SCENARIO FORECASTS OF THE CASPIAN SEA FLUCTUATIONS IN THE LEVEL UNDER CLIMATIC AND MAN-MADE IMPACTS ON THE SEA WATER BALANCE

Abstract

The paper deal with the scenario method for predicting long-term fluctuations in the Caspian Sea level. The scenario forecasts are included: Model of the sea level fluctuations mechanism, Models of the main components of the sea water balance, Morphometric characteristics of sea, Dependence between the outflow of water into the Kara-Bogaz-Gol Bay and the sea level, Assessments of possible direct technogenic impacts on the sea water balance, for example, the withdrawals of water from the inflow into the sea. The Caspian Sea level long-term fluctuations are considered by us as the output process of a non-linear hydrological system. The mechanism of the Caspian level fluctuations contains two negative and one positive feedback. The dependences of the Caspian sea area and the outflow from the sea into the Kara-Bogaz-Gulf bay on the sea level form negative feedbacks. Positive feedback is formed by the nonlinear dependence of evaporation from the sea area on the sea level. Under certain conditions, the effect of this dependence can lead to the sea level bimodal probability distribution density. A necessary (but not sufficient) condition for bimodality is the absence of free seawater inflow from the sea into Kara-Bogaz-Gol. The results of scenario forecasts of the Caspian Sea level developed within the framework of the Caspian Federal Targeted Program (1994-95) are presented. The linear and nonlinear models of the sea level fluctuations used in scenario forecasts are discussed. Failure to take into account of any kind of the feedbacks leads to incorrect predictive estimates of the sea level fluctuations statistical characteristics.