Origin and dynamics of mesoscale eddies in the Catalan Sea (NW Mediterranean): Insight from a numerical model study

Past observations and satellite sea surface temperature imagery indicate the presence of mesoscale anticyclonic eddies drifting along the Catalan coast. In September 2001 one of these anticyclonic eddies was surveyed over the shelf break during an oceanographic cruise which permitted the 3‐D description of its structure. In this work we investigate the origin and dynamics of such “Catalan eddies” using a numerical circulation model of the northwest Mediterranean at 3 km resolution driven by high‐resolution atmospheric analyses and compare model eddies with the observations in the Catalan Sea. We identify two zones of eddy formation in the Gulf of Lions, in front of the city of Marseille and at the southeast of coast of Roussillon, from which anticyclonic eddies are observed to drift toward the Catalan Sea. The hydrology and dynamics of the structures observed in the simulations are characterized. Sensitivity experiments and energy analysis are performed which allow us to identify the mechanisms associated with their generation. Properties of the eddy observed during the 2001 cruise at the Catalan shelf break are found to compare well with model eddies generated at the southeast of the Roussillon coast. The model relates the origin of these eddies to the separation of the coastal current downstream from Creus Cape: flow separation is linked to intense downwelling taking place in front of the Roussillon coast when strong northwesterly winds events occur.