Spatio-temporal variability of the carbonate system and air-sea CO2
fluxes in the South Yellow Sea and East China Sea during the warm
seasons
Abstract
Due to the complex physical and biogeochemical conditions, the adjacent
South Yellow Sea (SYS) and East China Sea (ECS) are ideal sites for
studying different carbonate characteristics in marginal seas. The
distributions of carbonate system parameters were investigated in this
region in early spring and summer. Overall, dissolved inorganic carbon
(DIC) and alkalinity concentrations in the SYS were higher than those in
the ECS due to the Yellow River runoff which was featured with intensive
carbonate weathering and erosion. Low DIC, alkalinity and high pH values
were observed in the Zhe-Min Coastal Current with intensive primary
production in spring caused by the Changjiang River and Taiwan Warm
Current. Temperature and biological activities were the primary drivers
in controlling the partial pressure of CO2 (pCO2) variability in the
SYS, whereas temperature was the only dominant factor in the outer shelf
of the ECS, which was heavily impacted by the Kuroshio Current. The pCO2
dynamics was controlled by primary production and physical mixing in the
Changjiang River plume and the inner and middle shelves of the ECS, due
to the influence of the Changjiang River with high nutrient supply.
Overall, strong CO2 sinks (-4.11 ± 5.28 mmol m-2d-1) turned into weak
sources (0.88 ± 5.09 mmol m-2d-1) in the entire study area from spring
to summer. Specifically, the SYS and ECS offshore waters changed from
CO2 sinks in spring to sources in summer, while the Changjiang River
plume always served as a CO2 sink.