Arctic Ocean CO2 uptake: An improved multiyear estimate of the air-sea CO2 flux incorporating chlorophyll a concentrations

We estimated monthly air–sea CO 2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014. This was done by mapping partial pressure of CO 2 in the surface water ( p CO 2w ) using a self-organizing map (SOM) technique incorporating chlorophyll  a concentration (Chl  a ), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO 2 mixing ratio, and geographical position. We applied new algorithms for extracting Chl  a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl  a values. The overall relationship between p CO 2w and Chl  a was negative, whereas the relationship varied among seasons and regions. The addition of Chl  a as a parameter in the SOM process enabled us to improve the estimate of p CO 2w , particularly via better representation of its decline in spring, which resulted from biologically mediated p CO 2w reduction. As a result of the inclusion of Chl  a , the uncertainty in the CO 2 flux estimate was reduced, with a net annual Arctic Ocean CO 2 uptake of 180 ± 130 Tg C yr −1 . Seasonal to interannual variation in the CO 2 influx was also calculated.