French Research Institute for Exploitation of the Sea
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Sizing the largest ocean waves using the SWOT mission
No full textWinds generate waves over the oceans with a wide range of properties. The largest wave heights and periods are important parameters in the design of marine structures. Extreme waves also play an outsize role in air–sea fluxes and coastal dynamics, and leave imprints on seismic and sediment records. Rare events have so far escaped measurements, with few wave heights from satellite altimeters exceeding 16 m, and no associated measurement of wave periods. Here, we use swells radiated from storms to reveal long wave periods within the storms, and their generation mechanism. Swells are resolved in the Surface Water and Ocean Topography (SWOT) satellite sea level measurements. Patterns of increasing swell wavelength and decreasing swell height away from storms are consistent with a nonlinear transfer of energy from short to long period waves. We propose an updated parametric shape for wave spectra in storms that aligns with SWOT swell measurements. It reduces energy levels by a factor of 20 at 1.2 to 1.4 times the peak period compared to commonly used spectral shapes and allows estimation of storm wave periods from swell heights. Consistent with less extreme conditions, the peak period generally increases with wave height. This was particularly verified for the largest storm peak period of 20.2 0.6 s, obtained for the event with the largest significant wave height 19.7 0.3 m measured by altimeters. These observations of long period swells should have a wide range of applications from coastal dynamics to seismology
Heat Transport toward Sea Ice by Transient Processes and Coherent Mesoscale Eddies in an Idealized Southern Ocean
No full textThe oceanic mesoscale variability contributes significantly to meridional heat transport (HT), especially in regions with high eddy kinetic energy such as the Southern Ocean (SO). However, there are gaps in our understanding of mesoscale contributions toward and within sea ice–covered regions due to the lack of observations and resolution in ocean and climate models. Using output from an idealized configuration of a coupled ocean–sea ice model simulating the SO at 10-km horizontal resolution, the contribution of the full spectrum of resolved transient mesoscale variability to the total meridional HT toward and under sea ice is investigated. The total HT is poleward, dominated by the transient HT which is primarily along isopycnals and closely follows the residual overturning circulation. The HT induced by coherent mesoscale eddies is extracted using an eddy detection and tracking algorithm. Coherent eddies contribute up to 20%–30% to the meridional transient HT, depending on latitude, with equal contributions from cyclones and anticyclones. The meridional HT by coherent eddies is predominantly accomplished by stirring with only 30% contributed by heat trapped inside these eddies. The majority of the transient HT across the ice edge occurs below the mixed layer, and this heat is then upwelled toward the surface with coherent eddies contributing between 20% and 30%. Within the mixed layer, 15%–25% of the upwelled heat is transferred to the pack ice. Albeit significant, coherent mesoscale eddies play a secondary role in the SO’s poleward HT that is primarily achieved by other transient mesoscale processes
Etude sanitaire de la zone 76.03 « Le Tréport » - groupe 2 (coquillages bivalves fouisseurs)
No full textSuite à la demande du Comité Régional des Pêches Maritimes et des Elevages Marins de Normandie d’agrandir la zone de production 76.03 « Le Tréport », et comme cette zone n’avait pas fait l’objet d’une étude sanitaire avant son classement, la Direction Départementale des Territoires et de la Mer (DDTM) de Seine-Maritime a demandé la réalisation d’une étude sanitaire afin de se mettre en conformité avec le Règlement d’exécution (UE) 2019/627 et de réévaluer la pertinence de la stratégie d’échantillonnage microbiologique en fonction des différentes sources de contamination connues. Au regard de l’étude des sources de contamination microbienne potentielles, le lieu actuellement utilisé pour le suivi REMI des coquillages fouisseurs de la zone 76.03 « Le Tréport » (008-S-074 - Tréport_large) est bien placé pour assurer la sécurité du consommateur (il se trouve dans le secteur de la zone le plus exposé aux sources de contamination) et est donc conservé. Au regard des critères microbiologiques et chimiques définis par la réglementation, le lieu est estimé en qualité A pour la période 2021-2024. Il sera suivi à fréquence bimensuelle de juin à septembre (plus un prélèvement en mai, avant le démarrage de l’exploitation) chaque année, sur le taxon amandes de mer (Glycymeris glycymeris).
Chemical Reference Materials for Oceanography. History, Production, and Certification
No full textThis open access book explores the history, production, and certification of reference materials for essential parameters in oceanography and provides a comprehensive understanding of them to readers. Because inorganic macro-nutrients, salinity, dissolved oxygen, and carbonate system parameters, including dissolved inorganic carbon, total alkalinity, and pH, are essential parameters in oceanography, they can be used to define biogeographic provinces, monitor ocean health, and detect decadal-scale oceanic climate changes. Without reference materials for these parameters, it would be difficult to produce reliable data sets or long-term baseline studies that are required to verify global change and oceanic stability.
The book includes chapters on developing new reference materials for density, dissolved oxygen, dissolved organic carbon, dissolved organic matter, and trace metals, which are also important in oceanographic studies. The lead authors of each chapter regarding these parameters are top scientists in these areas; hence, this is the most comprehensive book of chemical reference materials for ocean science, written by experts in each field. The book is a useful resource for readers to find the latest information and status of certified reference materials (CRM) and reference materials (RM) and of ways to use CRM in their studies.
We are in the middle of the United Nations Decade of Ocean Science for Sustainable Development (2021–2030), to which this book makes a timely contribution
An improved long-term high-resolution surface pCO2 data product for the Indian Ocean using machine learning
No full textAccurate estimation of surface ocean pCO2 is crucial for understanding the ocean’s role in the global carbon cycle and its response to climate change. In this study, we employ a machine learning algorithm to correct the deviations in high-resolution (1/12°) model simulations of surface pCO2 from the INCOIS-BIO-ROMS model (pCO2model) for the period 1980–2019, using available observations (pCO2obs). We train the XGBoost model to generate spatio-temporal deviations (pCO2obs − pCO2model) of pCO2model. The interannually and climatologically varying deviations are then added back to the original model separately, which results in an improved surface pCO2 data product. A comparison of our surface pCO2 data product with moored observations, gridded SOCAT, CMEMS-LSCE-FFNN, and OceanSODA demonstrates an improvement by approximately 40% ± 3.31% in RMSE. Further analysis reveals that adding climatological deviations to pCO2model results in greater improvements than adding interannual deviations. This analysis underscores the ability of machine learning algorithms to enhance the accuracy of model-simulated surface pCO2 outputs
Contrôle de surveillance DCE 2024 de la masse d’eau côtière « FRFC02 - Pertuis charentais » et de la masse d’eau de transition « FRFT09 - Estuaire de la Gironde » pour les herbiers de Zostera noltei Hornemann : Rapport final
No full textL’objet du présent document est de faire état des résultats du contrôle de surveillance DCE 2024 dans la masse d’eau côtière « FRFC02 - Pertuis charentais » et dans la masse d’eau de transition « FRFT09 - Estuaire de la Gironde » pour les échantillonnages stationnels sur l’élément de qualité herbier intertidaux à Zostera noltei. Un rappel des résultats antérieurs est fait afin de resituer ces informations dans le cours de la dynamique temporelle propre à chaque station d’herbier
Species of the Eel Family Colocongridae (Order Anguilliformes), with Description of a New Species
No full textThe short-tail eel family Colocongridae is a group of small to moderately large eels found in the mid- to upper-continental slope of all oceans except the eastern and central Pacific. The taxonomy of this group is still poorly known, and many diagnostic characteristics have never been tested and verified. Museum specimens were examined, and data were taken by following methods provided in previous studies, as well as some newly introduced. A total of seven species are recorded for the only genus, Coloconger, including a new species described herein from the Solomon Islands and Vanuatu. The diagnostic characters distinguishing species of Coloconger are discussed, comments are made on previous records, and a key to all known species is provided. Morphology of the post-metamorphic stage and transforming leptocephalus is also provided
Liquid and gas mid-infrared integrated spectroscopic sensor
No full textMid-infrared (mid-IR) waveguide sensors were fabricated using two platforms: chalcogenide glasses (ChGs) and porous silicon (PSi). ChGs layers were deposited through RF magnetron sputtering while PSi layers were prepared by electrochemical anodization. Ridge waveguides were patterned using standard i-line photolithography and reactive ion etching for both platforms. The ChGs waveguides exhibit a wide transparency range from λ = 3.94 to 8.95 µm, with a minimum propagation losses value of 2.5 dB/cm at λ = 7.58 µm, while PSi transparency range is from λ = 3.94 to 4.55 µm with a minimum propagation losses value of 9.1 dB/cm at λ = 4.12 µm. To validate the proposed ChGs sensor, a spectroscopic liquid sensing experiment was performed using acetonitrile and isopropanol. The results showed an estimated limit of detection (LoD) of 610 ppm at λ = 4.44 µm for acetonitrile and a LoD of 300 ppm at λ = 7.25 µm for isopropanol, enabled by the evanescent field interaction. Regarding gas sensing, CO2 was used as the analyte. A LoD of 17000 ppm at λ = 4.28 µm was achieved using the ChGs platform. The sensing application was improved with the PSi platform. Due to the open pores, light and gas molecules interact within the internal volume, unlike the ChGs platform, where the interaction occurs with the evanescent part of the light. This results in an exalted external confinement factor, Γ, over 75 times greater for the PSi platform, achieving a LoD of 600 ppm at λ = 4.26 µm for CO2 sensing. Estimation of concentrations from mixtures of two solutions through deconvolution of the measured spectra was also achieved with good approximations, validating the transduction capabilities in a complex environment using the ChGs platform
Fatty acid analysis in an estuarine fish species to assess the health status of hydrosystems impacted by eutrophication and multistressors
No full textThe originality of this research lies in the use of fish lipid markers, which highlights the importance of fatty acid profiles as biomarkers to evaluate the health status of estuarine systems subject to eutrophication or multistress. In the present paper, we developed an approach combining lipid class and fatty acid analyses on juvenile European flounder muscle, watershed geographic metrics and pollutant levels in sediments, to assess the ecological status of seven small estuaries mainly impacted by agricultural activities in the watersheds. The estuaries showed contrasted fatty acids compositions in flounder muscle. Marked differences in polyunsaturated fatty acid (PUFA) proportions, particularly docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA), reflected not only the state of cell membranes but also variations in the quality of food sources. High levels of PUFA were associated with better ecological conditions, while reduced PUFA availability was clearly linked to eutrophication and multistress. In addition, higher flounder lipid reserve content was clearly identified in the system highly impacted by fish farming, reflecting a contamination of the entire trophic chain by aquaculture waste