Evidence for westward-flowing Weddell Sea Deep Water in the Falkland Trough, western South Atlantic

The North Scotia Ridge controls the eastward and northward flow of the Antarctic Circumpolar Current (ACC) emerging from Drake Passage. Existing physical oceanographic data in this region are sparse and do not define the flow pattern of Circumpolar Deep Water (CDW) within the ACC, or of Weddell Sea Deep Water (WSDW) heading northward beneath it, in the region of the North Scotia Ridge and Falkland Trough. 3.5-kHz reflection profiles show mudwaves at the surface of a sediment drift along the axis of the eastern Falkland Trough that have a consistent NE-SW alignment and are migrating SE, indicating persistent westward bottom-current flow along the trough axis. Sediment thinning and non-deposition at the southern drift margin indicate intensified westward flow, considered to be Weddell Sea Deep Water from the Malvinas Outer Basin to the east. This flow probably continues to 48°W, but beyond there its fate is unknown. Similar non-deposition along the northern margin of the drift is considered to result from intensified eastward return flow of WSDW, or from CDW. The mudwave geometry appears to extend to at least 400-m depth within the drift, which therefore most probably contains a record of southern-origin bottom water (presently WSDW) extending back for several million years

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