Rebound from ice sheets or glaciers that have retreated long ago tends to happen very slowly - less than a centimeter per year (and in fact, it is still happening in the Great Lakes region that was covered by the Laurentide Ice Sheet). However, GPS stations on Antarctica have found that land on the Antarctic Peninsula is rising by over 1.5 cm per year. Right next to the thinning ice sheets, there are no GPS stations, but the land could be rising by over 4 cm per year from model estimates. The amount of uplift that would take thousands of years has occurred in over a decade. This means the uplift witnessed must be from more than just isostasy. It turns out that the Earth's mantle under Antarctica flows faster and is "runnier" (less viscous) than other parts of the mantle, and this can cause the mantle to push up the crust faster after an ice sheet retreats than normal.
(My apologies that the link didn't show for the past week . . . I will have to be more careful with previewing on Weebly, as it showed up in the draft. As a scientist, I certainly want to cite the source of my information!)