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., van Heuven, Steven, Mathis, Jeremy T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: article; Verlagsveröffentlichung; Arctic; Arctic Ocean; Sea ice
• Online Access: https://doi.org/10.5194/bg-15-1643-2018; https://noa.gwlb.de/receive/cop_mods_00006955; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00006912/bg-15-1643-2018.pdf; https://bg.copernicus.org/articles/15/1643/2018/bg-15-1643-2018.pdf

We estimated monthly air–sea CO2 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 CO2 in the surface water (pCO2w) 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 pCO2w 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 pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w 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 Tg C yr−1. Seasonal to interannual variation in the CO2 influx was also calculated.