Warm, salty Circumpolar Deep Water (CDW) is recognized as the primary
driver for Antarctic glacial melt, but the mechanism by which it reaches
the continental shelves remains highly uncertain from an observational
standpoint. With the scarcity of eddy flux estimation in the Antarctic
margin, we quantify the isopycnal diffusivity of CDW using hydrographic
variability and satellite altimetry under the mixing length framework.
For comparison, the spiciness and thickness are used as isopycnal
tracers, and the two tracers yield qualitatively similar estimates. Over
the Antarctic Circumpolar Current (ACC), spatial variation of mixing
length is generally aligned with the jet-induced mixing suppression
theory, including its exception in the lee of the topography. In
contrast, the mixing length does not depend on the mean flow in the
subpolar zone, likely reflecting the relatively quiescent flow regime.
The estimated isopycnal diffusivity ranges from 100 to 500 m2 s-1 south
of the ACC. The eddy diffusivity tends to be enhanced where the gradient
of isopycnal thickness becomes small and CDW intrudes onshore. The
cross-slope eddy CDW flux is estimated, and the associated onshore heat
flux across is calculated as ~3.6 TW in the eastern
Indian sector. The eddy heat flux and coastal solar heating are
generally balanced with cryospheric heat sinks including glacial melting
and surface freezing, suggesting that the eddy advection is substantial
for the onshore CDW flux. The thickness field is essential for
determining mixing length and eddy fluxes in the subpolar zone, whereas
the situation does not hold for the ACC domain.