Huge Antarctic ice chunk collapses

A chunk of Antarctic ice about seven times the size of Manhattan suddenly collapsed, putting an even greater portion of glacial ice at risk, scientists said on Mar. 25. Scientists flocked to take pictures and shoot video after a massive chunk of the Wilkins ice shelf collapsed in Antarctica. Satellite images show the runaway disintegration of a 160-square-mile chunk in western Antarctica, which started on Feb. 28. It was the edge of the Wilkins ice shelf and has been there for hundreds, maybe 1,500 years. This is the result of global warming, said British Antarctic Survey scientist David Vaughan. Because scientists noticed satellite images within hours, they diverted satellite cameras and even flew an airplane over the ongoing collapse for rare pictures and video. "It's an event we don't get to see very often," said Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. While icebergs naturally break away from the mainland, collapses like this are unusual but are happening more frequently in recent decades, Vaughan said. The collapse is similar to what happens to hardened glass when it is smashed with a hammer, he said. The rest of the Wilkins ice shelf, which is about the size of Connecticut, is holding on by a narrow beam of thin ice. Scientists worry that it too may collapse. Larger, more dramatic ice collapses occurred in 2002 and 1995. Vaughan had predicted the Wilkins shelf would collapse about 15 years from now. Scientists said they are not concerned about a rise in sea level from the latest event in Antarctica, but say it's a sign of worsening global warming. Such occurrences are "more indicative of a tipping point or trigger in the climate system," said Sarah Das, a scientist at the Woods Hole Oceanographic Institute. The Wilkins ice shelf–previously some 16,000 square kilometers in area–has been disintegrating fast. "I would be very surprised if it survives more than a couple more melt seasons," says Scambos of the University of Colorado. Other researchers, including David Vaughan of the British Antarctic Survey, believe it could be gone within weeks. "The ice shelf is hanging by a thread–we'll know in the next few days or weeks what its fate will be," he says. "There now remains just a narrow beam of ice, roughly 6 km wide, which is bracing the rest of the shelf," says Scambos. "If that beam breaks up, about half of the ice shelf will probably very quickly break apart." However Scambos says this is not likely to happen this year, as the southern winter is settling in. Normally, a slurry of sea ice floating in front of the ice shelf would act as a wave breaker, keeping the surrounding waters still. But this year–as in 2002 when the Larsen B shelf dramatically disappeared in just 30 days–warm temperatures melted away much of the sea ice. The glaciologists believe this is what has caused the break up of the Wilkins ice shelf in recent weeks.