Factors affecting cirumpolar transport

Factors determining the transport of the Antarctic Circumpolar Current are considered in the context of a stratified quasigeostrophic model. Work by Tansley and Marshall (2002) suggests that circumpolar transport is only a weak function of windstress, provided the windstress is sufficiently strong; however, an understanding of what determines this apparent saturation level remains lacking. We reproduce their results (although at considerably higher resolution) and test dependence of the transport on geometric factors such as the length of the channel, the width of an idealized Drake Passage and the position of a bathymetric ridge. We further test whether a turbulent version of the classic Stommel model (in which circumpolar transport is determined by a Sverdrup transport southward into Drake Passage) is satisfied and, if so, whether it can explain the transport. The extent to which accounting for an ocean surface velocity dependence in the specification of the air-sea momentum flux affects the transport is also considered.