Circulation in the Western Mediterranean Sea

Abstract

During the last decade, a considerable amount of work has been made and definite results obtained about the circulation in the Western Mediterranean Sea. The diagrams presented 10 years ago [Millot, C., 1987a. Circulation in the Western Mediterranean. Oceanol. Acta, 10, 2, 143–149.] have been confirmed and complemented, mainly in the south where all water masses appear to flow anticlockwise along the continental slope, as they do everywhere else in the sea. Definitive results have also been obtained about the mesoscale phenomena in the Algerian Basin which induce a dramatic variability of the circulation of all water masses, as far as around the Balearic Islands and through the Channel of Sardinia. Extremely interesting observations have been collected between Sicily, Tunisia and Sardinia about the hydrological and dynamical characteristics of the waters entering the Tyrrhenian Sea. Finally, the dense water formation processes have been specified, mainly since some uncommon situations have been encountered. As a whole, the relatively large importance of the seasonal (resp. mesoscale) variability in the north (resp. south) has been documented. Together, the observations in nature, the laboratory experiments and the numerical models have thus provided a more thorough understanding of the sea dynamics. Nevertheless, uncertainties remain about the amount of the waters formed in the sea mainly at intermediate depths, for these waters are often not easily distinguished from the surrounding ones. This is of major importance for, a priori, intermediate waters can flow out of the sea more easily than deep waters. In any case, the southern Tyrrhenian Sea appears to be a key place for the functionning of the whole sea.