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

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Abstract
A method has been developed to produce high‐resolution maps of pCO2 in surface water for the North Pacific using satellite sea surface temperature (SST) data and statistical relationships between measured pCO2 and temperature. In the subtropical North Pacific the pCO2 in seawater is controlled primarily by temperature. Accordingly, pCO2 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 pCO2 is controlled not only by temperature, but also by significant seasonal changes in the total CO2 concentration, which are caused by seasonal changes in primary production, mixing with subsurface waters, and sea‐air exchange. Consequently, the parameterization of oceanic pCO2 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 pCO2 variability caused by seasonal changes in the total CO2 concentration. The net CO2 flux for the area of the North Pacific included in this study (north of 10°N) has been calculated using the monthly pCO2 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 1.9×1012 to 5.8×1012 moles of CO2 per year (or 0.02–0.07 Gt C/yr), most of the outflux occurring in the sub tropics.

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