R. Boscolo and H. Bryden

The recent observation of newly formed deep water in the Aegean Sea (Roether, et al. 1996) prompts this analysis of whether such deep water could be formed locally by wintertime water mass transformations. The recent 1995 profiles of temperature and salinity and some stations from the 1960's and 1987 are examined to estimate the heat and freshwater losses required to create deep water in the Aegean Sea. The Aegean Sea is primarily stratified by temperature above 500 m depth and by salinity below. As the thermal stratification in the upper waters weakens during wintertime, the primary barrier to local deep water formation in the 1960's or in 1995 was a layer of low salinity intermediate water at 400 to 800 m depth that separates high salinity surface water from high salinity deep water. Wintertime net evaporation is not sufficient to erode this low salinity intermediate water layer. In 1987, the low salinity intermediate water was nearly absent and typical wintertime net evaporation could then lead to local deep water formation. Based on 1987 hydrographic conditions and observed wintertime air-sea exchanges, formation of new deep water in the Aegean Sea is likely to have occurred during the severe winters of 1991 to 1993 in the absence of low salinity intermediate water.