FIRST SIGNS OF MELTING SEEN IN EAST ANTARCTICA

Earth's last great icy citadel, the East Antarctica Ice Sheet, is beginning to crumble.

Antarctica's western ice sheet has been under siege from global warming for some time, with billions of tons of ice melting into the ocean each year and contributing to sea level rise. By contrast, the east has appeared to hold out, its mass staying stable.

Now a new set of satellite measurements indicate the East may have begun to succumb to warmer temperatures, losing as much as 57 billion tons of ice a year since 2006. There is still a lot of uncertainty in the readings, but if the readings hold up under scrutiny, it would mark an important change in the world's largest ice sheet.