8 research outputs found
Etude analytique de la reponse transitoire de l'ocean aux forcage atmospheriques
No full textSIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Seasonal and inter-annual variations in the surface freshwater flux in the Mediterranean Sea from the ECMWF re-analysis project
No full textWater Mass Transformation in a Secluded Bay of the Mediterranean Sea
No full textThis case study demonstrates how water transformation in a secluded bay can be investigated using a range of Lagrangian analysis methods that can be calculated with a mass-conserving Lagrangian trajectory model. The study focuses on analysing the water mass transformation and overturning circulation in the Gulf of Gabès. The gradual transformation of water masses flowing through the Gulf was analysed using model-simulated Lagrangian trajectories. It was found that the overturning circulation in the Gulf gradually deepens, although it is falsely exaggerated by up to 50 metres when computed as a simple longitude-depth Lagrangian stream function.The Lagrangian method enabled the determination of the spatial dependence of transit time. The analysis revealed that most of the water in the Gulf has a transit time short enough to adjust to seasonal variability. However, in the innermost part of the Gulf, there exists an anticyclonic vortex that tends to trap water on longer timescales, preventing it from adjusting to seasonal variability. The trajectories were computed using velocity and mass transport fields from a high-resolution (1/96°) hydrodynamic ROMS model, which includes the relatively strong tides in this region of the Mediterranean.</p
Sensitivity of the sea circulation to the atmospheric forcing in the Sicily Channel
No full textInternational audienceWe investigate the sensitivity of the sea surface circulation in the Sicily Channel to surface winds, using a15-year long (1994–2008) air-sea coupled numerical simulation. Analysis is based on the clustering of sixmain wind regimes over the Sicily Channel domain. The analysis of the corresponding sea current clustersshows that sea circulation in this area is sensitive to surface wind patterns. This wind modulates thestrength of the two main branches of the sea circulation in the Sicily Channel (i.e. the AtlanticTunisian Current and the Atlantic Ionian Stream). The modulation of these two currents depends onthe wind regime, and displays a strong seasonal variability. It is also shown that the sea circulation inthe Sicily Channel is strongly controlled by the thermohaline circulation and the bathymetry (geostrophiccurrent). However, the contribution to the total current of its ageostrophic component forced by thesurface winds is significant, with a correlation coefficient varying from 0.3 to 0.7
Microplastics in surface waters of the Gulf of Gabes, southern Mediterranean Sea: Distribution, composition and influence of hydrodynamics
No full textInternational audienceThe Mediterranean Sea has been described as one of the most affected areas by marine litter in the world. Although microplastics and their effects have been investigated in this area, most of the currently available studies have been limited to the northwestern part of the basin. This study constitutes a first attempt to determine the abundance, characteristics and composition of microplastics in near surface waters of the Gulf of Gabes (southern Mediterranean Sea, Tunisia). Samples were collected using a 200 μm-mesh size trawl net along two transects. The study revealed an average concentration of 63,739 items/km2 where fragments and films were the most frequent microplastics. Polyethylene, reformulated polyethylene and polypropylene were the most abundant plastics identified among the samples (86–100%). The influence of hydrodynamics on microplastics in the Gulf of Gabes was investigated through the use of a Lagrangian tracking model to simulate the dispersion of particles in water. Modelling results seem to be in agreement with the reported distribution and characteristics of microplastics in this area
Evolution of the Distribution and Dynamic of Microplastic in Water and Biota: A Study Case From the Gulf of Gabes (Southern Mediterranean Sea)
No full textMarine plastic pollution represents a major problem owing to its increasing presence in the environment, persistence and ability to spread in every compartment in the form of small plastic particles, namely microplastics (MPs). Studies concerning MPs abundance in the Mediterranean Sea are growing, but their occurrence in the Southern regions remains largely unexplored. In this study, distribution, abundance, size, and polymer type of microplastics were investigated in surface water samples collected with a Manta net (200 μm mesh size) and in 118 marine specimens of commercial interests, including fishes, crustaceans, and mollusks, during Spring and Autumn 2019 EU H2020 Claim Project sampling Campaigns in the Gulf of Gabes (Southern Mediterranean Sea). Laboratory characterization showed significant plastic pollution concentrations, with an average abundance of 312,887 and 77,110 items/km2 in surface water samples collected in Spring and Autumn, respectively. A 3D hydrodynamic and Tracking Model was used to identify dispersal and transport pathways of the floating plastics, reporting a seasonal variability observed in MPs distribution between I (Spring) and II Campaign (Autumn). Despite the high values of MPs abundance found in surface water samples, an overall low frequency of ingestion among studied species was observed, with a maximum value of 20% of individuals (in Scomber scombrus) found with ingested MPs. The present study contributes to expand our state of knowledge regarding MPs pollution level in water and biota samples collected in the Gulf of Gabes, an area of particular interest for its biological resources, but still little investigated
