OSLO (Reuters) -- An ice bridge which had apparently held a vast Antarctic ice shelf in place during recorded history shattered on Saturday and could herald a wider collapse linked to global warming, a leading scientist said.

"It's amazing how the ice has ruptured. Two days ago it was intact," David Vaughan, a glaciologist with the British Antarctic Survey, told Reuters of a satellite image of the Wilkins Ice Shelf on the Antarctic Peninsula.

The satellite picture, from the European Space Agency (ESA), showed that a 40 km (25 mile) long strip of ice believed to pin the Wilkins Ice Shelf in place had splintered at its narrowest point, about 500 meters wide.

"We've waited a long time to see this," he said.

The Wilkins, now the size of Jamaica or the U.S. state of Connecticut, is one of 10 shelves to have shrunk or collapsed in recent years on the Antarctic Peninsula, where temperatures have risen in recent decades apparently because of global warming.

The ESA picture showed a jumble of huge flat-topped icebergs in the sea where the ice bridge had been on Friday, pinning the Wilkins to the coast and running northwest to Charcot Island.

"Charcot Island will be a real island for the first time in history," Vaughan said.

Vaughan, who landed on the flat-topped ice bridge on the Wilkins in January in a ski-equipped plane with other scientists and two Reuters reporters, said change in Antarctica was rarely so dramatic. It was the first -- and last -- visit to the area.

The loss of the ice bridge, jutting about 20 meters out of the water and which was almost 100 km wide in 1950, may now allow ocean currents to wash away far more of the Wilkins shelf.

"My feeling is that we will lose more of the ice, but there will be a remnant to the south," said Vaughan. Ice shelves float on the water, formed by ice spilling off Antarctica, and can be hundreds of meters thick.

Nine other shelves have receded or collapsed around the Antarctic Peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002 further north.

DISAPPEAR FROM MAP

Cores of sediments on the seabed indicate that some of these ice shelves had been in place for at least 10,000 years. Vaughan said an ice shelf would take many hundreds of years to form.

Vaughan landed on the narrow ice bridge, which jutted about 20 meters above the sea, in January with a group of scientists and two Reuters reporters. He predicted that it would snap this year.

In January, the remaining ice bridge had been surrounded by icebergs the size of shopping malls, many of them trapped in sea ice. A few seals were visible lolling on sea ice in the low Antarctic sunshine.

On that visit, Vaughan put up a GPS satellite monitoring device and predicted the ice bridge would break within weeks. The plane left quickly, in case the ice was unstable on a part of the world about to disappear from the map.

Temperatures on the Antarctic Peninsula have risen by up to about 3 °C (5.4 °F) in the past 50 years, the fastest rate of warming in the Southern Hemisphere.

"We believe the warming on the Antarctic Peninsula is related to global climate change, though the links are not entirely clear," Vaughan said. Antarctica's response to warming will go a long way to deciding the pace of global sea level rise.

About 175 nations have been meeting in Bonn, Germany, since March 29 as part of a push to agree by the end of 2009 a new U.N. treaty to combat climate change. The talks end on April 8.

The loss of ice shelves does not affect sea levels -- floating ice contracts as it melts and so does not raise ocean levels. But their loss can allow glaciers on land to slide more rapidly toward the sea, adding water to the oceans.

The Wilkins does not have much ice pent up behind it. But bigger ice shelves to the south on the frozen continent, where no major warming has been detected, hold back far more ice.

Link to article: http://www.sciam.com/article.cfm?id=ice-bridge-holding-antarc

KANSAS CITY, Mo. -- No longer is David Braaten constantly cocooned in his red super parka. He left the insta-freeze winds of the Antarctic interior in January.

But as cold as the trip was for the University of Kansas scientist, he recognizes what one discovery after the next has demonstrated this year: It's getting remarkably warm for down there, and it's heating up incredibly fast.

"We're trying to find out what's happening to the ice," said Braaten, the deputy director of the KU-based Center for Remote Sensing of Ice Sheets.

Even as changing climate brings more moisture, and ice, to Antarctica's center, on its edges the frozen continent is becoming less so. Melting skyscrapers of ice crash into the ocean at ever faster rates.

That's raising sea levels, disrupting ocean food chains and reducing the region's ability to moderate the planet's climate.

Climate scientists once were befuddled about why Antarctica seemed, if anything, to be cooling while the rest of the world got toastier. It turns out the bottom of the world has been warming after all.

"More is happening than we thought, and it's happening faster," said Douglas Martinson, who studies the impact of polar oceans on global climate at Columbia University.

Average winter temperatures on the Antarctica peninsula -- changing more than the rest of the continent -- have risen 11 degrees since 1950. That's five times the global warm-up and disastrous to the ice shelves that hang over water and act as corks to bottle up glaciers on land.

In 1950, the Wilkins Ice Shelf was bonded to Antarctica with a 62-mile wide block of ice. Now it clings by an hourglass-shaped link that narrows to just a third of a mile. The Jamaica-size shelf could tumble into the ocean any time.

Last week, the World Meteorological Organization said northern Arctic sea ice shrunk to its lowest in the summers of 2007 and 2008 since satellites began watching 30 years ago.

The Southern Ocean, meanwhile, is warming at rates faster than the rest of the Earth.

"We are basically looking now at a future climate that's beyond anything we've considered seriously," Chris Field of Stanford University told a meeting in Chicago.

In 2007, the Intergovernmental Panel on Climate Change won a Nobel Prize for its scientific consensus on the reality of global warming from human activity. Fresh research suggests the vaunted report lowballed the pace of the problem.

The changes seen now are much faster and parallel the increase in greenhouse gases such as carbon dioxide.

The National Oceanic and Atmospheric Administration said in January that although 2008 was one of the world's coolest years this decade, it was still the ninth warmest on record. Since 1880, 10 of the warmest years are since 1997.

A recent column by conservative George Will, in which he argued that concerns about global warming were overwrought and unfounded, was condemned by mainstream climate scientists both for his conclusion and his specifics.

For instance, he said that "global sea ice levels now equal those of 1979." But the very authority he cited, the University of Illinois' Arctic Climate Research Center, said the amount of sea ice in the world was down about 8% over the last three decades, or the equivalent of "Texas, California and Oklahoma combined."

The West Antarctic Ice Sheet covers a third of the continent as well as great expanses of the Weddell and Ross seas.

Fortunately, no one foresees its collapse for centuries, as it could be more catastrophic than previously understood. A recent paper in the journal Science predicted it would shift the planet's axis by a third of a mile and send rising waters sloshing northward.

"It's the difference between spinning a ball with a lump of something on the side, or taking that material and distributing it more evenly around the surface," said Peter Clark, a geosciences professor at Oregon State University.

Scientists had believed such an ice dump would universally raise ocean levels 16.5 feet worldwide, but new computer modeling suggests the shores of North America could face yet five feet more of water.

Braaten and his colleagues try to sort out the complicated question of how much ice still exists. They experiment with high-tech flights to decipher how deep the snow and ice is.

"When you're there, you just see that it looks flat," Braaten said. "Flatter than Nebraska."

But beneath -- the glaciers average 1.5 miles thick in Eastern Antarctica -- sit undulating mountain ranges for Braaten and his colleagues to chart.

Understanding that terrain below and the glaciers piled on top will offer a better idea how much ice may be accumulating in Antarctica's middle -- a consequence of climate change bringing more moisture to the region -- and how much is calving away at the edges.

Particularly on the Antarctica peninsula to the west, the rapid retreat of sea ice has profound consequences for penguins and other wildlife.

"Penguins and seals and whales need that sea ice," said Hugh Ducklow, who also returned from Antarctica to the Marine Biological Laboratory in Woods Hole, Mass. "All these ice-loving species are contracting their ranges to the south," chasing after the ice.

The average time per year the ocean around the peninsula is covered by sea ice has fallen by 90 days since 1978. Whaling records suggest the ice began to withdraw as early as the 1930s.

That's meant tiny invertebrates like krill -- which hide from predators and feed on plant matter that grows in the ice -- decline when the ice declines. So do the fish that feed on them, and so on.

"The Arctic was the canary in the coal mine, and we didn't pay much attention when it got sick," said Martinson. "Now the penguins are the canaries down there, and they're not looking too good."

Link to article: http://www.tri-cityherald.com/tih/story/502230.html