Satellite radar composite view of Antarctica. The West Antarctic Ice Sheet (WAIS) is penned in by mountain ranges and the floating ice of the Ross Ice Shelf. Most of the WAIS rests on rock that is below sea level; if the Ross Ice Shelf broke up, the entire mass of ice could gradually disintegrate, raising sea level about 3 meters (11 feet). The process would probably be spread out over several centuries or millennia. Glaciers at Pine Island already seem to be dumping ice rapidly into the ocean.

courtesy NASA blue marble dataset
with text added