Tendencies of long-term changes of temperature fields, salinity and water level of the North-Western part of the Black Sea

The paper analyzes the variability of hydrological characteristics of the North-Western part of the Black for different temporal scales: long-term, seasonal and synoptic. The traditional methods of geographic investigations, such as comparative-geographic, retrospective and cartographic methods, were used. When analyzing sea level data packages and thermohaline characteristics mathematical methods, including statistical, correlation and regression analysis, were used. As a result of the conducted research quantitative estimates of tendencies of long-term changes of the thermohaline characteristics and level in the North-Western part of the Black Sea were received. Over the period of 1982-2005 an increase of water temperature in the North-Western part of the Black Sea was observed: in winter water temperature in the surface layer increased by 2оC, in the bottom layer – by more than 2оC. Over the period of 1990-2005 an increase of an average annual water temperature in Odesa area constituted 1,2°C. The most considerable and statistically significant temperature increase took place during the summer hydrological season: an average summer temperature increased during this period by 2,7оC. During transitional seasons (autumn and spring) there was also a tendency of temperature increase, however, statistically significant trend was observed only during the autumn period. There is a statistically significant negative trend observed for long-term changes of salinity. For the period of 1990-2005 an average annual salinity decreased by 1.36 ‰. A tendency of salinity decrease was observed for all seasons of the year, however, statistically significant trends are observed only in winter and summer. A close relationship between long-term changes in water salinity and runoff of the Dnieper River was also established. A sea level rise is observed at all stations of the North-Western part of the Black Sea. Over the period of 1947-2012 an average annual sea level in Odesa increased by 14 cm. An analysis of climatic changes of wind-induced sea level fluctuations showed that the frequency of surges of varying intensity remained almost unchanged, however, the frequency of sweeps changed significantly. Over the period of 1980-2012, as opposed to the period of 1947-1979, the frequency of minor sweeps (no more than 30 cm) increased, and the frequency of significant (more than 30 cm) and very significant (more than 50 cm) sweeps, on the contrary, decreased by about 5%-6%. Changes of wind-induced sea level fluctuations' character harmonize with wind direction and wind speed over the North-Western part of the Black Sea.