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Etude lagrangienne de circulations tourbillonnaires de subméso et mésoéchelle en Mediterranee occidentale sur la base d'observations et de simulations numériques : phénoménologie et interaction avec la circulation générale

Abstract : This study is mainly based on lagrangian data from subsurface floats and numerical simulations to reconsider the circulation patterns in the Western Mediterranean Sea. The main results deal with the circulation of intermediate and deep waters and show the importance of intermittent processes and coherent eddies, which are responsible for significant fluxes through the basin interior. About 40% of the deep waters newly-formed in the Gulf of Lion spread during the post-convective phase over the entire Western Mediterranean Sea in the cores of submesoscale coherent eddies (their lifetime can exceed 1.5 years). They are subsurface eddies characterized by a radius is around 5-10km, a large vertical extension O(1-2 km) centered around 1000 m depth, and a rotational period of a few days (corresponding to a relative vorticity of around +f/2 for the cyclonic eddies or -f/2 f or the anticyclonic ones). The trajectories of such eddies and the properties of the water in their cores are constrained by general circulation features, but also by mesoscale circulations (topographic Rossby waves, eddies, jets). In the Algerian Basin, a barotropic and cyclonic gyre circulation is revealed by the observations and corroborated by the numerical simulations from the prototype MERCATOR. The analysis and intercomparison of the observations and the numerical model show this gyre is constrained by the topography and the general circulation of the western Mediterranean sea. This gyre, detaching from the slope, induces the formation of "Sardinian Eddies" at the south-west corner of Sardinia. These eddies are anticyclonic, strongly barotropic and characterized by a radius of around 30 km and a relative vorticity of -f/16. The "Sardinian Eddies", in addition to the "Algerian Eddies" generated by the instability of the coastal Algerian Current, are promoting the Algerian Basin as a region characterized by a strong mesoscale activity. During their formation, the "Sardinian Eddies" can trap LIW and TDW coming from the Tyrrhenian Sea and constrained to circulate between the gyre and the slope. About half of these waters coming from the Tyrrhenian Sea through the Sardinia-Tunisia Channel are thus advected towards the basin interior. The other half participates to the general boundary circulation.
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https://tel.archives-ouvertes.fr/tel-00010060
Contributor : Pierre Testor <>
Submitted on : Wednesday, September 7, 2005 - 5:17:02 PM
Last modification on : Wednesday, December 9, 2020 - 3:10:40 PM
Long-term archiving on: : Friday, April 2, 2010 - 9:50:56 PM

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  • HAL Id : tel-00010060, version 1

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Pierre Testor. Etude lagrangienne de circulations tourbillonnaires de subméso et mésoéchelle en Mediterranee occidentale sur la base d'observations et de simulations numériques : phénoménologie et interaction avec la circulation générale. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00010060⟩

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