Isotopic studies of environmental changes in the basins of the Caspian Sea and the Aral Sea

During the last thirty years environmental changes in the Caspian and Aral Sea basins were studied measuring the isotopic composition of water and bottom sediments of the two seas, neighboring lakes and inflowing rivers. Results of these studies related to the impact of climate variations of the past and present-day hydrologic regime, water dynamics, sea level variation and sedimentation process are discussed in this paper. Evidence is given for eight short-periodic cycles of regression and transgression of the Caspian Sea in the Late Pleistocene-Holocene. The Caspian Sea was formed by two lakes separated by the natural Apsheron sill/dam. The discussion includes also the environmental conditions in the Aral Sea basin, especially the recent drying up of this Sea. Finally, the physical basis for understanding the nature of the short and long-periodic climate variation is emphasized by presenting the solution of the problem of rotation and oscillation of the Earth in its own force field. (author)