Energetics of ocean circulation models

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Ocean circulation plays a key role in the earth's climate system. Relevant to the work proposed here, it redistributes heat, provides an important boundary condition for the atmosphere and provides a sink for atmospheric CO2. There is a growing awareness in the oceanographic community that knowledge of a very fundamental aspect of ocean circulation is lacking: we do not understand its energetics. This has practical implications (e.g., to climate modelling) in that the response of these models to changes in forcing are likely dependent on model energetics. For example, although a coupled atmosphere-ocean model may be tuned to adequately reproduce current conditions, its response to changes in atmospheric composition will likely differ from that of the actual coupled system if the model energetics do not reflect those of the actual system.Here, we focus on two aspects of ocean circulation energetics: the wind power source and a potentially important exchange of energy between essentially geostrophic currents (such as the Gulf Stream, etc.) and high frequency (near-inertial) gravity waves. The work considers both rectangular basin and Southern Ocean (allowing for a "Drake Passage") geometries and uses a range of models from relatively approximated to increasingly complete representation of the dynamics. In all cases, we focus on high resolution, for which the mesoscale eddy field is well resolved. Since the Southern Ocean figures prominently into an overall picture of the energetics, we also reconsider theories of its dynamics. Also, because a mechanism we consider as important to determing the wind power input to the geostrophic circulation also affects the vertical Ekman pumping velocity over mesoscale eddies and currents, we also examine the effect of this on uptake of passive scalars input from above. Finally, note that other recent work in ocean energetics focuses on tidal mixing and the meridional overturning circulation: this is not the focus of the work proposed here (which deals more with wind-driven circulation).