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 global sea level about 3 meters (11 feet). The full process would be spread out over several centuries or millennia but there might be occasional abrupt surges. The Thwaites Glaciar and others near Pine Island already seem to be dumping ice rapidly into the ocean; by 2025 some experts thought the disintegration had become irreversible.

courtesy NASA blue marble dataset
with text added