AN IMPROVED ESTIMATE OF THE ISOTOPIC AIR-SEA DISEQUILIBRIUM OF CO2: IMPLICTIONS FOR THE OCEANIC UPTAKE OF ANTHROPOGENIC CO2

Reference
Gruber, N., and C.D. Keeling, An improved estimate of the isotopic air-sea disequilibrium of CO2: Implications for the oceanic uptake of anthropogenic CO2, Geophysical Research Letters, 28(3), 555-558, 2001.

Abstract
We reevaluate the isotopic air-sea disequilibrium of CO2 on the basis of a new high-quality global data set of surface observations of the reduced isotopic ratio (d13C) of dissolved inorganic carbon (DIC). We find a global mean isotopic air-sea disequilibrium of 0.62+/-0.10 permil for 1990. Inserting our estimate into an anthropogenic 13C budget for the period from 1985 to 1995 yields an oceanic uptake of about 1.5+/-0.9 Pg C/yr, consistent with a wide range of independent methods. The reduction of the large uncertainty of this estimate requires (i) better characterization of the surface ocean variability in d13C, (ii) improved knowledge of the air-sea gas exchange coefficient, and (iii) a significant reduction in the uncertainty associated with the air-land biosphere disequilibrium.

see related article by Gruber et al. [1999]

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