the southern ocean sink for atmospheric co 2
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The Southern Ocean sink for atmospheric CO2
Nicolas Gruber(1), S. Fletcher-Mikaloff(1), A. Jacobson(2), M. Gloor(2), J.L. Sarmiento(2)
(1) Department of Atmospheric and Oceanic Sciences & IGPP, UCLA(2) AOS Program, Princeton University
Takahashi et al. (2002) u2 a la Wanninkhof et al. (2001)
TWO VIEWS OF CO2 FLUXES IN THE SOUTHERN OCEAN
TRANSCOMGurney et al. (2002)
• 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
INVERSION OF OCEAN INTERIOR OBSERVATIONS AS A CONSTRAINT ON CO2 FLUXES
estimated fluxes
OCEAN INVERSION RESULTS
COMPARISON WITH TAKAHASHI AND TRANSCOM
MODEL SENSITIVITY
DATA: Cant and Cgasex
Cgasex = DICobs - Cbio - Cant - const
Gruber et al., (1996) Gruber and Sarmiento (2002)
Cant : estimated by C* method
Summary
• Our inversion of ocean interior Cant and Cgasex 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 pCO2 data
Pre-industrial CO2 fluxes
THE CHANGE OF SOUTHERN OCEAN CO2 FLUXES OVER TIME
1995 CO2 fluxes
(mol m-2 yr-1)
KVLOW-AILOW model
Pre-industrial CO2 fluxes
NATURAL VS ANTHROPOGENIC CO2 FLUXES IN THE SOUTHERN OCEAN
1995 Anthropogenic CO2 fluxes
(mol m-2 yr-1)
KVLOW-AILOW model
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