Two-dimensional numerical simulation of vertical distributions of dissolved oxygen in Huanghai Sea

A two-dimensional model is established to study the temporal evolution of the maximum of vertical distribution of dissolved oxygen in the Huanghai Sea. Three major processes which regulate the variations of dissolved oxygen, i. e.,vertical mixing, biological activity of marine organisms and gas exchange at the air-sea interface, are discussed. It is shown that the major mechanisms of forming and retaining the maximum of dissolved oxygen are the weakened vertical mixing near the bottom of the thermocline, the gas exchange at the air-sea interface and the consumption of oxygen due to the oxidation of organic matter under euphotic layer and at the bottom during the warming periods. Since the thermocline lies in the euphotic zone in the Huanghei Sea area, the biological production contributes to the maximum but does not determine the maximums formation or retention. Most of the biological production in the upper mixing layer get into the air by the gas exchange in the air-sea interface. The transfer velocity of gas exchange can affect the concentration of dissolved oxygen in the upper mixing layer, but has very little influence on the maximum.