Coupled ocean/sea ice dynamics of the Antarctic Slope Current driven by
topographic eddy suppression and sea ice momentum redistribution
Abstract
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.