Volume Transport of the Antarctic Circumpolar Current from Bottom Pressure Measurements

Abstract

Meausrements from bottom pressure gauges located at the north and south sides of Drake Passage are used to extend the one-year time series of volume transport of the Antarctic Circumpolar Current (ACC) given previously by Whitworth. A small error in that paper is corrected, and a revised transport time series is presented which shows the importance of including the transport in the northern and southern margins of Drake Passage. Direct measurements of vertical shear averaged across the passage, are in good agreement with geostrophic shear and suggest that the ACC is in geostrophic balance. Although most of the ACC transport is in the baroclinic field, transport fluctuations are mainly barotropic. Transport estimates based on pressure difference alone differ from the estimates of Whitworth by less than 10 ? 106 m3 s?1. Fluctuations in transport of almost half of the mean value occur over periods as short as two weeks.