The Antarctic Slope Front (ASF) is a strong gradient in water mass properties close to the Antarctic margins. Heat transport across the ASF is important to Earth’s climate, as it influences melting of ice shelves, the formation of bottom water, and thus the global meridional overturning circulation. Previous studies based on relatively low-resolution models have reported contradictory findings regarding the impact of additional meltwater on onshore heat transport onto the Antarctic continental shelf: it remains unclear whether meltwater enhances shoreward heat transport, leading to a positive feedback, or further isolates the continental shelf from the open ocean. In this study, heat transport across the ASF is investigated using high-resolution, process-oriented simulations. It is found that shoreward heat transport is primarily controlled by the salinity gradient of the shelf waters: both freshening and salinification of the shelf waters relative to the offshore waters lead to increased heat flux onto the continental shelf. For salty shelves, the overturning consists of a dense water outflow that drives a shoreward heat flux near the seafloor; for fresh shelves, there is a shallow, eddy-driven overturning circulation that is associated with an export of fresh surface waters and a near-surface shoreward heat flux. The eddy-driven overturning associated with coastal freshening may lead to a positive feedback in a warming climate: large volumes of meltwater increase shoreward heat transport, causing further melt of ice shelves.

The Antarctic Slope Current (ASC) plays a central role in redistributing water masses, sea ice, and tracer properties around the Antarctic margins, and in mediating cross-slope exchanges. While the ASC has historically been understood as a wind-driven circulation, recent studies have highlighted important momentum transfers due to mesoscale eddies and tidal flows. Furthermore, momentum input due to wind stress is transferred through sea ice to the ASC during most of the year, yet previous studies have typically considered the circulations of the ocean and sea ice independently. Thus it remains unclear to what extent the momentum input from the winds is mediated by sea ice, tidal forcing, and transient eddies in the ocean, and how the resulting momentum transfers serve to structure the ASC. In this study the dynamics of the coupled ocean/sea ice ASC circulation are investigated using high-resolution process-oriented simulations, and interpreted with the aid of a reduced-order model. In almost all simulations considered here, sea ice redistributes almost 100% of the wind stress away from the continental slope, resulting in approximately identical sea ice and ocean surface flows in the core of the ASC. This ice-ocean coupling results from suppression of vertical momentum transfer by mesoscale eddies over the continental slope, which allows the sea ice to accelerate the ocean surface flow until the speeds coincide. Tidal acceleration of the along-slope flow exaggerates this effect, and may even result in ocean-to-ice momentum transfer. The implications of these findings for along-and across-slope transport of water masses and sea ice around Antarctica are discussed.