Two teams of scientists say the long-feared collapse of the West Antarctic Ice Sheet has begun, kicking off what they say will be a centuries-long, "unstoppable" process that could raise sea levels by as much as 15 feet. "There's been a lot of speculation about the stability of marine ice sheets, and many scientists suspected that this kind of behavior is under way," Ian Joughin, a glaciologist at the University of Washington in Seattle, said in a news release about one of the studies published Monday. "This study provides a more qualitative idea of the rates at which the collapse...
