While the area of collapse involves 160 square miles at present, a large part of the 5,000-square-mile Wilkins Ice Shelf is now supported only by a narrow strip of ice between two islands, said Ted Scambos, lead scientist at NSIDC.

"If there is a little bit more retreat, this last 'ice buttress' could collapse and we'd likely lose about half the total ice shelf area in the next few years," he added.

In the past 50 years, the western Antarctic Peninsula has experienced the biggest temperature increase on Earth, rising by 0.9 degree F (0.5 Celsius degree) per decade. "We believe the Wilkins has been in place for at least a few hundred years, but warm air and exposure to ocean waves are causing a breakup," said Scambos, who first spotted the disintegration activity in March.

The Wilkins Ice Shelf is a broad sheet of permanent floating ice on the southwest Antarctic Peninsula roughly 1,000 miles south of South America.

Satellite images indicate the Wilkins began its collapse on Feb.28. Data revealed that a large iceberg, measuring 25.5 by 1.5 miles (2.4 kilometers), fell away from the ice shelf's southwestern front, triggering a runaway disintegration of 220 square miles of the shelf interior.

With Antarctica's summer melt season drawing to a close, scientists do not expect the Wilkins to further disintegrate in the next several months. "This unusual show is over for this season," Scambos said. "But come January, we'll be watching to see if the Wilkins continues to fall apart."

The Wilkins is one of a string of ice shelves that have collapsed in the West Antarctic Peninsula in the past 30 years. The Larsen B became the most well-known of these, disappearing in just over 30 days in 2002. The Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller and Jones ice shelf collapses also underscore the unprecedented warming in this region of Antarctica, said Scambos.