Articles | Volume 10, issue 3
Biogeosciences, 10, 1983–2000, 2013

Special issue: REgional Carbon Cycle Assessment and Processes (RECCAP)

Biogeosciences, 10, 1983–2000, 2013

Research article 22 Mar 2013

Research article | 22 Mar 2013

Global ocean carbon uptake: magnitude, variability and trends

R. Wanninkhof1, G. -H. Park1,2,*, T. Takahashi3, C. Sweeney4,16, R. Feely5, Y. Nojiri6, N. Gruber7, S. C. Doney8, G. A. McKinley9, A. Lenton10, C. Le Quéré11, C. Heinze12,13,14, J. Schwinger12,13, H. Graven7,15, and S. Khatiwala3 R. Wanninkhof et al.
  • 1Ocean Chemistry Division, NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149, USA
  • 2Cooperative Institute for Marine and Atmospheric Studies, University of Miami, Miami, FL 33149, USA
  • 3Lamont-Doherty Earth Observatory of Columbia University, Route 9W, Palisades, NY 10964, USA
  • 4NOAA/ESRL Carbon Cycle Group Aircraft Project Lead, 325 Broadway GMD/1, Boulder, CO 80304, USA
  • 5Ocean Climate Research Division, NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, USA
  • 6Center for Global Environmental Research National Institute for Environmental Studies Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan
  • 7Environmental Physics Group, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland
  • 8Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
  • 9Atmospheric and Oceanic Sciences and Center for Climatic Research, University of Wisconsin – Madison, WI 53706, USA
  • 10CSIRO Marine and Atmospheric Research, P.O. BOX 1538 Hobart Tasmania, Australia
  • 11Tyndall Centre for Climate Change Research, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
  • 12Geophysical Institute, University of Bergen, Allegaten 70, 5007 Bergen, Norway
  • 13Bjerknes Centre for Climate Research, Bergen, Norway
  • 14Uni Bjerknes Centre, Uni Research, Bergen, Norway
  • 15Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
  • 16CIRES, University of Colorado, Boulder, CO 80304, USA
  • *now at: East Sea Research Institute, Korea Institute of Ocean Science & Technology, Uljin, 767–813, Korea

Abstract. The globally integrated sea–air anthropogenic carbon dioxide (CO2) flux from 1990 to 2009 is determined from models and data-based approaches as part of the Regional Carbon Cycle Assessment and Processes (RECCAP) project. Numerical methods include ocean inverse models, atmospheric inverse models, and ocean general circulation models with parameterized biogeochemistry (OBGCMs). The median value of different approaches shows good agreement in average uptake. The best estimate of anthropogenic CO2 uptake for the time period based on a compilation of approaches is −2.0 Pg C yr−1. The interannual variability in the sea–air flux is largely driven by large-scale climate re-organizations and is estimated at 0.2 Pg C yr−1 for the two decades with some systematic differences between approaches. The largest differences between approaches are seen in the decadal trends. The trends range from −0.13 (Pg C yr−1) decade−1 to −0.50 (Pg C yr−1) decade−1 for the two decades under investigation. The OBGCMs and the data-based sea–air CO2 flux estimates show appreciably smaller decadal trends than estimates based on changes in carbon inventory suggesting that methods capable of resolving shorter timescales are showing a slowing of the rate of ocean CO2 uptake. RECCAP model outputs for five decades show similar differences in trends between approaches.

Final-revised paper