A comparison of ΔpCO2 distributions in the northern North Pacific using results from a commercial vessel in 1995–1999

Monthly distribution maps of ΔpCO2 (oceanic pCO2 minus atmospheric pCO2) in the northern North Pacific were constructed based on observations from a commercial vessel in March 1995–1999. These maps clearly show the seasonal progression of ΔpCO2 for the entire region. The results were compared with those of Takahashi et al. (Proc. Natl. Acad. Sci., USA 94 (1997) 8292), who derived global ΔpCO2 distributions using a different data set and method of interpolation. The annual mean difference between the two sets of ΔpCO2 is 3 μatm, much smaller than the annual mean ΔpCO2 of −14 μatm obtained by this study. However, monthly mean differences can be as large as the annual mean ΔpCO2, and the monthly difference in individual 4°×5° boxes can be as large as 70 μatm. There is no grid box that shows consistently large or small differences throughout the year. We also compared CO2 fluxes estimated from the two different sets of ΔpCO2 but the same set of wind, sea-surface temperature and salinity. Both studies find that the northern North Pacific is a small sink for carbon (−0.26 Gt C yr−1, this study; and −0.33 Gt C yr−1, Takahashi et al., 1997). Monthly fluxes based on the two data sets show larger differences, especially in spring and autumn. Further observations will help to reduce the difference in calculating monthly ΔpCO2 distributions by different interpolation algorithms and, therefore, improving the estimation of CO2 fluxes in the northern North Pacific.