Dynamic-Stochastic Modeling of Long-Term Level Regime of the Caspian Sea during Early Khvalynsk and Late Khvalynsk Transgressions

Abstract

The article presents the results of dynamic-stochastic modeling of long-term variations of Caspian Sea level during the Early khvalyn (Buinak stage) and the Late khvalyn (Makhachkala stage) transgressions. A linearized model of Caspian level variations with a negative feedback due to the dependence of sea water area on water level is shown to be applicable to the paleo-Caspian. The calculations were based on the results of simulation and analytical modeling. The regimes of long-term level variations in the paleo-Caspian Sea for the considered transgressions are shown to differ. For example, the variance of the Caspian Sea level for the Early and Late khvalyn transgressions is equal to 4.2 and 2.5 m², respectively, and the average duration of the level rise above its equilibrium value during a single event is ~50 and ~40 years, respectively. Estimates of the duration of sea level rises can be used to assess the possibility of formation of various coastal–shelf geomorphological forms during long-term level rises. The obtained characteristics of the processes of long-term sea level variations, including the variance, autocorrelation, probability distribution density, the mean duration of level rises above (or level drops below) specified level marks during one such event, the dependence of the parameter of inertia of level variations significantly expand our knowledge about the character of Caspian Sea level variations in the paleotime.