Multi-Satellite Altimeter Validation along the French Atlantic Coast in the Southern Bay of Biscay from ERS-2 to SARAL
Monitoring changes in coastal sea levels is necessary given the impacts of climate change. Information on the sea level and its changes are important parameters in connection to climate change processes. In this study, radar altimetry data from successive satellite missions, European Remote Sensing-2 (ERS-2), Jason-1, Envisat, Jason-2, and Satellite with ARgos and ALtiKa (SARAL), were used to measure sea surface heights (SSH). Altimetry-derived SSH was validated for the southern Bay of Biscay, using records from seven tide gauges located along the French Atlantic coast. More detailed comparisons were performed at La Rochelle, as this was the only tide gauge whose records covered the entire observation period for the different radar altimetry missions. The results of the comparison between the altimetry-based and in-situ SSH, recorded from zero to five kilometers away from the coast, had root mean square errors (RMSE) ranging from 0.08 m to 0.21 m, 0.17 m to 0.34 m, 0.1 m to 0.29 m, 0.18 m to 0.9 m, and 0.22 m to 0.89 m for SARAL, Jason-2, Jason-1, ENVISAT, and ERS-2, respectively. Comparing the missions on the same orbit, ENVISAT had better results than ERS-2, which can be accounted for by the improvements in the sensor mode of operation, whereas the better results obtained using SARAL are related to the first-time use of the Ka-band for an altimetry sensor. For Jason-1 and Jason-2, improvements were found in the ocean retracking algorithm (MLE-4 against MLE-3), and also in the bi-frequency ionosphere and radiometer wet troposphere corrections. Close to the shore, the use of model-based ionosphere (GIM) and wet troposphere (ECMWF) corrections, as applied to land surfaces, reduced the error on the SSH estimates.
(Remote Sensing. vol. 10, n° 2072-4292, pp. 93, 01/01/2018)
GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, SYRTE, INSU - CNRS, CNRS, PSL, SU, CNRS, ECOLA, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Spatial and temporal patterns of shoreline change of a 280-km high-energy disrupted sandy coast from 1950 to 2014: SW France
(Estuarine, Coastal and Shelf Science. vol. 200, n° 0272-7714, pp. 212-223, 01/01/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record
(Sedimentary Geology. vol. 363, n° 0037-0738, pp. 200 - 220, 01/01/2018)
ULiège, IRSNB / RBINS, UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOPS, UP11, CNRS, AORI, UTokyo
Long-term (1998 vs. 2010) large-scale comparison of soft-bottom benthic macrofauna composition in the Gulf of Lions, NW Mediterranean Sea
We achieved a long term (i.e., 1998 vs. 2010) large scale (i.e., whole Gulf of Lions) study of benthic macrofauna composition in the Gulf of Lions based on the resampling of 91 stations located along 21 inshore-offshore transects. Results show that the 3 main benthic communities identified in 1998 were still present in 2010 although their composition changed. Using only year and station of sampling we found a significant space-time interaction explaining changes in macrofaunal community composition, and, in this study, stations differ primarily in terms of depth and distance to the Rhône river mouth. Temporal changes in benthic macrofauna composition were clearly most important at shallow stations (i.e., in the Littoral Fine Sand community) than at deep ones (i.e., Terrigenous Coastal Mud community). These results are in good agreement with the current paradigm according to which climatic oscillations such as NAO (North Atlantic Oscillation) and WeMO (Western Mediterranean Oscillation) are indirectly (i.e., through changes in the frequency of occurrence and the intensity of storms) controlling benthic macrofauna composition in the Gulf of Lions. This hypothesis is further supported by a meta-analysis of changes in the average and maximal yearly abundances of the polychaete Ditrupa arietina. At last, the spatial modelling of 1998 and 2010 benthic macrofauna compositions both suggested a significant effect of Rhône River inputs on the spatial distribution of benthic macrofauna in the Gulf of Lions.
(Journal of Sea Research (JSR). vol. 131, n° 1385-1101, pp. 32-45, 01/01/2018)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LECOB, SU, CNRS, OOB, SU, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS
Human-induced river runoff overlapping natural climate variability over the last 150 years: Palynological evidence (Bay of Brest, NW France)
For the first time a very high resolution palynological study (mean resolution of 1 to 5 years) was carried out over the last 150 years in a French estuarine environment (Bay of Brest; NW France), allowing direct comparison between the evolution of landscapes, surface water, and human practices on Bay of Brest watersheds, through continental (especially pollen grains) and marine (phytoplanktonic microalgae: cysts of dinoflagellates or dinocysts) microfossils. Thanks to the small size of the watersheds and the close proximity of the depositional environment to the mainland, the Bay of Brest represents an ideal case study for palynological investigations. Palynological data were then compared to published palaeo-genetic analyses conducted on the same core and to various available instrumental data, allowing us to better characterize past environmental variability since the second half of the 19th century in Western Brittany. We provide evidence of some clues of recent eutrophication and/or pollution that affected phytoplankton communities and which appears linked with increased runoff (higher precipitations, higher percentages of riparian forest pollen, decline of salt marsh-type indicators, and higher values of the XRF Ti/Ca signal), mainly explained by the evolution of agricultural practices since 1945 superimposed on the warming climate trend. We assume that the significant relay observed between dinocyst taxa: Lingulodinium machaerophorum and Spiniferites bentorii around 1965 then followed by Spiniferites membranaceus after 1985, attests to a strong and recent eutrophication of Bay of Brest surface waters induced by high river runoff combined with abnormally elevated air temperatures, especially obvious in the data from 1990. The structure of the dinocyst community has thus been deeply altered, accompanied by an unprecedented increase of Alexandrium minutum toxic form at the same period, as confirmed by the genetic quantification. Despite this recent major anthropogenic forcing, the fossil pollen sequence also records natural climate variability. We highlight, for the first time, a possible connection between climate (AMO modes) and fossil pollen records (especially tree pollination rates) in coastal sediments using tree percentage fluctuations as an indirect proxy for past sea surface and atmospheric temperatures.
(Global and Planetary Change. vol. 160, n° 0921-8181, pp. 109 - 122, 01/01/2018)
LGO, UBS, IFREMER, UBO EPE, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, DYNECO, IFREMER, GM, IFREMER, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modeling analysis of tidal bore formation in convergent estuaries
Despite the recognized impact of tidal bores on estuarine ecosystems, the large scale mechanism of bore formation in convergent alluvial estuaries is still under investigation. So far, field data exist only for a small number of estuaries, while numerical simulations employ the shallow water equations mainly focusing on the small-scale and local processes. In this work, firstly we apply the fully nonlinear weakly dispersive Serre-Green–Naghdi equations to simulate the tide propagation in a convergent estuary of idealized form, verifying that the local dispersion effects, responsible for the appearance of the secondary waves, do not influence the tidal bore onset, which only results from the large scale processes of amplification/damping and distortion of the incoming wave. In a second part, we numerically investigate (225 runs) the estuarine parameter space in order to identify the physical conditions that lead to tidal bore generation. In this parameter space, we determine a critical curve which divides estuaries according to tidal bore occurrence. As a result of this investigation we have shown that bore formation is controlled by the competition between two physical processes: (a) the knee-shaped distortion of the tidal wave, with flood dominance and eventually bore inception; (b) the dissipation of the tidal wave, which is unfavorable to bore formation. We also provide evidence that amplification due to topographic convergence is not a necessary condition for tidal bore generation and that there exist estuaries which display both wave damping and bore development. Finally, the validity of the results has been also assessed in the presence of freshwater river discharge, showing that for low river discharge, its effect on estuarine dynamics can be neglected.
(European Journal of Mechanics - B/Fluids, n° 0997-7546, 01/01/2018)
CARDAMOM, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Are deep-sea ecosystems surrounding Madagascar threatened by land-use or climate change?
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 131, n° 0967-0637, pp. 93-100, 01/01/2018)
IFREMER, JAMSTEC, GM, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, RIKEN
FAME (v1.0): a simple module to simulate the effect of planktonic foraminifer species-specific habitat on their oxygen isotopic content
The oxygen-18 to oxygen-16 ratio recorded in fossil planktonic foraminifer shells has been used for over 50 years in many geoscience applications. However, different planktonic foraminifer species generally yield distinct signals, as a consequence of their specific living habitats in the water column and along the year. This complexity is usually not taken into account in model-data integration studies. To overcome this shortcoming, we developed the Foraminifers As Modeled Entities (FAME) module. The module predicts the presence or absence of commonly used planktonic foraminifers and their oxygen-18 values. It is only forced by hydrographic data and uses a very limited number of parameters, almost all derived from culture experiments. FAME performance is evaluated using the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) Late Holocene planktonic foraminifer cal-cite oxygen-18 and abundance datasets. The application of FAME to a simple cooling scenario demonstrates its utility to predict changes in planktonic foraminifer oxygen-18 to oxygen-16 ratio in response to changing climatic conditions.
(Geoscientific Model Development. vol. 11, n° 1991-9603, pp. 3587-3603, 01/09/2026)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Gestion et valorisation des carottes sédimentaires à but scientifique en France : vers un système intégré
Les carottes sédimentaires font l'objet d'un intérêt grandissant de la part des paléo-environnementalistes mais également d’écologues qui s'intéressent à la trajectoire des écosystèmes (Pansu et al., 2015; Perga et al., 2015). Les carottes marines ou continentales prélevées dans le cadre de consortiums internationaux (IODP, ICDP) donnent l’exemple depuis des décennies en terme de partage d’échantillons pour ce type d’étude ; plus récemment l’augmentation de ré-études massives de données publiées (Bolliet et al., 2016; Cartapan is et al., 2016) démontrent la valeur de ces échantillons et des données associées. De leur côté depuis quelques années, les législateurs et financeurs poussent à l’ouverture, au partage et à la traçabilité des données : on peut citer l’OCDE, l’UE, l’ERC... Comment notre communauté peut-elle s’inscrire au quotidien dans ces processus qui demandent de profonds changements culturels dans nos pratiques de recherche ? C’est pour tenter d’apporter une réponse à cette question que nous avons cherché à développer un système intégré de captation et de gestion des métadonnées des échantillons issus de forages scientifiques, qui puisse être implémenté au niveau national et connecté à des initiatives internationales, sur lequel pourront venir s’appuyer les futurs Plans de Gestion de Données. Par une approche bottom-up, pragmatique et au plus près des pratiques des équipes de recherche, nombreuses, dispersées, aux moyens inégaux, et en s’appuyant sur des initiatives existantes, nous tentons de répondre petit à petit à différents niveaux - de la mission de prélèvement jusqu'à leur stockage, en passant par la mise à disposition, le suivi et la valorisation des échantillons et des métadonnées qui leur sont associées. Des avancées rapides ont pu être obtenues par la rencontre entre une communauté de paléoécologues et des équipes techniques novatrices dans le domaine du partage et de l’interopérabilité mêlant des informaticiens, géomaticiens, curateurs d’échantillons et de données. Cette dynamique s’appuie sur 3 projets nationaux (Cyber-Carothèque nationale s/c Equipex CLIMCOR ANR-11-EQPX-0009 ; QR-Code LTSER- France ; ROZA LTSER-France) et s’inscrit dans le cadre du Centre de Carottage et de Forage National (C2FN), une cellule de la division technique de l’INSU. Nous présenterons dans cette intervention 4 outils qui seront à court terme interconnectés : i)CoreBOOK, une application mobile de terrain dédiée à la captation des métadonnées de forage ; ii) le portail de la cyber-carothèque national, un hub accueillant les données nouvellement acquises et les inventaires de carothèques ; iii) Collec-Science, outil générique de gestion de collections d’échantillons naturels adapté à nos besoins (s/c projet QrCODE); enfin iv) ROZA (Rétro-Observatoire des Zones Ateliers), un prototype de découvreur et visualiseur de données destiné à favoriser la réutilisation des échantillons et des données paléoenvironnementales en mettant à disposition les données essentielles à la capitalisation des connaissances d’études successives sur un même site. Les perspectives aujourd'hui sont grandes, le système modulaire qui commence à se dessiner doit permettre à chacun de trouver son compte, à son rythme, où opérationnel peut enfin rimer avec standardisation, traçabilité et interopérabilité tout en conservant une utilisabilité au plus proche des activités et besoins quotidiens des chercheurs et personnels d’accompagnement, afin d’opérer un virage en douceur vers des pratiques de la science dite « ouverte
(01/09/2026)
EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, DTI, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMD, INSU - CNRS, X, IP Paris, ENPC, SU, CNRS, ENS-PSL, PSL, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LCE, CNRS, UMLP, UBFC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEDI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GRESE, UNILIM, DYNAFOR, INRA, ENSAT, INP-ENSAT, AgroToulouse, INP-AgroToulouse, Toulouse INP, Comue de Toulouse, Toulouse INP, Comue de Toulouse, LEHNA IPE, LEHNA, UCBL, ENTPE, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, UR EABX, IRSTEA, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
A Bayesian approach to estimate biodynamic model parameters: bioaccumulation of PCB 153 by the freshwater crustacean Gammarus fossarum
The first step to evaluate the effects of contamination on organisms is to study toxicokinetics. The bioaccumulation of contaminants by aquatic species is a variable phenomenon, since it depends on the characteristics of the environment, the properties of the contaminants and the species. Different toxicokinetic models have been developed to describe the accumulation of contaminants in aquatic food webs. In these models, the organism is often considered as a single compartment: the bioaccumulation is then described as the balance between uptake and elimination processes. The absorption process can involve both dissolved or trophic route. The diet of aquatic organisms is known to be an important route of bioaccumulation of contaminants. The elimination process includes excretion, metabolism and dilution by growth. To date, there are few models focusing on persistent organic contaminants. Furthermore, estimating models' parameters is generally done through a frequentist approach in two steps: first by estimating parameter(s) related to depuration and then estimating parameter(s) related to accucumulation. The problem by doing this is that depuration during the accumulation phase is neglected, while this process occurs in the two phases. The aim of our study is to propose a Bayesian framework to estimate the parameters of a biodynamic model together by considering simultaneously accumulation and depuration data. The posterior distribution obtained for all parameter will enable a more accurate assessment of bioaccumulation uncertainty. We illustrate our approach with the freshwater benthic invertebrate Gammarus fossarum exposed for 7 days to a sediment spiked with PCB153 and transferred to a clean media for 7 more days. The PCB153 concentrations in Gammarus fossarum increased from an initial concentration of 0.32 to 12.36 ng.g-1 ww (wet weight) at the end of accumulation step. When gammarids were transferred into a clean media, the PCB153 concentration in organisms decreased to 6.41 ng.g-1 ww at day 14. The bioaccumulation model assuming first-order kinetics was fitted to the data using Bayesian inference. The inference process quickly converged and thin posterior distributions were obtained for each parameter, meaning that data brough enough information to estimate preciselly each parameter. The median model predictions and their 95% credibility intervals showed a good fit of the model to the data.
(pp. 1, 01/09/2026)
IRSTEA, LBBE, UCBL, VAS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS