The data set of dissolved oxygen concentrations in the South China Sea off the Pearl River Estuary in July 2018
- 海洋环境－科研数据 
We examined the evolution of intermittent hypoxia off the Pearl River Estuary based on three cruise legs conducted in July 2018: one during severe hypoxic conditions before the passage of a typhoon and two post-typhoon legs showing destruction of the hypoxia and its reinstatement. The lowest ever recorded regional dissolved oxygen (DO) concentration of 3.5 μmol kg-1 (~ 0.1 mg L-1) was observed in bottom waters during Leg 1, with a ~ 660 km2 area experiencing hypoxic conditions (DO < 63 μmol kg-1). Hypoxia was completely destroyed by the typhoon passage but was quickly restored ~ 6 days later, resulting primarily from high biochemical oxygen consumption in bottom waters that averaged 14.6±4.8 μmol O2 kg-1 d-1. The shoreward intrusion of offshore subsurface waters contributed to an additional 8.6±1.7 % of oxygen loss during the reinstatement of hypoxia. Freshwater inputs suppressed wind-driven turbulent mixing, stabilizing the water column and facilitating the hypoxia formation. The rapid reinstatement of summer hypoxia has a shorter timescale than the water residence time, which is however comparable with that of its initial disturbance from frequent tropical cyclones that occur throughout the wet season. This has important implications towards better understanding the intermittent nature of hypoxia and predicting coastal hypoxia in a changing climate.