Tidally-induced submesoscale features in the atlantic jet and Western Alboran Gyre. A study based on HF radar and satellite images

Abstract

An analysis is presented of the submesoscale tidally-induced anticyclonic eddies formed at the eastern mouth of the Strait of Gibraltar and their role in explaining mesoscale features of the Atlantic Jet – Western Alboran Gyre (AJ-WAG) system. These eddies have been identified for the first time using an observational approach based on the analysis of High Frequency Radar (HFR) derived surface currents on the eastern mouth of the Strait which has been complemented with the analysis of Sea Surface Temperature (SST) satellite images. It is found that the major source of positive vorticity to the AJ is provided by its interaction with these anticyclonic eddies which in turn help maintain the water feeding of the upper branch of the WAG. This new role in maintaining the WAG is added to others previously recognized by other authors based on the supply of negative vorticity that these eddies provide to the whole WAG. In addition, these tidally-induced eddies may contribute to the destabilization of the AJ-WAG system when strong and persistent easterly winds coincide with periods of high tidal current amplitude. In these cases, meteorological forcing produces a weak and southward deflected AJ almost disconnected from a displaced eastward WAG. The WAG in turn is being flattened by an overdeveloped North Western Cyclonic Gyre (NWCG) that may be favored by the action of the mentioned eddies.