Effects of Typhoons on Surface Seawater p CO 2 and Air‐Sea CO 2 Fluxes in the Northern South China Sea

This study assessed the effects of typhoons on sea surface p CO 2 and CO 2 flux in the northern South China Sea (SCS). During the passage of three major typhoons from May to August 2013, sea surface p CO 2 , surface seawater temperature (SST), and other meteorological parameters were continuously measured on a moored buoy. Surface water in the region was a source of CO 2 to the atmosphere with large variations ranging from hours to months. SST was the primary factor controlling the variation of surface p CO 2 through most of the time period. Typhoons are seen to impact surface p CO 2 in three steps: first by cooling, thus decreasing surface p CO 2 , and then by causing vertical mixing that brings up deep, high‐CO 2 water, and lastly triggering net uptake of CO 2 due to the nutrients brought up in this deep water. The typhoons of this study primarily impacted air‐sea CO 2 flux via increasing wind speeds. The mean CO 2 flux during a typhoon ranged from 3.6 to 5.4 times the pretyphoon mean flux. The magnitude of the CO 2 flux during typhoons was strongly inversely correlated with the typhoon center distance. The effect of typhoons accounted for 22% of the total CO 2 flux in the study period, during which typhoons occurred only 9% of the time. It was estimated that typhoons enhanced annual CO 2 efflux by 23–56% in the northern SCS during the last decade. As such, tropical cyclones may play a large and increasingly important role in controlling CO 2 fluxes in a warmer and stormier ocean of the future.