The effect of ocean mixing parametrisation on the enhanced CO2 response of the Southern Hemisphere midlatitude jet -: art. no. L06811

The use of a more physically based parametrisation scheme for sub-grid scale ocean mixing produces a more spatially uniform surface warming in the Southern Hemisphere in transient global warming simulations of the CCCma climate model than when an older scheme is used. Here we examine the effect of this different warming pattern on the tropospheric circulation response, by comparing simulations of two versions of the model implementing these two mixing parametrisations. It is found that use of either scheme produces a southward shift of the midlatitude jet, but that this shift is considerably smaller when the new parametrisation is implemented. These results suggest that the magnitude of the Southern Annular Mode-like response noted in some global warming simulations may be sensitive to the representation of ocean processes.