Air‐sea flux of CO 2 in the Arctic Ocean, 1998–2003

The Arctic Ocean has experienced an unprecedented reduction in sea ice over the last 3 decades, increasing the potential for greater exchange of gases such as carbon dioxide (CO 2 ) between the atmosphere and the upper ocean. The present study utilizes remotely sensed data on distributions of both sea ice and chlorophyll a , together with modeled temperature and salinity fields, to obtain high‐resolution basin‐scale estimates of the air‐sea flux of CO 2 (FCO 2 ) in the Arctic Ocean for the years 1998–2003. Concentrations of dissolved inorganic carbon (DIC) were derived from multiple linear regression relationships with sea surface temperature, salinity, and chlorophyll a . The partial pressure of carbon dioxide (pCO 2 ) in surface waters was computed from DIC and alkalinity, the latter of which varied with salinity. FCO 2 was calculated from the air‐sea difference in pCO 2 and wind speed. Annual FCO 2 was highest in the Atlantic‐dominated Greenland and Barents sectors due to their lower sea ice cover, although area‐normalized FCO 2 in these sectors was low. Only the Siberian sector exhibited a significant increase in annual FCO 2 during the time of our study, due to a corresponding increase in ice‐free water. Overall, the Arctic Ocean was a net atmospheric sink for CO 2 , with annual FCO 2 averaging 118 ± 7 Tg C yr −1 during 1998–2003.