Two different dynamical regimes of the Antarctic Circumpolar Current are considered: the Sverdrup regime and the frictionally controlled one. In the former the intensity of the current does not depend on friction, while in the latter it is inversely proportional to the coefficient of friction. The transition between these two regimes is studied. It is shown that the frictionally controlled regime is generated not only in the case of closed isolines of ambient potential vorticity q. The regime is formed in the case of blocked (or partially blocked) q isolines as well, if the slope of the q isolines in the zonal direction is sufficiently small.