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There is a continuous inflow of surface water from the Atlantic Ocean. After passing through the Straits of Gibraltar, the main body of the incoming surface water flows eastward along the north coast of Africa. This current is the most constant component of the circulation of the Mediterranean. It is most powerful in summer, when evaporation in the Mediterranean is at a maximum. This inflow of Atlantic water loses its strength as it proceeds eastward, but it is still recognizable as a surface movement in the Sicilian channel and even off the Levant coast.
This is the surface current. Into the Mediterranean
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In summer Mediterranean surface water becomes more saline through the intense evaporation, and, correspondingly, its density increases. It therefore sinks, and the excess of this denser bottom water emerges into the Atlantic Ocean over the sill forming the shallow Strait of Gibraltar as a westward subsurface current below the inward current. The inflowing water extends from the surface down to 230 or 260 feet. The Mediterranean has been metaphorically described as breathing, inhaling surface water from the Atlantic and exhaling deep water in a countercurrent below.
This is the deep sea current back into the Atlantic.