The flow of the Antarctic Circumpolar Current over the North Scotia Ridge

Abstract

The transports associated with the Subantarctic Front (SAF) and the Polar Front (PF) account for the majority of the volume transport of the Antarctic Circumpolar Current (ACC). After passing through Drake Passage, the SAF and the PF veer northward over the steep topography of the North Scotia Ridge. Interaction of the ACC with the North Scotia Ridge influences the sources of the Malvinas Current. This ridge is a major obstacle to the flow of deep water, with the majority of the deep water passing through the 3100 m deep gap in the ridge known as Shag Rocks Passage. Volume transports associated with these fronts were measured during the North Scotia Ridge Overflow Project, which included the first extensive hydrographic survey of the ridge, carried out in April and May 2003. The total net volume transport northward over the ridge was found to be 117 ± 10 Sv (1 Sv = 106m3s- 1). The total net transport associated with the SAF was approximately 52 ± 4 Sv, and the total transport associated with the PF was approximately 58 ± 5 Sv. Weddell Sea Deep Water was not detected passing through Shag Rocks Passage, contrary to some previous inferences.