Implementation and Evaluation of Breaking Detection Criteria for a Hybrid Boussinesq Model
The aim of the present work is to develop a model able to represent the propagation and transformation of waves in nearshore areas. The focus is on the phenomena of wave breaking, shoaling and run-up. These different phenomena are represented through a hybrid approach obtained by the coupling of non-linear Shallow Water equations with the extended Boussinesq equations of Madsen and Sørensen. The novelty is the switch tool between the two modelling equations: a critical free surface Froude criterion. This is based on a physically meaningful new approach to detect wave breaking, which corresponds to the steepening of the wave's crest which turns into a roller. To allow for an appropriate discretization of both types of equations, we consider a finite element Upwind Petrov Galerkin method with a novel limiting strategy, that guarantees the preservation of smooth waves as well as the monotonicity of the results in presence of discontinuities. We provide a detailed discussion of the implementation of the newly proposed detection method, as well as of two other well known criteria which are used for comparison. An extensive benchmarking on several problems involving different wave phenomena and breaking conditions allows to show the robustness of the numerical method proposed, as well as to assess the advantages and limitations of the different detection methods.
(Water Waves, n° 2523-367X, pp. 207–241, 17/10/2026)
CARDAMOM, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Assessment of swimming behavior of the Pacific oyster D-larvae (Crassostrea gigas) following exposure to model pollutants
This study describes an image analysis method that has been used to analyze the swimming behavior of native oyster D-larvae (Crassostrea gigas) from the Arcachon Bay (SW, France). In a second time, this study evaluated the impact of copper and S-metolachlor pollutants on D-larvae swimming activity and the possible relationship between developmental malformations and abnormal swimming behavior. Analyses in wild and cultivated oyster D-larvae were investigated during two breeding-seasons (2014 and 2015) at different sampling sites and dates. In controlled conditions, the average speed of larvae was 144 µm s '1 and the maximum speed was 297 µm s '1 while the trajectory is mainly rectilinear. In the presence of environmental concentration of copper or S-metolachlor, no significant difference in maximum or average larval speed was observed compared to the control condition but the percentage of circular trajectory increased significantly while the rectilinear swimming larvae significantly declined. The current study demonstrates that rectilinear trajectories are positively correlated to normal larvae while larvae with shell anomalies are positively correlated to circular trajectories. This abnormal behavior could affect the survival and spread of larvae, and consequently, the recruitment and colonization of new habitats. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
(Environmental Science and Pollution Research. vol. 27, n° 0944-1344, pp. 3675-3685, 17/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
Clouds damp the radiative impacts of polar sea ice loss
Clouds play an important role in the climate system: (1) cooling Earth by reflecting incoming sunlight to space and (2) warming Earth by reducing thermal energy loss to space. Cloud radiative effects are especially important in polar regions and have the potential to significantly alter the impact of sea ice decline on the surface radiation budget. Using CERES (Clouds and the Earth's Radiant Energy System) data and 32 CMIP5 (Coupled Model Intercomparison Project) climate models, we quantify the influence of polar clouds on the radiative impact of polar sea ice variability. Our results show that the cloud short-wave cooling effect strongly influences the impact of sea ice variability on the surface radiation budget and does so in a counter-intuitive manner over the polar seas: years with less sea ice and a larger net surface radiative flux show a more negative cloud radiative effect. Our results indicate that 66±2% of this change in the net cloud radiative effect is due to the reduction in surface albedo and that the remaining 34±1 % is due to an increase in cloud cover and optical thickness. The overall cloud radiative damping effect is 56±2 % over the Antarctic and 47±3 % over the Arctic. Thus, present-day cloud properties significantly reduce the net radiative impact of sea ice loss on the Arctic and Antarctic surface radiation budgets. As a result, climate models must accurately represent present-day polar cloud properties in order to capture the surface radiation budget impact of polar sea ice loss and thus the surface albedo feedback.
(The Cryosphere. vol. 14, n° 1994-0424, pp. 2673-2686, 17/10/2026)
LaRC, CNRM, INSU - CNRS, CNRS, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Short-term variations of platinum concentrations in contrasting coastal environments: The role of primary producers
Short-term variations of Pt concentrations and primary production indicators were compared in three contrasting coastal sites during spring bloom: (i) the Gironde Estuary mouth (SW France), (ii) the semi-enclosed Arcachon Bay (SW France), and (iii) the urbanized Genoa Harbor (NW Italy). At each site, surface seawater sampling and physical-chemical measurements were combined to study diel cycles (over 25 h) of dissolved Pt concentrations in seawater (PtD) and master variables reflecting primary production activity (chlorophyll-a, phaeopigments, and particulate organic carbon, POC concentrations). Plankton nets were used in all sites, providing for the first time plankton Pt concentrations (PtPK) over a whole diel cycle (Gironde Estuary mouth) and spot sampling (Arcachon Bay and Genoa Harbor) in the coastal zone. Bivalves (wild oysters or mussels), reflecting organisms at higher trophic levels, were also collected at all sites. The POC/Chl-a ratios in the collected particulate material suggested high contribution of phytoplankton to the particulate matter in the productive Gironde Estuary mouth. At this site, phytoplankton activity partly controlled Pt cycling and particle/dissolved Pt partitioning during daytime. During the night, zooplankton grazing may release Pt into the dissolved phase. These processes are partly masked by external factors such as tide or local Pt sources, especially in more confined and/or urbanized coastal water bodies such as the Arcachon Bay and the Genoa Harbor. Platinum levels in plankton and bivalves from these contrasting sites along the Atlantic and Mediterranean coasts tended to reflect the general Pt levels in seawater. These results clearly suggest that (i) Pt contamination of coastal waters and marine organisms has become a common feature in urbanized sites and (ii) Pt transfer to the marine food chain starts at the basic level of primary producers. By concentrating Pt (Bioconcentration Factor: BCF ~ 104), phytoplankton may serve as a biomonitor to assess Pt contamination in coastal environments.
(Marine Chemistry. vol. 222, n° 0304-4203, pp. 103782, 17/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIGE, IIM, CSIC, UniGe
Microbial Communities of the Shallow-Water Hydrothermal Vent Near Naples, Italy, and Chemosynthetic Symbionts Associated With a Free-Living Marine Nematode
Shallow-water hydrothermal vents are widespread, especially in the Mediterranean Sea, owing to the active volcanism of the area. Apart free microbial communities’ investigations, few biological studies have been leaded yet. Investigations of microbial communities associated with Nematoda, an ecologically important group in sediments, can help to improve our overall understanding of these ecosystems. We used a multidisciplinary-approach, based on microscopic observations (scanning electron microscopy: SEM and Fluorescence In Situ Hybridization: FISH) coupled with a molecular diversity analysis using metabarcoding, based on the 16S rRNA gene (V3-V4 region), to characterize the bacterial community of a free-living marine nematode and its environment, the shallow hydrothermal vent near Naples (Italy). Observations of living bacteria in the intestine (FISH), molecular and phylogenetic analyses showed that this species of nematode harbors its own bacterial community, distinct from the surrounding sediment and water. Metabarcoding results revealed the specific microbiomes of the sediment from three sites of this hydrothermal area to be composed mainly of sulfur oxidizing and reducing related bacteria.
(Frontiers in Microbiology. vol. 11, n° 1664-302X, pp. 2023, 17/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LM2E, IFREMER, UBO EPE, CNRS, LEP, EEP, IFREMER, PARTHENOPE
Human settlement and landscape dynamics on the coastline south of the Gironde estuary (SW France): a multi-proxy approach
The Gironde estuary in SW France is the largest in Western Europe and has attracted human populations since prehistoric times. From the 1970s to the 1990s, intense archaeological research was undertaken on the long and highly dynamic coastline just south of the estuary mouth. In recent years, the combined action of increased coastal erosion and human pressure has proved a serious threat to the integrity of archaeological sites in the area. As a consequence, a whole array of previously unrecorded archaeological remains across the intertidal zone and coastal strip is being exposed. In this context, innovative interdisciplinary research since 2014 is yielding new information about the settlement and landscape dynamics and about the long-term interaction between human societies and the environment. The sedimentary context and the exceptional preservation conditions of organic remains have made possible a multi-proxy approach combining archaeological, geomorphological, palaeobiological, and archaeoentomological methods. In this paper we discuss the different approaches and the way they jointly contribute to the project. The results obtained so far from this multi-proxy approach challenge the traditional view of the historic occupation and the landscape dynamics around the Gironde estuary from prehistoric times to antiquity. They show that the intense occupation of this area during certain periods of human history is related to the development of marshy environments, which can now be analyzed at higher temporal resolution owing to this approach.
(Journal of Island and Coastal Archaeology. vol. 18, n° 1556-4894, pp. 53-74, 17/10/2026)
UCM, UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, TRACES, EHESS, UT2J, Comue de Toulouse, MCC, Inrap, CNRS, PACEA, UB, CNRS, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN
A Simple and Efficient Image Stabilization Method for Coastal Monitoring Video Systems
Fixed video camera systems are consistently prone to importune motions over time due to either thermal effects or mechanical factors. Even subtle displacements are mostly overlooked or ignored, although they can lead to large geo-rectification errors. This paper describes a simple and efficient method to stabilize an either continuous or sub-sampled image sequence based on feature matching and sub-pixel cross-correlation techniques. The method requires the presence and identification of different land-sub-image regions containing static recognizable features, such as corners or salient points, referred to as keypoints. A Canny edge detector (CED) is used to locate and extract the boundaries of the features. Keypoints are matched against themselves after computing their two-dimensional displacement with respect to a reference frame. Pairs of keypoints are subsequently used as control points to fit a geometric transformation in order to align the whole frame with the reference image. The stabilization method is applied to five years of daily images collected from a three-camera permanent video system located at Anglet Beach in southwestern France. Azimuth, tilt, and roll deviations are computed for each camera. The three cameras showed motions on a wide range of time scales, with a prominent annual signal in azimuth and tilt deviation. Camera movement amplitude reached up to 10 pixels in azimuth, 30 pixels in tilt, and 0.4°in roll, together with a quasi-steady counterclockwise trend over the five-year time series. Moreover, camera viewing angle deviations were found to induce large rectification errors of up to 400 m at a distance of 2.5 km from the camera. The mean shoreline apparent position was also affected by an approximately 10-20 m bias during the 2013/2014 outstanding winter period. The stabilization semi-automatic method successfully corrects camera geometry for fixed video monitoring systems and is able to process at least 90% of the frames without user assistance. The use of the CED greatly improves the performance of the cross-correlation algorithm by making it more robust against contrast and brightness variations between frames. The method appears as a promising tool for other coastal imaging applications such as removal of undesired high-frequency movements of cameras equipped in unmanned aerial vehicles (UAVs).
(Remote Sensing. vol. 12, n° 2072-4292, 24/12/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SIAME, UPPA
Clouds damp the impacts of Polar sea ice loss
Abstract. Clouds plays an important role on the climate system through two main contrasting effects: (1) cooling the Earth by reflecting to space part of incoming solar radiation; (2) warming the surface by reducing the Earth’s loss of thermal energy to space. Recently, scientists have paid more attention to the warming role of clouds because of the acceleration of Arctic sea ice melting and because of recent studies that did not find any response of cloud cover fraction to reduced sea ice in summer. On the contrary, with this work based on satellite CERES data and 32 CMIP5 climate models, we reveal that the cooling role of clouds is dominant. Indeed, cloud dynamic occurring in combination with sea-ice melting plays an important cooling effect by altering the surface energy budget in an apparently contradicting way: years with less sea ice are also those that show an increase of the radiative energy reflected back to space by clouds. An increase in absorbed solar radiation when sea ice retreats (surface albedo change) explains 66 ± 2 % of the observed signal. The remaining 34 ± 1 % are due to the increase in cloud cover/thickness when sea ice retreat and associated reflection to space. This interplay between clouds and sea ice reduces by half the increase of net radiation at the surface that follows the sea-ice retreat, therefore damping the impact of polar sea ice loss. We further highlight how this process is mis-represented in some climate models.
(The Cryosphere, n° 1994-0424, 19/12/2019)
CNRM, INSU - CNRS, CNRS, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Reconstruction des changements océanographiques et atmosphériques dans l’Océan Indien Oriental (NO-Australie, IODP Exp 356) pendant le quaternaire
Les sédiments marins des sites de forage U1460 et U1461 recueillis pendant l’expédition IODP 356 constituent l’un des rares enregistrements au niveau du plateau australien Nord-Ouest. Ils fournissent des informations sur l’intensité de l’aridité en Australie pendant les principaux cycles glaciaires-interglaciaires du Quaternaire, en raison de leur proximité avec le continent. Outre la reconstitution du climat continental, ces sériés sédimentaires permettent de reconstruire le fonctionnement des courants océaniques passés au large de la côte Ouest australienne.Sur le site U1461, la chronostratigraphie a permis d’identifier deux glaciations majeures du Pléistocène (MIS 2 et MIS 12). Les assemblages de la microfaune benthique (principalement les foraminifères benthiques, les coraux et les bryozoaires) ont été analysés afin de reconstruire les paléo-environnements et les paléo-profondeurs du milieu sédimentaire. Malgré la présence d’un hiatus dans l’enregistrement (incluant une partie du MIS 2 et l’ensemble du MIS 3-MIS 7), l’excellente conservation du contenu de la microfaune benthique suggère que les sédiments préservés peuvent être considérés comme in situ.Sur ce même site, les isotopes du Nd et du Sr ainsi que d’autres traceurs (à citer) déterminés dans les sédiments indiquent d’une part que les apports fluviaux ont probablement été réduits en raison de l'aridité accrue au cours du MIS 12, et d’autre part que la source des sédiments (principalement transportés par voie atmosphérique) pourrait se trouver au centre (Lake Eyre) ou à l’Est du continent (Murray-Darling Basin) australien. Le MIS 2 s’avère être l’une des périodes les plus sèches enregistrées en Australie avec des sources de poussière mixtes provenant de l’Est et de l’Ouest du continent. Des conditions plus humides pouvant correspondre au maximum de la Mousson d’été Indo-Australienne ont suivi après le maximum glaciaire.Sur le site U1460, une étude approfondie des assemblages de la méiofaune benthique et de l'abondance d’une espèce de foraminifère planctonique (Globorotalia mernardii ) donne de bons indices prouvant un changement majeur et soudain de la circulation océanique au cours de l'événement de Bruhnes Moyen (Mid-Bruhnes Event, MIS 11). L'une des hypothèses privilégiées pour ce changement pendant cette période serait liée à la mise en place du courant de Leeuwin moderne.
(19/12/2019)
CEFREM, UPVD, INSU - CNRS, CNRS
Ecology and behaviour of bottlenose dolphins (Tursiops truncatus) in a coastal area subject to shellfish farming
Studying the ecology of cetaceans living under the pressure of anthropogenic activities is essential for their conservation. Yet, there is a paucity of information on cetaceans and shellfish farming. Using a long-term and year-round dataset, this study investigates the ecology and the behaviour of a coastal cetacean, the bottlenose dolphin (Tursiops truncatus), in an important area for shellfish farming (Ría de Arousa, North-West Spain). A resident population of bottlenose dolphins was present year-round in this area. Their seasonal abundance varied from 56 to 144 individuals and their apparent survival was high. Of the investigated environmental factors, depth and shellfish farms were influencing dolphins habitat use, and chlorophyll-a and dissolved oxygen were influencing their spatio-temporal aggregation patterns. Foraging behaviour was mainly determined by the sea surface temperature, time of the day, and whether the dolphins were foraging within shellfish farm areas. Dolphins were predicted to be more likely found foraging inside these areas than outside (57% vs. 43%). Findings of this study also revealed variation in foraging behaviour among dolphins, with some individuals foraging more frequently than others within the shellfish farms. In turn, individuals that frequently foraged within shellfish farms had weaker associations compared to others. This study generates key insights into the ecology and the behaviour of a coastal cetacean living under the pressure of the shellfish farming industry. It further provides valuable information on conservation priorities for coastal cetaceans living under such pressures as well as regulations for the shellfish farming industry.
(17/12/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS