Isotope studies in the Caspian Sea

Oceanographic and isotopic investigations in the Caspian Sea and the analys es of the available data on the discharge to the sea and the observed sea l evel changes suggest that climatically caused changes of river inflow are t he major cause of the sea level fluctuations over the last century. Hydroge n-3 and H-3-He-3 data indicate that the deep basins of the sea are rapidly ventilated, although the hydraulic turnover time of the sea is approximatel y 200 years. The concentration levels of the anthropogenic radionuclides Sr -90, Cs-137 and (PU)-P-239,240 in the water column can be explained by glob al fallout and therefore, at the sampling sites visited, there were no sign s of dumping of radioactive wastes. The anthropogenic radionuclide data sup port the idea of fast exchange of water masses in the Caspian Sea. The isot opic and oceanographic data collected during the cruises have shown potenti al to allow for a better understanding of the water circulation in the Casp ian Sea. (C) 1999 Elsevier Science B.V. All rights reserved.