Annual mean meridional energy transport modelled by a general circulation model for present and 2 × CO2 equilibrium climates

The meridional energy flux modelled by the Bureau of Meteorology Research Centre general circulation model is examined. It is divided into atmospheric and oceanic components, and the resolved atmospheric components in turn into mean and eddy circulations. Comparison with observations shows the modelled total planetary meridional energy transport to be low, but shows better agreement for the resolved atmospheric component alone. The overall patterns of the individual circulation and energy components of the model also agree well, although strengths and locations do show some discrepancies. The doubled CO₂ climate change is analyzed in terms of the changes in each of the circulation and energy components. It is found that the changes are the relatively small residual of larger, and generally opposing changes in sensible heat and potential energy fluxes. Despite the general decrease in poleward energy flux, the poleward latent heat flux is found to increase. The reduction in poleward transport is found to be dominated by changes in the mean meridional circulation at low southern latitudes, and changes in both mean circulations and eddy fluxes elsewhere.