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

We estimated monthly air-sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60 degrees N from 1997 to 2014. This was done by mapping partial pressure of CO2 in the surface water (pCO(2w)) using a self-organizing map (SOM) technique incorporating chlorophyll a concentration (Chl a), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO2 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 pCO(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 pCO(2w), particularly via better representation of its decline in spring, which resulted from biologically mediated pCO(2w) reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180 +/- 130 TgCyr(-1). Seasonal to interannual variation in the CO2 influx was also calculated.