An Empirical Estimate of the Southern Ocean Air-Sea CO2 Flux
Date: Tuesday, September 27 @ 09:28:28 MDT
Topic: The Fate of Fossil-Fuel Emissions

by Ben McNeil

A discrepancy exists between current estimates of the Southern Ocean air-sea flux of CO2. The most recent estimate using a combination of direct and climatologically-derived pCO2 measurements [Takahashi et al., 2002] (herein referred to as T02) suggests a Southern Ocean CO2 sink that is nearly two times greater that that suggested from general circulation models, atmospheric inverse models [Gurney et al., 2002] and oceanic inverse models [Gloor et al., 2003]. Here we employ an independent method to estimate the Southern ocean air-sea flux of CO2. Our method exploits all available surface measurements for Dissolved Inorganic Carbon (DIC) and total alkalinity (ALK) from 1986 to 1996. We show that surface age-normalized DIC can be predicted to within ~8mmol/kg and ~10mmol/kg for ALK using standard hydrographic properties, independent of season. The predictive equations are used in conjunction with World Ocean Atlas (2001) climatologies to estimate an annual cycle of DIC and ALK, while the pCO2 distribution is calculated using standard carbonate chemistry. For consistency we use the same gas transfer relationship and wind product from Takahashi et al, [2002] however, we include the effects of sea-ice. We estimate a Southern Ocean CO2 sink (>40°S) of -0.19±0.26 Pg C for 1995. Our estimates are smaller than those estimated by Takahashi et al, [2002], but consistent with atmospheric / oceanic inverse methods, general circulation models and provides further evidence that the Southern Ocean CO2 sink in relation to its oceanic surface area, is moderate on a global scale.

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This article comes from The 7th International CO2 Conference Web Site

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