# Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport

Author(s) Mikaloff Fletcher, S. E., Gruber, N., Jacobson, A. R., Gloor, M., Doney, S. C., Dutkiewicz, S., Gerber, M., Follows, M., Joos, F., Lindsay, K., Menemenlis, D, Mouchet, A., Müller, S. A., Sarmiento, J. L.
Publication Type Journal Items, Publication Status: Published
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Title Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport
Author(s) Mikaloff Fletcher, S. E.
Gruber, N.
Jacobson, A. R.
Gloor, M.
Doney, S. C.
Dutkiewicz, S.
Gerber, M.
Follows, M.
Joos, F.
Lindsay, K.
Menemenlis, D
Mouchet, A.
Müller, S. A.
Sarmiento, J. L.
Description 19 p.
Journal or Series Title Global biogeochemical cycles
Volume Number 21
Issue Number 1
Start Page GB1010
ISSN 0886-6236
1944-9224
Publisher American Geophysical Union
Publication Place Washington, DC
Publication Date 2007-00-00
Keyword(s) air-sea CO2 exchange
natural carbon cycle
ocean inversion
Abstract We use an inverse method to estimate the global-scale pattern of the air-sea flux of natural CO2, i.e., the component of the CO2 flux due to the natural carbon cycle that already existed in preindustrial times, on the basis of ocean interior observations of dissolved inorganic carbon (DIC) and other tracers, from which we estimate Delta C-gasex, i.e., the component of the observed DIC that is due to the gas exchange of natural CO2. We employ a suite of 10 different Ocean General Circulation Models (OGCMs) to quantify the error arising from uncertainties in the modeled transport required to link the interior ocean observations to the surface fluxes. The results from the contributing OGCMs are weighted using a model skill score based on a comparison of each model's simulated natural radiocarbon with observations. We find a pattern of air-sea flux of natural CO2 characterized by outgassing in the Southern Ocean between 44 degrees S and 59 degrees S, vigorous uptake at midlatitudes of both hemispheres, and strong outgassing in the tropics. In the Northern Hemisphere and the tropics, the inverse estimates generally agree closely with the natural CO2 flux results from forward simulations of coupled OGCM-biogeochemistry models undertaken as part of the second phase of the Ocean Carbon Model Intercomparison Project (OCMIP-2). The OCMIP-2 simulations find far less air-sea exchange than the inversion south of 20 degrees S, but more recent forward OGCM studies are in better agreement with the inverse estimates in the Southern Hemisphere. The strong source and sink pattern south of 20 degrees S was not apparent in an earlier inversion study, because the choice of region boundaries led to a partial cancellation of the sources and sinks. We show that the inversely estimated flux pattern is clearly traceable to gradients in the observed Delta C-gasex, and that it is relatively insensitive to the choice of OGCM or potential biases in Delta C-gasex. Our inverse estimates imply a southward interhemispheric transport of 0.31 +/- 0.02 Pg C yr(-1), most of which occurs in the Atlantic. This is considerably smaller than the 1 Pg C yr(-1) of Northern Hemisphere uptake that has been inferred from atmospheric CO2 observations during the 1980s and 1990s, which supports the hypothesis of a Northern Hemisphere terrestrial sink.
DOI 10.1029/2006GB002751
Additional Notes Received 8 May 2006, revised 16 October 2006, accepted 15 November 2006, Published 10 February 2007
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
03267
Organisational Unit(s)
NEBIS System Number 000041178
Source Database ID PP-38770
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@article{Mklff2007,
author = "Mikaloff Fletcher, S. E. and Gruber, N. and Jacobson, A. R. and Gloor, M. and Doney, S. C. and Dutkiewicz, S. and Gerber, M. and Follows, M. and Joos, F. and Lindsay, K. and Menemenlis, D and Mouchet, A. and M{\"{u}}ller, S. A. and Sarmiento, J. L.",
title = "{I}nverse estimates of the oceanic sources and sinks of natural {C}{O}2 and the implied oceanic carbon transport",
journal = "Global biogeochemical cycles",
year = 2007,
volume = "21",
number = "1",
pages = "GB1010--",
}


E-Citations record created: Thu, 01 Apr 2010, 21:24:47 CET