Arctic Ocean CO 2 uptake: an improved multiyear estimate of the air–sea CO 2 flux incorporating chlorophyll a concentrations

• Published in: Biogeosciences
• Main Authors: S. Yasunaka, E. Siswanto, A. Olsen, M. Hoppema, E. Watanabe, A. Fransson, M. Chierici, A. Murata, S. K. Lauvset, R. Wanninkhof, T. Takahashi, N. Kosugi, A. M. Omar, S. van Heuven, J. T. Mathis
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Arctic Ocean; Sea ice
• Online Access: https://doi.org/10.5194/bg-15-1643-2018; https://doaj.org/article/dc3d1258c03f47c9a53ccb2ae62745eb

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.