Recent thermohaline trends of the Atlantic waters inflowing to the Mediterranean Sea.

Abstract

A total of 5077 Argo float profiles in the period 01/2002-05/2010 have been used to analyze salinity and temperature trends in the Atlantic waters adjacent to the Strait of Gibraltar in order to identify the source of recent changes observed in the inflow to the Mediterranean Sea. Positive salinity trends of 0.038 +/- 0.009 psu/year and 0.013 +/- 0.003 psu/year have been found for the Surface Atlantic Water and the Eastern North Atlantic Central Water, respectively. For temperature, no significant trend is observed in the surface layer while positive trend of 0.05 +/- 0.02 °C/year is obtained for the thermocline waters. The Mediterranean Water layer does not show any significant trend for the entire period, but a switch from positive to negative trends is observed in year 2006. In contrast to previous findings, these thermohaline variations are driven by intrinsic water masses changes, instead of isopycnal vertical displacements, proba- bly related to an enhancement of the net freshwater losses in the area.