Sea‐air flux of CO₂ in the North Pacific using shipboard and satellite data

A method has been developed to produce high‐resolution maps of p CO 2 in surface water for the North Pacific using satellite sea surface temperature (SST) data and statistical relationships between measured p CO 2 and temperature. In the subtropical North Pacific the p CO 2 in seawater is controlled primarily by temperature. Accordingly, p CO 2 values that are calculated from the satellite SST data have good agreement with the measured values (rms deviation of ±17 μatm). In the northwestern subpolar region the p CO 2 is controlled not only by temperature, but also by significant seasonal changes in the total CO 2 concentration, which are caused by seasonal changes in primary production, mixing with subsurface waters, and sea‐air exchange. Consequently, the parameterization of oceanic p CO 2 based on SST data alone is not totally successful in the northwestern region (rms deviation of ±40 μatm). The use of additional satellite products, such as wind and ocean color data, as planned for a future study, is considered necessary to account for the p CO 2 variability caused by seasonal changes in the total CO 2 concentration. The net CO 2 flux for the area of the North Pacific included in this study (north of 10°N) has been calculated using the monthly p CO 2 distributions computed, and monthly wind speeds from the European Centre for Medium‐Range Weather Forecasts. The region is found to be a net source to the atmosphere of 1.9×10 12 to 5.8×10 12 moles of CO 2 per year (or 0.02–0.07 Gt C/yr), most of the outflux occurring in the sub tropics.