Mediterranean oceanic response to the interannual variability of a high-resolution atmospheric forcing: A focus on the Aegean Sea

Abstract

We investigated the interannual variability of the Mediterranean Sea thermohaline circulation under present climate conditions using an oceanic model of 1/8° resolution. Two numerical simulations of 50 year duration were performed. In a control simulation the model was forced by a perpetual year forcing inferred from the climatology of the ECMWF fields, while in a random simulation the 6 years of the ECMWF fields were randomly applied. In this way we were able to test the sensitivity of the thermohaline circulation under an atmospheric interannual variability. In particular, during the last 10 years of the random simulation a succession of cold winters led to anomalous deep water formation in the Aegean Sea. We focused our analysis on this event. This anomalously dense water mostly forms in the Central and Southern Aegean subbasins with a formation rate of about 0.6 Sv. This led to strong modifications in water mass budgets and circulation with intensified exchanges between these two subbasins. The export of those dense waters to the Levantine basin remains weak except for a few particular years. Thus the impact of this event is localized as opposed to the Eastern Mediterranean Transient. These results show the possibility for transient events to reoccur in the Eastern basin in the forthcoming years. Copyright 2006 by the American Geophysical Union.