Massive Ice Shelf Collapses  

The British Antarctic Survey has a report (including video) on the collpase of part of the Wilkins ice shelf in Antarctica. More at The Australian.

A CHUNK of Antarctic ice about seven times the size of Manhattan has suddenly collapsed, putting an even greater portion of glacial ice at risk. Satellite images show the disintegration of a 415 sq km chunk in western Antarctica, which started on February 28. It was the edge of the Wilkins ice shelf and has been there for hundreds, perhaps 1500, years.

British Antarctic Survey scientist David Vaughan said the collapse was the result of global warming. Because scientists noticed satellite images within hours, they diverted satellite cameras and even flew an airplane over the 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. "The cracks fill with water and slice off and topple... That gets to be a runaway situation."

While icebergs naturally break away from the mainland, collapses like this are unusual but are happening more frequently in recent decades, Mr 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 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. Mr 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, 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 in the US.

WINTER sea ice around a Norwegian Arctic island has thinned to less than one metre since the 1960s, according to a study of a region that may be more attractive to oil firms because of climate change. The Norwegian Polar Institute said ice around Hopen island south-east of the Svalbard archipelago had thinned by more than 40cm over the past 40 years, in what it called the first long-term study of ice thickness in the Barents Sea.

"Since the year 2000 there have been no observations of ice thicker than one metre at Hopen, and the local air and water temperature has also risen," the institute said in a statement.

Hopen is a narrow island about 30km long off north Norway which is home to polar bears. Ice around the entire Arctic reached a record low in September 2005, the end of the northern summer.

The UN Climate Panel says temperatures are rising more rapidly in the Arctic than on most of the planet because of global warming, stoked by human use of fossil fuels. Darker water and land soak up more heat than reflective ice and snow.

"The reduced see ice thickness at Hopen is in line with the generally reduced volume of ice in the Barents Sea and the whole Arctic," said Sebastain Gerland of the Polar Institute. The study was being published in the journal Geophysical Research Letters, the institute said.

Oil and gas companies are pushing north into the Barents Sea, seeking new reserves. Scientists say climate change may make the region less inhospitable and prices around $US100 a barrel can justify exploration despite high costs.