Dynamics of Atmospheric-Driven Surface Currents on The Gulf of Cadiz Continental Shelf and its link with The Strait of Gibraltar and The Western Alboran Sea.

Abstract

Several studies about the coastal circulation over the continental shelf of the Gulf of Cadiz have been published in the last twenty years. One of the most studied features in these papers are the so-called Coastal Counter Currents (CCCs) which are located roughly between the 100 m isobath and the coastline and are directed westwards. Despite the considerable number of articles devoted to the analysis of this phenomenon, the actual along-coast extension and origin of these CCCs currently remain unclear. In the present study, different mechanisms are proposed to explain the development of these CCCs. They have been revised and discussed taking into account the latest findings from a recent analysis that utilized surface currents derived from High Frequency Radar (HFR) as well as numerical model simulations. The most interesting finding is that the most intense CCCs events are initiated on the coastal margin of the westernmost side of the Strait of Gibraltar, and they are extended further west of Cape Santa Maria. Furthermore, these intense and extensive CCCs seem to be triggered by the joint action of local winds over the Gulf of Cadiz and additional remote effects which are coming from (i) the wind forcing over the Alboran Sea and the easternmost side of the Strait of Gibraltar, and (ii) the Sea Level Atmospheric Pressure forcing over the Ligurian Sea (western Mediterranean Sea). In addition, the same forcing mechanisms are valid to explain the eastward intensification of the coastal currents. The most relevant feature of the hydrodynamic pattern originated by this combination of forcing agents is its quasi-geostrophic adjustment against the coast in the whole spatial dominion. In addition, these results offer a clear example of how important the effects of forcing in rather remote regions may be in defining the hydrodynamic patterns of certain oceanographic regions.