Environmental history of the South Caspian Sea basin and its relation to the Siberian High dynamics since 14,000 years ago

Abstract

The Caspian Sea (CS) is an endorheic basin located at the boundary of Asia and Europe, which has undergone remarkable environmental transformations since the late glacial period. Its present dimensions and oceanographic features are determined by a complex interaction between climatic change and tectonic processes. However, the link between past climatic variations, especially the dynamics of the Siberian High (SH), and the CS oceanographic characteristics remains poorly constrained, leading to uncertainty in projecting its future rapid changes. In this study, a 1.7 m sediment core from the 584 m of water depth at the eastern side of the southern CS was obtained to reconstruct the climatically-driven environmental changes in the CS region during the last 14,000 years. High-resolution XRF measurements and detailed sedimentological analyses were conducted on the core samples. The outcomes were then systematically compared with a diverse array of extant palaeoclimatological datasets from Central Asia and Europe, regions dominated by two pivotal climatic systems impacting the CS. The objective of this comparative analysis was to clarify the impact of the SH and to define its dynamic interaction with the Westerlies over the CS. It was demonstrated that the SH dynamics exerted a significant influence on the CS environment. When the SH was strong and expanded over a large area, precipitation occurred outside of the CS watershed area and led to sea-level fall. Conversely, when the SH expansion was confined to the CS catchment basin, precipitation over the basin and lower evaporation resulted in sea-level rise.