On the Transport and Angular Momentum Balance of Channel Models of the Antarctic Circumpolar Current

Abstract

Angular momentum balances are discussed, both in general as well as in the context of simple channel models of the Antarctic Circumpolar Current (ACC). Particular emphasis is placed on the close relationship between the angular momentum balance and the meridional circulation. It is found that topographic form drag is established very early in the integration, whereas interfacial form drag can take much longer to develop. Restrictions on the geostrophic portion of the meridional circulation imposed by zonally reconnecting potential vorticity contours in the upper ocean allow derivation of an estimate for the steady-state transport. The estimate assumes there to be little or no circumpolar flow at great depth, an assumption that stems from the belief that the band of zonally reconnecting geostrophic contours in the Southern Ocean does not extend to the ocean floor. The predicted transport is proportional to the strength of the stratification and compares favorably with numerical results in the literature. Interaction of the ACC with the two adjoining gyres, however, is not accounted for by this estimate. The implications of this for the total transport through Drake Passage are discussed.