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

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 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 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 pCO2 plays a minor role, in determining the interannual variation of CO2 uptake in this area.