The impact of model resolution on the Southern Hemisphere in CCSM4 idealized climate simulations

Ocean model resolution plays a large role in accurately simulating the Southern Hemisphere circulation in both the ocean and atmosphere. Resolving the ocean mesoscale field is important as it has been shown to have a significant impact on the large-scale climate in eddy rich regions (i.e., western boundary currents, the Antarctic Circumpolar Current) which also are regions of large CO₂ absorption. The presence of ocean mesoscale features can affect sea surface temperatures, the strength and location of the storm tracks, and many other air-sea processes. Additionally, with an improvement in resolution, the eddy kinetic energy in the ocean can be expected to change considerably. The significance model resolution has on the Southern Hemisphere is examined using Community Climate System Model, version 4 ocean eddy-parameterizing and eddy-resolving simulations. The CO₂ concentrations and ozone levels are specified independently to better understand how the mesoscale field responds to extreme changes in the external forcing and the resulting climate impacts. Overall, in the eddy-parameterizing simulations, the ozone forcing is found to be more important than the changes in CO₂ concentrations for the zonal mean atmospheric temperature, zonal mean zonal wind, sea surface temperature, sea surface height, eddy kinetic energy, zonal mean ocean temperature, convective precipitation, and surface temperature. In the case of the eddy-resolving simulations, however, the CO₂ concentrations are found to be more dominant, especially in eddy-rich regions.