Wind-Driven Flow over Topography in a Zonal β-Plane Channel: A Quasi-geostrophic Model of the Antarctic Circumpolar Current

The paper gives a detailed account of the dynamical balance of a wind-driven zonally un- bounded flow over topography. The problem is investigated with a quasigeostrophic fl—plane channel with two layers and eddy resolution. The channel has a width of 1500 km and a zonal periodicity of 4000 km. Apart from the dimensions the model structure is similar to the one used by McWilliams, Holland and Chow (1978). The experiments with this model address the problem of the relative role of transient and standing eddies as well as bottom friction and topographic form stress in the balance of a current driven by a steady surface windstress. The response of the system is investigated for different values of the friction parameter and various locations of topo- graphic obstacles in the bottom layer of the channel. The principal momentum balance emerging from these experiments supports the concept of Munk and Palmén (1951) for the dynamics of the Antarctic Circumpolar Current, which proposes that the momentum input by the windstress is transferred to the deep ocean - in the present model by vigorous eddy activity - where it leaves the system by topographic form stress. Frictional effects in the balance of the Circumpolar flow may thus be of minor importance. This concept is confirmed in simulations over more complex topographies. Here we have taken two differently scaled versions of the highly resolved bottom relief in the Macquarie Ridge area. The flow in these simulations is virtually frictionless