On the stability and interannual variability in the hydrochemical structure of the redox layer of the Black Sea

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The publication presents the results of the studies of the vertical hydrochemical structure of the northeastern part of the Black Sea. New data on the detailed distribution of the hydrochemical parameters in the redox zone are presented, including the compounds of nutrients, reduced sulfur forms, oxygen, metals, methane, and pH value. This area is not affected by the waters supplied via the Bosporus Strait and the Danube River runoff; therefore, the vertical structure of the area is more stable and, as compared to the western part of the Black Sea, represents an integrated rather than a local variability of the sea. By means of the task-oriented database developed for the redox layer, the interannual variability of the redox zone characteristics was calculated. The results obtained illustrate the mechanism of the response of the Black Sea environmental system to global climate variations. As seen from a comparison of the estimates available, the change in sea surface temperature and in the cold intermediate layer (CIL) renewal occurring in the winter causes changes in the oxygen content in the CIL core. The oxygen stock here is a kind of accumulator providing its downward supply throughout the year implemented mainly by diffusion. The interannual variations in this supply also cause the variations in the redox layer density structure and in the location of the upper hydrogen sulfide boundary. Thus, the distribution of the chemical parameters of the redox layer with respect to the density field provides an excellent indicator of global climate variations. Copyright © 2005 by Pleiades Publishing, Inc.

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