Water Balance of the Caspian Sea in the Last Glacial Maximum and Pre-Industrial Conditions Based on the Experiments with the INMIO-CICE General Sea Circulation Model

The INMIO-CICE hydrodynamic model of the Caspian Sea was used to calculate equilibrium river runoff and evaporation from the sea surface over a wide range of sea levels (from –85 to +50 m a.s.l.) for different climatic conditions: the Last Glacial Maximum (about 21 ka BP) and the pre-industrial climate (~1850). Data from the INMCM4.8 climate model were used as boundary conditions. It was found out that a river runoff of about 400 km 3 /yr was required in the Last Glacial Maximum to maintain the sea level at 35–50 m a.s.l. corresponding to the maximum values of the Khvalynian transgression. In the Last Glacial Maximum, evaporation from the sea surface decreased by 105–175 mm (12–22%), and a precipitation layer, according to the INMCM4.8 model, decreased by 50–70 mm (15–30%). These conditions caused the equilibrium runoff to decrease by about 10–20% compared to the pre-industrial conditions. Smaller absolute and relative changes corresponded to lower sea levels. The maximum evaporation decrease occurred at 5 m a.s.l.