THE PAST 23-KYR EASTERN MEDITERRANEAN SEA CIRCULATION INFERRED FROM AUTHIGENIC ND ISOTOPES, FORAMINIFERAL STABLE ISOTOPES AND BULK ELEMENTAL COMPOSITION
Résumé
The Eastern Mediterranean Sea (EMS) circulation is sensitive to climate changes as documented by the recent Eastern Mediterranean Transient and repeated occurrence of organic-rich layers (sapropels) in precession cycle. It is well known that excess fresh water inputs to the EMS in relation to African monsoon variability and consequent stagnant circulation are a key to sapropel formation. Increased Nile discharge has been considered to be a main source of fresh water. However, recent studies on the sapropel S1 (ca 11-6 kyr cal.B.P.) revealed the importance of glacial termination conditions as well as the influence of the Atlantic inflow and water exchange between western and eastern basins as factors modulating freshwater budget in the EMS. In this presentation, we combine multi-proxy results obtained for two cores collected in the Levantine Sea and the Strait of Sicily at 1,780 m and 771 m water depth to further examine the circulation variability for the last 23 kyr. Authigenic Nd isotopic composition, benthic foraminiferal stable isotopes and redox sensitive elements are used as tracers of bottom water mass and oxygenation whereas planktonic foraminiferal stable isotopes and detrital elements are treated as indicators of hydroclimate changes (Tachikawa et al., 2015; Cornuault et al., 2016, 2018). Our main findings are a reduced ventilation and strong stratification in the Levantine Sea that started during the last deglaciation and modification of water masses and/or circulation pattern in the Levantine Sea and the Strait of Sicily from the last glacial maximum to mid-Holocene relative to the present-state. Comparison with available Nd isotopic data suggests that water mass exchange was markedly reduced and limited to surface layer between the western and eastern basins during S1 formation.