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Interactions Tectonique-Sédimentation dans les bassins du Boulonnais et de Dieppe-Hampshire (Manche orientale) : approche intégrée Terre-Mer le long du littoral du Nord de la France
No full textThe Eastern Channel is a complex geological area. Its current morphology results from major tectonic deformations during the Mesozoic and early Cenozoic, including extension and subsidence coeval with the opening of the North Atlantic Ocean, as well as compression involving basin inversion related to the Iberian-Eurasian convergence. The primary objective of this thesis is to refine the geometry of the deformations in the bedrock of the Eastern Channel, while evaluating their relationship at the land-sea interface along the northern coast of France. This thesis focuses on the inverted Boulonnais basin and particularly, of its southern and northern boundaries.The work relies on new structural surveys onshore, along the coast and the analysis of new high-resolution seismic data (Sparker type), complemented by lower resolution old industrial seismic data. The seismic data analysis allowed for a detailed description of the Meso-Cenozoic stratigraphic column along the Eastern Channel's border, providing further details on the spatial distribution of the Jurassic and Cretaceous series. An attempt was made to correlate the mapped seismic units with the known series onshore. The most significant stratigraphical surfaces (unconformities, erosional surfaces) were identified in the series. Structural analysis of the bedrock reveals that the Jurassic series of Kimmeridgian-Tithonian age as well as the Wealden series (Lower Cretaceous) are affected and controlled by major normal faults (E-W and N120) dipping to the south, along with antithetic faults, which have smaller displacements and dip to the north, conferring a general asymmetric half-graben structure to the basin. Several markers indicate the tectonic inversion of the Boulonnais basin, both onshore, along the coast and in the offshore domain. This inversion phase is characterized by a general parallelism between the pre-existing normal faults, locally reactivated as reverse faults, and the main anticline folds associated with them. Some major faults in the basin (Slack-Epitre, Wimereux-Belle, Nord-Bassurelle) show lateral attenuation and transfer onto parallel faults. This phenomenon is also observed for longitudinal fold axes, such as the Crèche anticline, transferred southward into the Boulogne anticline offshore. This general configuration of structural relay, between land and sea, is exemplified by the Sangatte fault, which is linked onshore to the Cap Gris-Nez-Landrethun fault system through two transfer faults with a N020-030 orientation (Wissant-Les Quénocs zone). The deformed area of Cap Gris-Nez, which stands out from the rest of the study area due to the concentration of an extensive fault network, results from the inversion process of a major normal fault (the Courte-Dune fault), coeval with the formation of the basin. This compressional reactivation results in the development of asymmetric anticlines, buttressing against an inverted fault zone, thereby characterizing a general model of "buttress folds" against a normal fault. On the southern border of the basin, the inversion of the Nord-Bassurelle fault zone and its satellites induces the formation of forced folds into the Mid-Upper Cretaceous discordant cover, directly above the reverse fault. Inverted faults rarely propagate into the Upper Cretaceous and Cenozoic cover, where deformation is essentially accommodated by folding of the cover series.La Manche orientale est une zone géologique complexe. Sa morphologie actuelle résulte des déformations tectoniques majeures du Mésozoïque et du début du Cénozoïque, comprenant l'extension et la subsidence contemporaines de l'ouverture de l'océan Atlantique Nord, ainsi que la compression impliquant une inversion des bassins liée à la convergence Ibérie-Eurasie. L'objectif principal de cette thèse est de préciser la géométrie des déformations du substratum rocheux de la Manche orientale, en particulier en évaluant leur relation à l'interface Terre-Mer le long des côtes du nord de la France. Cette thèse s'est ainsi intéressée à la géométrie du bassin inversé du Boulonnais, avec un focus particulier sur ses bordures méridionales et septentrionales. Les travaux reposent sur l'apport de nouvelles campagnes de relevés structuraux le long des côtes à terre et sur l'analyse de nouvelles données sismiques de très haute résolution (type Sparker), complétées par des données sismiques industrielles anciennes de faible résolution.L'analyse des données sismiques a permis de réaliser une description assez détaillée de la séquence stratigraphique méso-cénozoïque du substratum de la bordure nord de la Manche orientale, apportant ainsi des précisions sur la distribution cartographique des séries jurassiques et crétacées. Une tentative de corrélation des unités sismiques répertoriées en mer avec les séries connues à terre a été effectuée. Les surfaces stratigraphiques remarquables (discordances, surfaces d'érosion) ont été identifiées au sein de la série. L'analyse structurale du substratum révèle que les séries jurassiques du Kimméridgien-Tithonien et celles du Wealdien (Crétacé inférieur) sont affectées et contrôlées par des failles normales majeures (E-W et N120) à pendage vers le sud, ainsi que par leurs failles antithétiques, à déplacement plus faible et à pendage vers le nord, conférant au bassin une structuration globalement asymétrique, en large demi-graben. Plusieurs marqueurs témoignent de la phase d'inversion du bassin du Boulonnais, tant le long de la côte à terre que dans le domaine sous-marin. Cette phase d'inversion se caractérise par un parallélisme entre les failles normales préexistantes, réactivées localement en inverse, et les principaux plis anticlinaux qui leur sont associés. Certaines failles majeures du bassin (Slack-Epitre, Wimereux-Belle, Nord-Bassurelle) présentent un amortissement latéral et se transfèrent en mer sur des failles parallèles. Ce phénomène est également observé pour des axes de plis longitudinaux, tel que l'anticlinal de la Crèche, transféré en mer vers le sud, au sein de l'anticlinal de Boulogne. Ce dispositif général de relais Terre-Mer est explicité par la faille de Sangatte, relayée à terre par le système de failles du Cap Gris-Nez-Landrethun via deux failles de transfert d'orientation N020-N030 (zone de Wissant-Les Quénocs). La zone déformée du Cap Gris-Nez, qui se distingue du reste du secteur d'étude par la concentration d'un important réseau de failles, résulte du processus d'inversion d'une faille normale majeure (la faille de Courte-Dune), contemporaine de la mise en place du bassin. Ce rejeu se manifeste par le développement d'anticlinaux dissymétriques, butant contre une zone de faille inversée ; ce processus correspond à un modèle général de plis de butoir (« buttress folds ») contre une faille normale. Sur la bordure sud du bassin, le rejeu inverse de la zone de faille Nord-Bassurelle et de ses satellites entraîne la formation de plis forcés dans la couverture discordante crétacée, directement à l'aplomb de la faille inversée. Les failles inversées affectent rarement la couverture crétacée supérieure et cénozoïque, où l'on observe principalement le plissement des séries de couverture au-dessus des failles profondes
Research that has shaped the thinking of mid-career snow hydrologists
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Variabilité de la salinité de surface de l'océan à partir d'observations satellitaires et in situ autour du Groenland.
No full textInternational audienceSea Surface Salinity (SSS) is investigated south of Greenland using products derived from satellite radiometric data at pixel resolution: the weekly CCI SSS+ V4.4 dataset from the Climate Change Initiative (CCI) for 2010–2022 and a higher temporal resolution dataset, CATDS-HR, for 2015–2022. These are compared to quality assured in situ measurements. Both satellite data products reveal large positive biases on the shelves. The CCI product removes more data on the Greenland shelves and underestimates variability in this region by almost twice as much as CATDS-HR. In contrast, in regions with low SSS variability in the central North Atlantic subpolar gyre, satellite salinity products overestimate variability by 40% (0.17 instead of 0.12 pss, Practical Salinity Scale), due to uncertainties of about 0.14 pss in SSS retrievals. Nevertheless, there, CATDS-HR is 10% closer to in situ data than CCI-V4. In regions with high SSS variance, farther than 100 km from the Greenland coast, the two products capture significant seasonal and interannual SSS variability of salinity, resolving variability at 50 km length scales. Both satellite products and in situ data from 2010–2022 indicate that the freshest water in the eastern Labrador Sea occurred in September-October 2021. Then, the satellite products show a larger than 2 pss drop in SSS over the slope, and still over 1 pss 300 km further offshore, lagging behind the variability near the shelf break. This suggests that satellite SSS products contribute to resolve freshwater exchange from the shelves to the ocean interior, albeit adjustments are needed on the shelves closer to Greenland to adequately correct for systematic biases.La salinité de surface de la mer (SSS) est étudiée au sud du Groenland à l’aide de produits dérivés de données radiométriques satellitaires à résolution pixel : le jeu de données hebdomadaire CCI SSS+ V4.4 du programme Climate Change Initiative (CCI) pour la période 2010–2022, et un jeu de données à plus haute résolution temporelle, CATDS-HR, pour la période 2015–2022. Ces jeux de données sont comparés à des mesures in situ vérifiées. Les deux produits satellitaires présentent de forts biais positifs sur les plateaux continentaux. Le produit CCI élimine davantage de données sur les plateaux du Groenland et sous-estime la variabilité dans cette région presque deux fois plus que CATDS-HR. En revanche, dans les zones de faible variabilité de salinité situées dans le gyre subpolaire de l’Atlantique Nord central, les produits satellitaires surestiment la variabilité de 40 % (0,17 au lieu de 0,12 pss, selon l’échelle de salinité pratique), en raison d’incertitudes d’environ 0,14 pss dans les restitutions de SSS. Néanmoins, dans cette région, CATDS-HR est 10 % plus proche des données in situ que CCI-V4. Dans les zones à forte variance de SSS, situées à plus de 100 km des côtes groenlandaises, les deux produits capturent une variabilité saisonnière et interannuelle significative de la salinité, en résolvant les échelles spatiales de l’ordre de 50 km. Les deux produits satellitaires et les données in situ entre 2010 et 2022 indiquent que les eaux les plus fraîches de la mer du Labrador orientale ont été observées en septembre-octobre 2021. À cette période, les produits satellitaires montrent une chute de plus de 2 pss de la SSS sur le talus continental, et de plus de 1 pss à 300 km au large, avec un décalage par rapport à la variabilité près de la rupture de pente du plateau. Cela suggère que les produits satellitaires de SSS contribuent à révéler les échanges d’eau douce entre les plateaux et l’intérieur de l’océan, bien que des ajustements soient nécessaires sur les plateaux proches du Groenland pour corriger adéquatement les biais systématiques
Therapeutic Potential of Pistacia Extracts in the Prevention and Treatment of Oxidative Stress-Related Diseases: The Role of Nanotechnology in Improving Bioavailability
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Origine, distribution en taille et hygroscopicité des aérosols marins observés sur le sud-ouest de l'océan Indien à bord du Marion Dufresne
No full textMarine aerosol observations during 6 campaigns carried out in 2021 and 2023 in the south-western Indian Ocean onboard the Marion Dufresne vessel are presented. A set of aerosol instruments (SMPS, OPC-N3, CCN-100) was used to study the spatial and temporal variability of the aerosol size distri- bution, cloud condensation nuclei (CCN), activation diameters, and hygroscopicity (k). The total number of aerosols exhibited strong variability, with concentrations greater than 1500 cm-3 north of Madagascar as well as in the middle of the subtropical Indian Ocean, and lower than 200 cm-3 in the eastern part of the subtropical Indian Ocean. The strongest concentrations of supermicronic aerosols were observed south of 40 °S and were associated with primary emissions during strong winds and heavy swells. CCN measured at 0.4 % supersaturation generally fluctuated between 100 cm-3 and 500 cm-3, with occasional minima as low as 50 cm-3 . At 0.2 % supersaturation, the average activation diameter was 104 nm, with an associated k of 0.36. At 0.4 % supersaturation, the average activation diameter was 76 nm, with an average k of 0.25. Using a back-trajectory model, the aerosol data were classified according to their main source regions: continental, Subtropical Indian Ocean, and Southern Indian Ocean. The coarse mode was centered at 1.7 μm of mean diameter, with its maximum number concentration measured for the Southern Indian Ocean air masses. Aerosols were more hydrophobic for continental air masses (k from 0.1 to 0.13), hydrophilic for subtropical In- dian Ocean air masses (k from 0.24 to 0.4), and intermediate values were found for Southern Indian Ocean air masses (k from 0.17 to 0.22). Southern Indian Ocean air masses exhibited a significant drop in k values (between 0.2 % and 0.4 % supersaturation) when the wind speed increased, likely due to a higher concentration of organic species on the surface of the smallest particles. Three specific events highlighted high aerosol concentrations. Elevated Na observed during a pollution event north of Madagascar matched the passage of air masses through a well-developed boundary layer over Madagascar before their subsidence toward the ship's location. Na reaching 4000 cm-3 north of Crozet Island was related to a nucleation event, which was possible when the ship encountered clear sky conditions between two periods of cloudy sky. Finally, Na exhibited high concentrations as the ship moved away from a storm that occurred between the Kerguelen Islands and Réunion Island. Two additional case studies were carried out to observe the size distribution of aerosols under pristine conditions in the southern Indian Ocean and under the influence of Antarctic air masses south of Kerguelen.Six campagnes océanographiques ont permis de collecter des observations d'aérosols marins sur la partie sud-ouest de l'océan Indien en 2021 et 2023. Un ensemble d'instruments dédiés à la mesure d'aérosols (SMPS, OPC-N3, CCN-100) a été utilisé pour étudier la variabilité spatiale et temporelle de la distribution en taille des aérosols, des noyaux de condensation nuageux (CCN), des diamètres d'activation et de l'hygroscopicité (k). Le nombre total d'aérosols varie fortement avec des concentrations supérieures à 1500 cm-3 au nord de Madagascar et au milieu de l'océan Indien, et des concentrations inférieures à 200 cm-3 dans la partie est de l'océan subtropical Indien. Les plus fortes concentrations d'aérosols dans le mode grossier sont observées au sud de 40 °S et associées à la production primaire d'aérosols marins en condition de vent fort et de forte houle. La concentration de CCN à 0.4 % de sursaturation est globalement comprise entre 100 cm-3 et 500 cm-3 mais des valeurs aussi faibles que 50 cm-3 sont occasionnellement mesurées. À 0.2 % de sursaturation, le diamètre d'activation moyen est de 104 nm et est associé à un k de 0.36. À 0.4 % de sursaturation, le diamètre est de 76 nm et le k de 0.25. Les aérosols ont été classés selon l'origine des masses d'air en trois catégories : continentale, subtropicale indienne, océan Indien sud. Le mode grossier de la distribution en taille des aérosols est centré autour de 1.7 μm et sa concentration est maximale pour les masses d'air provenant du sud de l'océan Indien. Les aérosols des masses d'air continentales sont plus hydrophobes et associés à un k compris entre 0.1 et 0.13, ceux des masses d'air subtropicales indiennes sont plus hydrophiles et associés à des k compris entre 0.24 et 0.4, et ceux des masses d'air provenant du sud de l'océan Indien sont associés à des k compris entre 0.17 et 0.22. Une chute significative du k entre 0.2 % et 0.4 % de sursaturation lorsque la vitesse du vent augmente est observée pour les masses d'air sud indiennes, et est probablement liée à une plus forte présence d'espèces organiques à la surface des plus petits aérosols. Trois cas d'étude associés à de fortes concentrations en aérosols ont été analysés. Une période au nord de Madagascar pendant laquelle le navire est sous l'influence de masses d'air passant dans une couche limite peu développée au-dessus de Madagascar. Un cas de nucléation au milieu de l'océan Indien déclenché en période de temps clair entre deux périodes nuageuses. Une période de tempête au cours de laquelle la concentration en aérosols diminue dans un premier temps lorsque le navire est sous l'influence de masses d'air ayant traversé une zone de précipitation, puis augmente ensuite à mesure que le navire s'éloigne du système. Deux cas d'étude supplémentaires ont permis d'observer la distribution en taille des aérosols en condition pristine dans la partie sud de l'océan Indien et sous l'influence de masses d'air provenant de l'Antarctique au sud de Kerguelen
Italian still life paintings as a resource for reconstructing past Mediterranean aquatic biodiversity
No full textInternational audienceOur study explores the use of Italian still-life paintings from the Early Modern Period (16th-18th centuries) as historical records of past Mediterranean aquatic biodiversity. Following an environmental history approach, we analysed taxonomic composition in paintings, first examining geographic and temporal variations shaped by technical and socio-cultural influences. After consideration of these factors, we performed a detailed ecological interpretation of depicted taxa. Our findings reveal a shift from freshwater to marine resource use, driven by evolving fishing practices and technological advances. Socio-cultural elements, such as culinary traditions, religion and aesthetics also strongly shaped species representation. We discuss ecological interpretation of the representation of vulnerable and emblematic Mediterranean species in light of climate change, overexploitation and species biogeography. Our research highlights the powerful role of paintings in reconstructing past exploited ecosystems, offering a unique perspective for informing contemporary conservation efforts
Flow dynamics of volumes of large light particles released on submerged steep slopes
No full textInternational audienceThe aim of the study is to carry out two-phase gravity driven flows of large light particles on submerged steep slopes and, from their characteristics, identify the criteria that govern the transition between a purely dense and a mixed (dense-suspended) regime. For that, volumes of large light particles are released without any initial velocity at the top of a 2D flume immersed in a 20 m3 tank filled with tap water. The particles are spherical, monodisperse, with two different diameters: 10.6 and 14.4 mm. The volume expansion β, the height H and the front velocity Uf of the heavy flows are investigated varying the volume released between 0.2 L and 3 L, and the tilt angle of the flume (θ) between 30° and 60°. Two different regimes are observed, one where all the particles move in close contact with each other (dense regime), and as the volume and/or flume angle increases, another where part of the particles are suspended (mixed regime). We find that the overall dynamics of the flow is governed by a buoyancy/drag equilibrium ruled by the densimetric Froude number Fr = Uf/(√(∆ρg/ρw)H, with g the gravity acceleration and ∆ρ = ρ - ρw. ρ is the density of the flow and ρw that of the ambient fluid: water. The corresponding drag coefficient exerted on the particles volume is found to vary as Cd ≈ 2Fr-1.6 . The key parameter for the onset of the flow of some of the particles in suspension and the transition to the mixed regime proves to be S tθ = S t cos θ/(1 -S t sin θ), with S t = vs /Uf the Stokes number comparing the settling velocity of the particles to the flow front velocity. While pressure remains hydrostatic within the flow in the dense regime (S tθ > 0.9), it increases as suspension occurs in the mixed case and S tθ decreases. The dynamic pressure at the forehead of the volume then evolves as Ps ≈ ∆ρgHcos(θ)(1.9 - S tθ)2
Atomic-scale Insights into the Effects of Diffusion on the Binding of Adsorbed Sodium on the Surfaces of the Moon and Mercury
No full textInternational audienceThe collisionless atmospheres of the Moon and Mercury allow for different space weathering processes to occur on their surfaces. During these processes, atoms can be ejected ballistically into the exosphere, a portion of which will eventually return to the surface. These returning atoms can then adsorb on the surface with a binding energy (BE) different than that of the mineral. However, it is unknown how adsorbates sample the different possible binding sites on the surface, or how diffusion can dynamically affect the BEs and eventual desorption process. Here, we conduct molecular dynamics simulations of the adsorption, diffusion, and desorption of sodium (Na) atoms on different silicates relevant to the Moon and Mercury. We consider the effect of crystallinity and temperature on the BE and diffusion behavior of adsorbed Na over time. Results show that Na adsorption strongly depends on the surface mineral composition and the presence of bridging and nonbridging oxygen. Na on silica surfaces had the highest adsorption energy compared to albite and anorthite due to the higher proportion of exposed nonbridging oxygens on the surface. We also observe that the BE increases as the Na atoms are allowed to diffuse and desorb. This suggests that while adsorbates may initially randomly sample different binding sites, with time they will diffuse toward high-BE sites. Finally, our simulations show that with an increase in temperature, there is an increased probability of desorption
Harmonized Annual Averaged Traffic Data at Street Segment Level for European Cities
No full textInternational audienceTraffic flow data in Europe are collected locally by city authorities using different systems and standards, making it difficult to compare cities or evaluate large-scale maps, such as those used for emission inventories. To address this gap, we compiled and harmonized publicly available traffic data for 36 European cities, linking geolocalized information to road segments, spanning years from 2015 to 2024 depending on data availability. Annual Average Daily (or Weekday) Traffic is provided, and supplementary variables (e.g., truck flow percentages and speed metrics) are included where available. The data are georeferenced, with geometries corresponding to each measurement location. The dataset was enriched with additional attributes through map matching of traffic measurement locations to OpenStreetMap. Code and methodology for transforming raw data into a uniform structure are documented in Python Jupyter Notebooks, ensuring transparency and reproducibility. This dataset in a unified format facilitates cross-city comparisons and supports applications in environmental science, including the estimation of greenhouse gas and pollutant emissions, as well as urban planning and road transport management.</div
Reduction in Earth’s carbon budget imbalance
No full textInternational audienceThe Global Carbon Project (GCP) compiles an updated global carbon budget each year, synthesizing state-of-the-art estimates of anthropogenic CO 2 emissions, land and ocean sinks, and the atmospheric CO 2 growth rate. The residual between these terms, referred to as the global carbon budget imbalance, reflects the aggregate inaccuracies of the individual component estimates. Growth rates derived from marine boundary layer (MBL) surface flask mixing ratio observations are assumed to be highly accurate. Hence, land and ocean sink estimates from process models are viewed as the primary source of the imbalance. Here we show that substantial discrepancies arise when marine boundary layer growth rate estimates are used to represent the whole atmosphere. Correcting for this discrepancy using atmospheric flux inversion estimates reduces the 0.76 petagrams of carbon per year (PgC yr -1 ) root-mean-square (RMS) imbalance (from the 2023 GCP report) by up to 25%. Further investigation into the imbalance metric between the 2017 and 2023 GCP reports shows a reduction in imbalance resulting from updates to each carbon budget component, leading to a 16% overall reduction. These reductions provide quantitative evidence of improvements in process models and inventory emission estimates, driven by enhanced forcing data and the inclusion of new carbon cycle processes. Overall, we report a 37% reduction in the root-mean-square imbalance, from 0.91 to 0.57 PgC yr -1 , between the 2017 and 2023 GCP reports by combining process model and inventory improvements with atmospheric growth rate corrections. Our findings indicate that land and ocean process models are more accurate than previously believed and that the scientific understanding of Earth's carbon cycle is improving.Accurate quantification of anthropogenic carbon dioxide (CO 2 ) emissions and their redistribution among Earth's major carbon reservoirs (atmosphere, oceans, and terrestrial biosphere) is essential for tracking mitigation progress, informing climate policy, and projecting future climate trajectories 1-3 . As global temperatures rise and the impacts of climate change intensify, the scientific community is refining observational and modeling tools to constrain each component of the carbon cycle. The Paris Agreement's five-year Global</div