6 of the Agenda 2030 highlights the importance of protecting and restoring water-related ecosystems. Wetlands are a substantial part of this, having a high carbon storage capability, the property of mitigating floods, and purifying water. All things accounted for, the withdrawal of anthropogenic environment alterations can be on the horizon, even more because ditches are also strong emitters of methane and other greenhouse gases due to their anoxic water and sediment accumulation. However, streams and ditches that are missing from maps and databases are difficult to manage.The main focus of this study was to develop a method to map channels combining deep learning and national Aerial Laser Scans (ALS). The performance of different topographical indices derived from the ALS data was evaluated, and two different Digital Elevation Model (DEM) resolutions were compared. Ditch channels and natural streams were manually digitized from ten regions across Sweden, summing up to 1923km of ditch channels and 248km of natural streams. The topographical indices used were: high-passing median filter, slope, sky-view factor and hillshade (with azimuths of 0°, 45°, 90° and 135°); while 0.5m and 1m were the DEM resolutions analysed. A U-net model was trained to segment images between ditches and stream channels: all pixels from each image were labelled in a way that those with the same class display similar attributes.Results showed that ditches can be successfully mapped with this method and it can generally be applied anywhere since only local terrain indices are required. Additionally, when the natural streams are present in the dataset the model underperformed in predicting the location of ditches, while a higher resolution had the opposite effect. Streams were more challenging to map, and the model only indicated the channels, not whether or not they contained water. Further research will be required to combine hydrological modelling and deep learning.
Parallel-in-time solution of finite element atmospheric models using ParaDiag
Authors: Hope-Collins Josh , Cotter Colin
Published: February 2023

Modern numerical weather prediction requires vast amounts of computing power, so highly scalable algorithms are essential on massively parallel modern hardware. However, once the strong scaling limit is reached for spatial parallelism, the wallclock time increases with the number of timesteps. This limits the ability to provide higher resolution forecasts on an operational schedule. Parallel-in-time methods overcome this limit by exposing time parallelism, in addition to the spatial parallelism exposed by traditional domain decomposition.ParaDiag is one such method, which reduces the coupled system for multiple time-steps into a block-diagonal matrix that can be solved in parallel. We will present recent progress on the application of ParaDiag to compatible finite element discretisations of PDEs for atmospheric flow, which are particularly challenging for time-parallel methods due to their highly oscillatory nature. These solvers are implemented as an open source general library using Firedrake, an automated code generation framework for the solution of finite element methods.Various ParaDiag formulations are explored for linear and non-linear models, and their parallel scaling is compared. Their performance is compared against time serial methods to find the parameter ranges where the greatest speedups are achieved. We identify the main difficulties faced by ParaDiag and describe our approaches to overcoming these, including solution strategies for the block systems within the ParaDiag matrix, and improving the convergence of nonlinear models.
Microbial Dissolved Organic Matter utilisation at the nearsediment waters in the Baltic Sea Deeps
Authors: Loginova Alexandra , Hoszek Kinga , Kowalczuk Piotr
Published: February 2023

Recent studies suggested that sediment pore waters may serve as a source of bioavailable DOM to the overlying water column, which may stimulate microbial activity in the nearbottom waters. However, a combination of DOM measurements with proxies of heterotrophic activity was not a priority of those studies. In this study, we aim to assess the bioavailability of DOM, released by sediments, and whether it may stimulate an increase in heterotrophic cell number. For this, we conduct the measurements of dissolved organic carbon (DOC) and DOM optical properties, such as chromophoric (CDOM) and fluorescent (FDOM) DOM, from the sediment pore waters of the Baltic Sea Deeps and in the water column in order to evaluate the initial supply flux (return flux) to the bottom waters and provide essential insights on the starting composition of DOM. We combine those measurements with the temporal changes of DOC, CDOM and FDOM during ex-situ incubations of the sediment cores with overlying water to infer quantitative and qualitative transformations of DOM during the incubation time. We discuss those data in combination with microbial abundance, oxygen and nutrient consumption as a proxy for sediment released DOM to serve as a substrate for heterotrophic communities to grow and function.
Quantifying impact-relevant heatwave durations
Authors: De Polt Kelley , Ward Philip J. , de Ruiter Marleen , Bogdanovich Ekaterina , Reichstein Markus , Frank Dorothea , Orth René
Published: February 2023

Heatwaves are weather hazards which can influence societal and natural systems. Recently, heatwaves have increased in frequency, duration, and intensity, and this trend is projected to continue as a consequence of climate change. This has triggered extensive research aiming at a better understanding of their impacts and underlying processes. However, the study of heatwaves is hampered by the lack of a common definition, which limits comparability between studies. This applies in particular to the considered time scale. Here, we determine impact-relevant temporal scales of heatwaves. For this purpose we characterise societal metrics related to health (heat-related hospitalizations, mortality) as well as public attention (Google trends, news articles) in Germany. We calculate country-averaged temperatures and select the warmest periods of varying durations between 1 and 90 days. For each time scale, the societal response is assessed to find the heat wave durations with the most pronounced impacts. This way, we yield impact-relevant heat wave durations for Germany. The results differ slightly between the considered societal metrics but indicate overall that heat waves are most relevant at weekly to monthly time scales. Finally, we also compare impact-relevant heat wave durations between moderate and extreme heat waves, as well as between heat waves occurring individually or jointly with droughts.Our methodology can be extended to other societal indices, countries, and hazard types to form more meaningful definitions of climate extremes in order to guide future research on these events.  An improved understanding of weather and climate hazards with their impacts on society, economy and environmental systems will support better communication for preparation, response, and future adaptation.
Effect of stress biaxiality on fracture energy and microstructures of tensile cracks
Authors: Guggisberg Antoine , Lebihain Mathias , Moore Jo , Violay Marie
Published: February 2023

The onset of crack propagation is often described with a unique threshold and intrinsic material property, the fracture energy. However, in geomaterials, this parameter varies with environmental and loading conditions (e.g., temperature, confining pressure, humidity, loading rate, etc.). This can be explained by more elaborate models in which the fracture energy is set by the weakening mechanisms at stake during material breakdown. Variations in fracture energy may then be attributed to a change in the failure mechanisms occurring in a dissipative region located very near the crack tip. Here, we show how stress biaxiality can cause a shift in the mechanisms dictating crack propagation and how they consequently affect the fracture energy. To this end, we performed modified ring tests (MRT) and wedge splitting tests (WST) on Carrara marble. These tests were selected for their stable configurations, while they have opposite stress biaxiality levels; -8 and +5 MPa respectively for MRT and WST. These tests also allow continuous fracture energy measurements thanks to a compliance method previously calibrated on PMMA experiments. We halted crack propagation and extracted thin sections at the tip, on which we acquired backscatter electron (BSE) and electron backscatter diffraction (EBSD) maps using a scanning electron microscope. These experiments showed that the fracture energy is test dependent: it ranges between 20 to 30 J/m2 on the MRT, and 20 to 80 J/m2 on the WST, depending on the crack tip position. Interestingly, the variations of fracture energy seem correlated with variations of stress biaxiality and associated microstructures. The BSE and EBSD scans show that the crack is mostly intra-granular and straight at a negative stress biaxiality level on the MRT. While at a positive level on the WST, the crack travels through grain boundaries with significant branching and higher tortuosity. These observations are in good agreement with theoretical studies on crack path in heterogeneous materials. However, one may expect that a shift from inter-granular (WST) to intra-granular (MRT) fracture would be associated with higher fracture energy, as the crack crosses through tough grains rather than weak grain boundaries. The opposite is measured as “en-passant” cracks occasionally form on the crack path during wedge-splitting tests. It creates bridging patches that oppose crack opening and double the fracture energy. These microstructures might be key to large variations of tensile fracture energy observed in geomaterials, whose fracture behavior is strongly influenced by stress biaxiality.
Risk assessment of high-temperature heat storage (HT-ATES) at the DeepStor demonstrator site
Authors: Stricker Kai , Egert Robert , Fokker Peter , Vardon Phil J. , van Wees Jan Diederik , Schill Eva , Kohl Thomas
Published: February 2023

In central Europe, the majority of the CO2 emissions in the energy sector are related to the provision of building and process heat. Due to seasonal fluctuations in demand, especially to provide heat for residential and industrial buildings, local storage of excess heat in summer for utilization in winter is becoming increasingly important. With the current state of technology and foreseeable developments, sufficient amounts of heat can only be stored underground, taking advantage of the large available storage volumes. In contrast to typical near-surface aquifer thermal energy storage (ATES), the utilization of deep reservoirs enables the storage of much larger thermal energies due to potentially significantly higher injection temperatures (e.g. > 80 °C).Previous studies demonstrated the high potential of deep reservoirs for high-temperature (HT) ATES, in particular for former hydrocarbon reservoirs in the Upper Rhine Graben. However, these studies focused on thermo-hydraulic processes, only rarely considering the impact of coupled mechanical processes. Using the case study of the DeepStor project, a demonstrator for HT-ATES under development in the north of Karlsruhe (Germany), the present study investigates the influence of coupled thermo-hydraulic-mechanical (THM) processes during the operation of HT-ATES systems.In particular, we investigate the impact of seasonal HT-ATES with biannual injection/production cycles on the stress distribution in the subsurface and subsequently caused displacements in the reservoir and the surface as well as the shear capacity at faults. This study further aims at improving the understanding of poro- and thermoelastic processes related to HT-ATES. Whereas the thermoelastic component dominates the vertical displacements at the top of the reservoir, the uplift at the surface is primarily controlled by the poroelastic component. Furthermore, an assessment of potential risks such as surface uplift or shear capacity at faults is performed. Our results show that surface uplift is primarily controlled by the reservoir depth, Young’s modulus, and the injection/production flow rate.
Landlab: a modeling platform that promotes the building of FAIR research software
Authors: Hutton Eric , Tucker Gregory
Published: February 2023

Landlab is an open-source Python package designed to facilitate creating, combining, and reusing 2D numerical models. As a core component of the Community Surface Dynamics Modeling System (CSDMS) Workbench, Landlab can be used to build and couple models from a wide range of domains. We present how Landlab provides a platform that fosters a community of model developers and aids them in creating sustainable and FAIR (Findable, Accessible, Interoperable, Reusable) research software.Landlab’s core functionality can be split into two main categories: infrastructural tools and community-contributed components. Infrastructural tools address the common needs of building new models (e.g. a gridding engine, and numerical utilities for common tasks). Landlab’s library of community-contributed components consists of several dozen components that each model a separate physical process (e.g. routing of shallow water flow across a landscape, calculating groundwater flow, or biologic evolution over a landscape). As these user-contributed components are incorporated into Landlab, they are able to attach to the Landlab infrastructure so that they also become both findable and accessible (through, for example, standardized metadata and versioning) and are maintained by the core Landlab developers.One key aspect of Landlab’s design is its use of a standard programming interface for all components. This ensures that all Landlab components are interoperable with one another and with other software tools, allowing researchers to incorporate Landlab's components into their own workflows and analyses. By separating processes into individual components, they become reusable and allow researchers to combine components in new ways without having to write new components from scratch.Overall, Landlab's design and development practices support the principles of FAIR research software, promoting the ability for scientific research to be easily shared and built upon. This design also provides a platform onto which model developers are able to attach their model components and take advantage of Landlab’s development practices and infrastructure and ensure their components also follow FAIR principles.
Improved predictions of thermal fluid pressurization in hydro-thermal models based on consistent incorporation of thermo-mechanical effects - Application study of the FE-Experiment at Mt. Terri
Authors: Buchwald Jörg , Kaiser Sonja , Wang Wenqing , Kolditz Olaf , Nagel Thomas
Published: February 2023

In deep underground storage facilities, coupled thermo-hydro-mechanical models are used to simulate the changes in temperature, pore pressure, and stress surrounding canisters containing high-level radioactive waste. Their numerical modeling is often computationally highly demanding, especially if an investigation is conducted that requires many model evaluations, like a sensitivity analysis or a parameter identification. In these analyses, the thermally driven pore pressure evolution and the subsequently altered flow processes are usually the primary targets of interest. In our contribution, we show the derivation of a hydro-thermal (HT) model with consistent incorporation of thermo-mechanical effects, allowing it to profit from its computational efficiency while maintaining most of its accuracy. We show its applicability to a 3D model of the FE experiment, a full-scale multiple heater experiment at the URL site in Mt. Terri.
Adjustment of Remotely Sensed Precipitation using Discharge
Authors: O'Loughlin Fiachra , Bruen Michael
Published: February 2023

With the expected increase in flooding due to climate change, accurate estimation of precipitation and the resulting modelled hydrographs are an essential requirement for reliable flood forecasts. At present, most adjustment methods for remotely sensed precipitation require raingauge data to increase the accuracy of the precipitation estimates. One disadvantage is that raingauges only measure precipitation at a given point and usually there are a relatively small number of these points in a typical catchment (and some smaller catchments may not have any raingauges). River discharge from the catchment integrates the influence of catchment-wide precipitation and can often be more accurately measured than the areal rainfall, especially in areas with a sparse raingauge network. Here, we present a non-raingauge adjustment method for remotely sensed precipitation estimates that utilises discharge data only to adjust these estimates for input to hydrological models. This method allows a hydrological model to adjust its treatment of precipitation input, through an additional model parameter, by comparing the observed and modelled hydrographs. This proposed method is comparable to a traditional raingauge adjustment methods over a number of catchments and hydrological models, for both peak flows and for the entire hydrograph. Additionally, this method allows for the adjustment of catchment averaged raingauge precipitation measurements to correct for any possibly errors due to using point data i.e. spatial density or representative issues. This results in a substantial improvement in discharge estimation compared to the un-adjusted raingauge measurements.
A new paradigm for lateral stirring and lateral stirring surfaces in the oceans
Authors: Tailleux Remi , Wolf Gabriel
Published: February 2023

By analogy with the case of a simple fluid, lateral stirring in the oceans has been traditionally envisioned as the notional form of stirring that minimally perturb the ocean stratification and its potential energy, as originally proposed over 80 years ago. If considered from the viewpoint of adiabatic and isohaline permutations of two fluid parcels, such a view leads to the idea that lateral stirring preferentially takes place on the ‘locally-referenced potential density surfaces’. To remedy the mathematically and physically ambiguous character of the latter, oceanographers then developed the concepts of potential density surfaces, patched potential density surfaces, and approximately neutral surfaces, which have been the cornerstone of isopycnal analysis for many decades. It has also provided the justification for constructing rotated diffusion tensors in terms of the directions parallel and perpendicular to the neutral directions. Nevertheless, while the concepts of neutral directions and neutral surfaces have been around for decades, their validity has never been really challenged nor confirmed experimentally. Worse, there has been little clue so far about how one might go about testing or refuting these concepts.Part of the problem is that the current theory of quasi-neutral density variables is not currently formulated as a classical falsifiable (in Popper’s sense) physical theory capable of making testable predictions but more as unfalsifiable dogma. To improve on this situation, this work shows how to embed the theory of lateral stirring and lateral stirring surfaces into the APE-based study of the compressible Navier-Stokes equations for realistic seawater (APE standing as Available Potential Energy, as per Lorenz concept). Doing so succeeds in identifying the kind of models that can be studied to shed light on the issue while also making new predictions about lateral stirring that significantly depart from the prevailing view. A key new result is that isoneutral stirring must involve compensating work between buoyancy and thermobaric forces, which cast doubt on its physical realisability. Another key result is that the ‘true’ neutral directions are not those associated with the standard neutral vector, but rather with an APE-based form of the P vector previously identified by Nycander. Although the P-neutrality thus defined appears to coincide with the standard N-neutrality in most of the oceans, the two are found to significantly differ in the polar region and Gulf Stream area, where neutral rotated diffusion tensors are likely to be potentially a significant source of spurious diapycnal mixing. Evidence that this is the case and how to go about remedying the problem will be discussed.
Investigating the relationships between the leaf area index and forest functions of dryland conifer forests along an aridity gradient using VENµS and Sentinel-2 satellites
Authors: Dubinin Moshe (Vladislav) , Osem Yagil , Yakir Dan , Paz-Kagan Tarin
Published: February 2023

Dryland forests are highly climate-sensitive are facing more frequent droughts and, consequently, increasing tree mortality, extreme wildfire events, and outbreaks of forest insects and pathogens. These changes, associated with climate change, are leading to biodiversity loss and the deterioration of related ecosystem services. Understanding the relationships between forest structure and function is essential for managing dryland forests to adapt to these changes. We studied the structure-function relationships in four dryland conifer forests distributed along a semiarid to sub-humid climatic aridity gradient. Forest structure was represented by leaf area index (LAI) and function by gross primary productivity (GPP), evapotranspiration (ET), and the derived efficiencies of water use (WUE= GPP/ET) and leaf area (LAE = GPP/LAI). The water and carbon fluxes at the ecosystem level were estimated by an empirical approach in which regression models were developed to relate multiple spectral data (VIs) derived from VENμS and Sentinel-2A satellites, combined with meteorological data, to local eddy covariance measurements from flux tower records available at three of the four study sites. The red-edge-based MERIS Terrestrial Chlorophyll Index (MTCI) from VENμS and Sentinel-2A showed strong correlations to flux tower GPP and ET measurements (R2cal >0.91, R2val >0.84). Using our approach, we showed that as LAI decreased with decreasing AI (dryer conditions), estimated GPP and ET decreased (R2>0.8 to LAI), while WUE (R2=0.68 to LAI) and LAE increased with decreasing AI. We propose that the higher WUE and LAE reflect an increased proportion of sun vs. shade leaves as LAI decreases. The results demonstrate the importance of high-resolution spectral and spatial data in low-density dry forests and the intricate structure-function interactions in the forests’ response to drying conditions.
Active tectonics from UAS-HR-DSM combined with PSInSAR: Case example along the Longitudinal Valley - Eastern Taiwan
Authors: Deffontaines Benoit , Chang Kuo-Jen , Li Ren-Fan , Lin Chii-Wen , Pasquali Paolo , Magalhaes samuel , Fortunato Gerardo
Published: February 2023

Taiwan result in the active collision of both Eurasian and Philippine Sea Plates characterized by an annual average convergence rate close to 10 cm.y-1. The Longitudinal Valley is parallel and eastward of the Central (Backbone) Range which is made of metamorphic rocks, and is also situated to the west of the Coastal Range (of volcanic affinity). In between both, lay the Longitudinal Valley (125km long and N020°E trending) which behave as the active crustal suture zone. The latter presents both inter-seismic creeping displacement (Champenois et al., 2013, Deffontaines et al., 2018) and was hit by 7 major earthquakes of magnitudes larger than 5 during the last 70 years which highlights its high seismic hazards.We combine herein a preseismic UAS survey (May 20, 2015) with one done immediately after the last large earthquake on the eastern Central Range (Oct 07, 2022). We therefore study both (1) the differences from a quantitative point of view; and (2) from a morpho-structural qualitative analysis point of view.We acquired so many high-resolution photographs using several drones flying at 350 meters above the ground. After photogrammetric processing, we calculate both (1) a high-resolution Digital Elevation Model (UAS-HR-DSM) that takes into account buildings and vegetations, and deduce (2) a Digital Terrain Model (UAS-HR-DSM) corresponding to the ground. Our ground validation (GCP’s) leads us to get a 7cm planimetric resolution (X, Y) and below 40cm vertical accuracy.This UAS-HR-DSM combined with field work and the preliminary PSInSAR (PALSAR-JAXA) processing led us to better characterize the active tectonic features through a detailed morphostructural analysis. It also permit us to map into much details the active structures and consequently to up-date the pre-existing geological mappings (e.g. CGS geological maps, Lin et al., 2009; Shyu et al., 2005, 2006, 2007, 2008). Then we up-date and combined our new structural scheme with geodetic data (levelings, GPS…) and PALSAR PSInSAR results acquired during the same monitoring time period to locate, characterize and quantify the active tectonic structures, taking into account previous works (e.g. Yu et al., 1997; Lee et al., 2008; Hsu et al., 2009; Huang et al., 2010…). We then precise structural geometries and some geological processes as well as the location of active folds and active faults during the PSInSAR monitoring time-period.This may lead us to better constrain the seismic hazards and the earthquake cycles of the place.
Rayleigh phase velocity maps for central Europe including the Eifel volcanic province
Authors: Weiler Tatjana , El-Sharkawy Amr , Meier Thomas
Published: February 2023

High-resolution Rayleigh phase velocity maps can help to improve our understanding of the 3-D vs anisotropic structure of the lithosphere of central Europe and its relationship to surface tectonics and volcanism.Using seismic broad-band recordings for the time period from 1990 to 2020, 600,000 inter-station fundamental mode Rayleigh wave phase velocities have been automatically determined by performing strict quality checks. Only smooth and reliable phase velocity curves with path-wise averaging and a standard error of 0.5% were chosen. For periods between 8 s and 350 s azimuthally anisotropic phase velocity maps were calculated for Central Europe. The phase velocity maps at short periods of up to 30 seconds show an NW-SE fast propagation direction along the East European Craton. At periods longer than 60 s, the anisotropic fast propagation direction shows slight variations from NE-SW to ∼N-S. At 150 s map, a NE-SW fast direction is observed. This might indicate a layering of anisotropy. Along the Tornquist-Teisseyre Zone, the fast propagation direction at all periods is NW-SE, except along its northern part as it shows slight variations. This might be due to the sharp change from the Precambrian continental mantle lithosphere to the younger Phanerozoic Europe. At short periods, central Europe anisotropy is following the Variscan front which changes abruptly to SE-NW near the Elbe line, whereas at longer periods the fast direction follows the Rheic suture and Saxothuringian suture. For the inversion of local azimuthally anisotropic phase velocity curves, we apply a newly elaborated stochastic inversion algorithm, the Particle Swarm Optimization algorithm (PSO). The result for extensive inversion and parameter tests of Rayleigh dispersion curves tests are shown. The lateral, as well as the vertical resolution of the resulting azimuthally anisotropic S-wave velocities and indications for layered anisotropy, are discussed.  
Multi-model approach in a variable spatial framework for streamflow simulation
Authors: Thébault Cyril , Perrin Charles , Andréassian Vazken , Thirel Guillaume , Legrand Sébastien , Delaigue Olivier
Published: February 2023

Accounting for the variability of processes and climate conditions between catchments and within catchments remains a challenge in hydrological modelling. To address this issue, various approaches were developed over the past decades. Among them, multi-model approaches provide a way to quantify and reduce the uncertainty linked to the choice of model structure, and semi-distributed approaches propose a good compromise to account for spatial variability of the processes by dividing the catchment in sub-catchments while maintaining a limited level of complexity. However, these two approaches were barely applied together. The aim of this work is to answer the following question: what are the contributions of multi-model approaches in a variable spatial framework for the simulation of streamflow over a large sample of catchments?To this end, a large set of 121 uninfluenced catchments in France was assembled, with precipitation, evapotranspiration and streamflow data at an hourly time step over the 1998-2018 period. The semi-distribution set-up was kept simple by considering a single intermediate catchment between a downstream station and one or more upstream catchments. The multi-model approach was implemented with 13 hydrological structures, three calibration options and two spatial frameworks, for a total of 78 distinct modelling options. A simple average method was used to combine the streamflow at the outlet of the catchments and sub-catchments. In this work, the benchmark considered is the most efficient lumped model considered individually on each catchment.The semi-distributed multi-model approach generates better performance at the time-series scale than the lumped models. The gain is mainly brought by the multi-model aspect while the spatial framework gives a more occasional benefit. This study also highlight the advantages of using a large set of models in a semi-distributed multi-model framework to simulate streamflow in a large sample hydrology context.
Microbial degradation of PFAS for remediation of contaminated soil and groundwater (bioPFAS)
Authors: Fagerlund Fritjof , Messinger Nicola , Ahrens Lutz , Bertilsson Stefan , Berggren Kleja Dan , Bergman Jonny , Naji Qusay , Leonard Gareth , Sahlin Sara , Westling Sofia
Published: February 2023

Per- and polyfluoroalkyl substances (PFAS) are very challenging to remediate and remove from contaminated soil and groundwater. While there is ongoing research on the topic, there is still a lack of cost-efficient techniques for in-situ or on-site PFAS degradation, largely due to the extreme recalcitrance of perfluoroalkyl acids (PFAAs), which are often the end-products of environmental PFAS transformations. Microbial degradation is a key process for the removal of many organic contaminants from the environment. There is also growing evidence from laboratory studies that under the right conditions microbial degradation of PFAS, including PFAAs occurs, indicating that microbial degradation potentially can be developed into a useful PFAS remediation method. At the same time, there is a lack of knowledge about microbial PFAS-degradation processes and the organisms involved. Improved knowledge of PFAS biodegradation is also necessary to better understand PFAS mass transport from contaminated hotspots.Here, the aims, methods and preliminary results of a newly started research project: “Microbial degradation of PFAS for remediation of contaminated soil and groundwater” (bioPFAS) are presented. The project aims at investigating how conditions for microbial degradation can be stimulated at PFAS-contaminated sites, the degree and rates of degradation that can be achieved, the main environmental factors governing degradation and the organisms involved. Systematic laboratory studies will be performed using a large number of incubations to identify and characterize PFAS-active microbial strains and consortia as well as governing environmental factors. PFAS transformations will be quantified and characterized and the potential for field application will be investigated first in soil columns and subsequently in a small field demonstration test. Geochemical and PFAS-transport models will be used to further investigate the feasibility of microbial PFAS degradation and any associated risks.
Soil carbon-sequestration and climate mitigation – definitions and their implications
Authors: Seidel Felix , Don Axel , Chenu Claire , Seitz Daria , Kätterer Thomas , Leifeld Jens
Published: February 2023

Carbon sequestration has become a buzz word and generates large expectations on ecosystems to take up carbon (C) from the atmosphere. These so-called negative emissions could compensate greenhouse gas emissions and help to stabilise the global climate.  However, the term C sequestration is often misleadingly used fostering biased conclusions and exaggerated expectations. C sequestration is defined as net uptake of C from the atmosphere. Soils have a particularly large potential to take up C yet many soils currently continuously loose C. Measures to build up soil C may only reduce soil C losses (C loss mitigation) but will not result in a net C sequestration. While checking 100 recent papers we found only 5% correctly using the term C sequestration. Even worse, 13% of the papers used C sequestration equivalent to soil C stocks. Here we call for a rigorous and concise use of the term C sequestration and discuss implications of misleading applications.
How obliquity controls the surface appearance of Triton, Pluto and other volatile-rich Transneptunian objects
Authors: Bertrand Tanguy , Forget François , Lellouch Emmanuel
Published: February 2023

Triton is often seen as Pluto’s sibling, as both objects share similar sizes, densities, and atmospheric and surface ice composition. Yet Triton’s surface appearance, including its topography, surface albedo and volatile ice distribution, strongly differs from Pluto’s. For instance, Triton is relatively flat and uniformly bright, with permanent nitrogen ice deposits likely covering its entire southern hemisphere. In contrast, Pluto’s landscape includes tall mountains and deep basins, a surface with very bright and very dark features, and permanent nitrogen ice deposits located in the mid-latitudes and equatorial regions, and in particular in the topographic basin Sputnik Planitia.These differences suggest a different geological history. In fact, Triton and Pluto are both thought to have formed beyond Neptune and then to have evolved differently. On the one side, Pluto remained in the Kuiper Belt and was hit by a twin to form the Pluto-Charon moon system. On the other side, Triton was captured by Neptune, as strongly suggested by its retrograde and highly inclined orbit around the Ice Giant planet, and its interior subsequently experienced intense tidal deformation and heating. Geological activity on Triton may still be powered today by tidal activity.  Previous modeling studies also highlighted the importance of the Milankovitch parameters (obliquity, eccentricity, solar longitude of perihelion) on Pluto in controlling the surface temperatures and therefore the ice sublimation and condensation rates. In particular, the high obliquity of Pluto’s spin axis seems to explain the presence of massive volatile ice deposits in the equatorial regions. Could Triton’s and Pluto’s volatile ice distributions be distinct mainly because of differences in obliquity?To answer this question, we performed new numerical simulations of Pluto’s and Triton’s volatile transport using the same climate model for both simulations, and the same initial states, but changing only the topography as well as the obliquity and orbital parameters specific to each object. The comparison of these simulations highlight the impact of obliquity in controlling the location of the permanent deposits of volatile ices on Pluto and Triton. At the conference, we will present these results and show that the impact of obliquity on Pluto and Triton, and on similar volatile-rich Transneptunian objects, goes beyond the volatile ice distribution.