Physical characteristics and dynamics of the coastal Latex09 Eddy derived from in situ data and numerical modeling.
Résumé
We investigate the dynamics of a coastal anticyclonic eddy in the western part of the Gulf of Lion (GoL) in the northwestern Mediterranean Sea during the Latex campaign in the summer 2009 (Latex09). The sampling strategy combines SST satellite imagery, hull-mounted ADCP data, CTD casts and drifter trajectories. Our measurements reveal an anticyclonic eddy (Latex09 eddy) with a diameter of ~23 km and maximum depth of 31 m, centered at 3°34'E - 42°33'N. We use a high resolution, 3-dimensional, primitive equation numerical model to investigate its generation process and evolution. The model is able to reproduce the observed eddy, in particular its size and position. The model results suggest that the Latex09 eddy is induced by a large anticyclonic circulation in the northwestern part of the GoL, pushed and squeezed toward the coast by a meander of the Northern Current. This represents a new generation mechanism that has not been reported before. The post generation dynamics of the eddy is also captured by the model. The collision of the Latex09 eddy with Cape Creus results in a transient structure, which is depicted by the trajectories of two Lagrangian drifters during Latex09. The transient structure and its advection lead to a transfer of mass and vorticity from the GoL to the Catalan shelf, indicating the importance of mesoscale structures in modulating such exchanges in the region.
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