Articles | Volume 6, issue 3
Biogeosciences, 6, 375–390, 2009
Biogeosciences, 6, 375–390, 2009

  16 Mar 2009

16 Mar 2009

The role of ocean transport in the uptake of anthropogenic CO2

L. Cao1, M. Eby2, A. Ridgwell3, K. Caldeira1, D. Archer4, A. Ishida5, F. Joos6, K. Matsumoto7, U. Mikolajewicz8, A. Mouchet9, J. C. Orr10, G.-K. Plattner6,14, R. Schlitzer11, K. Tokos7, I. Totterdell12,15, T. Tschumi6, Y. Yamanaka13, and A. Yool12 L. Cao et al.
  • 1Department of Global Ecology, Carnegie Institution, Stanford, California, USA
  • 2School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada
  • 3School of Geographical Sciences, University of Bristol, Bristol, UK
  • 4Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
  • 5Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
  • 6Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 7Department of Geology and Geophysics, University of Minnesota, Minneapolis, USA
  • 8Max Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, Germany
  • 9Department of Astrophysics, Geophysics and Oceanography, University of Liege, Liege, Belgium
  • 10Marine Environment Laboratories, International Atomic Energy Agency, Monaco
  • 11Alfred Wegener Institute, Bremerhaven, Germany
  • 12National Oceanography Centre, Southampton, UK
  • 13Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan
  • 14Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Universitätstr., Zürich, Switzerland
  • 15Met Office Hadley Centre, Exeter, UK

Abstract. We compare modeled oceanic carbon uptake in response to pulse CO2 emissions using a suite of global ocean models and Earth system models. In response to a CO2 pulse emission of 590 Pg C (corresponding to an instantaneous doubling of atmospheric CO2 from 278 to 556 ppm), the fraction of CO2 emitted that is absorbed by the ocean is: 37±8%, 56±10%, and 81±4% (model mean ±2σ ) in year 30, 100, and 1000 after the emission pulse, respectively. Modeled oceanic uptake of pulse CO2 on timescales from decades to about a century is strongly correlated with simulated present-day uptake of chlorofluorocarbons (CFCs) and CO2 across all models, while the amount of pulse CO2 absorbed by the ocean from a century to a millennium is strongly correlated with modeled radiocarbon in the deep Southern and Pacific Ocean. However, restricting the analysis to models that are capable of reproducing observations within uncertainty, the correlation is generally much weaker. The rates of surface-to-deep ocean transport are determined for individual models from the instantaneous doubling CO2 simulations, and they are used to calculate oceanic CO2 uptake in response to pulse CO2 emissions of different sizes pulses of 1000 and 5000 Pg C. These results are compared with simulated oceanic uptake of CO2 by a number of models simulations with the coupling of climate-ocean carbon cycle and without it. This comparison demonstrates that the impact of different ocean transport rates across models on oceanic uptake of anthropogenic CO2 is of similar magnitude as that of climate-carbon cycle feedbacks in a single model, emphasizing the important role of ocean transport in the uptake of anthropogenic CO2.

Final-revised paper