On the fate of the Antarctic Slope Front and the origin of the Weddell Front

Abstract

Data from the Deep Ocean Ventilation Through Antarctic Intermediate Layers (DOVETAIL) and Antarctic Large‐Scale Box Analysis and the Role of the Scotia Sea (ALBATROSS) projects are combined in the region of the Antarctic Peninsula and the South Scotia Ridge to determine the paths and transports associated with the Antarctic Coastal Current, the Antarctic Slope Front, and the Weddell Front. The Antarctic Coastal Current flows over the Antarctic continental shelf and is not tied to a particular isobath. It transports ∼1 Sv westward to the Bransfield Strait. Its subsequent course is uncertain, but we speculate that it may continue southwest along the western side of the Antarctic Peninsula, close to the coast. The Antarctic Slope Front, present almost all the way around Antarctica tied to the continental slope, has not previously been mapped after it reaches the tip of the Antarctic Peninsula. We show that the frontal jet splits into two branches in the northwest Powell Basin where the isobaths diverge. The shoreward portion of the water associated with the front (lying above isobaths shallower than 1500 m) is able to cross the South Scotia Ridge and head northwestward and retains many of the properties of the Antarctic Slope Front. It is associated with a transport of ∼7 Sv. The portion of the front constrained to lie above isobaths deeper than 1500 m becomes the Weddell Front. This takes a path around the northern Powell Basin and south of the South Orkney Islands. Of the ∼13 Sv that circulates around the southern flank of the South Orkney Plateau, ∼8 Sv of Weddell Sea Deep Water and Warm Deep Water leaves the front to continue west. The remaining shallow and intermediate water retroflects and returns south associated with the Weddell Front through the Orkney Passage. Approximately 5–7 Sv is transported eastward associated with the Weddell Front, tied closely to the southern flanks of the Bruce and Discovery Banks above the 2000–2500 m isobaths, and forming the southern boundary of the Weddell Scotia Confluence.