bluuebunny/crossref_metadata_2025 huggingface dataset:
The dynamics of persistent hotspells in European summers
Authors: Pappert Duncan , Tuel Alexandre , Coumou Dim , Vrac Mathieu , Martius Olivia
Published: March 2024

Persistent summer weather can result in extreme events with enormous socio-economic impacts; recent summers in Europe have notably demonstrated this. The dynamics that cause persistent surface weather, as well as potential changes under anthropogenic climate change, are the subject of active scientific debate. Summertime atmospheric dynamics have nevertheless received less attention and we are far from obtaining a comprehensive understanding of the mechanisms involved in the formation of persistent weather conditions in summer. This study investigates the drivers responsible for making some surface extreme events more prone to being long-lasting than others.Gaining a comprehensive understanding of such processes poses challenges due to the complex interactions of variables and fluxes operating at various timescales – from individual weather events (daily to weekly), to the general circulation of the atmosphere and its modulation by specific changes in sea surface temperature or soil moisture interactions (monthly, seasonal to interannual). Furthermore, studies are recently observing that persistent (quasi-stationary or recurrent) circulation patterns do not necessarily always translate to extreme events and persistence at the surface. This discussion extends to open questions about, such as the potential role of soil moisture preconditioning in extending the lifetime of these events.Starting from an impact-based definition of persistent hot conditions for different European regions, we characterise their persistence by looking at the associated circulation patterns and surface conditions. Through a comparison of long-lived (persistent) and short-duration events, we discern dynamical differences and regional variations that shed light on the common ingredients and potential mechanisms influencing the persistence of extreme heat events in summer. We use the ERA5 reanalysis dataset to take advantage of its high spatiotemporal resolution and relatively long temporal coverage from the 1950s up to today.A deeper investigation into the dynamical processes controlling persistent surface conditions over Europe in summer is essential for improved predictability at the sub-seasonal to seasonal (S2S) timescale, and it holds significant relevance for risk preparedness. Results from the study aim to advance the discussion on summer dynamics, weather persistence and climate impacts.
Framing co-production in socio-hydrological modelling for drought impact assessment and mitigation
Authors: Piemontese Luigi , De Angeli Silvia , Castelli Giulio , Villani Lorenzo , Boni Giorgio , Bresci Elena
Published: March 2024

Drought is an increasingly widespread and impactful disaster across the world, causing serious impacts on health, agriculture, societies and the environment. For its complex nature, assessing the present and future impacts of droughts is a prominent challenge. Droughts can be defined differently according to the sectoral, disciplinary, and socio-economic domains, making drought impact assessment often ill-defined or incomplete. For example, droughts may or may not occur after a period of scarce precipitation, depending on local water access and use. Drought impacts are increasingly understood to be socially-influenced processes instead of mere hydro-climatic events. Transdisciplinary approaches to co-producing drought impact assessments and co-defining drought mitigation strategies are therefore particularly needed, while presenting specific challenges and differences compared to participatory approaches traditionally used for other natural hazards. Drawing from a diverse body of literature on participatory modelling research in the fields of transdisciplinary sustainability science, integrated water resources management, socio-hydrology and hydrosocial studies, we introduce a comprehensive framework for guiding participatory socio-hydrological modelling oriented to problem solving and real case applications. The framework is composed of two parts. The first part sets up a collaborative space by defining 1) a fitting drought governance space, 2)  potential shared definitions of drought impact; while the second part provides a practical guidance on 3) the biophysical as well as perceived features contributing to drought impact, 4) how and in which phase of the workflow to promote a proactive stakeholders involvement and 5) the potential pitfalls and uncertainty analysis to assess the equity and sustainability of the identified solutions. We further illustrate how such a framework can capture the different dimensions of participation throughout the modelling phases in some case studies to elucidate the applicability of the proposed approach in advancing research and action on drought impact assessment and mitigation.
Spatial organization of a soil cyanobacterium and its cyanosphere through GABA/Glu signaling to optimize mutualistic nitrogen fixation
Authors: Nelson Corey , Dadi Pavani , Shah Dhara D. , Garcia-Pichel Ferran
Published: March 2024

Soil biocrusts are characterized by the spatial self-organization of resident microbial populations at small scales. The cyanobacterium Microcoleus vaginatus, a prominent primary producer and pioneer biocrust former, relies on a mutualistic carbon (C) for nitrogen (N) exchange with its heterotrophic cyanosphere microbiome, a mutualism that may be optimized through the ability of the cyanobacterium to aggregate into bundles of trichomes. Testing both environmental populations and representative isolates, we show that the proximity of mutualistic diazotroph populations results in M. vaginatus bundle formation orchestrated through chemophobic and chemokinetic responses to Gamma-aminobutyric acid (GABA) / Glutamate (Glu) signals. The signaling system is characterized by: 1) high GABA sensitivity (nM range) and low Glu sensitivity (µM - mM); 2) GABA and Glu are produced by the cyanobacterium as an autoinduction response to N deficiency; and 3) interspecific signaling by heterotrophs in response to C limitation. Further, it crucially switches from a positive to a negative feed-back loop with increasing GABA concentration, thus setting maximal bundle sizes. The unprecedented use of GABA/Glu as an intra- and interspecific signal in the spatial organization of microbiomes highlights the pair as truly universal infochemicals.
Icy Moon Surfaces Microstructure through Multiphysics Simulations
Authors: Mergny Cyril , Schmidt Frédéric
Published: March 2024

Water ice has a microstructure shaped by a complex interplay of coupled multi-physics processes. Among them, ice sintering—also referred to as metamorphism or annealing—transports material from ice grains into their neck region, resulting in changes in the mechanical and thermal properties of the ice. Understanding sintering is essential to investigate the properties and microstructure of ice. While the sintering process of snow on Earth has been extensively studied, there is a scarce amount of information regarding the alteration of ice in planetary surface environments characterized by low temperatures and pressures.Here we present a multiphysics simulation model designed to study the evolution of planetary ice microstructure.  Coupled to a heat transfer solver, we have built a new model for the sintering of ice grain  with mathematical refinement to the diffusion process. As changes in ice microstructure affect the thermal properties we have expressed the heat conductivity with a formulation that consider microstructure and porosity which enables a two coupling between sintering and heat transfers.Our simulations of Europa's icy surface spanned a million years, allowing us to thoroughly explore the evolution of ice microstructure. Results show that the hottest regions experience significant sintering, even if high temperatures are only reached during a brief portion of the day. This process takes place on timescales shorter than Europa's ice crust age, suggests that these regions should currently have surface ice composed of interconnected grains. Accurately simulating these highly coupled processes, plays a crucial role in accurately determining the microstructure and quantitative composition of Europa's surface, a key objective for upcoming missions such as JUICE and Europa Clipper.
Trans-regional pollution between different areas within South – Eastern Romania is very strong
Authors: Mihalache Bianca , Stefan Sabina , Iorga Gabriela
Published: March 2024

High levels of atmospheric pollution degrade air quality, affect the climate and have significant impacts on human health. The climate maps show that the region of South-Eastern Romania (SERO) has started to be to be affected by significant climate changes. Therefore, the spatial variations of the trace gases (NO2, CO, SO2, and O3) by investigating their levels and variations in the atmosphere both from ground based measurements, but also from remote sensing in different areas of this region need to be investigated. The selected sites (urban, suburban and rural types) are subject to different sources of pollution and represent well the pollution spread over a larger area within SERO region. A database (2019-2021) was created for each site considering the ground-based data retrieved from Romanian National Air Quality Network, the remote-sensing data retrieved from the Sentinel 5P TROPOMI instrument and also, for one of the sites studied, we used the data available from Pandonia Global Network Pandora instrument. The meteorological parameters were extracted from the European Centre for Medium-Range Weather Forecasts (ECMWF) Era5 single level products and pressure level products.During the observation period, univariate and bivariate LISA cluster maps indicate the spatial and temporal behavior is linked to local and regional pollution sources, social behavior and the level of economic development. Trans-regional pollution between different areas within SERO region was found to be very strong. Moreover, the statistical analysis of studied trace gasses (NO2, CO, SO2, and O3) in the areas with lowest concentrations and highest concentrations confirmed the need to take in consideration more factors than just pollution sources (such as traffic, industry type, agricultural and biomass burning activities etc.). Results show that the complexity of atmospheric pollution is related to more than just the identification of pollution sources. It implies the necessity to take into account additional metadata. They also highlights important information on the distribution and variation of selected trace gases, with the potential to help the policy makers in addressing measures to reduce these pollutants.Acknowledgment: BM work was supported by the University of Bucharest, PhD research grant. The partial support from NO Grants 2014-2021, under Project EEA-RO-NO-2019-0423, contract no 31/01.09.2020 is also acknowledged. We thank R.V. Chiritescu for providing LISA maps.
Modelling the effects of changing extension directions in a segmented rift: application to the Eger Rift, Central Europe
Authors: Havlíček Filip , Uličný David , Krýza Ondřej , Machek Matěj , Warsitzka Michael , Závada Prokop
Published: March 2024

Continental lithosphere undergoing the process of rifting has typically previously experienced a complex deformation history resulting in a highly heterogeneous mechanical structure. This structural inheritance can affect the developing continental rift across all scales, from rift localization and segmentation to individual fault geometries. Assessing the impact of such inherited structures on extensional basin geometries can be difficult, especially in the case of fossil rifts where uncertainties may arise about the orientation of regional stresses during extension. One such example is the Eger Rift which developed during the Oligocene to early Miocene as the easternmost branch of the European Cenozoic Rift System (ECRIS). Earlier interpretation proposed a two-phase extensional history for the rift.We use a series of crustal-scale, brittle-viscous analogue models, based on the geometry of the central and eastern parts of the Eger Rift, to explore the development of a segmented rift in a multiphase setting with evolving extension direction. Our model crust rests on a basal velocity discontinuity (VD), a discrete boundary of a mobile base plate simulating a reactivated basement weakness localizing our model rift. The geometry of this weakness is a simplified representation of the geometry of older, mainly Upper Paleozoic basins, which are hypothesized to have greatly influenced the localization and geometry of principal fault systems and rift segments that they define. The VD thus consists of 3 segments oriented at various angles with respect to extension direction. The Model surface is imaged by stereoscopic cameras and analyzed by Particle Image Velocimetry (PIV) techniques to track surface deformation and topography evolution during the run.Our results confirm that in a setting with an abrupt change in extension direction, the first extensional phase plays a key role in defining the final observed fault pattern with new second-phase faults generally being few in number and of limited length. This effect is enhanced above a segmented VD. If a larger portion of the VD is optimally oriented with respect to the first-phase extension, the final fault pattern is dominated by first-phase structures with the growth of second-phase faults being nearly inhibited. In a contrasting scenario, where most of the VD is initially oblique to extension direction, second-phase faults are more abundant, leading to a bimodal final fault pattern. By comparing our results with newly mapped fault populations in the Eger Rift we conclude that the proposed two-phase history for the rift is plausible with a major role of the initial phase of approximately N-S extension.This research has been supported by the Czech Science Foundation (GAČR) project 22-13980S.
An interdisciplinary approach to understanding British resilient woodlands in an Anthropocene landscape
Authors: Sellers Hannah , Berrio Juan Carlos , Williams Mark , Jones Richard , De Sabbata Stefano , Evans Angharad , Neilson Andy , Burns Moya
Published: March 2024

Woodlands in the British landscape have been reduced to fragments and continue to decline in species diversity. In the heavily human-modified landscape of the English Midlands, Ancient Semi-Natural Woodland sites have undergone various human disturbance, including extensive modification such as clear-felling in the 20th century. Through the integration of information from the fossil pollen record, place-name evidence of past vegetation cover, archaeological records and recent botanical surveys, we examine the patterns of past resilience of woodlands to environmental disturbances, to understand more about their current status and future concerns to ensure the persistence of these now rare, socially and ecologically important habitats.  By adopting an interdisciplinary approach, we examine multiple sites across the English counties of Leicestershire and Rutland as case studies, integrating the different spatiotemporal datasets to provide new insights. The methodology aims to identify regions that have maintained long-term, stable woodland cover and to elucidate how ecosystems have changed and recovered after natural environmental or anthropogenic disturbances over the past 8,000 years and including more recent changes in the Anthropocene. Environmental change including deforestation and reforestation events have been identified with further details about the anthropogenic influence being provided by the historical (place-name evidence) and archaeological records. Our analysis is targeted at developing a replicable, spatiotemporal framework to identify future resilient woodland ecosystems in a time of Anthropocene environmental change, and to inform local policy and conservation efforts.
Contrail aging simulation of a supersonic aircraft
Authors: Muller Mathieu , Terrenoire Etienne , Bouhafid Younes , Bonne Nicolas
Published: March 2024

Over the last decades, the increasing globalisation and the associated need for substantially shortened travel times has led to public and privately-funded development of supersonic aircraft. The International Civil Aviation Organization (ICAO) needs to define standards for the advent of this new generation of supersonic aviation. The SENECA project (“noiSe and EmissioNs of supErsoniC Aircraft”) aims at developing supersonic aircrafts, investigating the impact of specifical supersonic engine technologies on the aircraft performance and noise, providing aircraft fuel burn, emitted CO2 data and engine emission indices for NOx, CO, HC, SOx and soot and quantifying a range of climate impacts of supersonic aviation.In the context of this project, the ONERA objectives are to model and characterize the contrails due to supersonic aircraft during cruise and to provide data to climatologists to calculate their global impact.In this study, a focus is made on the vortex phase of the contrail aging modelled with the CEDRE software from ONERA. The vortex phase strongly depends on both the aircraft geometry and the atmospheric conditions. So, first RANS simulations using mesh adaptation were performed to obtain an aerodynamical field used to initialize the vortex phase [1]. From the RANS field, a slice far from the aircraft is extracted, extruded and interpolated on a 3D mesh whose longitudinal dimension corresponds to the Crow wave length. Jet and atmospheric fluctuations are added to trigger the Crow instability, and the stratification of the atmosphere is also modelled corresponding to the lower stratosphere where the aircraft is flying in cruise regime. After those steps, a LES simulation is performed to simulate the contrail aging. [1] M. Muller and E. Terrenoire, Near-field mesh adaptation for contrail modeling of a supersonic aircraft, 3AF International Conference on Applied Aerodynamics, 29-31 March 2023, Bordeaux, France
Detection of slow slip events along the southern Peru - northern Chile subduction zone
Authors: Jara Jorge , Jolivet Romain , Socquet Anne , Comte Diana , Norabuena Edmundo
Published: March 2024

Detections of slow slip events (SSEs) are now common along most plate boundary fault systems at the global scale. However, no such event has been described in the south Peru - north Chile subduction zone so far, except for the early preparatory phase of the 2014 Iquique earthquake. We use geodetic template matching on GNSS-derived time series of surface motion in Southern Peru - Northern Chile to extract SSEs hidden within the geodetic noise. We detect 33 events with durations ranging from 9 to 40 days and magnitudes from $M_w$~5.6 to 6.2. The moment released by these aseismic events seems to scale with the cube of their duration, suggesting a dynamic comparable to that of earthquakes. We compare the distribution of SSEs with the distribution of coupling along the megathrust derived using Bayesian inference on GNSS- and InSAR-derived interseismic velocities. From this comparison, we obtain that most SSEs occur in regions of intermediate coupling where the megathrust transitions from locked to creeping or where geometrical complexities of the interplate region have been proposed. We finally discuss the potential role of fluids as a triggering mechanism for SSEs in the area. 
Slab reequilibration and slab roll back timing in the Cyclades: Evidence from garnet diffusion and P-T estimates (Naxos, Greece)
Authors: Peillod Alexandre , Hess Benjamin , Ring Uwe
Published: March 2024

Understanding the mechanisms of mountain building and its destruction poses significant challenges. Following subduction of a slab, an increase in the subduction rate and/or a decrease of the convergence rate, may lead to slab rollback. During slab rollback, segments of the middle-lower crust may undergo heating and partial melting due heating of thinned lithosphere by the asthenosphere and the migration of the magmatic arc. Alternatively, after accretion of radiogenic crust, the lower parts of the crust may relax through radiogenic decay. In both scenarios, the heating of the middle-lower crust reduces crustal strength, resulting in the development of metamorphic core complexes. The timing of lower crust heating is crucial for understanding the switchover from lithospheric shortening to extension.The Hellenides in the eastern Mediterranean constitute an arcuate orogen located north of the present-day active Hellenic margin, marking the site of NNE-ward subduction of the African plate beneath Eurasia. The Aegean Sea region in the Hellenide is a world-class example of large-scale continental extension above a retreating subduction zone. In the Cyclades, the Hellenide orogeny began in the early Cenozoic, causing subduction and sustained high-pressure (HP) metamorphism between approximately 53 and 30 Ma. The timing of slab rollback is subject of intense debate. A decrease in the convergence rate was interpreted to suggest that slab rollback initiated at around 35–30 Ma, during or even after the waning stages of HP metamorphism. In contrast, the formation of extensional sedimentary basins and radiometric dating of extension-related mylonite place rollback at approximately 23 Ma, distinctly after the final stages of HP metamorphism.Between about 30 Ma and 20 Ma, isobaric heating during the exhumation of some HP rocks has been proposed on some islands (Syros, Tinos, Andros, and Naxos). However, the precise timing and duration of this isobaric heating remains largely unconstrained. On Naxos, previous geothermobarometry estimates indicate isobaric heating occurred from 500 to 550°C from a middle segment of the nappe stack (Peillod et al., 2021). Garnet chemical zonation formed during exhumation allows for a heating timescale to be estimated via diffusion chronometry. We conducted Monte Carlo diffusion simulations to determine the best-fitting timescale based on Chi-square statistics, assuming three different heating paths. Diffusion model results for a heating path from 500 to 550°C indicate a 10 Myr timescale. A lower temperature path (from 400 to 450°C) requires heating over an unreasonable geological timescale (>100 Myr). Conversely, a higher temperature path (from 600 to 650°C) requires a timescale of
Turbulence generation by unresolved orography
Authors: Deshpande Shreyas , Ansorge Cedrick
Published: March 2024

Slope flows, resulting from the interplay between buoyancy and gravitational forces, are well-known to govern a plethora of local weather phenomena. In particular, orographic features and the associated surface roughness can induce turbulent mixing in the planetary boundary layer. While orographic drag models have been proposed to understand the effects of turbulence and waves due to orography, numerical simulations locally rely on closures based on the Monin-Obukhov Similarity Theory. The validity of these models and their interaction regarding turbulence production due to orography at unresolved scales is questionable. We study the turbulence generation by small-scale orography under the influence of stable stratification and weak mixing. To bypass the common complications with surface modeling, we use direct numerical simulation featuring a shallow valley to study the problem at a reduced scale. To imitate the intricate boundary conditions, an Immersed Boundary Method is used that features fully resolved three-dimensional roughness elements in the form of a local valley. However, modeling such flows also poses challenges due to the numerous parameters governing the triggering of turbulence. In this presentation, we introduce a scaling framework orographic for the problem and a viable numerical set-up along with the first results from preliminary studies at intermediate scale separation.* This work is funded by the ERC Starting Grant ”Turbulence-Resolving Approaches of the Intermittently Turbulent Atmospheric Boundary Layer [trainABL]” of the European Research Council (funding ID 851347).
Spectroscopy of Mars and Venus aurora: a remote sensing tool for similarities and differences
Authors: Gérard Jean-Claude , Soret Lauriane
Published: March 2024

Aurora has been detected on a few occasions on the Venus nightside with the Pioneer Venus UltraViolet Spectrometer (PVO-UVS). The main characteristics are the presence of the OI 130 and 136 nm emissions, a lack of discrete structure (diffuse aurora) and correlation with interplanetary shocks. Ground-based observations in the visible have shown that the [OI] green line at 557.7 nm is also observed following periods of the solar wind intensification. Although no concurrent measurement of auroral particle precipitation has been made, numerical simulations of the UV emissions have indicated that precipitation of soft auroral electrons (15-20 eV) and low energy fluxes is a likely candidate.A discrete aurora was first observed in the middle ultraviolet on the Martian nightside limb from the Mars Express orbiter in a region of strong crustal field in the southern hemisphere. Prominent emissions included the CO Cameron bands and the CO2+ UV doublet.  Limb observations have been made from Mars Express and MAVEN during the last 10 years. Recently, global auroral images have been collected with the UltraViolet Spectrometer (EMUS) on board the Emirates Mars Mission (EMM). These observations reveal a wide variety of auroral morphologies including discrete, diffuse, proton and sinuous aurora, each one bearing the signature of the interaction between the solar wind, the induced (or crustal) magnetic field and the atmosphere.In this presentation, we compare the characteristics of the Venus and Mars diffuse aurora observed by Pioneer Venus and MAVEN respectively. We focus on the determination of the charged particles characteristics (mean energy, flux, energy distribution) based on the brightness and intensity ratio of spectral emissions. Following recent laboratory measurement of the efficiency of the Cameron bands excitation by electron impact, we re-examine the dependence of the Cameron/CO2+ UVD intensity ratio on the auroral electron energy. Similarly, the different shapes of the electron excitation cross sections of the OI emissions at 130 and 136 nm induces an intensity ratio that depends on the energy of the precipitation. This dependence can be used to map the mean electron energy, based on FUV spectral observations with the EMUS. Finally, we discuss the expected brightness of the Mars visible aurora and set an upper limit on the intensity of the OI green line based on attempts to detect it with the UVIS spectrometer on board the Trace Gas Orbiter. We show that global observations with the M-AC visible camera on board the M-MATISSE orbiters will generate considerable progress in our understanding of the morphology, time variations and energetics of the Martian aurora. 
Improving landslide triggering thresholds using artificial neural networks and reanalysis multi-layer soil moisture information 
Authors: Palazzolo Nunziarita , Peres David J. , Distefano Pierpaolo , Piciullo Luca , Scandura Pietro , Cancelliere Antonino
Published: March 2024

Landslide prediction is crucial for the design of early warning systems, and the integration of soil moisture information aims to enhance the accuracy of such predictions. This study focuses on the development of artificial neural networks (ANNs) designed to recognize conditions that trigger landslides, incorporating soil moisture data alongside precipitation. Specifically, using ANNs, we investigate the advantage of deriving thresholds without a specific parametric equation, and, due to their flexibility to incorporate multiple input variables, they allow for a comprehensive analysis of landslides. Specifically, the research utilizes observed precipitation and ERA5-Land reanalysis soil moisture data at four different depth layers. To assess the effectiveness of the proposed approach under diverse climatic and geomorphological conditions, two distinct case studies are considered, namely Sicily Island (Italy) and a group of catchments in the Bergen area of Norway. The proposed methodology involves three main steps: i) the acquisition of rainfall and landslide data; ii) the creation of a database of triggering (TE) and non-triggering (NTE) events; iii) the development of ANNs predicting when a landslide is triggered from input precipitation and soil moisture data. A measure of the prediction uncertainty of the developed ANN models, related to the fact that a limited sample of triggering events may be available, is also carried out. Overall, the developed ANN classifiers, incorporating soil moisture information in addition to precipitation, prove to have better predictive performance than those relying solely on precipitation data. In our study, we also carry out comparisons to traditional power law thresholds, derived by optimizing the true skill statistic (TSS) based on cumulative precipitation and duration (E-D). While the power law E-D thresholds reach a TSS equal to 0.50 for both study areas, the inclusion of soil moisture information can lead to significant performance improvements, yielding TSS values up to about 0.90. These results corroborate the potentialities of the use of soil moisture information and machine learning techniques in improving landslide prediction. 
A subsurface oil spill study: integral ‘plume’ model and lagrangian oil droplets
Authors: Gronchi Giulia , Pinardi Nadia , Coppini Giovanni , Mannarini Gianandrea
Published: March 2024

Despite the imperative to mitigate climate change, most state governments still focus on oil extraction and production. This research aims to tackle the issue of oil entering the ocean from subsurface sources, such as drilling well blowouts or pipeline failures. The objective of this study is to develop a two-stage model for subsurface oil spills. Following a comprehensive review of state-of-the-art models, we delineated a near-field 'plume' phase, where buoyant oil collectively rises, and a far-field stage, characterized by the dispersion of oil droplets through ocean currents and turbulence after reaching a terminal intrusive level due to ocean stratification. UWORM (UnderWater Oil Release Model) includes an integral Lagrangian elements plume model, validated using both laboratory-scale and real-scale experiments in the North Sea. Entrainment is calibrated, demonstrating good agreement with in-situ data and length scales corresponding to different regimes. Following near-far field coupling, Lagrangian Particle Tracking is employed for individual oil droplets via OceanParcels. Size-dependent buoyancy results in the formation of distinct clusters with varying resurfacing times. Both near and far-field components utilize Copernicus Marine Service ocean state data, incorporating 3D fields of currents, temperature, and salinity.
Role of manganese, chromium and vanadium in the photoluminescence emission spectrum of grossular var. tsavorite from Tanzania.
Authors: Idini Alfredo , Angeli Celestino , Frau Franco , Argazzi Roberto
Published: March 2024

Tsavorite is the trade name for the green vanadium-chromium variety of grossular. The occurrence of tsavorite plays a key role in the geological research inherent to the formation of the Gondwana continent because it is hosted exclusively in the metamorphic unit from the Neoproterozoic Metamorphic Mozambique Belt (NMMB). The studies on the tsavorite deposit of the NMMB contributed to determining the metamorphic evolution of these Precambrian terrains. The areas of Merelani Hills (Tanzania) and Tsavo Park (Kenya) are by far the most important source of high-quality specimens of tsavorite that are extensively used for petrological studies. Furthermore, the tsavorite crystals from Merelani Hills exhibit a peculiar feature: the fluorescence is easily recognizable lighting up centimetric crystals with a common portable LED lamp. Using the long UV we observe a bright pink-orange colour, while exciting with the short UV the effect is a pale yellow. To the best of our knowledge, this phenomenon is unusual among the members of the garnet group and only a few research papers have investigated this phenomenon in natural garnets. To characterize the fluorescence, up to 25 grams of tsavorite crystals were meticulously sampled from the rocky matrix under the UV lamp and then pulverized in an agate mortar to perform an accurate XRPD acquisition. The results show that no other phases than garnet are present and, thanks to the high quality of the XRPD acquisition, the Electron Density Map was calculated and plotted against a CIF grossular standard, showing that an excess of negative charge is clearly pinpointed in the Y(6) crystallographic site, occupied by Al+3 in the grossular standard structure. The bulk elemental analysis, performed on the same powder used for XRPD acquisition, shows that the contents of Fe, Mg and Mn are < 0.5 wt.%, while V2O3  and Cr2O3 are respectively 0.32  and 0.015 wt.%, showing a good consistency with bibliographic data. The fluorometry with an excitation beam at 408 nm indicates a complex emission pattern with the most intense emission at 701 and 716 nm and subordinately at 592 nm. The colour perception of the emitted light is dominated by the emission band at 592 nm which is close to the peak sensitivity of the human eye at 555 nm, while the contribution of the red band, though more intense, is perceived as much weaker due to the lower eye sensitivity and modulates the colour ranging from bright orange to pink-red. Because of the characteristic colour perceived under UV light, the use of a common led lamp can serve as a diagnostic tool to identify tsavorite whenever a rapid test is required, e.g. in the case of field survey. The emitted photoluminescence lines, besides the very uncommon low andradite molarity, allow precise identification of the emissions of Mn2+, Cr3+ and V3+.  
Multi-scale experimental deformation and damage initiation of clay-rich rocks  : Coupling ultrasonic wave propagation and  full field deformation measurements by digital image correlation (DIC)
Authors: Lusseyran Matthieu , Dimanov Alexandre , Bonnelye Audrey , Fortin Jérôme , Tanguy Alexandre
Published: March 2024

Understanding the damage processes in clay-bearing rocks is a decisive factor in geological engineering, and for instance considering nuclear waste deep geological repositories. But, more generally they may also contribute to localized deformation, and thus the rupture of fault gauges in seismic zones. However, owing to their complex mineralogy, multiscale microstructures and anisotropy, the mechanisms of clay-rich rock damage and their chronology are not yet well understood..Here we focus on the impact of micro-damage on ultrasonic wave propagation velocity, which is confronted with the corresponding full deformation fields calculated by digital image correlation (DIC). The aim is to associate the acoustic signature with the active deformation mechanisms identified by DIC. To this end, an integrated experimental approach is proposed to  characterize localization and to identify the related deformation micro-mechanisms  during uniaxial compression of natural clayey rock samples (Tournemire shales) with two simultaneous measurements: 1) the evolution of P-wave velocity within the sample by active acoustics, 2) the development of the 2D mechanical full field by digital image correlation.Both experimental techniques are well known, but the innovation of our approach is to combine simultaneously both measurements. Deformation localization is a multiscale problem, which obviously occurs at the sample scale, but also at the fines scales of the microstructure. Therefore, we developed two different experimental setups. On the one hand, during uniaxial compression with a standard MTS loading frame the macro-scale localization patterns are characterized by optical observations, which image resolution is well suited to the cm sample scale (sample diameter: 3.6 cm and double in length). On the other hand, in order to characterize the initiation of micro-damage at the microstructure scale of the composite type of rock, the same loading protocol is reproduced (while keeping the acoustic diagnosis) on smaller scale mm-sized specimens (sample diameter : 8 mm, double in length), using a home-designed miniature loading frame fit for an environmental scanning electron microscope (ESEM). The latter analysis is carried out under  controlled relative humidity  of RH = 80%, hence preventing the samples to dry out due to the high vacuumA similar acoustic signature is identified at both scales of observation, in spite of the variations of experimental conditions imposed by the environmental SEM. We are therefore confident to be able to understand the fracturing process from micro-cracking initiation (microscale) to sample failure (macroscale), and to assess its impact on ultrasonic wave propagation.
Seismic evidence favoring depletion of Precambrian lithosphere and partial melt at the base of tectonic plates
Authors: Debayle Eric , Ricard Yanick , Stéphanie Durand , Bodin Thomas
Published: March 2024

Most global tomographic studies of the upper mantle and their thermochemical interpretations have focused on shear velocity (Vs). Shear attenuation has a different sensitivity to temperature, composition and melt content and therefore provides complementary constraints on the origin of seismic heterogeneities. In the upper mantle, shear attenuation is negligibly dependent on major element chemistry and exponentially dependent on temperature.Here, we first simultaneously interpret two recent global Vs and Qs models, which are obtained from the same Rayleigh-wave dataset, at the same resolution and using the same modelling approach. Comparison with mineralogical data suggests that partial melt occurs within the LVZ and down to 150–200 km beneath mid-ocean ridges, major hotspots and back-arc regions. A small part of this melt (less than 0.3%) remains trapped within the oceanic LVZ.Melt is mostly absent under continental regions. In these regions, we observe high seismic velocity keels extending to depths that often exceed 200 km. The thermochemical interpretation of our global shear velocity models requires mineralogical depletion and a decrease of compositional density beneath Precambrian cratons. These conditions ensure their preservation for billions of years in a convective mantle, in agreement with mantle xenoliths suggesting that high viscous keels formed early in the history of cratons. 
The Swedish state-of-the-art seasonal hydrological forecasting service - An example of successful science-policy-practice integration
Authors: Pechlivanidis Ilias , Popp Andrea , Du Yiheng , Bozhinova Denica , Berg Peter
Published: March 2024

The Swedish Meteorological and Hydrological Institute (SMHI) occupies a distinctive position at the intersection of science, policy, and practice. The institute is uniquely equipped to directly translate state-of-the-art research into its operational services. Seasonal hydro-meteorological forecasts have been used in decision support tools for various water-related sectors that require long-term planning. Several seasonal hydrological forecasting systems have been employed, with streamflow climatology, ensemble streamflow prediction (ESP), and dynamical GCM-based streamflow prediction (DSP) being among the most common systems. Each system has its advantages and disadvantages, however, DSP is overall considered the most accurate, particularly during the first lead weeks (about up to 6). Currently, SMHI provides seasonal hydrological forecasts based on climatology, which can be openly accessed (https://vattenwebb.smhi.se/ in Swedish). Building on its existing seasonal forecasting system, SMHI recently operationalized dynamical seasonal forecasts for Sweden, utilizing bias-adjusted ECMWF SEAS5 meteorological forecasts. With this work, we showcase the implementation of cutting-edge meteorological and hydrological research into a useful service for long-term decision-making. We present our workflow, address potential (scientific and technical) obstacles, and outline strategies for the accessible and reliable distribution of seasonal hydrological forecasts to the general public.
Mountains from sand grains: Advances in detrital provenance applied to orogens
Authors: Mark Chris , Neofitu Roland , O'Sullivan Gary , Glorie Stijn , Zack Thomas , Rösel Delia , Barfod Dan , Chew David , Daly J. Stephen , Clift Peter , Najman Yani
Published: March 2024

Detrital geochronology is a powerful tool to interrogate the sedimentary archive of (paleo-)hinterland tectonism, metamorphism, and exhumation, and can also be applied to modern river sediment as a first-pass tool to establish regional bedrock ages. The popular zircon U-Pb detrital geochronometer has seen widespread adoption for these tasks (4,173/5,100 results for the search term detrital geochronology also contain the term zircon U-Pb; Clarivate Analytics Web of Science). However, zircon fertility is strongly biased to intermediate to felsic source rocks. Moreover, zircon crystallization is volumetrically limited in metamorphic terranes which do not achieve anataxis (e.g., Moecher & Samson, 2006), and is typically restricted to rim overgrowths which are vulnerable to mechanical destruction during fluvial transport, and which are challenging to detect and analyse (e.g., Campbell et al., 2005).Therefore, it is desirable to develop complementary provenance tools for sub-anatectic settings, as well as tools targeting more abundant rock-forming minerals for use with small-volume samples (e.g., drillcore). Established alternative detrital phases include the U-Pb system in apatite, monazite, titanite, and garnet. The advent of LA-ICPMS systems equipped with mass-filtered online reaction cells now also permits the routine use of β-decay systems by overcoming parent-daughter isobaric interferences. These include Lu-Hf in garnet and apatite, and Rb-Sr in K-phases including K-feldspar and mica (Rösel & Zack, 2022; Woods 2016). K-phases are also amenable to conventional Ar-Ar detrital geochronology.Here, we present case studies of emerging detrital provenance techniques, with particular application to modern and past orogenic systems.Campbell, I., et al., 2005. Earth Planet. Sci. Lett. 237, 402-432,  doi: 10.1016/j.epsl.2005.06.043Moecher, D., & Samson, S., 2006, Earth Planet. Sci. Lett. 247, 252–266, doi: 10.1016/j.epsl.2006.04.035Rösel, D., & T. Zack, 2022. Geostandards and Geoanalytical Research 46.2, 143-168, doi: 10.1111/ggr.12414.Woods, G. 2016. Agilent Application Note. Agilent Technologies, Cheadle.
The inclusion of trees and the introduction of non-native earthworms may increase greenhouse gas emissions from riparian buffer strips.  
Authors: Boilard Gabriel , Cameron Ashley , Šimek Miloslav
Published: March 2024

     Forested riparian buffer strips (FRBS) are common in temperate agroecosystems due to their ability to sequester nutrients from agricultural runoff and to sequester carbon. The full environmental benefits of FRBS can only be evaluated, however, by accounting for a wide range of criteria that go beyond stream water quality. For example, it is important to determine the net greenhouse gas (GHG) balance of FRBS relative to adjacent agricultural fields. It is also important to identify the factors controlling these GHG emissions in order to propose optimal FRBS designs that maximize their environmental benefits. One such factor is the spread of non-native earthworms, whose burrowing activities may modify soil emission rates of CO2, N2O and CH4. To test the effects of earthworms on GHG emissions, microcosm studies were conducted using a replicated factorial design comprising of three soil origins (deciduous FRBS, coniferous FRBS, agricultural field) × two soil textures (field conditions, high clay) × three EW life habits (anecic, endogeic, no earthworms). At different intervals over the course of a 10-week trial, we measured net CO2 emissions under aerobic conditions, as well as potential N2O emissions in microcosms amended with acetylene gas.  In a separate trial using the same experimental design, we measured gross production and consumption rates of CH4, in both aerobic and anaerobic conditions, using an 13CH4 isotope dilution technique. Anecic earthworms had a positive effect on soil CO2 and denitrification, which decreased after a few weeks. Increasing soil clay content had a negative effect on the emission of these two GHGs. Additionally, soils from FRBS emitted more CO2, N2O and CH4 than soils from agricultural fields. Gross CH4 consumption rates were greater under aerobic than aerobic conditions, especially under deciduous trees.  Results suggest that the inclusion of trees in riparian buffer strips combined with the introduction of non-native earthworm species could substantially increase GHG emissions of agroecosystems and mitigate the environmental benefits of FRBS.(Note: The first and second authors contributed equally to this presentation).
Intermediate-depth icequakes at Greenland’s fastest outlet glacier: evidence for englacial thrust faulting?
Authors: Nap Ana , Walter Fabian , Lüthi Martin P. , Wehrlé Adrien , van Ginkel Janneke , Kneib-Walter Andrea , Rousseau Hugo
Published: March 2024

In traditional glacier flow laws and consequently glacier models, a widely used assumption is that the ice behaves as a non-Newtonian viscous fluid that slides either across hard bedrock or via deforming subglacial till. Elastic effects and brittle deformation within the ice are often neglected for simplicity, as even ubiquitous surface crevasses are difficult to capture in numerical schemes. While there is ample seismological evidence that stick-slip motion plays a significant role in basal sliding of both alpine and polar glaciers, similar evidence is lacking for brittle deformation within the ice mass itself. Instead, it is commonly assumed that the ice moves and deforms in a purely viscous or ductile manner, which may not be an accurate representation of reality.Here, we present observations of high-frequency (>50Hz) signals of intermediate-depth seismic sources occurring along the fast ice-stream of Sermeq Kujalleq in Kangia (Jakobshavn Isbræ), Greenland’s fastest flowing outlet glacier. The waveform characteristics of these events closely resemble the known characteristics of waveforms associated with basal stick-slip events, making them easily distinguishable from the more prevalent icequake signals generated by surface crevasse opening and propagation. However, differences in P and S wave arrival times as well as probabilistic source locations show that these events occur at ~170-400 m depth, whereas at those locations the glacier has a total depth of approximately 2000 m. Hence, these events cannot be caused by stick-slip motion at the base of the glacier, but must originate from englacial dislocations such as e.g., thrust faulting. Hundreds of these englacial icequakes are observed at several seismic arrays that were temporarily deployed in 2022 and 2023 along the fast ice-stream of Sermeq Kujalleq. Using waveform clustering and source mechanism analysis, we discuss the role of these events in ice dynamics and in particular englacial deformation. 