ANALYSIS OF SEA-LEVEL CHANGES IN THE BLACK SEA FOR THE PAST 140 YEARS AND FORECAST FOR THE FUTURE

For the period of investigation (1876-2006), basinal volume changes in the Black Sea caused by the components of the water balance equation, play the defining role in the formation of its sea-level regime. A significant role in the water balance is associated with the freshwater inflow. The leading component in freshwater flux (about 80%) belongs to the discharge of the rivers entering the northwest part of the sea – Danube (about 70% of the total river discharge), Dnieper, Dniester and Southern Bug. The changes in the Dnieper and Dniester discharge are substantially synchronous. Quasi-periodic discharge fluctuations of these rivers have identical periodicity and are in phase. Long-term fluctuations of Danube discharge are defined largely by changes in the regime of atmospheric precipitation which are positively linked with a number of types of easterly and meridional atmospheric circulation within the study region (northwest part of the Black Sea). Strengthening of atmospheric circulation of the specified types leads to increase in precipitation, increase in Danube River discharge, and increase in the Black Sea level. The same trend – sea-level lowering during epochs of western circulation and rise during eastern and meridional circulation, is characteristic of the Mediterranean Sea, as well as fluctuations of sea level in Southern Atlantic Ocean and eastern Pacific Ocean. The periods of accelerated rates of sea-level change (difference in levels between the present and previous years) coincide with periods of increased angular speed of the Earth's rotation (reduction in daily duration). Beginning in the 1920s, a correlation exists between quasi-periodic constituents with 25-to-60-year periodicities. Solar activity plays a significant role in the formation of atmospheric circulation. The general trends of sea level change agree well with changes in solar activity on centennial cycles. At existing rates of sea-level change, the absolute level of the Black Sea (taking into account negative movements of the Earth's crust) will increase by 15 cm by the year 2050 and by 30 cm by 2100. In a worst-case scenario, these numbers can reach 40 cm by 2050 and 100 cm by 2100.