Increased net CO₂ outgassing in the upwelling region of the southern Bering Sea in a period of variable marine climate between 1995 and 2001

We investigated seasonality and interannual variability of the surface water p CO 2 ( p CO 2 sw) and sea‐air CO 2 fluxes in the upwelling region of the southern Bering Sea (53°N to 55°N, 174°E to 194°E). Data of surface water and atmospheric p CO 2 , sea surface temperature and salinity were based on automated measurements on board cargo ships for 6 years (1995–2001). We observed a significant interannual trend towards more CO 2 supersaturated surface water relative to the atmosphere. From linear regression of seasonally detrended data we obtained an annual p CO 2 sw increase of 6.5 ± 1.4 μatm yr −1 and 11 ± 1.9 μatm yr −1 in the basin and shelf slope, respectively. This was higher than the observed p CO 2 air increase (between 0.47 ± 0.28 and 0.96 ± 0.62 μatm yr −1 ), indicating the importance of other processes than oceanic CO 2 uptake from the atmosphere to explain the p CO 2 sw increase. Sea surface temperature and salinity showed a trend towards cooler and more saline conditions. We estimated large interannual variability of net annual oceanic CO 2 outgassing, with low CO 2 outgassing in years before 1998 (<1 mol m −2 yr −1 ), increasing to a maximum of 4.5 mol m −2 yr −1 in 2000. Highest net CO 2 outgassing was observed in the relatively cold years of 1999 and 2000, whereas the exceedingly warm year 1997 showed four times lower CO 2 flux to the atmosphere. Interestingly, we found close coupling between the net CO 2 outgassing and biological production; years with less net CO 2 outgassing coincided with high biological CO 2 drawdown, especially evident in 1997.