From AMS Glossary
A part of the World Ocean with little communication with the major ocean basins, in which the circulation is controlled by density differences.
Two types of Mediterranean Seas are distinguished. In the arid type, evaporation exceeds precipitation, increasing the density of the Mediterranean Sea; this produces deep convection and an outflow of dense Mediterranean Water through the connection with the main ocean below an inflow of less dense oceanic water. Examples are the Eurafrican Mediterranean and the Red Sea. In the humid type, precipitation exceeds evaporation, lowering the density; this produces a two-layer structure and inflow of denser oceanic water below water of less dense Mediterranean Water. Examples are the Australasian Mediterranean (Indonesian Seas) and the Baltic Sea.