Vertical Water Exchange in the Caspian Sea Assessed by the Distribution of Transient Tracers

Abstract

The reliability of various scenarios of vertical structure formation in Caspian Sea water was analyzed based on the distribution of transient tracers (CFC-11, CFC-12, ³H, and ³He) at deep-water stations in the Middle and Southern Caspian in the course of international comprehensive isotope-geochemical studies in the period of maximal sea level rise in 1995–1996. The available hydrometeorological data and the specifics of water dating with the use of transient tracers suggested the conclusion that, after the large-scale gravitational convection in the Middle Caspian, caused by anomalous cooling of surface water in the Northern Caspian in the late winter of 1976, a structure of water masses has formed, barring the ventilation of deep water in the Middle and Southern Caspian up to the mid-1990s.