Variance of Short-Period Sea Level Oscillations in the Black Sea: Seasonal and Interannual Variations

Purpose . The study is aimed at investigating the peculiarities of seasonal and interannual variations of the variance of short -period sea level oscillations in the Black Sea. Methods and Results . The peculiarities of changes in the variance (energy) of synoptic (2-30 days) and mesoscale (2 h - 2 days) sea level oscillations in the Black Sea were studied based on the analyses of long-term sea level observation series. The results of spectral analysis made it possible to find out that on the eastern coast of the Black Sea, the spectral density of sea level oscillations increases from summer to winter and decreases from winter to summer within the frequency range of 0.1- 0.8 cycles/day. As for the northwestern and Crimean coasts, the spectral density is practically the same in autumn and winter, further it decreases in spring and summer. The interannual changes of the variance of synoptic oscillations on the eastern sea coast are characterized by a negative trend achieving - 0.25 cm(2) /year in Batumi and - 0.41 cm(2) /year in Poti. The variance of mesoscale sea level oscillations has negative trends with the rates from - 0.21...- 0.24 cm(2) /year in Odessa and Nikolaev to - 0.13 cm(2) /year in Gelendzhik. Conclusions. The variance of short -period sea level oscillations in the Black Sea increases from summer to winter and decreases from winter to summer that is related to the intensification of cyclonic activity in the atmosphere during autumn and winter. A local seasonal decrease in the variance of sea level oscillations is observed in the estuaries of large rivers in winter due to the developed ice cover preventing the formation of wind surges and seiches. At that, the higher the oscillation frequency, the stronger the ice cover influence.