East European river runoff and Black Sea and Caspian Sea level changes as simulated within the Paleoclimate modeling intercomparison project

Abstract

During the last late-Pleistocene and post-glacial epochs, the Caspian Sea fluctuated between regressive and transgressive stages. The Black Sea experienced fluctuations too, but their amplitude was smaller because they were mainly controlled by the World Ocean due to water exchange through the Bosporus Strait. In the water-budget equation, the change in storage over a time period is balanced by the sum of the inflows and outflows that occur during the time period. They can be calculated from atmospheric general circulation models (GCMs). A modeling initiative, the Palaeoclimate Modelling Intercomparison Project (PMIP), could help to resolve this question. The PMIP has focused on two slices of the past: the mid-Holocene (6ka calendar years Before Present (BP)) and the last cold event of the Late Quaternary (21ka calendar years BP). The PMIP GCM simulations indicate that changes in level are primarily influenced by changes of river runoff. Ocean precipitation and evaporation together play a minor role. At 21ka BP the estimated level lowering was ∼50 and ∼200m for the Caspian Sea and Black Sea, respectively. This lends credit to the idea of the connection between deep regressive states of Caspian Sea and Black Sea and mature stages of Late Quaternary glacial/cooling/drying planetary events.