Basin and channel contributions to a model antarctic circumpolar current

We revisit the Antarctic Circumpolar Current (ACC) transport problem considering the total transport to be the sum of a basin-like and a channel-like contribution. Our focus is primarily on the basin-like dynamics and its role in determining the total transport. The starting point is the classic mid-latitude ocean gyre problem in the context of the continuously stratified quasigeostrophic equations. We then apply this dynamics to the basin region of the Southern Ocean, north of Drake Passage. In this case, the baroclinic structure of a Sverdrup flux entering the channel region determines what fraction of this flux contributes to the ACC and what fraction is blocked by the bottom topography, feeding a recirculation gyre. This gives a simple analytic model describing the relationship between the wind stress and the transport. Two distinct dynamical regimes are found: a Stommel regime, for which transport increases linearly with forcing strength and a saturation regime, for which the transport levels off. The robustness of these ideas to the presence of a vigorous eddy field is then tested numerically.