Temporal and spatial variations of sea surface pCO2 in the East China Sea from spring to summer

The spring-summer pCO2 distribution in the East China Sea (ECS) was associated with the mixing of varied water masses, which had their own dominant governing factor of pCO2. pCO2 changes in the Kuroshio Waters (KW) and Taiwan Current Warm Waters (TCWW) were, for instance, mainly controlled by temperature effect, in the Changjiang Diluted Waters (CDW) by biological activity and in coastal waters (offshore < 100 km) by vertical mixing, respectively. A multivariate regression relationship was established (R2 = 0.86) according to temperature and chlorophyll-a as major controlling variables. Moreover, model relation as a polynomial of two parameters was applied to the areas of offshore >100 km by using remotely sensed data of temperature and chlorophyll-a (2003 2010). The model results showed that the concentration gradients of pCO2w were found i.e., an increasing trend from the CDW to TCWW and KW. The ECS overall acted as an atmospheric CO2 sink between May and October (-2.8 -0.3 mole C m-2 yr-1), except in August as a source ( 0.1 mole C m-2 yr-1). Finally, based on the model pCO2w data, the ECS was capable of absorbing atmospheric CO2 at a rate of 0.0042 Gt C yr-1 about 30% of the total in warm seasons (May October).