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Comparison of Machine Learning Algorithms for Daily Runoff Forecasting with Global Rainfall Products in Algeria
No full textInternational audienceRainfall–runoff models are crucial tools for managing water resources. The absence of reliable rainfall data in many regions of the world is a major limitation for these models, notably in many African countries, although some recent global rainfall products can effectively monitor rainfall from space. In Algeria, to identify a relevant modeling approach using this new source of rainfall information, the present research aims to (i) compare a conceptual model (GR4J) and seven machine learning algorithms (FFNN, ELM, LSTM, LSTM2, GRU, SVM, and GPR) and (ii) compare different types of precipitation inputs, including four satellite products (CHIRPS, SM2RAIN, GPM, and PERSIANN), one reanalysis product (ERA5), and observed precipitation, to assess which combination of models and precipitation data provides the optimal performance for river discharge simulation. The results show that the ELM, FFNN, and LSTM algorithms give the best performance (NSE > 0.6) for river runoff simulation and provide reliable alternatives compared to a conceptual hydrological model. The SM2RAIN-ASCAT and ERA5 rainfall products are as efficient as observed precipitation in this data-scarce context. Consequently, this work is the first step towards the implementation of these tools for the operational monitoring of surface water resources in Algeria
Aero-Map: A Data Compilation And Modeling Approach To Understand Spatial Variability In Fine- And Coarse-Mode Aerosol Composition
No full textInternational audienceAerosol particles are an important part of the Earth climate system, and their concentrations are spatially and temporally heterogeneous, as well as being variable in size and composition. Particles can interact with incoming solar radiation and outgoing longwave radiation, change cloud properties, affect photochemistry, impact surface air quality, change the albedo of snow and ice, and modulate carbon dioxide uptake by the land and ocean. High particulate matter concentrations at the surface represent an important public health hazard. There are substantial data sets describing aerosol particles in the literature or in public health databases, but they have not been compiled for easy use by the climate and air quality modeling community. Here, we present a new compilation of PM2.5 and PM10 surface observations, including measurements of aerosol composition, focusing on the spatial variability across different observational stations. Climate modelers are constantly looking for multiple independent lines of evidence to verify their models, and in situ surface concentration measurements, taken at the level of human settlement, present a valuable source of information about aerosols and their human impacts complementarily to the column averages or integrals often retrieved from satellites. We demonstrate a method for comparing the data sets to outputs from global climate models that are the basis for projections of future climate and large-scale aerosol transport patterns that influence local air quality. Annual trends and seasonal cycles are discussed briefly and are included in the compilation. Overall, most of the planet or even the land fraction does not have sufficient observations of surface concentrations – and, especially, particle composition – to characterize and understand the current distribution of particles. Climate models without ammonium nitrate aerosols omit ∼ 10 % of the globally averaged surface concentration of aerosol particles in both PM2.5 and PM10 size fractions, with up to 50 % of the surface concentrations not being included in some regions. In these regions, climate model aerosol forcing projections are likely to be incorrect as they do not include important trends in short-lived climate forcers
Melt inclusion bubbles provide new insights into crystallisation depths and CO<sub>2</sub> systematics at Soufrière Hills Volcano, Montserrat
No full textInternational audienceImproved understanding of the magmatic system of Soufrière Hills Volcano, Montserrat (SHV) is needed to inform future hazard management strategy, and remaining uncertainties include the depth of magma storage and the source of ongoing gas emissions. Eruptive activity between 1995 and 2010 has been proposed to be sourced from either a dual chamber or transcrustal mush-based magmatic system, with volatile solubility models using H2O and CO2 from melt inclusion (MI) glass estimating depths of 5–6 km. To date, published SHV MI volatile data have neglected the vapour bubbles now known to sequester the bulk of MI magmatic carbon. Total CO2 concentrations in SHV magma are therefore underestimated, together with volatile-derived entrapment pressures and inferred magma storage depths. Here, we present a new dataset of volatile (H2O and total CO2) and major element concentrations in plagioclase- and orthopyroxene-hosted SHV MI, that span almost all of the eruptive activity (Phases 1, 2, 4, and 5), and include the first measurement of bubble-hosted CO2 for SHV and indeed the Lesser Antilles Arc. Analyses were conducted using Raman spectroscopy, ion microprobe, and electron probe analysis. Dacitic–rhyolitic MI occur within andesitic whole rock compositions. Volatiles in MI glass are similar to published studies (H2O 2.47–7.26 wt%; CO2 13–1243 ppm). However, bubble-hosted CO2 contributes 9–3,145 ppm, to total inclusion CO2 with 5%–99% (median 90%) of CO2 sequestered within bubbles, and total CO2 concentrations (131–3,230 ppm) are significantly higher than previously published values. Inferred entrapment depths from our dataset range from 5.7 to 17 km – far greater than previous estimates – and support a vertically elongated magmatic system where crystallisation spanned both upper- and mid-crustal depths. Our CO2 measurements enable new estimation of CO2 sources and fluxes. As a total of 4.5 Mt of CO2 was held in SHV magma during the aforementioned phases, the maximum amount of CO2 that can be emitted from a batch of SHV magma is ∼1500–1750 tonnes/day. Measured CO2 fluxes are significantly higher, indicating additional input of CO2 into the system from greater depths. Our study shows that including bubble-hosted CO2 redefines understanding of the SHV plumbing system
Tenacibaculum platacis sp. nov., Tenacibaculum vairaonense sp. nov. and Tenacibaculum polynesiense sp. nov. isolated from batfish (Platax orbicularis) in Tahiti Island, French Polynesia
No full text[Éthique] Échantillonnages sur animauxInternational audienceTen novel Gram-negative, aerobic, non-sporulating, yellow-pigmented rod-shaped bacterial strains motile by gliding were isolated from marine organisms/environments in French Polynesia. Three of them designated as 190524A05c T , 190524A02b T and 190130A14a T were retrieved from orbicular batfish ( Platax orbicularis ) mucus. Online database comparisons using 16S rRNA amplicons resulted in over 95% similarity to the genus Tenacibaculum . Phylogenetic analyses based on 679 concatenated core protein sequences revealed that strains 190524A05c T , 190524A02b T and 190130A14a T showed the highest similarity to Tenacibaculum skagerrakense DSM 14836 T , Tenacibaculum xiamenense LMG 27422 T and Tenacibaculum holothuriorum S2-2 T , respectively. Digital DNA–DNA hybridization and average nt identity values between strains 190524A05c T , 190524A02b T and 190130A14a T and other type strains were less than 76.25 and 24.1%, respectively. The DNA G+C content was 31.48, 30.66 and 31.98 mol% for strains 190524A05c T , 190524A02b T and 190130A14a T , respectively. Menaquinone-6 was detected as the major isoprenoid quinone in these three strains. The major polar lipids (phosphatidylethanolamine and aminophospholipid) were similar to the chemotaxonomic profile of other species of the genus Tenacibaculum . Strain 190524A05c T contained summed feature 3 (comprising C 16:1 ω7c and/or iso-C 15:0 2-OH), iso-C 15:1 G, iso-C 15:0 and iso-C 17:0 3-OH as the major cellular fatty acids. Strain 190524A02b T contained summed feature 3 (comprising C 16:1 ω7c and/or iso-C 15:0 2-OH), iso-C 15:0 , iso-C 15:1 G and iso-C 17:0 3-OH as the major cellular fatty acids. Strain 190130A14a T contained iso-C 15:1 G, summed feature 3 (comprising C 16:1 ω7c and/or iso-C 15:0 2-OH), iso-C 15:0 and iso-C 17:0 3-OH as the major cellular fatty acids. Based on the phenotypic and molecular features, these three strains represent novel species of the genus Tenacibaculum for which the names Tenacibaculum platacis sp. nov., with 190524A05c T (= CIP 112470 T = DSM 118113 T ) as the type strain; Tenacibaculum vairaonense sp. nov., with 190524A02b T (= CIP 112469 T = DSM 118112 T ) as the type strain; and Tenacibaculum polynesiense sp. nov., with 190130A14a T (= CIP 112468 T = DSM 118111 T ) as the type strain, are proposed
Arctic sea-ice loss drives a strong regional atmospheric response over the North Pacific and North Atlantic on decadal scales
No full textInternational audiencePrevious studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is little scientific consensus on the features of these remote responses, with the opposite impacts reported. Here we present a multi-model analysis of the decadal climate response to Arctic sea-ice loss using state-of-the-art energy conserving methodologies to isolate the impacts of sea-ice decline. We observe weakening of the Aleutian Low and development of a geopotential ridge in the North Pacific, associated with drier winter conditions over the southwest United States. Over the Atlantic, a negative NAO-like response drives wetter winter conditions across the western Mediterranean. These decadal-scale impacts substantially differ from reported centennial-scale responses to Arctic sea-ice loss simulated using non-energy conserving methodologies. Factors such as the timescale of the response and methodologies used to isolate the impacts of disappearing sea-ice cover should be carefully considered when consolidating scientific understanding on the future impacts of changing Arctic
Compte-rendu de la réunion du comité scientifique et éditoriale de la revue Naturae - 11 mars 2025
No full textLa première réunion du comité scientifique et éditorial de la revue Naturae s’est tenue le 11 mars 2025.Cette journée fut l’occasion de présenter une synthèse complète depuis le lancement de la revue en 2017 (nombre d’articles publiés, refusés, thématiques abordées, structures des auteurs, nombres de relecteurs, etc.) mais aussi de faire le point sur les nouveautés et les projets en cours tel que la conversion des articles en xml.L’après-midi a permis aux membres de ce comité scientifique et éditorial d’échanger sur d’éventuels difficultés rencontrées, d’améliorations possibles et d’identifier les orientations et stratégies souhaitées pour les années à venir
Un outil d’aide à la décision pour élaborer une stratégie collective de sécurisation de l’AEP
No full textInternational audienceGrowing pressure on water resources is posing new challenges for stakeholders in the drinking water supply (DWS) sector, calling on them to think collectively on a larger scale than that on which they currently operate. To support these evolutions, the present article proposes an original decision-support approach, combining a participatory approach and modeling. The approach is based on the co-construction and participatory use of a hydro-economic model simulating the operation of the drinking water supply system, taking into account interdependencies between drinking water supply management entities (through shared resources and interconnection infrastructure). This approach makes it possible to explore different prospective scenarios, to collectively plan for future drinking water supply security on a relevant scale. The approach was implemented in Sud-Finistère (Brittany, France), engaging the different stakeholders involved with drinking water management in the region. It has built a shared vision of the challenges facing drinking water management in the region, and quantified the future water deficits for different prospective scenarios co-constructed with stakeholders. Various types of results and indicators, notably maps, are available for analysis to identify any limiting factors and bottlenecks. Building on these diagnoses, the approach has made it possible to assess the effectiveness of multiple adaptation measures and combinations of measures co-constructed by stakeholders. The simulations provide objective information on the expected effects of the measures, facilitating dialogue between stakeholders who may have differing preconceptions as to their effectiveness, thereby fuelling collective planning on the actions to be implemented to secure future drinking water security. The proposed approach was positively evaluated by the participants. It is replicable in other regions where needed.Les tensions croissantes sur les ressources en eau posent de nouveaux défis aux acteurs de l’alimentation en eau potable (AEP), les invitant à réfléchir collectivement à une échelle plus large que celle à laquelle ils fonctionnent actuellement. Pour accompagner ces évolutions, cet article propose une démarche d’aide à la décision originale, combinant approche participative et modélisation. La démarche s’appuie sur la co-construction et l’utilisation participative d’un modèle hydro-économique simulant le fonctionnement du système d’approvisionnement en eau potable, prenant en compte les interdépendances entre les collectivités (ressources partagées, interconnexions). L’approche permet d’explorer différents scénarios prospectifs pour réfléchir de façon collective à la sécurisation de l’AEP à une échelle pertinente. La démarche a été mise en œuvre dans le Sud Finistère, mobilisant les différents acteurs de la gestion de l’eau potable du territoire. Elle a permis de construire une vision partagée des enjeux de gestion de l’AEP sur le territoire, d’anticiper et de quantifier les déficits ressources-besoins des collectivités pour différents scénarios d’évolutions futures co-construits avec les parties prenantes. Différents types de résultats et d’indicateurs, notamment des cartographies, sont analysables en sortie de simulation pour identifier les éventuels facteurs limitants et points de blocage. Face à ces diagnostics, la démarche a permis d’évaluer l’efficacité de multiples mesures et combinaisons de mesures d’adaptation proposées par les acteurs. Les simulations fournissent une base d’information objective sur les effets attendus des mesures, facilitant le dialogue entre des parties prenantes pouvant avoir des a priori divergents quant à leur efficacité, et alimentant ainsi la réflexion sur les actions à entreprendre pour orienter favorablement l’avenir. La démarche proposée a été évaluée positivement par les participants. Elle est reproductible sur d’autres territoires
Vegetation and climate changes during the Middle to Upper Palaeolithic transition in the southwestern Mediterranean: What happened to the last Neanderthals during Heinrich stadial 4?
No full textInternational audienceDuring the last glacial period, and particularly Marine Isotope Stage 3 (MIS 3, dated 60–27 ka), various abruptand arid climate episodes impacted the northern hemisphere. These are known as Heinrich Stadials and arelinked with major iceberg discharged in the North Atlantic. Heinrich Stadial 4 (HS4), one of the strongest of theseevents occurring around 39 ka BP, has raised numerous debates regarding its potential impact on the Middle toUpper Palaeolithic transition (MUPT) and Neanderthal extinction, especially in the Iberian Peninsula where latepersistence of Neanderthals has been claimed beyond 40 ka BP. Although palynological studies from the Iberianmargins have previously highlighted vegetation changes during this period, these have generally been of lowresolution and thus, the environmental conditions during HS4 and the possible impact of this event on the lastNeandertal populations are still poorly understood.This study uses the marine core from Ocean Drilling Program (ODP) Site 976, located in the Alboran Sea, toprovide new ultra-high-resolution analyses for the interval between 41 and 34 ka BP, including the GreenlandStadial 9 (GS9)/HS4 and the Greenland Interstadial 8 (GI8). The aim is to reconstruct vegetation and climatechanges in southern Mediterranean with a resolution never achieved before and to discuss human occupation inthe frame of these changes. Vegetation, climate changes and human occupation are discussed on the basis of 1) pollen analysis, 2) quantitative climate reconstructions based on a multi-method approach, and 3) maps ofhuman occupation based on a synthesis of archaeological sites for western Mediterranean Europe in the 42–34 ka BP time interval. Results show a fast spread at centennial scale of steppe and semi-desert vegetation, with atypical three-phased pattern for the GS9 (HS4). This pattern is compatible with the results of various records from Greenland, southwestern Europe and Brazil. The description of these phases with an unpreceded resolution for the SW Mediterranean region supports the connection between the hydroclimatic changes in Greenland and lower latitudes, while the transition to the following GI8 climate amelioration displays a major vegetation instability that mimics the pattern of the last deglaciation at sub-millennial scale. The climate reconstructionshows cold conditions during HS4 and enhanced aridity mostly linked to the winter rainfall deficit caused by the abrupt disturbance of the Mediterranean seasonal regime of precipitations. The regional comparison with available palynological and paleoclimatic records from the western Mediterranean and the Atlantic sheds light on the spatial expression of the arid event, highlighting a south-westward trend in aridification in the Iberian Peninsula. The Alboran Sea appears as a critical area at the interface of the Atlantic and Mediterranean influences, recording the particular expression of fast climate oscillations in the westernmost part of the Mediterranean. The possible impact of such extreme climate event on the MUPT is discussed based on an updated dataset of archaeological sites and dates for western Mediterranean Europe in the 42–34 ka BP time interval.Maps of human occupation show that Neanderthals may have undergone population contraction during the aridconditions of HS4, but it is still challenging to place the MUPT in a sub-millennial chronological framework dueto the uncertainty and limitations of archaeological data
Seismic structure of Martian mantle inferred from in situ sound velocity measurements
No full textInternational audienceWe report elastic wave velocity (Vp: P-Waves velocity, and Vs: S-wave velocities) measurements of iron-enriched pyrolite aggregates by a combination of ultrasonic interferometry, synchrotron radiation techniques and multi-anvil apparatus experiments. We carried out eight synchrotrons in situ experiments on two different bulk pyrolite compositions with Fe/(Fe + Mg) ratio (Fe#) of 0.17 and 0.27, over a range of pressures from 3 to 16 GPa and temperatures up to 1000 °C. These data are complemented by seven laboratory ex situ experiments between 5 and 16 GPa and temperatures varying from 900 °C to 1300 °C, using the same starting compositions. Based on these results and previous data on pyrolite composition, we modeled the effect of iron on seismic profiles along several possible Martian areotherms.If, as reported in previous works, the Martian mantle had a very high Fe#, for instance Fe# = 0.27, it would be composed of four layers separated by three seismic discontinuities. They would be located at depths of ∼620 km (ΔVp of +8.25 %; ΔVs of +6.72 %), ∼880 km (ΔVp of +2.35 %; ΔVs of 0.03 %) and ∼ 1130 km (ΔVp of −17.88 %; ΔVs of −13.05 %). However, since there is no major discontinuity inferred by InSight's seismic data at depths shallower than 1000 km, we conclude that the Martian mantle presents a Fe# significantly lower than 0.20. For the Fe#0.17 composition, our experiments show a single discontinuity (ΔVp of +5.62 %; ΔVs of +10.44 %) induced by the transition from olivine to wadsleyite at ∼980 km depth, which is compatible with the seismic data
Soil Organic Carbon Turnover Following Afforestation of a Savanna Revealed by Particle-Size Fractionation and Natural <sup>13</sup>C Measurements in Ivory Coast
No full textInternational audienceSoil organic matter plays a crucial role in the global carbon cycle, yet the magnitude and direction of changes in soil carbon content following vegetation shifts in the tropics remain highly debated. Most studies have focused on short-term changes, typically spanning only a few months or years. In this study, we investigated the medium-term dynamics of organic matter at a site where savanna, protected from fire for 58 years, has gradually transitioned to woodland vegetation. Natural 13C abundance analysis combined with particle-size fractionation was used to characterize the changes in SOM over time. While carbon content remains relatively stable, δ13C exhibits a distinct shift, particularly in the surface layers, reflecting the gradual replacement of savanna-derived carbon with tree-derived carbon. All fractions were influenced by the inputs and outputs of carbon from both savanna and tree sources. In the coarse fractions, most of the carbon originates from trees; however, a significant proportion of savanna-derived carbon (ranging from 10% to 40%, depending on the fraction, depth, and patch) persists, likely in the form of black carbon. In the fine fractions, nearly half of the carbon (40% to 50%) remains derived from the savanna, highlighting the greater stability of organic matter that is physically bound to clays and protected within microaggregates