Mechanisms by which baroclinic eddies equilibrate in a realistically stratified, mid-latitude oceanic environment are described, paying particular attention to factors determining the scale and intensity of the eddies. Important in understanding this process are the presence of the combination of surface intensified stratification (i.e., the thermocline) and surface intensified mean shear, and its interaction with the inverse energy cascade of geostrophic turbulence. In 'classical' geostrophic turbulence, energy is generated at the first deformation scale, then undergoes barotropization and inverse cascade, and is finally halted by bottom drag at the largest scales of motion. This qualitative theory must be greatly modified for oceanic parameters. In a stratified fluid, the efficiency of the energy removal mechanism depends on the degree to which the motion becomes barotropic, and in the classic one and two-layer studies the inverse cascade indeed efficiently barotropizes the flow. However, in the presence of a non-uniform stratification and shear, the process of barotropization is less efficient than in the idealized cases considered in nearly all studies of geostrophic turbulence. Furthermore, because of the form of the thermocline, the energy generation scale itself does not necessarily correspond to the first deformation scale. A potentially important factor in the equilibration process is thermal damping at the surface, which acts as a direct sink of energy for baroclinic, surface intensified motion, as it will remove energy directly from baroclinic modes as it cascades from the baroclinic production scale to some arrest scale. Some additional form of energy removal mechanism --- drag or sidewall friction --- may ultimately be necessary to remove barotropic energy. Geostrophic turbulence experiments and scaling theory will be used to describe these and other problems, and the mechanisms giving rise to the final choice of scale of oceanic eddies will be described.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics