Dynamic-Stochastic Modeling of the Paleo-Caspian Sea Long-Term Level Variations (14–4 Thousand Years BC)

The article considers an estimate of the effect of positive feedback in the mechanism of level oscillations in the Caspian Sea on the long-term level regime. The study was based on a modified dynamic-stochastic model of level variations, taking into account the spatial heterogeneity of evaporation from sea water area. The evaporation from Caspian shallows is considered as the sum of a deterministic and a stochastic component. The probability density of Caspian level was obtained for supposed paleotime conditions as a solution of the steady-state Fokker–Planck–Kolmogorov equation. In addition, Caspian level variations were simulated by Monte-Carlo method, the results of which confirmed the analytical calculations. Under some realistic assumptions accepted in the modeling, long-term variations of the Caspian level can have a nonstationary character under steady-state climate. The main result of the study is the conclusion that the nonlinear dependence of evaporation on the Caspian level is to be taken into account not only in paleoclimatic reconstructions, but also in the estimates of the future sea level regime.