Regional differences in seasonal variation of air–sea CO2 exchange in the Yellow Sea

Abstract

Evidence suggests that the continental shelf CO2 influx rate might have increased globally during the past several decades. It remains a challenge to quantify air–sea CO2 fluxes in continental shelf regions and to understand their variations. The Yellow Sea on the western margin of the North Pacific represents one of the largest continental shelf regions. In this study, we conducted 10 carbonate surveying cruises between 2011 and 2018 that revealed regional differences in seasonal variation of surface fugacity of CO2 (fCO2) and air–sea CO2 fluxes on the Chinese side of the Yellow Sea. Results suggested that among various continental shelf CO2 sinks, the Yellow Sea represents one of the weakest marine CO2 absorbers. Despite the regionality of the study, we integrated spring/summer biological drawdown, summer/autumn vertical mixing, and universal warming/cooling and air–sea re-equilibration into an explanation of the seasonal variation in fCO2. These insights are fundamental to understanding sea surface carbonate chemistry in the Yellow Sea, and might help elucidate the biogeochemical controls of air–sea CO2 fluxes in other temperate seas.