The Wilkins Ice Shelf is a broad sheet of permanent floating ice that spans about 5,000 square miles (13,000 square km) and is located on the southwest Antarctic Peninsula about 1,000 miles (1,600 km) south of South America.

"Block after block of ice is just tumbling and crumbling into the ocean," Ted Scambos, lead scientist at the National Snow and Ice Data Centre, said in a telephone interview.

"The shelf is not just cracking off and a piece goes drifting away, but totally shattering. These kinds of events, we don't see them very often. But we want to understand them better because these are the things that lead to a complete loss of the ice shelf," Scambos added.

Scambos said a large part of the ice shelf is now supported by only a thin strip of ice. This last "ice buttress" could collapse and about half the total ice shelf area could be lost in the next few years, Scambos added.

British Antarctic Survey scientist David Vaughan said in a statement: "This shelf is hanging by a thread."

"One corner of it that's exposed to the ocean is shattering in a pattern that we've seen in a few places over the past 10 or 15 years. In every case, we've eventually concluded that it's a result of climate warming," Scambos added.

Satellite images showing the collapse began on Feb. 28, as a large iceberg measuring 25.5 by 1.5 miles (41 km by 2.4 km) fell away from the ice shelf's south-western front leading to a runaway disintegration of the shelf interior, Scambos said.

A plane also was sent over the area to get photographs of the shelf as it was disintegrating, he added.

Scambos said this ice shelf has been in place for at least a few hundred years, but warm air and exposure to ocean waves are causing a breakup. In the past half century, the Antarctic Peninsula has witnessed a warming as fast as anywhere on the planet, according to scientists.

"The warming that's going on in the peninsula is pretty clearly tied to greenhouse gas increases and the change that they have in the atmospheric circulation around the Antarctic," Scambos said.

With Antarctica's summer melt season coming to an end, the he said he does not expect the ice shelf to disintegrate further immediately, but come January scientists will be watching to see if it continues to fall apart.