Palaeohydrological reconstruction of the Eastern Mediterranean Sea during the Eemian

Abstract

The Mediterranean Sea's thermohaline circulation, sensitive to global climate changes, influences the Atlantic Meridional Overturning Circulation (AMOC) and the occurrence of sapropel layers in Mediterranean sediments. While sapropel formation is attributed to stagnant deep-water conditions and increased biological production during specific orbital cycles, debates persist concerning the complex interaction between high and low latitude climatic changes, circulation dynamics, and sapropel formation. We have investigated the hydrological dynamics of the eastern Mediterranean Sea during the Eemian using neodymium isotopes on foraminifera and other geochemical proxies. Cores from the southeastern Aegean Sea were compared with data from other Mediterranean regions to reconstruct water circulation patterns. Foraminiferal eNd records permit to identify two distinctive phases in the circulation patterns within the Sapropel S5. Initially, a large influx of freshwater causes water stratification, preventing the formation of deep-water layers and leading to localized signals observed in different cores. Cores located in the southern Mediterranean Sea exhibit prominent neodymium radiogenic signatures influenced by the Nile inputs. Conversely, cores positioned in the northern Mediterranean displays minimal Nile influence due to their more northerly location. During the deposition of the Sapropel S5, slight decreasing of sea levels and winter temperatures favored the formation of deep-water masses in the northern region, increasing basin-wide circulation. This enhanced circulation facilitates the transfer of radiogenic lithogenic Nd from the Nile to the northern part of the Eastern Mediterranean Sea. This change in circulation patterns highlights the influence of climate change on the deep hydrodynamics of the Eastern Mediterranean during the Eemian. Our data indicate for the first time that during the deposition of the sapropel S5, εNd not only exhibited vertical disparities and stratification but also shown noticeable large lateral variations in the Eastern Mediterranean Sea. Our new results highlight the importance of studying several cores in order to unravel the hydrodynamics on a basin scale and to elucidate the complex interactions within the Nd isotopic composition between freshwater input, circulation dynamics and fluvial sediment discharges in the eastern Mediterranean Sea during the last interglacial period.