Temporal and spatial variations of oceanic pCO₂ and air–sea CO₂ flux in the Greenland Sea and the Barents Sea

Abstract

In order to elucidate the seasonal and interannual variations of oceanic CO₂ uptake in the Greenland Sea and the Barents Sea, the partial pressure of CO₂ in the surface ocean (pCO₂^sea) was measured in all seasons between 1992 and 2001. We derived monthly varying relationships between pCO₂^sea and sea surface temperature (SST) and combined them with the SST data from the NCEP/NCAR reanalysis to determine pCO₂^sea and air–sea CO₂ flux in these seas. The pCO₂^sea values were normalized to the year 1995 by assuming that pCO₂^sea increased at the same growth rate (1.5 μatm yr^-1) of the pCO₂ in the air (pCO₂^air) between 1992 and 2001. In 1995, the annual net air–sea CO₂ fluxes were evaluated to be 52 ± 20 gC m^-2 yr^-1 in the Greenland Sea and 46 ± 18 gC m^-2 yr^-1 in the Barents Sea. The CO₂ flux into the ocean reached its maximum in winter and minimum in summer. The wind speed and Δ pCO₂ ( = pCO₂ air – pCO₂^sea) exerted a greater influence on the seasonal variation than the sea ice coverage. The annual CO₂ uptake examined in this study (70◦–80◦N, 20◦W–40◦E) was estimated to be 0.050 ± 0.020 GtCyr^-1 in 1995. The interannual variation in the annual CO₂ uptake was found to be positively correlated with the North Atlantic Oscillation Index (NAOI) via wind strength but negatively correlated with Δ pCO₂ and the sea ice coverage. The present results indicate that the variability in wind speed and sea ice coverage play a major role, while that in ΔpCO₂ plays a minor role, in determining the interannual variation of CO₂ uptake in this area.