Investigation of change in air-sea CO2 exchange over the East China Sea using biogeochemical ocean modeling

Abstract

A biogeochemical model was used to estimate air-sea CO2 exchange over the East China Sea. Since fresh water discharge from the Changjiang River and relevant chemistry were not considered in the employed model, we were not able to produce accurate results around the Changjiang River mouth. This factor aside, the model showed that the East China Sea, away from the Changjiang River mouth, takes approximately 1.5-2 mole m-2 yr-1 of CO2 from the atmosphere. The model also showed that biological factors modify the air-sea CO2 flux by only a few percent when we assumed that biological activity increased two-fold. Therefore, we can argue that the biological effect is not strong enough over this area within the framework of the current phosphate-based biological model. Compared to the preindustrial era, in 1995 the East China Sea absorbed 0.4-0.8 mole m-2 yr-1 more CO2. If warming of the sea surface is considered, in addition to the increase in atmospheric CO2 concentration, by 2045 the East China Sea would absorb 0.2-0.4 mole m-2 yr-1 less CO2 compared to the non-warming case.