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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 6 | Copyright
Biogeosciences, 15, 1643-1661, 2018
https://doi.org/10.5194/bg-15-1643-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 22 Mar 2018

Research article | 22 Mar 2018

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

Sayaka Yasunaka1,2, Eko Siswanto1, Are Olsen3, Mario Hoppema4, Eiji Watanabe2, Agneta Fransson5, Melissa Chierici6, Akihiko Murata1,2, Siv K. Lauvset3,7, Rik Wanninkhof8, Taro Takahashi9, Naohiro Kosugi10, Abdirahman M. Omar7, Steven van Heuven11, and Jeremy T. Mathis12 Sayaka Yasunaka et al.
  • 1Research and Development Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
  • 2Institute of Arctic Climate and Environment Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
  • 3Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
  • 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Climate Sciences Department, Bremerhaven, Germany
  • 5Norwegian Polar Institute, Fram Centre, Norway
  • 6Institute of Marine Research, Tromsø, Norway
  • 7Uni Research Climate, Bjerknes Centre for Climate Research, Bergen, Norway
  • 8National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, USA
  • 9Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA
  • 10Oceanography and Geochemistry Research Department, Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan
  • 11Energy and Sustainability Research Institute Groningen, Groningen University, the Netherlands
  • 12National Oceanic and Atmospheric Administration, Arctic Research Program, Seattle, WA, USA

Abstract. 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±130Tg C yr−1. Seasonal to interannual variation in the CO2 influx was also calculated.

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We estimated monthly air–sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014, after mapping pCO2 in the surface water using a self-organizing map technique. The addition of Chl a as a parameter enabled us to improve the estimate of pCO2 via better representation of its decline in spring. The uncertainty in the CO2 flux estimate was reduced, and a net annual Arctic Ocean CO2 uptake of 180 ± 130 Tg C y−1 was determined to be significant.
We estimated monthly air–sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of...
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