CO2 exchange at air-sea interface in the Huanghai Sea

Abstract

During the Huanghai Sea Circulation and Material Flux Expedition in Spring 1996, f(CO2) in surface water and atmosphere was measured. The f(CO2) in surface water varied in a range from 220 to 360 μatm while atmospheric concentration was nearly constant at 360 μatm, showing that the Huanghai Sea surface waters were undersaturated with respect to atmospheric CO2 during the time of investigation. A model was developed in this study in order to estimate the CO2 flux at the air-sea interface. The model incorporates the time-series variations of the distributions in SST (sea surface temperature), salinity, mixed-layer depth, atmospheric f(CO2), gas-transfer velocity, and CZCS chlorophyll concentration in the Huanghai Sea and was calibrated with the observed f(CO2) data. The primary parameter affecting f(CO2) in surface water is the variation of SST through time. The annual fluxes of CO2 are estimated as 0.033 Gt C from the sea into the atmosphere and 0.044 Gt C from the air into sea. The Huanghai Sea, thus behaves as a CO2 sink absorbing 0.011 Gt C of CO2 a year, which corresponds to about 0.5% of global oceanic absorption capacity.