how much antarctic ice will be needed for the sealevel to increase by 1 foot?

Answer 1

good thing you said antarctic. all of the artic ice can melt and not raise sea level at all, that is because it already displaces seawater. while much of the antarctic is also sea ice, there is a fraction that is mountainous. all of that could melt and not raise the sea by one foot, just not enough icepack on the land area.

the idea of melting icecap raising sealevel got traction because a similar event, the ice age, covered continents with up to a mile thickness of ice. this took so much water, that sea levels actually did lower. however the converse that sea levels might now rise is not the same at all. infact if the icecap is melted by global warming, the higher temperature will increase solar evaporation of water and thus lower the sea level again.