A multilayer study of pCO2 in the surface waters of the Yellow and South China Seas in spring and the sea-air carbon dioxide flux

Abstract

A multilayer study of pCO2 for the Yellow and South China Seas in the surface waters was conducted based on data from four cruises sponsored by the China SOLAS Project in 2005 and 2006, including data for the surface microlayer (SML), subsurface layer (SSL) and surface layer (SL). The carbon fluxes across the air-sea interface were calculated. The results showed that the pCO2 values in the surface waters of the study area decreased in the following order: pCO2 SML > pCO2 SSL > pCO2 SL. The highest values were found in March for all SML, SSL and SL, followed by those in April, and the lowest were in May. The pCO2 values had a significant positive correlation with temperature or salinity. While there was no relationship between pCO2 and longitude, there was a significant negative correlation between it and latitude, i.e., ‘high latitude low pCO2’. By using four calculation models, the carbon dioxide fluxes (\( F_{CO_2 } \) ) in spring in the Yellow and South China Seas, which were found to act as a ‘sink’ of atmospheric CO2, were preliminarily estimated on the basis of the pCO2 data in the SML to be −7.00×106t C and −22.35×106t C, respectively. It is suggested that the \( F_{CO_2 } \) calculated on the basis of pCO2 data in the SML is more reliable than that calculated on the basis of those in the SL.