A model for the structure and overturning of the Antarctic Slope Front

The Antarctic Slope Front (ASF) is a westward jet that encircles almost the entire Antarctic continent, separating the shelf waters from relatively warm Circumpolar Deep Water offshore. The dynamics of the ASF are intrinsically linked to shoreward heat transport towards the Antarctic ice shelves, and to formation rates of Antarctic Bottom Water (AABW), yet our understanding of this current remains limited to rather simple conceptual models. We present a model for the ASF that emphasizes the role of mesoscale eddies in setting the ASF's stratification and driving the overturning circulation. We test our model against idealized eddy-resolving simulations that incorporate the ocean's full equation of state. In AABW-forming regions of Antarctica the ASF is characterized by 'V'-shaped isopycnals at the shelf break. We show that this structure is required to support the overturning circulation via lateral eddy transports beneath an easterly surface wind stress. This model differs significantly from previous work that relied on turbulent entrainment to describe this 'V' shape. The export of AABW and the shoreward heat flux are found to be strongly sensitive to changes in the easterly winds. Wind modulation of the ASF may thereby modify glacial melt rates and alter the strength of the deep overturning circulation over millennial time scales.