Characterization of the Regional Climate and Large-Scale Atmospheric Circulation in the Caspian Sea Region During the Last Glacial Maximum

Abstract

The Caspian Sea is the largest inland water body on Earth. Still, this region is often not considered in paleoclimate model analyses. In this study, we examine the climate of the Caspian Sea region during the Last Glacial Maximum (LGM) and its driving large-scale atmospheric circulation using data from two global climate models (AWI-ESM-1-1LR and MPI-ESM1.2-LR) within the PMIP4 framework. We validate the simulation output against proxy data, including information derived from pollen, lake sediments, and loess deposits. Our results demonstrate that the global climate simulations align more closely with proxy data within the Caspian Sea region (mostly within one standard deviation) than the Mediterranean and Western Europe and can thus be further exploited. The subtropical jet stream is dominant in winter exhibiting higher wind speeds than in summer, where the jet stream undergoes a transition from a zonal structure under preindustrial conditions to a wave-like pattern during the LGM. Furthermore, there is an increase in extratropical cyclone activity during the LGM. The analysis of the near-surface circulation reveals the dominance of an anticyclonic flow in summer, which becomes even more frequent during the LGM (increase by up to 20%). The general characteristics of the rotational circulation weather types change toward an intensification during the LGM. Overall, the models demonstrate greater agreement at larger scales. However, to enable a more direct comparison with local proxy data, especially in the topographically complex region along the southern coast of the Caspian Sea, we suggest a follow-up study employing high-resolution climate simulations.