NOAA/WDS Paleoclimatology - Mediterranean Sea, sea surface (SST) and deep water temperature (DWT) reconstructions based on Mg/Ca ratios and d18O data over the past 15 kyrs

Deglacial and Holocene climate changes in the Mediterranean region altered the circulation dynamics, modifying the properties of the Eastern Mediterranean Sourced Waters (EMSW). EMSW flow into the Western Mediterranean and eventually into the North Atlantic Ocean through the Mediterranean outflow water (MOW). This study investigates the physicochemical changes in the EMSW properties during the Younger Dryas (YD; 12.9–11.65 kyr) and the youngest Sapropel (S1; 10.6–6.1 kyr), when major changes occurred in the Mediterranean circulation. We investigate these changes using stable oxygen isotopes (δ18O) and Mg/Ca in benthic and planktonic foraminifera from a sediment core located at the western flank of the Sicily channel (W-Sicily). Our data indicate a salinity enrichment of the EMSW during the late YD in consonance with a salinity increase in the MOW. This scenario would have represented a salinity injection into the Atlantic Ocean when the Atlantic meridional overturning circulation was weak. During the first part of the S1 (S1a), a decrease in salinity at the W-Sicily coincides with a reduced EMSW outflow, being consistent with an important reduction of the salinity and intensity of the MOW. At the last phase of the S1 (S1b), we detect for the first time, a significant change in both surface and deep hydrology of the Tyrrhenian Sea. We propose that increased evaporation in the basin led to higher salinity in the surface water layers favoring winter/spring vertical water mixing. This episode would have favored convection processes over the Tyrrhenian Sea leading to the formation of a higher-salinity intermediate-water mass.