A LINEAR EQUIVALENT BAROTROPIC MODEL OF THE ANTARCTIC CIRCUMPOLAR CURRENT WITH REALISTIC COASTLINES AND BOTTOM TOPOGRAPHY

A linear equivalent barotropic (EB) model is applied to study the effe cts of the bottom topography H and baroclinicity on the total transpor t and the position of the Antarctic Circumpolar Current (ACC). The mod el is based on the observation of Killworth that the time mean velocit y held of the FRAM Model is self-similar in the vertical. A realistic large-scale topography (H) over bar is constructed by filtering 5-minu te resolution data with an appropriate smoothing kernel. It is shown t hat the asymptotic behavior of the solution of the barotropic model (a particular case of the EB model) in the limit of very small bottom fr iction depends on subtle details of topography and basin geometry. Giv en the uncertainties of the smoothing procedure the authors conclude t hat the barotropic model is not robust with respect to possible variat ions of model topography. The authors found that the EB model with a v ertical profile function similar to that of Killworth reproduces the m ajor features of the time- and depth-averaged FRAM solution, including the position and the transport of the ACC, reasonably well. The solut ion is robust with respect to uncertainties in (H) over bar. The EB mo del is much improved by a parameterization of the bottom friction via near-bottom velocity, which tends to shut off the flow in the shallow regions.