Influence of the coastal upwelling on the dynamics of the upper boundary of the hydrogen sulfide zone off the Southern Crimea

A hydrodynamic model was used to study an upwelling and its influence on the distribution of oxygen and hydrogen sulfide in the zone of the Southern Crimean coast. Besides the dynamic factors, the chemical reaction between the dissolved gases was also taken into account. During the upwelling, the upward fluxes of cold bottom waters were found to be accompanied by displacements of the upper boundary of anaerobic and the lower boundary of aerobic zones and by the penetration of oxygen and hydrogen sulfide into the layers enriched by these gases. An extensive zone of coexistence of oxygen and hydrogen sulfide is formed over the shelf break at the place of the upwelled water. As a result of the chemical reaction between the dissolved gases in the upwelling zone, the formation of an area with a decreased content of oxygen is possible. Such an area with a low content of oxygen can be considered a trace of an upwelling.