Variability of Delta pCO(2) in the subarctic North Pacific. A comparison of results from four expeditions

Time-space variability of surface seawater pCO(2) is examined over the region (150 degrees W-180 degrees, 46 degrees N-50 degrees N) of the subarctic North Pacific where large meridional gradients of temperature and nutrient concentrations exist. The data were collected during four trans-Pacific expeditions in three different years (1985-1987), but within the same 30-day period of the year (August-September). Systematic measurement differences between the four data sets are estimated as <10 mu atm. The inter-expedition comparison suggests that surface seawater pCO(2) in the study area is quite variable, with mean differences of up to 25 mu atm and local differences up to 60 mu atm. Spatial and interannual variability of surface seawater pCO(2) were found to contribute significant uncertainty to estimates of the mean Delta pCO(2) for the study area. Fluxes were calculated using Delta pCO(2) values from the four expeditions combined with gas exchange coefficients calculated from four different wind fields giving a range of -0.94 to +4.1 mmol CO2 m(-2) d(-1). The range of fluxes from the study area is scaled to a larger area of the North Pacific to address how this variability can translate into uncertainties in basin-wide carbon air-sea exchange fluxes.