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Dense intermediate water outflow from the Cretan Sea: 1. A salinity-driven, recurrent phenomenon, connected to thermohaline circulation changes

July 30, 2014

Data collected from different platforms in the Cretan Sea during the 2000’s decade present evidence of gradually increasing salinity in the intermediate and deep intermediate layers after the middle of the decade. The observed gradual salt transport towards the deeper layers indicates contributions of dense water masses formed in various Aegean Sea sub-basins. The accumulation of these saline and dense water masses in the Cretan Sea finally led to outflow from both Cretan Straits, with density greater than typical Levantine/Cretan Intermediate water but not dense enough to penetrate into the deep layers of the Eastern Mediterranean. We name this outflowing water mass as dense Cretan Intermediate Water (dCIW). A retrospective analysis of in-situ data and literature references during the last four decades shows that similar events have occurred in the past in two occasions: a) in the 1970’s and b) during the Eastern Mediterranean Transient (EMT) onset (1987 – 1991). We argue that these salinity driven Aegean outflows are mostly attributed to recurrent changes of the Eastern Mediterranean upper thermohaline circulation that create favorable dense water formation conditions in the Aegean Sea through salinity preconditioning. We identify these phenomena as “EMT – like” events and argue that in these cases internal thermohaline mechanisms dominate over atmospheric forcing in dense water production. However, intense atmospheric forcing over an already salinity preconditioned basin is indispensable for creating massive deep water outflow from the Cretan Sea, such as the EMT event.

Velaoras D, Krokos G, Nittis K, Theocharis A, 2014: Dense intermediate water outflow from the Cretan Sea: 1. A salinity-driven, recurrent phenomenon, connected to thermohaline circulation changes, Journal of Geophysical Research – Oceans, doi:10.1002/2014JC009937. Article (subscription required).

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