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

• Published in: Biogeosciences
• Main Authors: Yasunaka, Sayaka, Siswanto, Eko, Olsen, Are, Hoppema, Mario, Watanabe, Eiji, Fransson, Agneta, Chierici, Melissa, Murata, Akihiko, Lauvset, Siv K., Wanninkhof, Rik, Takahashi, Taro, Kosugi, Naohiro, Omar, Abdirahman M., Heuven, Steven, Mathis, Jeremy T.
• Format: Text
• Language: English
• Published: 2019
• Subjects: Arctic; Arctic Ocean; Sea ice
• Online Access: https://doi.org/10.5194/bg-15-1643-2018; https://www.biogeosciences.net/15/1643/2018/

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.