Interannual variations of the air-sea carbon dioxide exchange in the different regions of the Pacific Ocean

Interannual variations of the air-sea CO₂ exchange from 1965 to 2000 in the Pacific Ocean are studied with a Pacific Ocean model. Two numerical experiments are performed, including the control run that is forced by climatological monthly mean physical data and the climate-change run that is forced by interannually varying monthly mean physical data. Climatological monthly winds are used in both runs to calculate the coefficient of air-sea CO₂ exchange. The analysis through the differences between the two runs shows that in the tropical Pacific the variation of export production induced by interannual variations of the physical fields is negatively correlated with that of the air-sea CO₂ flux, while there is no correlation or a weak positive correlation in the subtropical North and South Pacific. It indicates that the variation of the physical fields can modulate the variation of the air-sea CO₂ flux in converse ways in the tropical Pacific by changing the direct transport and biochemical process. Under the interannually varying monthly mean forcing, the simulated EOF1 of the air-sea CO₂ flux is basically consistent with that of sea surface temperature (SST) in the tropical Pacific, but contrary in the two subtropical Pacific Ocean. The correlation coefficient between the regionally integrated air-sea CO₂ flux and area-mean SST shows that when the air-sea CO₂ flux lags SST by about 5 months, the positive coefficient in the three regions is largest, indicating that in the tropical Pacific or on the longer time scale in the three regions, physical processes control the flux-SST relationship.