HAL-INSU
Not a member yet
203706 research outputs found
Sort by
The Holocene history of Arsine Glacier (Western European Alps): a detailed 10Be record of oscillations driven by climate and modulated by rock avalanches
No full textInternational audienceLateglacial to Early Holocene (EH) glacier variations in the Alps have recently been thoroughly refined using 10Be terrestrial cosmogenic nuclide (TCN) exposure dating of moraines. In contrast, knowledge of the spatial extent reached by glaciers during the Neoglacial period (∼4.2–0.14 ka) is still fragmentary because of the scarcity of preserved moraines predating the Little Ice Age (LIA). In addition, although the climatic meaning of the geomorphological imprints left by debris-covered glaciers or rock glaciers is increasingly investigated, direct comparison with those of debris-free glaciers is often not possible. Here, we provide an unprecedentedly large TCN dataset for the region (n = 53) constraining the behaviour of Arsine Glacier, French Alps, from the end of the Lateglacial to the end of the LIA. Stadial moraines are present in both the western and eastern valleys formerly occupied by two separate branches of the ice body, up to c. 3 km from the extant glacier front. Further upslope, the forefield of Arsine Glacier is characterized by two prominent geomorphic complexes. The first is a peculiar landform with concentric ridges, previously interpreted as a moraine-derived rock glacier. It is framed by an extensive and chaotic boulder field and is overtopped – in the most glacier-proximal part – by the second outstanding feature, a large complex of unvegetated lateral and frontal composite moraines. The chronological results indicate that the most distal moraine sets testify to five oscillations of the western glacier branch between 11.88 ± 0.43 ka and 11.10 ± 0.37 ka. Robust constraints on the spatial extent of these positions show depression of the glacier equilibrium line altitude ranging from 224 m to 169 m relative to the LIA. The innermost EH complex dated here is interpreted as being related to the regional expression of the Preboreal Oscillation (PBO). The previously interpreted moraine-derived rock glacier was found to rather represent a moraine complex deposited following a rock avalanche covering the eastern branch of the ice body and the surrounding floor. This catastrophic event occurred at 10.71 ± 0.42 ka, during the first significant warming of the Preboreal period, as shown by dating of the framing boulder field deposit. Dating of the ridges of the resulting moraine complex shows a subsequent advance of c. 1250 m peaking at 10.25 ± 0.42 ka, followed by persistence of the debris-covered eastern tongue outboard the LIA extent until 9.52 ± 0.43 ka. By contrast, during this interval no prominent moraine was deposited by the western glacier branch, not affected by the rock avalanche. Like elsewhere in the Alps, no 10Be boulder ages corresponding to the Mid-Holocene (8.2–4.2 ka) were found. Dating of the glacier-proximal moraine complex allows assigning its deposition to the Neoglacial period. The emplacement of this feature had started no later than 3.74 ± 0.02 ka. A subsequent period of glacier maxima deposited a till unit dated on both sides of the glacier at 2.69 ± 0.14 ka. During the Common Era, the first LIA-like advance occurred at 1.67 ± 0.05 ka. During the LIA, an early advance (eLIA) deposited the outermost Neoglacial frontal moraine 650 ± 30 a ago. Finally, the innermost preserved lateral moraine was deposited at the end of the LIA, 170 ± 10 a ago. The Arsine Glacier record is, to our knowledge, the most detailed 10Be-based Holocene-long glacier chronology in the Alps, and agrees well with other existing glacier records in the region. We propose that, apart from the directly climate-driven glacier advances and corresponding ice-marginal moraine deposits of the EH and the Neoglacial, a large EH rock avalanche occurred following warm-period-related destabilization of the cirque headwalls, bringing large amount of debris onto one part of the glacier. This excessive supply – estimated to a volume of c. 8.4 × 106 m3 – led the eastern glacier branch to evolve into a heavily debris-covered tongue that recorded climate-related oscillations between ∼10.3 and 9.5 ka outboard the LIA extent
Identifying signatures of past and present cryovolcanism on Europa
No full textInternational audienceEuropa, the most visibly active icy moon of Jupiter, is a prime target for the search for life in the outer solar system. Two spacecraft missions, Europa Clipper from the National Aeronautics and Space Administration (NASA) and the Jupiter Icy Moon Explorer (JUICE) from the European Space Agency (ESA), will observe its surface, probe its interior structure, and characterize the space environment starting in 2030. Occasional eruptions of water sourced from Europa’s interior may provide a window on the interior conditions and habitability of the moon. Here, we investigate the storage and evolution of briny water in Europa’s ice shell and propose a framework to interpret spectral, thermal, radar and gravity data collected by future missions. We show that it is possible to discriminate between water erupting from the deep ocean or from shallow liquid reservoirs using combined measurements of the material’s salinity, surface temperature and ice shell thickness
Methylmercury carbon isotope fractionation during biotic methylation by the bacterial BerOc1 strain
No full textInternational audienceBiotic methylation of inorganic mercury (iHg) in aquatic systems is largely driven by microorganisms such as sulfate-reducing bacteria (SRB). Using the SRB model strain Pseudodesulfovibrio hydrargyri BerOc1 we investigated biotic iHg methylation aiming to assess the rates of mono-methylmercury (CH3Hg) production and to characterize the carbon (C) isotopic signatures (δ13C) of the CH3Hg product. BiogenicCH3Hg exhibited δ13C values averaging −23.1 ± 2.0‰, representing a 13C-depletion of 14.4‰ compared to the pyruvate carbon source used for the growing of the strain and a 9‰ depletion relative to the microbial biomass. The maximum methylation yield observed in our samples was around 15% of the available iHg and a constant C isotope fractionation was detected over time. We propose that the methyl group is metabolically transferred from the carbon sources to cobalamin in the HgcA protein and subsequently to inorganic mercury (iHg), leading to consistent light C isotope enriched CH3Hg signatures
Health quality of urban particles according to their load in endocrine-disrupting compounds and associated toxic potential
No full textInternational audienceThe harmful effects of air pollution are partly linked to atmospheric particles (PM), due to their size, but their composition can also play a role. Indeed, they can adsorb semi-volatile organic compounds (SVOCs) with suspected or proven endocrine-disrupting (ED) properties. In order to better understand the link between contamination of PM in ED compounds and associated biological effects, 3 urban sites were selected in Paris region (France). On each site, 3 classes of PM were collected (PM2.5, PM10 and TSP), at 2 contrasting seasons and 62 SVOCs were investigated in the PM extracts. The estrogenic and dioxin-like potential were analysed by in vitro bioassays. The results of this work highlighted the highest contamination of PM2.5 in accordance with the toxic potential of their bounded-organic contamination. A non-monotonic dose-response effect was observed for estrogenicity of some PM organic extracts. These data allowed us to understand the complexity of the characterization of the health hazard linked to PM according to their size, their origin and in relation to the molecules they adsorb
Targeted oral delivery of microencapsulated TNF-α siRNA in an experimental model of colitis
No full textInternational audienc
Bare surface soil moisture and surface roughness estimation using multi-band multi-polarization NISAR-like SAR data
No full textInternational audienceThe upcoming NISAR Earth-observation satellite will utilize dual frequencies simultaneously, providing synthetic aperture radar (SAR) remote sensing data in both the L-band and S-band. With its ability to operate single-polarization, dual-polarization, and quad-polarization modes, NISAR will offer significant capabilities for land surface observation applications, particularly for estimating surface soil moisture (SSM) and surface roughness (Hrms). This study aims to demonstrate NISAR's future potential in SSM and Hrms estimation by evaluating the single (SP), double (DP) and quad (QP) polarization configurations. Noisy synthetic NISAR-like data was generated using the Dubois-B model for both Sand L-bands. The use of a priori information on the soil moisture was also examined for SSM and Hrms estimations. Various neural networks (NNs) were trained using the noisy synthetic dataset. Validation was performed on noisy synthetic data, as real NISAR data is not yet available. Out of the NISAR configurations tested, the QP configuration was shown to be the most performant, with RMSE on SSM estimation of 4.2 vol.%, for QP configuration compared to 5.1 and 8.2 vol.% for SP and DP configurations when not using a priori knowledge of soil moisture conditions. RMSE on Hrms was 0.3 cm for QP configuration, compared to 0.7 and 0.6 cm for SP and DP configurations. The QP was also shown to be more capable of mitigating the effect of the incidence angle on the estimation of SSM and Hrms compared to the two other configurations. Moreover, simultaneous use of S-and L-bands enhances SSM and Hrms estimation compared to using either of these frequency bands alone in single-, dual-, or quad-polarization configurations. Furthermore, using a priori knowledge of soil moisture conditions was successful in improving the estimation precision for SSM for all NISAR configurations. Notably, for QP configuration, RMSE on SSM estimation was 3.9 vol.% and 3.2 vol.% when a priori information on SSM was considered respectively in dry to slightly wet and very wet conditions. These findings demonstrate the high potential of the future NISAR sensor for estimating SSM and Hrms
Quantification de la recharge par caractérisation hydrodynamique de la zone non saturée : recherche de critères de spatialisation et application au site du CEA de Cadarache
No full textAs part of the improvement of the hydrogeological model of the CEA Cadarache site, particularly for a better understanding of recharge processes, this doctoral research focuses on the study of the unsaturated zone (UZ) through the analysis of its hydrodynamic properties. This work is structured around three main objectives : to determine the hydrodynamic properties of the UZ at the scale of an experimental plot equipped on the CEA Cadarache site ; to evaluate recharge at the one-dimensional scale using experimental data and simulations performed with the HYDRUS-1D model ; and to identify criteria for spatializing the hydrodynamic parameters of the van Genuchten-Mualem model at the site scale, particularly the saturated hydraulic conductivity Ks.This approach relies on soil analyses, surface Ks measurements conducted using a disk infiltrometer, and the evaluation of pedotransfer functions (PTFs).At the experimental plot scale, in situ measurements of volumetric water content, matric suction, and hydraulic conductivity K_s were conducted at different depths. These data were then used to determine the hydrodynamic parameters of the UZ, particularly those of the van Genuchten-Mualem model (θr, θs ,α,n et Ks), by analyzing water retention and hydraulic conductivity curves. The obtained parameters were subsequently integrated into the numerical model HYDRUS-1D, enabling the simulation of vertical water transfers in the soil and the evaluation of the so-called “reference” recharge over the period 2014-2023.To assess the soil's infiltration capacity at the Cadarache site scale, surface Ks measurement campaigns were also conducted. The results of the infiltration tests allowed for selecting the most suitable method for determining Ks at the site. The analysis of hydraulic conductivity curves K(h) highlighted the effects of macropores, which are associated with the presence of roots, organic matter, and gravel in specific areas of the site.Moreover, to better understand the spatial variability of Ks, statistical analyses were carried out to identify the factors influencing its distribution, taking into account soil physico-chemical properties, vegetation, and geology. The results revealed a significant relationship between Ks and the various geological formations present at the site.Simultaneously, pedotransfer functions (PTF) were investigated to estimate the hydrodynamic parameters of the UZ based on the physico-chemical properties of the soil. The evaluation of these PTF confirmed their relevance for estimating hydrodynamic parameters required to reproduce the reference recharge obtained from the model calibrated and validated on data from the soil pit. However, certain limitations were observed regarding the estimation of Ks. Indeed, the development of these PTF did not account for the effects of macropores, leading to a significant underestimation of Ks and limiting their ability to accurately predict surface saturated hydraulic conductivity.Dans le cadre de l’amélioration du modèle hydrogéologique du centre du CEA Cadarache, en particulier pour une meilleure compréhension de la recharge, ce travail de thèse se concentre sur l’étude de la zone non saturée (ZNS) à travers l’analyse de ses propriétés hydrodynamiques. Il s’articule autour de trois objectifs principaux : déterminer les propriétés hydrodynamiques de la ZNS à l’échelle d’une parcelle expérimentale équipée sur le site du CEA Cadarache ; évaluer la recharge à l’échelle unidimensionnelle en utilisant des données expérimentales et des simulations réalisées avec Hydrus-1D ; et rechercher des critères permettant de spatialiser les paramètres hydrodynamiques de van Genuchten-Mualem à l’échelle du site, en particulier la conductivité hydraulique à saturation Ks. Cette démarche repose sur des analyses de sol, des mesures de Ks effectuées à l’aide d’un infiltromètre à disque, ainsi que sur l’évaluation de fonctions de pédotransfert (FPT).À l'échelle de la parcelle expérimentale, des mesures in situ de la teneur en eau volumique, de la succion et de la conductivité hydraulique Ks ont été réalisées à différentes profondeurs. Ces données ont ensuite été exploitées pour déterminer les paramètres hydrodynamiques de la ZNS, notamment ceux du modèle de van Genuchten-Mualem (θr, θs ,α,n et Ks) en s'appuyant sur l'analyse des courbes de rétention en eau et de conductivité hydraulique. Les paramètres obtenus ont ensuite été intégrés dans le modèle numérique HYDRUS-1D, permettant ainsi de simuler les transferts verticaux d'eau dans le sol et d'évaluer la recharge dite « de référence » sur la période 2014-2023.Pour évaluer la capacité d'infiltration du sol à l'échelle du site de Cadarache, des campagnes de mesures de Ks en surface ont également été réalisées. Les résultats des tests d’infiltration ont permis de sélectionner la méthode la plus appropriée pour déterminer Ks sur le site de Cadarache. L’analyse des courbes de conductivité K(h) a mis en évidence les effets des macropores, associés à la présence de racines, de matière organique et de cailloux dans certaines zones du site. De plus, pour mieux comprendre la variabilité spatiale de Ks, des analyses statistiques ont été menées pour identifier les facteurs influençant sa distribution, en tenant compte des propriétés physico-chimiques du sol, de la végétation et de la géologie. Les résultats ont permis de mettre en évidence une relation entre Ks et les différentes formations géologiques présentes à l’affleurement sur le site.Parallèlement, les FPT ont été explorées pour estimer les paramètres hydrodynamiques de la ZNS en se basant sur les propriétés physico-chimiques du sol. L'évaluation de ces FPT a confirmé leur pertinence pour l'estimation de paramètres hydrodynamiques qui permettent de reproduire la recharge de référence obtenue à partir du modèle calé et validé sur les données de la fosse pédologique. Cependant, certaines limitations ont été observées concernant la détermination de Ks. En effet, le développement de ces FPT n'a pas pris en compte l'effet des macropores, ce qui entraîne une sous-estimation significative de Ks et limite leur capacité à prédire avec précision la conductivité hydraulique à saturation en surface
Vegetation and climate reconstructions from “in and out” of archaeological contexts of the Southwest Asia
No full textInternational audienc
The MMX InfraRed Spectrometer (MIRS) for the spectral characterization of the Martian system
No full textInternational audienceMIRS (MMX InfraRed Spectrometer) is a push-broom imaging spectrometer onboard of the JAXA sample return MMX mission. It has been built by the French laboratory LESIA, today LIRA (Laboratory for Instrumentation and Research in Astrophysics) of Paris Observatory-PSL in collaboration with five other French laboratories, collaboration and financial support of CNES and close collaboration with JAXA and MELCO. MIRS, designed to accomplish the MMX scientific objectives, has been built to be adapted on MMX Exploration Module. MIRS will remotely observe the Martian system for three years. MIRS will observe Phobos, Deimos and Mars in the spectral range 0.9-3.6 µm to characterize surface composition of the satellites and investigate Martian atmospheric variations
WMSAN Python Package: From Oceanic Forcing to Synthetic Cross-correlations of Microseismic Noise
No full textInternational audienceSeismic ambient noise spectra ubiquitously show two amplitude peaks corresponding to distinct oceanic wave interaction mechanisms called primary (seismic period (T) ~ 14 s) and secondary (T ~ 7 s) microseism. Seismic noise records are used in a wide range of applications including crustal monitoring, imaging of the Earth's deep interior using noise correlations, and studies on the coupling between oceans and solid Earth. All of these applications could benefit from a robust knowledge of spatiotemporal dynamics of microseismic sources. Consequently, seismologists have been studying how to model microseismic sources of ambient noise with the recent improvements in ocean wave models. Global sea state and its derivative products are now covering the past decades in models such as the WAVEWATCHIII hindcast. This paper introduces the Wave Model Sources of Ambient Noise (WMSAN, pronounced [wam-san]) Python package. This modular package uses standardized wave model outputs to visualize ambient noise source maps and efficiently compute synthetics of seismic spectrograms and cross-correlations for surface waves (Rayleigh) and body waves (P, SV), in a user-friendly way