NASA spots worrisome Antarctic ice sheet melt

Two new studies indicate that part of the huge West Antarctic ice sheet is starting a slow collapse in an unstoppable way. Alarmed scientists say that means even more sea level rise than they figured.

This won't happen fast. Scientists are talking hundreds of years, but over that time the melt that has started could eventually add 4 to 12 feet to current sea levels.

That's faster than scientists had predicted.

A NASA study in the journal Geophysical Research Letters uses 40 years of observations and sees the falling apart of what had been an obstacle to major melt in the Thwaites glacier, about the size of New Mexico and Arizona combined. The other study in the journal Science uses computer simulations and determines that early stage collapse has begun.