Remolinos de mesoescala en el mediterraneo noroccidentalgeneracion y evolucion

Resumen

Mesoscale variability in the Catalan Sea is related to the presence of anticyclonic eddies. These eddies, which are characterized by diameters of 40-50 Km, are responsible for local flow inversions over the shelf, variations in the shelf/slope exchanges and modifications in the biological activity. Historically, their origin has been related to local processes linked to the density front variability, the spatial variability of the wind field or to bathymetric effects. However, recent studies have suggested that these eddies could also be generated upstream, in the Gulf of Lions. The main objective of this thesis is to study the characteristics of these eddies as well as their origins and paths. In a first stage, the study of these eddies is carried out by means of an experimental approximation involving an oceanographic cruise in the Catalan Sea. During this oceanographic cruise, SST images are used to conduct the survey in order to characterize an isolated eddy. The joint analysis of in-situ data and the SST images gives us a 3D description of one of these anticyclonic eddies and allows us to follow its temporal evolution during the survey. Furthermore, based on previous work, the analysis of SST images suggests, as a first approximation, three hypotheses concerning the eddie's origin and path. In a second part a numerical model is used in the NW Mediterranean in order to study of the origin of theses eddies. The validation of the model results shows that the model is able to reproduce realistically the main characteristics of the circulation as well as the generation of coherent eddies in two areas of the Gulf of Lions: Marseilles and Roussillon coasts. The model suggests that in both cases the eddy generation is linked to a flow separation mechanism. On the one hand, off the Marseilles coast, this mechanism is related to the variations in slope direction and is triggered by the Northern Current intensifications. As a result of flow separation anticycloni