Recent changes in the physicochemical parameters of the Black Sea

Authors: EBRU YEŞİM ÖZKAN, HASAN BAHA BÜYÜKIŞIK

Abstract: Temperature and salinity values from CTD profiles at 9 stations in the southern Black Sea were analyzed. Temporary water types were determined along with the basic 3 types consisting of Black Sea surface water (BSW), Black Sea cold intermediate Water (BCIW) and Black Sea deep water (BDW). From the 1960s to the 1990s, firstly, the changing of dissolved oxygen (DO) concentrations in the middle of the pycnocline by eutrophication and cooling has created another equilibrium situation with lower DO values; later, in 2003, with the decrement in eutrophication and global warming, another equilibrium was formed and it was shown that this equilibrium still holds in 2009. An important difference between today and the 1960s is that DO levels have decreased and the suboxic zone top boundary has increased. The BCIW temperature has increased by 1 °C since the 1960s. Because the residence time of overall BCIW is approximately 5 years, the observations made correspond to the date 5 years earlier. With cooling in 2007, another new equilibrium will be observed after the 2010s that will allow us to more accurately predict the relative importance of convective cooling and eutrophication.

Keywords: CTD data, Black Sea, cold intermediate water, dissolved oxygen, salinity, soboxic zone

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