North–Central Aegean Sea surface and intermediate water masses and their role in triggering the Eastern Mediterranean Transient

Abstract

Interrannual variability in the surface and intermediate water masses of the North–Central Aegean Sea is being investigated through data collected by the Hellenic Navy Hydrographic Service (HNHS) during the Eastern Mediterranean Transient (EMT) post-peak period. Data suggest that following the last major deep-water formation episode in the Aegean Sea (1993), Black Sea Water (BSW) is confined to the northernmost part of the basin, while saline Levantine Surface Water (LSW) becomes the dominant Central Aegean surface water mass, intruding below the BSW layer even north of Lemnos Island. Furthermore, highly saline intermediate masses transfer additional salt to the North–Central Aegean basin. After the early 90s, BSW gradually reclaims most of the Central Aegean while the salinity of both LSW and intermediate masses is reduced. The enhanced presence of these highly saline water masses in the early 90s, presumably signifies the intrusion of high salinity water of Levantine origin into the North–Central Aegean following the massive outflow of dense Aegean water into the Eastern Mediterranean. This salinity intrusion was one of the preconditioning factors that enhanced dense water formation in the Aegean during the last major deep-water formation phase of the EMT, affecting the characteristics of the deep-water masses produced.