Long-Term Variability of the Dissolved Oxygen Content and Water Temperatures in the Upper Layer of the Black Sea

Abstract

Based on the archival oceanographic databank of the Institute of Natural and Technical Systems, the annual and interannual variability was analyzed for the dissolved oxygen content and temperatures in the upper deep-water layer and northwestern parts of the Black Sea from 1923 to 2013. The seasonal variations in the dissolved oxygen content and temperatures are in antiphase. On average, over the considered time frame, the dissolved oxygen content was maximum in winter in the northwestern area of the sea and minimum in the open parts in summer. The amplitude of seasonal variations was over 50 µM/L. In general, this is in agreement with earlier publications. However, the seasonal trend changes considerably within certain 20- to 30-year time intervals, which is related to quasiperiodic variability of the oxygen content on a typical time scale of several decades, exhibited differently in different seasons and sea areas.