Variability of the Antarctic slope current system in the northwestern Weddell Sea

The dense water outflow from the Antarctic continental shelf is closely associated with the strength and position of the Antarctic Slope Front. We explore the short-term and spatial variability of the Antarctic Slope Front system and the mechanisms that regulate cross-slope exchange using highly temporallyand spatially-resolved measurements from three ocean gliders deployed in 2012. Twenty-two sections along the eastern Antarctic Peninsula and west of the South Orkney Islands are grouped regionally and composited by isobaths. There is consistency in the front position around the Powell Basin, varying mostly between the 500 and 800m isobaths. In most of the study area the flow is bottom-intensified. The along-slope transport of the Antarctic Slope Current (upper 1000 m) varies between 0.2 and 5.9 Sv and does not exhibit a regional pattern. The magnitude of the velocity field shows substantial variability, up to twice its mean value. Higher eddy kinetic energy (0.003m2 s−2) is observed on sections with dense water, possibly due to baroclinic instabilities in the bottom layer. Distributions of potential vorticity show an increase towards the shelf along isopycnals and also in the dense water layer. Glider sections located west of the South Orkney Islands indicate a northward direction of the flow associated with the Weddell Front, which differs from previous estimates of the mean circulation. This study provides some of the first observational confirmation of the high frequency variability associated with an active eddy field that has been suggested by recent numerical simulations in this region.