The potential for using chlorofluorocarbons (CFCs) to assess ocean cli
mate models is explored within a series of global ocean experiments. T
he ocean model simulations are run under identical wind stress and the
rmohaline forcing, but with three different formulations of subgrid-sc
ale mixing. Two passive tracers are included in the equilibrated model
s, representing the dissolved concentrations of CFC-11 and CFC-12 in s
eawater. The resulting model simulations are then compared directly wi
th observed CFC levels in key areas for deep and bottom water formatio
n. CFC-II uptake is found to be overestimated in the Southern Ocean wh
en mixing rates are defined in traditional Cartesian co-ordinates. The
inclusion of an isopycnal mixing scheme (which is often used in coupl
ed ocean-atmosphere models) actually degrades the CFC-11 simulation by
blending water masses too strongly, particularly in the Southern Ocea
n. The spurious uptake of CFC-II at 55 degrees-70 degrees S suggests t
hat certain climate models might overestimate the role of the Southern
Ocean in moderating climate change. A more sophisticated mixing param
eterization that simulates the effects of subgrid-scale eddies on the
mean ocean flow (and allows for zero lateral diffusion) is seen to gre
atly reduce CFC-11 uptake in the Southern Ocean, Climate models that a
dopt this new mixing scheme are likely to predict a more rapid CO2-ind
uced warming over the Southern Hemisphere.