The hydrological characteristics of the waters exchanged between the eastern and the western basins of the Mediterranean

Abstract

An analysis is done of hydrographic data obtained in 1965 and 1966 in the region of Tunis-Sicily-Malta. Vertical sections permit to follow the opposite spreadings of the surface water of Atlantic origin and the levantine intermediate water; the evolution of the characteristics are studied on Tis diagrams. The Atlantic water with low salinity is strongly influenced by evaporation, especially in the vicinity of the 15th East meridian. The levantine water, characterized by the maximum of salinity, goes over the Malta sill, the deep Ionian water however does not. Between this eastern sill and the western sills, opening on the western Mediterranean, there is an intermediate basin filled right to the bottom (1600m) by this levantine water. On the deeper western sill, the characteristics of this outgoing flow are aI'ound~ S %0 = 38.74 - 38.75 and TO = P 14.00 - l4.l00 C. These values are modified by sinking and mixing processes after the flow has passed the sill. The levantine water filling the intermediate basin is supposed to be renewed rapidly because of a low vertical stability combined with an important undercurrent over the Sicilian Strait. An attempt to establish the water budget of the eastern Mediterranean permits to estimate the order of magnitude of the opposite flows (Atlantic and levantine). These estimates emphasize the close similarity between the Strait of Sicily and the Strait of Gibraltar.