Level Variations in the Caspian Sea under Different Climate Conditions by the Data of Simulation under CMIP6 Project

Water balance components for the territory of the Volga basin and Caspian Sea water area have been analyzed using the results of climatic simulation under CMIP6 Project for reproducing the modern (1859–2014) and preindustrial (~1850) climate, as well as the climate of Holocene optimum (6 thousand years ago) and the Last Glacial Maximum (21 thousand years ago). Volga runoff for the modern and preindustrial periods has been reproduced by models close enough to its actual values, while its components (precipitation and evaporation) have been overestimated. The analysis of the distribution functions of precipitation and evaporation in the Caspian Basin has shown the fluctuations of precipitation to contribute more to the natural variability of the Caspian level. A probability distribution function of possible fluctuations of the Caspian Sea was derived based on the theory of Brownian motion.