DATE2019-01-08 12:44:22
IDABSTRACT2014/202
CONTACTdvelaoras@hcmr.gr
PRESENTATIONORAL
INVITED0
IDSESSION2
TITLEA RECURRENT, SALINITY DRIVEN, DENSE INTERMEDIATE WATER OUTFLOW FROM THE CRETAN SEA AS A MANIFESTATION OF THERMOHALINE CIRCULATION CHANGES
AUTHORSDimitris Velaoras (1)|George Krokos (1)|Alexander Theocharis (1)
AFFILIATIONS
  1. Institute of Oceanography, Hellenic Centre for Marine Research (HCMR), Anavyssos, Greece
ABSTRACTRecent studies have shown increasing salinities in the surface and intermediate layers of the eastern part of Eastern Mediterranean Sea after the middle of the 2000’s decade. In – situ data collected from different platforms in the Cretan Sea during the 2000’s decade, almost 15 years after the end of the Eastern Mediterranean Transient (EMT), present evidence of gradually increasing salinity in the intermediate and deep-intermediate layers of the basin during the same period. The accumulation of these saline water masses favored dense water formation processes which finally led to outflow from both West and East Cretan Straits. The density of the outflowing water masses was greater than typical Levantine/Cretan Intermediate water but not dense enough to penetrate into the deep/bottom layers of the Eastern Mediterranean. These outflowing masses comprise a discrete water mass named dense CIW (dCIW) with density ranging between 29.1<s?<29.2 kgr/m3. When the Aegean Sea produces similar dCIW masses, we characterize the event as “EMT-like”, but when the Aegean Sea produces water masses denser than ~29.20 kgr/m3 then these masses reach the deep/bottom layers of the EMed, which is the case of the EMT event. A retrospective analysis of in-situ data and literature references during the last four decades, showed that similar EMT-like events have appeared in the past in two occasions: a) in the 1970’s and b) during the EMT onset (1987 – 1991). We argue that dCIW export from the Cretan Sea and the consequent EMT-like events are recurrent, salinity driven phenomena that appear at quasi regular, almost decadal time intervals. Such events are mostly due to periodical changes of the Eastern Mediterranean upper thermohaline circulation attributed to an internal oscillating thermohaline pump mechanism that creates favorable dense water formation conditions in the Aegean Sea through salinity preconditioning. This internal mechanism seems to dominate over the atmospheric forcing in provoking dense water formation processes in the Aegean Sea. The role of the atmosphere is nonetheless significant in regulating the amplitude of the dense water formation events and mainly defines whether dense water formation processes would create an EMT or EMT-like event.
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