PROGRESS IN THE STUDY OF THE COUPLED BLACK SEA – CASPIAN SEA SYSTEM DURING RECENT GEOLOGICAL PAST USING CLIMATE SIMULATION

As hypotheses concerning the origin of lake or inland sea level change accumulate, there is an increasing need to synthesize data and to develop methods that may help assess their strengths and inconsistencies. Among the techniques that can be used to piece together the common elements of observations and theories given knowledge of a system's physics are methods of climate simulation within the framework of a general circulation model (GCM). Here, I demonstrate the potential of this approach by estimating the changes both the Black Sea and the Caspian Sea. During the last late-Pleistocene and postglacial epoch the Caspian Sea were fluctuated between regressive and transgressive stages. Black Sea was experienced fluctuations too, but the World Ocean due to water exchange through the Bosporus Strait mainly controls them. Sometimes Caspian Sea overflowed to Black Sea and they were periodically coalesced. In other cases Caspian Sea and Black Sea existed separately but the drop in Caspian level and Black Sea level was approximately ~50 m and ~150-200 m, respectively. The change of the seas levels is forced by global climatic processes determining water-budget change and in some aspects controlled by tectonics. All of components of the water cycle can be calculated by atmospheric GCMs. The results of modeling have shown that during the planetary scale last glacial maximum, the runoff of the rivers of the East European Plane was considerably decreased (variation of the difference “precipitation mines evaporation” over sea surface has a minor contribution) and provided strong regression of the Caspian Sea and Black Sea. This lends credit to the idea of connection between Late Quaternary glacial/cooling/drying planetary events and deep regression states of the Caspian Sea and the Black Sea. During the postglacial epoch, the runoff of the rivers was not increased substantially to provide strong transgression of the Caspian Sea needed to the Caspian Sea could be coupled with the Black Sea. In this case there is a necessity of search of the source of "additional volume of water" capable to establish a Caspian sea level on a mark permitting an overflowing from the Caspian Sea to the Black Sea. This model exercise allowing to simulate lake changes within a GCM, can be used in broad area of geological tasks.