The collapse reported last week of the Larsen B Ice Shelf in Antarctica was "a wakeup call to expect more collapses," said Tim Naish, a senior researcher at the government-owned Institute of Geological and Nuclear Sciences.

Such collapses would have "a dramatic effect on global climate" by disrupting ocean currents, he said.

The Larsen B ice shelf, a large floating ice mass on the eastern side of the Antarctic Peninsula, has shattered and separated from the continent In this image taken March 7, 2002 by NASA's Terra satellite and released Thursday, March 21, 2002. The ice shelf, which has existed since the last Ice Age 12,000 years ago, collapsed starting in January with staggering speed during one of the warmest summers on record there, scientists say. The collapsed area was designated Larsen B. The blue area is the shelf's shattered ice. The lost surface area measured 1,040 square miles, which would dwarf Rhode Island. The collapse released 720 billion tons of ice.(AP Photo/NASA, National Snow and Ice Data Center, University of Colorado,Ted Scambos )

Larsen B, made up of about 720 billion tons of ice, disintegrated after 50 years of sharp temperature rises on the Antarctic Peninsula unmatched elsewhere in the world.

Ted Scambos, of the National Snow and Ice Data Center at the University of Colorado, one of three American researchers monitoring the Larsen ice shelf by satellite, said other ice shelves were closer to the breaking point than previously thought. Ice shelves form when ice sheets spread off the land mass.

Naish said Larsen's collapse was a warning about the stability of Antarctica's largest ice shelf, the Ross Ice Shelf, which at 332,000 square miles covers an area the size of France.

"It is becoming especially vulnerable as huge ice streams that feed it from West Antarctica begin to slow or have stopped," Naish said in an interview Friday.

Naish said even a partial collapse of the Ross Ice Shelf would be globally significant, as it would "dramatically affect ocean circulation and climate."

If average global temperatures continued to rise this century by up to 3 degrees Celsius, as climate models currently predict, he believes the bigger Antarctic ice shelves – also including several in the Weddell Sea – could become vulnerable.

He said scientists still know too little about the behavior of Antarctic ice sheets to predict whether these ice shelves will remain intact for decades or centuries.

A six-nation science team will next year drill into the seabed of the Ross Sea ice shelf as part of a study to understand the behavior of the region's ice shelves during climatic change.

The project will include the deepest core drilling yet attempted in Antarctica.

© 2002 The Associated Press

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