Huge chunk of Antarctic ice sheet set to break free

Antarctica's Pine Island Glacier is preparing to shed a 300-square-mile chunk of its ice to the ocean in a process of ice loss that has been accelerating in recent years.  Even at 300 square miles, the chunk is modest by historical standards. In 1956, for instance, the crew of the icebreaker USS Glacier spotted a Belgium-sized berg from Antarctica floating near Scott Island in the South Pacific Ocean.

Still, the Pine Island Glacier's losses probably represent Antarctica's largest contribution so far to global sea-level rise, notes Hamish Prichard, a researcher with the British Antarctic Survey in Cambridge, England.