Water from melting ice sheets and glaciers is gushing into the world’s oceans much faster than previously thought possible, sending scientists scrambling to explain why.

The unexpected deluge is raising global sea levels, which scientists say could eventually submerge island nations, flood cities, and expose millions of coastal residents to destructive storm surges.

By the end of this century the seas may be three feet (one meter) higher than they are today, according to a pair of studies that appear in tomorrow’s issue of the journal Science.