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The Southern Ocean sink for atmospheric CO 2

The Southern Ocean sink for atmospheric CO 2. Nicolas Gruber (1) , S. Fletcher-Mikaloff (1) , A. Jacobson (2) , M. Gloor (2) , J.L. Sarmiento (2) Department of Atmospheric and Oceanic Sciences & IGPP, UCLA AOS Program, Princeton University. TWO VIEWS OF

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The Southern Ocean sink for atmospheric CO 2

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  1. The Southern Ocean sink for atmospheric CO2 Nicolas Gruber(1), S. Fletcher-Mikaloff(1), A. Jacobson(2), M. Gloor(2), J.L. Sarmiento(2) Department of Atmospheric and Oceanic Sciences & IGPP, UCLA AOS Program, Princeton University

  2. TWO VIEWS OF CO2 FLUXES IN THE SOUTHERN OCEAN Takahashi et al. (2002) u2 a la Wanninkhof et al. (2001) TRANSCOM Gurney et al. (2002)

  3. INVERSION OF OCEAN INTERIOR OBSERVATIONS AS A CONSTRAINT ON CO2 FLUXES • Basis functions are model simulated footprints of unit emissions from a number of fixed regions • Estimate linear combination of basis functions that fits observations in a least squares sense. • Inversion is analogous to linear regression footprints fluxes obs Premultiply both sides by inverse of A estimated fluxes

  4. OCEAN INVERSION RESULTS

  5. COMPARISON WITH TAKAHASHI AND TRANSCOM

  6. MODEL SENSITIVITY

  7. DATA: DCant and DCgasex DCgasex = DICobs - DCbio - DCant - const DCant : estimated by DC* method Gruber et al., (1996) Gruber and Sarmiento (2002)

  8. Summary • Our inversion of ocean interior DCant and DCgasex data suggests that the Southern Ocean south of 44ºS is currently about neutral with regard to the atmosphere. • This neutral flux is due to a compensation between outgassing of natural CO2 and uptake of anthropogenic CO2. • Our inversion results suggest a weaker Southern Ocean sink for atmospheric CO2 than inferred by Takahashi et al. (2002). Possible reasons for the discrepancy are: - inversion biases (model transport, data) - summer bias of DpCO2 data

  9. THE CHANGE OF SOUTHERN OCEAN CO2 FLUXES OVER TIME (mol m-2 yr-1) Pre-industrial CO2 fluxes 1995 CO2 fluxes KVLOW-AILOW model

  10. NATURAL VS ANTHROPOGENIC CO2 FLUXES IN THE SOUTHERN OCEAN (mol m-2 yr-1) Pre-industrial CO2 fluxes 1995 Anthropogenic CO2 fluxes KVLOW-AILOW model

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