Environmental changes in SW France during the Middle to Upper Paleolithic transition from the pollen analysis of an eastern North Atlantic deep-sea core
Evaluating synchronies between climate and cultural changes is a prerequisite for addressing the possible effect of environmental changes on human populations. Searching for synchronies during the Middle-Upper Paleolithic transition (ca. 48–36 ka) is hampered by the limits of radiocarbon dating techniques and the large chronological uncertainties affecting the archaeological and paleoclimatic records, as well by their low temporal resolution. Here, we present a high-resolution, pollen-based vegetation record from the Bay of Biscay, sea surface temperature changes, additional 14 C ages, and a new IRSL date on the fine-sediment fraction of Heinrich Stadial (HS) 6. The IRSL measurements give an age of ca. 54.0 ± 3.4 ka. The paleoclimatic results reveal a succession of rapid climatic changes during the Middle-Upper Paleolithic transition in SW France (i.e. D-O 12–8 and two distinct climatic phases during HS 4). Comparison of the new paleoclimatic record with chronologically well-constrained regional archaeological changes shows that no synchronies exist between cultural transitions and environmental changes. The disappearance of Neanderthals and the arrival of Homo sapiens in SW France encompassed a long-term forest opening, suggesting that Homo sapiens may have progressively replaced Neanderthals from D-O 10 to HS 4 through competition for the same ecological niches.
(Quaternary Research, n° 0033-5894, pp. 1-18, 30/05/2022)
UB, UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPHE, PSL, LMJL, CNRS, Nantes univ - UFR ST, Nantes Univ
AMOC thresholds in CMIP6 models: NAHosMIP
The Atlantic meridional overturning circulation (AMOC) is an important part of our climate system, which keeps the North Atlantic relatively warm. It is predicted to weaken under climate change. The AMOC may have a tipping point beyond which recovery is difficult, hence showing quasi-irreversibility (hysteresis). Although hysteresis has been seen in simple models, it has been difficult to demonstrate in comprehensive global climate models. We present initial results from the North Atlantic hosing model intercomparison project, where we applied an idealised forcing of a freshwater flux over the North Atlantic in 9 CMIP6 models. The AMOC weakens in all models from the freshening, but once the freshening ceases, the AMOC recovers in some models, and in others it stays in a weakened state. We discuss how differences in feedbacks affect the AMOC response.
(27/05/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Persistent influence of precession on northern ice sheet variability since the early Pleistocene
Prior to ~1 million years ago (Ma), variations in global ice volume were dominated by changes in obliquity; however, the role of precession remains unresolved. Using a record of North Atlantic ice rafting spanning the past 1.7 million years, we find that the onset of ice rafting within a given glacial cycle (reflecting ice sheet expansion) consistently occurred during times of decreasing obliquity whereas mass ice wasting (ablation) events were consistently tied to minima in precession. Furthermore, our results suggest that the ubiquitous association between precession-driven mass wasting events and glacial termination is a distinct feature of the mid to late Pleistocene. Before then (increasing), obliquity alone was sufficient to end a glacial cycle, before losing its dominant grip on deglaciation with the southward extension of Northern Hemisphere ice sheets since ~1 Ma.
(Science. vol. 376, n° 0036-8075, pp. 961-967, 27/05/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of volcanic eruptions in CMIP6 decadal prediction systems: a multi-model analysis
In recent decades three major volcanic eruptions of different intensity have occurred: Mount Agung (1963), El Chichón (1982) and Mount Pinatubo (1991), with reported climate impacts on seasonal-to-decadal timescales and providing a high prediction potential. The Decadal Climate Prediction Project component C (DCPP-C) includes a protocol to investigate the impact of such volcanic eruptions on decadal prediction, which consists in performing initialised sets of predictions just before the three historical volcanic eruptions, but in which the volcanic aerosol forcing is excluded. The impact of the volcanic eruptions is therefore determined by comparing these new forecasts with those included in the corresponding retrospective prediction experiment DCPP-A, which include historical volcanic aerosol forcing. Here we present the results from six CMIP6 decadal prediction systems (CanESM5, CESM1, EC-Earth3, HadGEM3, IPSL-CM6A and CMCC-CM2-SR5). The global mean temperature cooling is comparable among models and consistent with previous studies. The surface temperature response pattern in the first years is similar across all the models and for the individual volcanic eruptions. At later forecast times (years 6-9), differences among the models and eruptions emerge. Preliminary results show that the volcanic eruptions impact the atmospheric and oceanic dynamics, as shown in previous studies, although some differences across models emerge, specifically on the ocean overturning and gyre circulation changes.
(pp. EGU22-13395, 27/05/2022)
BSC-CNS, CMCC, MOHC, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, CCCma, ECCC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NCAR
Fire variability in the southeastern France over the past 8500 years
(23/05/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, HNHP, MNHN, UPVD, CNRS
Effects of Biofilms and Particle Physical Properties on the Rising and Settling Velocities of Microplastic Fibers and Sheets
Vertical dynamics of microplastics (MPs) in the water column are complex and not fully understood due to the diversity of environmental MPs and the impact of weathering and biofouling on their dynamical properties. In this study, we investigate the effects of the particle properties and biofilm on the vertical (settling or rising) velocity of microplastic sheets and fibers under laboratory conditions. The experiments focus on 3 types of MPs (polyester PES fibers, polyethylene terephthalate PET sheets, and polypropylene PP sheets) of 9 sizes and 2 degrees of biological colonization. Even though pristine PES fibers and PET sheets had a similar density, the sinking velocity of fibers was much smaller and independent of their length. The settling or rising velocity of sheets increased with the particle size up to a threshold and then decreased due to the wake of horizontal oscillations in large particles. Biofilm had unexpected effects on vertical velocities. Irregular biofilm distributions can trigger motion instabilities that decrease settling velocities of sheets despite the increase of density. Biofilm can also modify the orientation of fibers, which may increase their settling velocity. Finally, we selected the most performant theoretical formulation for each type of particle and proposed modifications to consider the effect of biofilm distribution.
(Environmental Science and Technology, n° 0013-936X, 20/05/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, SIAME, UPPA
Approche multi-analytique optique et moléculaire pour construire des empreintes de matière organique dissoute (MOD) typiques de sources naturelles et anthropiques
Dans un contexte d’amélioration de la connaissance des apports anthropiques dans les cours d’eau, la question de l’utilisation de la matière organique dissoute (MOD) pour différencier les types d’apports (e.g. agricoles, industriels et urbains) reste un réel défi. L’objectif de cette étude est de déterminer des marqueurs physico-chimiques caractéristiques de sources naturelles (e.g. apports terrigènes, production autochtone) et anthropiques (e.g. rejets de stations de traitement des eaux usées STEU, ruissellement urbain) de MOD à l’échelle de bassins versants. Pour cela, les principaux types de sources de MOD ont été identifiés et échantillonnés à partir de ressources géographiques. Ensuite, la MOD de chaque type de source a été caractérisée en utilisant un large panel de techniques analytiques : dosage du carbone organique dissous, analyse par spectroscopie UV-Visible et fluorescence 3D, analyse par chromatographie d’exclusion stérique couplée à la détection UV et fluorescence (HPSEC-UV/Fluo), et analyse moléculaire par chromatographie liquide couplée à la spectrométrie de masse haute résolution (LC-HRMS). Enfin, une série de tests statistiques (analyses classiques et multivariées) appliquée à un jeu de données qui regroupe plus de 200 échantillons, a permis d’identifier des marqueurs et de construire des empreintes spécifiques des sources de MOD sélectionnées apriori.
(18/05/2022)
RiverLy, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Characterization of the metabolomic response of freshwater biofilms to urban wastewater
Urban wastewater treatment plants (WWTPs) release large amounts of pollutants (e.g. chemicals, microbes) into aquatic environments that may impact exposed organisms. Among these organisms, aquatic biofilms as a complex assemblage of microorganisms with a short life cycle (e.g. microalgae, bacteria, etc.) and by their key role in aquatic ecosystems (e.g. primary production) are relevant and increasingly used to investigate the impact of chemical contamination at the community level. Despite increasing knowledge on the impact of chemical stress on these communities, the underlying (molecular/biochemical) mechanisms remain poorly described while usual descriptors provide a partial picture of phenotype. To tackle this issue, untargeted metabolomics approach is relevant through the simultaneous characterization of chemical exposure and the global response of the whole biofilm. In this context, this study focuses on the characterization of the potential impact of urban (WWTPs) on aquatic periphytic microbial communities by implementing an untargeted metabolomic approach. To do so, colonization/exposure was carried out during 4 weeks at upstream and downstream sites from three WWTPs along a tributary of the Arcachon Basin (Belin Beliet: upstream, Salles: intermediate; Mios: downstream). First, multivariate analyses (PCA and HCA) showed discrepancies in the metabolomics profile between the three WWTPs and between upstream and downtream site of each WWTP. This difference is more marked at the downstream site (Mios), likely because of increasing disturbances along the tributary (e.g detection of pesticides only on the downstream site). Moreover, the strong discrimination between upstream and dowstream sites at Mios suggested that this WWTP is a source of pollutants. At this site, further univariate analysis combined to pathways analysis allowed preliminary annotation (i.e. based only on MS1) that highlighted a potential impact on the respiration and photosynthesis pathways. Further investigations are ongoing to improve the annotation through the analysis of MS² spectra and by using an internal database. Overall, this study confirms the relevance of untargeted metabolomics to highlight potential impact of urban discharges on aquatic microbial communities.
(15/05/2022)
UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, CNRS, INRAE
Estimation of Local Equilibrium Foam Model Parameters as Functions of the Foam Quality and the Total Superficial Velocity
In this paper, the behavior of foam in a porous medium is studied in order to understand the effect of the fluid velocity on foam properties. This aspect is crucial during foam injection, as due to radial effects the foam velocity largely decreases around the injection well. The foam properties are detailed through the use of a new local equilibrium foam model parameter estimation approach using an improved new shear function and based on the most widely used STARS model developed by the Computer Modeling Group (CMG). A new mode of calculation of the STARS model parameters is then presented in order to allow both a semiautomated fitting of several quality scan pressure curves and a consideration of the role of the total velocity. The approach is tested through column experiments done at various velocities and gas fractions. Furthermore, the proposed model is also tested on literature results in order to validate it for very different experimental conditions. This study and the fitted results are then used to understand, on both our column experiments and the literature data, the existence of two shear effects and their origins.
(ACS Omega. vol. 7, n° 2470-1343, pp. 16866-16876, 12/05/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Bordeaux INP, UBM, I2M-BX, UB, CNRS, INRAE
Performance and Uncertainty of Satellite-Derived Bathymetry Empirical Approaches in an Energetic Coastal Environment
Objectives of this study are to evaluate the performance of different satellite-derived bathymetry (SDB) empirical models developed for multispectral satellite mission applications and to propose an uncertainty model based on inferential statistics. The study site is the Arcachon Bay inlet (France). A dataset composed of 450,837 echosounder data points and 89 Sentinel-2 A/B and Landsat-8 images acquired from 2013 to 2020, is generated to test and validate SDB and uncertainty models for various contrasting optical conditions. Results show that water column optical properties are characterized by a high spatio-temporal variability controlled by hydrodynamics and seasonal conditions. The best performance and highest robustness are found for the cluster-based approach using a green band log-linear regression model. A total of 80 satellite images can be exploited to calibrate SDB models, providing average values of root mean square error and maximum bathymetry of 0.53 m and 7.3 m, respectively. The uncertainty model, developed to extrapolate information beyond the calibration dataset, is based on a multi-scene approach. The sensitivity of the model to the optical variability not explained by the calibration dataset is demonstrated but represents a risk of error of less than 5%. Finally, the uncertainty model applied to a diachronic analysis definitively demonstrates the interest in SDB maps for a better understanding of morphodynamic evolutions of large-scale and complex coastal systems
(Remote Sensing. vol. 14, n° 2072-4292, pp. 2350, 12/05/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM