Variations in Dissolved Oxygen Induced by a Tropical Storm Within an Anticyclone in the Northern South China Sea

Tropical storms (TSs) can induce sea surface cooling, freshening, and phytoplankton blooms. The dissolved oxygen (DO) concentration response to TSs within an anticyclone is still unclear due to the rarity of in situ observations. In this study, we investigate the variations in DO concentration attributed to TS ‘Haitang’ within an anticyclonic eddy in the northern South China Sea based on Chinese underwater glider data. DO concentrations have a higher value at the edge of eddy than at the core. Influenced by TS, DO concentrations decrease remarkably in the subsurface layer in all three regions (inside, edge, and outside of the anticyclonic eddy). The mean DO concentrations decrease more at the edge of the anticyclone than those inside the anticyclone. The recovery time of DO concentration after TS is around one week at the edge of the anticyclone and is >10 days within the eddy. Our observations show that the DO concentrations decrease above the subsurface chlorophyll a maxima layer. Quantitative analysis shows that variations in DO concentration are dominated by horizontal advection and vertical advection terms in the subsurface layer.