FY 1998

Variability of ΔpCO₂ in the subarctic north Pacific. A comparison of results from four expeditions

Murphy, P.P., D.E. Harrison, R.A. Feely, T. Takahashi, R.F. Weiss, and R.H. Gammon

Tellus, 50B(2), doi: 10.1034/j.1600-0889.1998.t01-1-00006.x, 185–204 (1998)

Time-space variability of surface seawater pCO₂ is examined over the region (150°W-180°, 46°N-50°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 µatm. The inter-expedition comparison suggests that surface seawater pCO₂ in the study area is quite variable, with mean differences of up to 25 µatm and local differences up to 60 µatm. Spatial and interannual variability of surface seawater pCO₂ were found to contribute significant uncertainty to estimates of the mean ΔpCO₂ for the study area. Fluxes were calculated using ΔpCO₂ 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.