If the ice was above sea level to start, then it does create a void (OK, a space filled with air). The mountain of ice turns into liquid water and flows all over the earth.
Gotcha. I thought the article was referring to polar ice in general, not just specifically ice sheets (over land areas). Still, the gravity produced by that mass doesn't seem to be enough to make a real difference (see my other comment questioning the comparison with the moon/tides).