| Summary: | We produced 204 monthly maps of the air–sea CO2 flux in the Arctic north of 60°N, including the Arctic Ocean and its adjacent seas, from January 1997 to December 2013 by using a self-organizing map technique. The partial pressure of CO2 (pCO2) in surface water data were obtained by shipboard underway measurements or calculated from alkalinity and total inorganic carbon of surface water samples. Subsequently, we investigated the basin-wide distribution and seasonal to interannual variability of the CO2 fluxes. The 17-year annual mean CO2 flux shows that all areas of the Arctic Ocean and its adjacent seas were net CO2 sinks. The estimated annual CO2 uptake by the Arctic Ocean was 180 TgC yr−1. The CO2 influx was strongest in winter in the Greenland/Norwegian Seas (>15 mmol m−2 day−1) and the Barents Sea (>12 mmol m−2 day−1) because of strong winds, and strongest in summer in the Chukchi Sea (∼10 mmol m−2 day−1) because of the sea-ice retreat. In recent years, the CO2 uptake has increased in the Greenland/Norwegian Sea and decreased in the southern Barent
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