Bear in mind that underneath the ice, Antarctica is an archipelago, not a continuous land mass.
https://worldbuilding.stackexchange.com/questions/18757/what...
https://worldbuilding.stackexchange.com/questions/18757/what...
I have no idea how much can be expected to come up but my very quick and inaccurate estimation would be something like 1/8th to 1/5th of the ice thickness pressing it down.
Randall Carlson has some interesting theories.
There are several places currently where glaciers have melted and are experience uplifts on the order of inches a year.