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Published December 2005 | Supplemental Material + Published
Journal Article Open

Influence of reduced carbon emissions and oxidation on the distribution of atmospheric CO_2: Implications for inversion analyses


Recent inverse analyses constraining carbon fluxes using atmospheric CO_2 observations have assumed that the CO_2 source from atmospheric oxidation of reduced carbon is released at the surface rather than distributed globally in the atmosphere. This produces a bias in the estimates of surface fluxes. We used a three‐dimensional (3D) atmospheric chemistry model (GEOS‐CHEM) to evaluate the magnitude of this effect on modeled concentrations and flux estimates. We find that resolving the 3D structure of the atmospheric CO_2 source, as opposed to emitting this reduced carbon as CO_2 at the surface, yields a decrease in the modeled annual mean interhemispheric gradient (N‐S) of 0.21 ppm. Larger adjustments (up to −0.6 ppm) are apparent on a regional basis in and downwind of regions of high reduced carbon emissions. We used TransCom3 annual mean simulations from three transport models to evaluate the implications for inversion estimates. The main impacts are systematic decreases in estimates of northern continental land uptake (i.e., by 0.22 to 0.26 Pg C yr^(−1)), and reductions in tropical land carbon efflux with smaller changes over oceans and in the Southern Hemisphere. These adjustments represent a systematic bias in flux estimates, accounting for changes of 9 to 27% in the estimated northern land CO_2 sink for the three models evaluated here. Our results highlight the need for a realistic description of reduced carbon emission and oxidation processes in deriving inversion estimates of CO_2 surface fluxes.

Additional Information

© 2005 by the American Geophysical Union. Received 24 January 2005; revised 27 May 2005; accepted 15 July 2005; published 11 October 2005. This work was supported by the NOAA OGP Global Carbon Cycle Program. The GEOS‐CHEM model is managed at Harvard University with support from the NASA Atmospheric Chemistry Modeling and Analysis Program. N. Y. K. was supported by a graduate fellowship from the Betty and Gordon Moore Foundation. J. T. R. gratefully acknowledges support from NASA (NNG04GK49G) and NOAA (NA03OAR4310059). We thank Arlene Fiore and Bryan Duncan for helpful discussions.

Attached Files

Published - Suntharalingam_et_al-2005-Global_Biogeochemical_Cycles.pdf

Supplemental Material - downloadSupplement_doi=10.1029_2F2005GB002466_file=gbc1199-sup-0001-t01.txt

Supplemental Material - downloadSupplement_doi=10.1029_2F2005GB002466_file=gbc1199-sup-0002-t02.txt


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