The maximum global sea-level rise from the collapse of the rapidly warming West Antarctic ice sheet may be 3.2 meters—not five meters or more as predicted in the past. The revision comes from a new model suggesting that only parts of the ice sheet will collapse—namely, those that are grounded below sea level or sloping downward. Areas of the sheet grounded above sea level or on upward-sloping bedrock would remain in place. The results, in the May 15 Science, say nothing about disappearing ice sheets elsewhere, however. Greenland, for instance, holds enough ice to raise sea levels by seven meters.
This article was originally published with the title "A Lower High-Water Mark" in Scientific American 301, 1, 29 (July 2009)