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Modélisation à phase résolue de la transformation des vagues en zone de surf sur des fonds rugueux idéalisés
No full textRough rocky seabeds dominate world's coastlines, making accurate modeling of wave transformation in such environments essential for understanding coastal processes and hazards. Wave breaking and friction are critical drivers of wave dissipation over rough seabeds, especially in the surf zone. Phase-resolved wave models, often relying on classical bed shear stress or canopy drag approaches, can fail to capture these processes due to limitations in their physical assumptions, especially for large roughness elements typical of rocky seabeds. The present study adapts the Bulk Canopy Drag (BCD) parameterization, inherited from vegetation and porous media studies, into the 3D non-hydrostatic phase-resolved SYMPHONIE model to simulate wave dissipation over rough seabeds. The model was tested against laboratory experiments (LEGOLAS), using controlled irregular wave forcing propagating over a rough ramp. Results reveal that turbulent drag dominates the outer surf zone, while inertial drag plays a key role in the inner surf zone. A combined optimization of these influences achieved strong agreement with experimental measurements under one irregular wave forcing and a specific bottom configuration. These findings underscore the importance of accurately incorporating both turbulent and inertial contributions into wave dissipation models for the rocky surf zone. The proposed BCD approach provides a promising framework for improving phase-resolved modeling of wave dynamics, with potential applications for more complex field conditions. Future work will aim to extend the approach to diverse roughness configurations and refine empirical coefficients for broader scalability and in situ applicability.Les fonds marins rocheux rugueux dominent les côtes du monde entier, ce qui rend la modélisation précise de la transformation des vagues dans de tels environnements essentielle à la compréhension des processus et des risques côtiers. Le déferlement et le frottement des vagues sont des facteurs essentiels de la dissipation des vagues sur les fonds marins rugueux, en particulier dans la zone de déferlement. Les modèles de vagues à phase résolue, qui reposent souvent sur les approches classiques de la contrainte de cisaillement de fond ou de la traînée de canopée, ne parviennent pas toujours à capturer ces processus en raison des limites de leurs hypothèses physiques, en particulier pour les grands éléments de rugosité typiques des fonds marins rocheux. La présente étude adapte la paramétrisation de la traînée de canopée (Bulk Canopy Drag), héritée des études sur la végétation et les milieux poreux, du modèle non hydrostatique 3D à phase résolue SYMPHONIE pour simuler la dissipation des vagues sur des fonds marins rugueux. Le modèle a été testé par rapport à des expériences en laboratoire (LEGOLAS), en utilisant un forçage de vagues irrégulières se propageant sur une rampe rugueuse. Les résultats révèlent que la traînée turbulente domine la zone de déferlement extérieure, tandis que la traînée inertielle joue un rôle clé dans la zone de déferlement intérieure. Une optimisation combinée de ces influences a permis d'obtenir une forte concordance avec les mesures expérimentales sous un forçage de vague irrégulier et une configuration de fond spécifique. Ces résultats soulignent l'importance d'incorporer avec précision les contributions turbulentes et inertielles dans les modèles de dissipation des vagues pour la zone de déferlement rocheuse. L'approche BCD proposée fournit un cadre prometteur pour l'amélioration de la modélisation de la dynamique des vagues résolue en phase, avec des applications potentielles pour des conditions de terrain plus complexes. Les travaux futurs viseront à étendre l'approche à diverses configurations de rugosité et à affiner les coefficients empiriques en vue d'une plus grande applicabilité sur divers sites rugueux
Global Carbon Budget 2024
No full textInternational audienceAccurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize datasets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC) are based on land-use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The global net uptake of CO2 by the ocean (SOCEAN, called the ocean sink) is estimated with global ocean biogeochemistry models and observation-based fCO2 products (fCO2 is the fugacity of CO2). The global net uptake of CO2 by the land (SLAND, called the land sink) is estimated with dynamic global vegetation models. Additional lines of evidence on land and ocean sinks are provided by atmospheric inversions, atmospheric oxygen measurements, and Earth system models. The sum of all sources and sinks results in the carbon budget imbalance (BIM), a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2023, EFOS increased by 1.3 % relative to 2022, with fossil emissions at 10.1 ± 0.5 GtC yr−1 (10.3 ± 0.5 GtC yr−1 when the cement carbonation sink is not included), and ELUC was 1.0 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission (including the cement carbonation sink) of 11.1 ± 0.9 GtC yr−1 (40.6 ± 3.2 GtCO2 yr−1). Also, for 2023, GATM was 5.9 ± 0.2 GtC yr−1 (2.79 ± 0.1 ppm yr−1; ppm denotes parts per million), SOCEAN was 2.9 ± 0.4 GtC yr−1, and SLAND was 2.3 ± 1.0 GtC yr−1, with a near-zero BIM (−0.02 GtC yr−1). The global atmospheric CO2 concentration averaged over 2023 reached 419.31 ± 0.1 ppm. Preliminary data for 2024 suggest an increase in EFOS relative to 2023 of +0.8 % (−0.2 % to 1.7 %) globally and an atmospheric CO2 concentration increase by 2.87 ppm, reaching 422.45 ppm, 52 % above the pre-industrial level (around 278 ppm in 1750). Overall, the mean of and trend in the components of the global carbon budget are consistently estimated over the period 1959–2023, with a near-zero overall budget imbalance, although discrepancies of up to around 1 GtC yr−1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows the following: (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the mean ocean sink. This living-data update documents changes in methods and datasets applied to this most recent global carbon budget as well as evolving community understanding of the global carbon cycle. The data presented in this work are available at https://doi.org/10.18160/GCP-2024 (Friedlingstein et al., 2024)
Socio-economic inequalities in access to COVID-19 tests in France in 2020: evidence from the EPICOV socio-epidemiological cohort
No full textInternational audienceTesting for COVID-19 has been strongly recommended for individuals experiencing COVID-19-like symptoms or those with a close relative who tested positive. In France, tests were free of charge until mid-October 2021 and became widely available after June 2020. Our main objective was to investigate whether access to COVID-19 testing in France was associated with socio-economic conditions, considering gender and ethno-racial status. Methods A random population-based cohort survey was conducted in France in May 2020 and November 2020, including 95,388 participants aged 18 and over. We used logistic regressions to identify how having been tested in 2020 was associated with socio-economic status and exposure factors among two groups of individuals. The first group consisted of individuals who had no close relative test positive but reported experiencing Covid-19-like symptoms, such as cough, fever, dyspnea, or sudden onset of ageusia, dysgeusia, or anosmia (N=12,729). The second group included individuals, with or without symptoms, who reported that a close relative had tested positive for Covid-19 (N=5,360). Findings In both groups, testing was more frequent among individuals living in urban areas. For individuals who had no close relative test positive but reported Covid-19-like symptoms, women were 1.04 (95%CI [1.01-1.06]) more likely than men to be tested, and testing decreased with age up to 35. Individuals holding a university degree were 1.08 [1.04-1.12]) more likely than those who only completed high school to be tested, as well as those in one of the three top income deciles with reference to the bottom decile (OR 1.07, [1.02-1.13] for the top decile). Ethno-racial status was not significantly associated with testing. For respondents who had a close relative test positive, testing was strongly associated with having experienced some symptoms, especially after September 1 (OR 1.34, 95%CI [1.30-1.39]). However, there was no link between testing and income, education, or ethno-racial status. Interpretation When an individual experiences symptoms but has no close relative who is positive, the motivation to test to avoid transmitting the virus to relatives by isolating oneself is particularly strong. This strategy makes sense when there are actual possibilities to isolate, which may explain why higher income and education positively impact the propensity to test. For individuals who had a close relative test positive, most socio-economic variables were no longer related to testing once infection risk was controlled for. The availability of tests at no cost is not sufficient in itself to eliminate socio-economic inequalities in testing
Alpha and beta diversities of hydrothermal vent macrofaunal communities along the southwestern Pacific back-arc basins
No full textInternational audienceEcosystems face various pressures, often leading to loss of biodiversity. Understanding how biodiversity is spatially structured, what are the driving factors, and the ecological and evolutionary processes involved is essential to assess communities’ resilience to disturbances and guide efficient conservation measures. Hydrothermal vents from national waters of the West Pacific are targeted by mining industries for their mineral resources that include metals used in high-tech equipment. Although exploitation has not yet started, such activity could significantly affect ecosystem biodiversity and functioning. Here, we describe the distribution of hydrothermal biodiversity in the Southwest Pacific back-arc basins and the Futuna Volcanic Arc at different spatial scales in relation to environmental conditions and geography. We focused on three assemblages dominated by symbiotic megafauna: snails (Alviniconcha spp. and Ifremeria nautilei) and mussels (Bathymodiolus spp.). Faunal assemblages exhibit strong spatial structuring: between habitats along the dilution gradient of the hydrothermal fluid, and between geographic basins, with a faunal split between the Western and the Eastern basins of this region, and to a lesser extent, between fields in a basin. Species replacement along the chemical gradient drives faunal changes between Ifremeria and Bathymodiolus assemblages, while a drop in the number of species is noted when making this comparison with the Alviniconcha assemblage. While these local changes may result from environmental filtering along the diffuse flow gradient, geological settings and current geographic barriers, which drive colonization and speciation at larger scales, are likely shaping the vent community changes between the Eastern and Western basins. This result has significant implications for biodiversity conservation, especially in this mineral-rich setting. The Manus Basin is isolated and displays the highest proportion of endemism while the Woodlark Basin represents an important stepping-stone between the Eastern basins and Manus Basin, making them potentially highly vulnerable to mining with a risk of biodiversity loss
Analysis of the abundance of radiocarbon samples as count data
No full textPreprint version 3 of this article has been peer-reviewed and recommended by Peer Community In Archaeology (https://doi.org/10.24072/pci.archaeo.100583; Hanna, 2025). Recommandation by Jonathan Hanna based on reviews by Thomas Huet and 1 anonymous reviewer: https://archaeo.peercommunityin.org/articles/rec?id=583.International audienceThe analysis of the abundance of radiocarbon samples through time has become a popular method to address questions of demography in archaeology. The history of this approach is marked by the use of the Sum of Probability Distributions (SPD), a key methodological development that first allowed researchers to visualize the abundance of radiocarbon samples on a calibrated temporal scale. However, the lack of a mathematical definition hinders the use of SPD in a proper statistical framework. Recent developments of model-based approaches have allowed a more rigorous statistical analysis of the abundance of radiocarbon data. Despite these advances, these methods inherit from the SPD an interpretation of the abundance of samples as a probability distribution. In this work we propose a change of perspective by treating radiocarbon data as count data. We present an approach that models the expected number of samples occurring at each year. We argue that this model provides more interpretable parameters and better accounts for the uncertainty in the number of samples. The performance of the proposed approach is evaluated through simulations and compared to an alternative state-of-the-art approach. Our new method is competitive with the state-of-theart model. Furthermore, we demonstrate the computational burden of using the SPD as summary statistics under an approximate Bayesian computation analysis and propose more efficient summary statistics. Finally, we use a dataset of radiocarbon samples from Ireland and Britain to provide an application example. The results of these analyses are largely congruent with previous work on the same dataset except in revealing an earlier start of the Neolithic demographic expansion
Malian field isolates provide insight into Plasmodium malariae intra-erythrocytic development and invasion
No full textInternational audiencePlasmodium malariae is the third most prevalent human malaria parasite species and contributes significantly to morbidity. Nevertheless, our comprehension of this parasite’s biology remains limited, primarily due to its frequent co-infections with other species and the lack of a continuous in vitro culture system. To effectively combat and eliminate this overlooked parasite, it is imperative to acquire a better understanding of this species. In this study, we embarked on an investigation of P. malariae , including exploring its clinical disease characteristics, molecular aspects of red blood cell (RBC) invasion, and host-cell preferences. We conducted our research using parasites collected from infected individuals in Mali. Our findings revealed anaemia in most of P. malariae infected participants presented, in both symptomatic and asymptomatic cases. Regarding RBC invasion, quantified by an adapted flow cytometry based method, our study indicated that none of the seven antibodies tested, against receptors known for their role in P. falciparum invasion, had any impact on the ability of P. malariae to penetrate the host cells. However, when RBCs were pre-treated with various enzymes (neuraminidase, trypsin, and chymotrypsin), we observed a significant reduction in P. malariae invasion, albeit not a complete blockade. Furthermore, in a subset of P. malariae samples, we observed the parasite’s capability to invade reticulocytes. These results suggest that P. malariae employs alternative pathways to enter RBCs of different maturities, which may differ from those used by P. falciparum
How Well Do AMIP6 and CMIP6 Reproduce the Specific Extreme El Niño Teleconnections to North America?
No full textInternational audienceExtreme El Niño events (e.g., 1982–1983, 1997–1998) are characterized by strong, eastward‐shifted warm Sea Surface Temperature anomalies, and a southward migration of the eastern Pacific Inter‐Tropical Convergence Zone (ITCZ) to the equator. Using an ensemble simulation with a single AMIP6 model, Beniche et al. (2024, https://doi.org/10.1038/s41598‐024‐52580‐9 ) suggested that such events uniquely yield an eastward shift of the Pacific‐North American (PNA) teleconnection pattern, with specific impacts over North America. Here, we first examine the robustness of these results in 135 ensemble members from 23 different AMIP6 models. The specific, eastward‐shifted extreme El Niño teleconnection pattern is robust in all models but one. It is also highly reproducible across years and ensemble members, due to stronger teleconnection amplitude than that of internal atmospheric noise. This yields specific, predictable impacts (defined as 0.5 STD) such as warm conditions over Northeast America (69% chances), and wet anomalies over California (77%) and Florida (97%). We then show that 26 out of the 42 CMIP6 models we examined reproduce extreme El Niño events, defined as El Niño events associated with large eastern Pacific rainfall anomalies. These models tend to have a weaker cold tongue bias than the rest of CMIP6. Despite a degradation in performance from AMIP6 to CMIP6, 18 out of the 26 selected models capture the specific extreme El Niño teleconnections, albeit with some underestimation of wet anomalies over California and Florida. We end by discussing implications for future North American climate projections based on CMIP6
Metabolic versatility and nitrate reduction pathways of a new thermophilic bacterium of the Deferrivibrionaceae: Deferrivibrio metallireducens sp. nov isolated from hot sediments of Vulcano Island, Italy
No full textInternational audienceA novel thermophilic (optimum growth temperature ~ 60 °C) anaerobic Gram-negative bacterium, designated strain V6Fe1 T , was isolated from sediments heated by the hydrothermal circulation of the Aeolian Islands (Vulcano, Italy) on the seafloor. Strain V6Fe1 T belongs to the recently described family Deferrivibrionaceae in the phylum Deferribacterota. It grows chemoorganotrophically by fermentation of proteinaceous substrates and organic acids or by respiration of organic compounds using fumarate, nitrate, Fe(III), S°, and Mn(IV) as electron acceptors. The strain V6Fe1 T can also grow chemolithoautotrophically using H 2 as an electron donor and nitrate, nitrous oxide, Fe(III), Mn(IV), or sulfur as an electron acceptor. Stable isotope probing showed that V6Fe1 T performs denitrification with nitrate reduction to dinitrogen and Dissimilatory Nitrate Reduction to Ammonium (DNRA). Culture experiments with RT-qPCR analysis of target genes revealed that strain V6Fe1 T performs DNRA with the nitrite reductase formate-dependent NrfA and denitrification with an Hcp protein and other redox partners yet to be identified. Genomic analysis and experimental data suggest that strain V6Fe1 T performs autotrophic carbon fixation via the recently discovered reversed oxidative TCA cycle (roTCA cycle). Based on genomic (ANI) and phenotypic properties, strain V6Fe1 T ( = DSM 27501 T = JCM 39088 T ) is proposed to be the type strain of a novel species named Deferrivibrio metallireducens.</div
Restricted feeding of goats during the last third of gestation and trans-generational effects on plasma progesterone in their female offspring
No full textInternational audienceFeeding levels can vary in goat farms for several reasons. Underfeeding of gestating dairy goats can occur and may influence fetal follicle development and future reproductive performance in their offspring. The objective of this experiment was to study the effect of restricted feeding during the last third of gestation on some reproductive parameters in female offspring (F1). Two feeding groups were formed using 60 Alpine and Saanen dairy goats to produce the F1 female offspring. The control group (C, n = 30) was fed to requirements. The restricted group (R, n = 30) was given the same diet, but the quantity corresponded to 50% of the amount given to the C group between -8 and -4 weeks, 60% between -5 and -4 weeks, 70% between -4 and -3 weeks and 80% from -2 weeks to parturition. Estrus was synchronized at 7 months of age in female F1 goats born to C (n = 17) or born to R goats (n = 15) with a progestagenimpregnated sponge and prostaglandin F2α and eCG injections, and the goats were inseminated. Serial blood samples were collected over this period. After mating, plasma progesterone rose more slowly to reach a maximum plateau concentration in females born to R goats compared to females born to C goats (P < 0.05). The lag time was approximately 2 days. There was no difference in dam F0 prolificacy (C, 2.4 ± 0.6 vs. R, 2.1 ± 0.8, P > 0.05), length of gestation (C, 151 ± 2 days vs. R, 151 ± 2 days) and kid mortality rate (mummified fetuses, stillbirth or death in first 48h) between the groups. However, birth weight was lower in R kids compared to C kids (4.0 ± 0.11 kg vs. 4.5 ± 0.10 kg, P = 0.007). In conclusion, maternal feed restriction during late pregnancy modified progesterone patterns after insemination in female offspring, although there was no effect on reproductive success