Characteristics of dissolved oxygen and its physical and chemistry influence factors in the slope break zone in northern South China Sea

On the basis of the data obtained in the field survey of the northern South China Sea in January 2010, it was discovered that DO, at the depth of 150-1 000 m, decreased from northeast to southwest. Meanwhile, the vertical distribution of DO reduced from surface to bottom. The concentration of DO contour line more than 8 mg/dm³ occupied the 50 m shallow water influenced by strongly water exchange. It was showed that the spatial distribution in the middle and the bottom layer of DO changed greatly by mesoscale vortex, which lead to the concentrations of DO nearby the center of warm vortex at the depth from 150 m to 500 m being remarkably higher than in other areas. Furthermore, DO shows great correlation with nutrients, temperature, salinity and pH in different layers, which indicated that the distribution of DO was influenced by physical and biochemistry process.