Using this graphic and referring to it is encouraged, and please use it in presentations, web pages, newspapers, blogs and reports.
For any form of publication, please include the link to this page and give the cartographer/designer credit (in this case GRID-Arendal)
Adapted from Zavattarelli, M., and Mellor, G.L., A Numerical Study of the Mediterranean Sea Circulation, American Meteorological Society, 1995.
Uploaded on Tuesday 19 Nov 2013
Mediterranean Sea water masses: vertical distribution
Schematically, the Mediterranean Sea comprises three main water
masses (EEA and UNEP 1999):
• the Modified Atlantic Water (MAW), found in the surface layer,
with a thickness of 50–200 m and characterised by a salinity of 36,2 psu (practical salinity units) near Gibraltar to 38,6 psu
in the Levantine basin;
• the Levantine Intermediate Water (LIW), formed in the Levantine
basin, lying in depth between 200 and 800 m, and characterised by temperatures of 13–15,5°C and salinity of
• the Mediterranean Deep Water (MDW), formed in both the Western and Eastern basins. The Western Mediterranean Deep Water (WMDW) is characterised by a temperature of 12,7°C and a salinity of 38,4 psu, while the Eastern Mediterranean Deep Water (EMDW) is characterised by a temperature of 13,6°C and a salinity of 38,7 psu.
Within the sea, the incoming Atlantic water is continuously
modified by interactions with the atmosphere and mixing with
older surface waters and with the waters underneath. All along
its course, MAW is seasonally warmed or cooled, but overall its
salt content increases and it becomes denser. In autumn, in the
northern parts of both basins, MAW remains at the surface. In
winter, cold and dry air masses induce marked evaporation and
direct cooling of MAW, resulting in a dramatic increase in its
density, which makes it sink. This sinking occurs in a series of
specific zones, generally located in the northern parts of the
basins, and is responsible for the formation of the deeper waters in the Mediterranean.