Although the atmospheric accumulation of anthropogenic carbon dioxide (CO2) is known to be modulated by large natural sinks in the world ocean and terrestrial biosphere, the exact processes driving these sinks have been the subject of intense scientific debate. Recent convergence of several independent estimates of the contemporary ocean sink based on observational tracer data [Bopp et al., 2002; Plattner et al., 2002; Takahashi et al., 2002; McNeil et al., 2003], ocean forward model results [Matsumoto et al., 2004] and a combination of the two via inverse techniques [A. R. Jacobson et al., A joint atmosphere-ocean inversion for surface fluxes of carbon dioxide, submitted to Global Biogeochemical Cycles, 2005, hereinafter referred to as Jacobson et al., submitted manuscript, 2005; S. E. M. Fletcher et al., Robust estimates of anthropogenic carbon uptake, transport, and storage by the ocean, submitted to Global Biogeochemical Cycles, 2005, hereinafter referred to as Fletcher et al., submitted manuscript, 2005] tightly constrains the amount of carbon entering the ocean today and would seem to similarly constrain the set of mechanisms governing this uptake. However, large differences in the regional attribution of sinks between forward and inverse models (Jacobson et al., submitted manuscript, 2005; Fletcher et al., submitted manuscript, 2005) as well as within the existing suite of forward models [Orr, 2002] belies this intuitive interpretation. Forward simulations alone differ in their estimates of the Southern Ocean sink by as much as 70%, according to an early comparison of ocean general circulation model (OGCM) results [Orr et al., 2001] and by more than 200% in a more recent comparison involving a larger number of such models (K. Matsumoto, unpublished data, 2005).
 In this paper, we have chosen to explore the extent to which differences in wind forcing and eddy mixing at high southern latitudes can alter the magnitude and distribution of anthropogenic carbon uptake in an OGCM. This particular focus is motivated by compelling evidence that Southern Hemisphere winds and eddies profoundly impact the circulation and density structure of the global ocean [Gnanadesikan, 1999] and by the additional realization that both the isopycnal diffusion coefficient and the historical wind stress field over the Southern Ocean are poorly constrained at present, with two popular observational wind stress products used in existing model comparisons [e.g., Matsumoto et al., 2004] differing in their estimates of the average stress by a factor of two in some regions of the extratropical Southern Hemisphere (see Table 1 and Figure 1). These considerations suggest that a significant fraction of the observed variability in carbon uptake between OGCMs may simply be an expression of uncertainty in the underlying physical circulation, derived in part from uncertainty in the high-latitude wind stress field and isopycnal diffusion coefficient.