Massive ice shelf 'may collapse without warning'

[Timewarp Profile]

The Ross Ice Shelf, a massive piece of ice the size of France, could break off without warning causing a dramatic rise in sea levels, warn New Zealand scientists working in Antarctica.

A New Zealand-led ice drilling team has recovered three million years of climate history from samples which gives clues as to what may happen in the future.

Initial analysis of sea-floor cores near Scott Base suggest the Ross Ice Shelf had collapsed in the past and had probably done so suddenly.

The team's co-chief scientist, Tim Naish, told The Press newspaper the sediment record was important because it provided crucial evidence about how the Ross Ice Shelf would react to climate change, with potential to dramatically increase sea levels.

"If the past is any indication of the future, then the ice shelf will collapse," he said.

"If the ice shelf goes, then what about the West Antarctic Ice Sheet? What we've learnt from the Antarctic Peninsula is when once buttressing ice sheets go, the glaciers feeding them move faster and that's the thing that isn't so cheery."

Antarctica stores 70 per cent of the world's fresh water, with the West Antarctic Ice Sheet holding an estimated 30 million cubic kilometres.

In January, British Antarctic Survey researchers predicted that its collapse would make sea levels rise by at least 5m, with other estimates predicting a rise of up to 17m.

Dr Naish, a sedimentologist with the Institute of Geological and Nuclear Sciences, said one day the drilling team retrieved a core of 83m, far greater than expected, which contained climate records spanning about 500,000 years.

"We're really getting everything we've dreamed of. What we're getting is a pretty detailed history of the ice shelf," he said.

"You go from full glacial conditions to open ocean conditions very abruptly. It doesn't surprise us that much that the transition was dramatic."

Scientists knew from the collapse of the Larsen Ice Shelf in 2002 that expanses of ice could collapse "extremely quickly".

Once dating of the sample was completed, researchers would be able to look at what the ice shelf was doing during periods when scientists knew from other evidence that it was 2degC to 4degC warmer than today, Dr Naish said.

http://www.nzherald.co.nz/technology/ne ... d=10412954

[Timewarp Profile]

BREAKING up is getting easier to do, it seems, especially when it comes to the Antarctic Peninsula. On 3 April, satellite images showed that an ice bridge which connected two islands to the Wilkins ice shelf had shattered. This has left the shelf vulnerable to the ocean and in danger of breaking away from the peninsula.

Last year, the 13,000-square-kilometre Wilkins ice shelf released huge chunks of ice, leaving a narrow ice bridge as the only connection between the northern front of the ice shelf and the ice surrounding nearby Charcot and Latady islands.

Now that ice bridge has collapsed - leaving an iceberg-filled channel in its wake - the northern front of the shelf is exposed. "We expect in the next few days and weeks that the northern ice front will lose between 800 and 3700 square kilometres of ice," says Angelika Humbert of the Institute of Geophysics at Münster University, Germany.

The break-up of the Wilkins ice shelf will not lead to sea-level rise as it is already floating on water, and nor will it speed up the movement of any glaciers into the oceans. Nevertheless, these events serve as a dire warning, says Humbert: "It shows us that ice shelves have the potential to become unstable on very short timescales."

If other ice shelves in the region start calving, then the glaciers that feed them could slip faster into the ocean, leading to sea-level rise.

http://www.newscientist.com/article/mg2 ... posed.html

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The fate of FL and LA if we’re myopic and greedy enough to let the West Antarctic Ice Sheet (WAIS) collapse.

A new study in Science finds that sea level rise from a collapse of the WAIS would likely be 25% higher for North America than previously estimated:

The catastrophic increase in sea level, already projected to average between 16 and 17 feet around the world, would be almost 21 feet in such places as Washington, D.C., scientists say, putting it largely underwater. Many coastal areas would be devastated. Much of Southern Florida would disappear.

This article has already started to make news around the globe (Reuters story here). But, frankly, divining the difference between a rise of 16.5 feet (an incalculably devastating catastrophe) and 21 feet (an incalculably devastating catastrophe) is like trying to count the number of devils on a pin.

Nonetheless, WAIS collapse is all but inevitable given business-as-usual warming of 5-7°C. As I explained in my book:

Perhaps the most important, and worrisome, fact about the WAIS is that it is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level.

For a longer discussion of WAIS and its unique instability, see “Antarctica has warmed significantly over past 50 years.”

So what is new in the Science article, “The Sea-Level Fingerprint of West Antarctic Collapse” (subs. req’d)? Study coauthor and geophysicist Jerry X. Mitrovica, director of the Earth System Evolution Program at the Canadian Institute for Advanced Research, explains:

The typical estimate of the sea-level change is five metres, a value arrived at by taking the total volume of the West Antarctic Ice Sheet, converting it to water and spreading it evenly across the oceans. However, this estimate is far too simplified because it ignores three significant effects:

* When an ice sheet melts, its gravitational pull on the ocean is reduced and water moves away from it. The net effect is that the sea level actually falls within 2,000 km of a melting ice sheet, and rises progressively further away from it. If the West Antarctic Ice Sheet collapses, sea level will fall close to the Antarctic and will rise much more than the expected estimate in the northern hemisphere because of this gravitational effect;
* The depression in the Antarctic bedrock that currently sits under the weight of the ice sheet will become filled with water if the ice sheet collapses. However, the size of this hole will shrink as the region rebounds after the ice disappears, pushing some of the water out into the ocean, and this effect will further contribute to the sea-level rise;
* The melting of the West Antarctic Ice Sheet will actually cause the Earth’s rotation axis to shift rather dramatically — approximately 500 metres from its present position if the entire ice sheet melts. This shift will move water from the southern Atlantic and Pacific oceans northward toward North America and into the southern Indian Ocean.

And this all means that if WAIS collapses, “the rise in sea levels around many coastal regions will be as much as 25 per cent more than expected, for a total of between six and seven metres if the whole ice sheet melts.”

A digital animation of various sea-level rise scenarios up to six metres is at www.cresis.ku.edu/research/data/sea_level_rise.

The time to act is now.

http://climateprogress.org/2009/02/05/a ... us-coasts/

[Tunique1 Profile]

Has anybody thought about, concerning an intruder body (nibiru) or galactic gravy waves from the center (2012), how ice behaves on water??

Swuuuuush it goes forms another himalaya


How about moving the entiry ice?
Good night.....