Nasa data reveals West Antarctic ice sheet is melting at an 'unstoppable' speed

New studies say the melting of the West Antarctic ice sheet is unstoppable

Parts will completely melt in a few centuries and drastically raise sea levels

Combined with other glaciers it could add four feet to Earth's oceans

It is occuring faster than predicted and has 'passed the point of no return'

Curbing carbon emissions won't stop it but could slow the process



The data was compiled from 40 years of ground, air and satellite data

Vast glaciers in West Antarctica seem to be locked in an irreversible thaw linked to global warming that may push up sea levels for centuries, according to scientists.

In a few hundred years they say the irreversible melt that has already started could eventually add four to 12 feet (1.2 to 3.7 metres) to current sea levels.

A Nasa study looking at 40 years of ground, airplane and satellite data of what researchers call 'the weak underbelly of West Antarctica' shows the melt is happening faster than scientists had predicted, crossing a critical threshold that has begun a domino-like process.

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Two new studies indicate that part of the huge West Antarctic ice sheet is starting a slow collapse in an unstoppable way. Six glaciers, eaten away from below by a warming of sea waters around the frozen continent, were flowing fast into the Amundsen Sea, according to the report based on data from 1992 to 2011 Evidence shows 'a large sector of the West Antarctic ice sheet has gone into a state of irreversible retreat', says lead author Eric Rignot of the University of California, Irvine, and Nasa's Jet Propulsion Laboratory in Pasadena, California. The coastal ends of the glaciers rest on bedrock below sea level, holding back a vast weight of ice and making them vulnerable to melt, he said.

'It does seem to be happening quickly,' says University of Washington glaciologist Ian Joughin, lead author of a separate study into the same phenomenon. RELATED ARTICLES Previous

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It's likely because of man-made global warming and the ozone hole which have changed the Antarctic winds and warmed the water that eats away at the feet of the ice, researchers said at a Nasa news conference Monday.

'The system is in sort of a chain reaction that is unstoppable,' continued Rignot.



'Every process in this reaction is feeding the next one. It's passed the point of no return.'



Rignot and other scientists said the 'grounding line' which could be considered a dam that stops glacier retreat has essentially been breached.



Another way to think of it is like wine flowing from a horizontal uncorked bottle, they said.

The only thing that could stop the retreat in this low-altitude region is a mountain or hill.



But ice-penetrating radars showed there are no mountain ranges entombed under the ice that could halt the flow.

Despite ice coverage increasing in some areas, Nasa claims that in a few hundred years the irreversible melt that has already started from the Amundsen Sea sector of the West Antarctica ice sheet, pictured, has now 'passed the point of no return' and could eventually add four to 12 feet (1.2 to 3.7 metres) to current sea levels

Scientists say curbing carbon emissions won't be able to stop the collapse of these glaciers, but may slow the process and at least prevent the them from melting at their current speed

This part of Antarctica would be a major contributor to sea level rise in coming decades and centuries since the glaciers hold enough ice to raise sea levels by more than four feet (1.2 metres).



The fastest retreat from 1992 to 2011 was 21 to 23 miles (34 to 37 kilometres) over the period in the Smith/Kohler glacier.

Reducing carbon emissions from fossil fuels to slow climate change could slow the speed of the problem, Rignot said , although it will probably not completely halt the melting.



Cuts in greenhouse gas emissions, part of efforts to rein in global warming, could at least slow the slide of the Pine Island, Thwaites, Haynes, Pope, Smith and Kohler glaciers.

'We do think this is related to climate warming,' Rignot added.



The scientists believed that a build-up of man-made greenhouse gases in the atmosphere was affecting wind patterns around Antarctica, driving warmer waters towards the continent.

Almost 200 nations have agreed to work out a UN pact by the end of 2015 to combat global warming, which the UN Intergovernmental Panel on Climate Change (IPCC) says will cause more floods, droughts, heat waves and higher seas.



Although the Amundsen Sea region (shown shrinking over the last decade) is only a fraction of the whole West Antarctic Ice Sheet, the region contains enough ice to raise global sea levels by four feet (1.2 meters)

Rignot looked at six glaciers in the region with special concentration on the Thwaites glacier, about the size of New Mexico and Arizona combined.



Thwaites is so connected to the other glaciers that it helps trigger loss elsewhere, said Joughin, whose study was released in the journal Science.

Joughin's study used computer simulations and he concluded 'the early-stage collapse has begun.'

Rignot, who used data that showed a speed up of melt since the 1990s, said the word 'collapse' may imply too fast a loss - it would be more the start of a slow-motion collapse and 'we can't stop it.'

A separate study of the Thwaites glacier by the University of Washington in the journal Science also said it may have begun an unstoppable collapse that could last from 200 to 1,000 years.

A disappearance of the Thwaites alone would raise world sea levels by 1.96 feet (60 centimetres) but the 'glacier also acts as a linchpin on the rest of the ice sheet, which contains enough ice to cause another three to four metres (10 to 13 feet) of sea level rise,' it said.

Scientists say the early stages of collapse have already begun and there's nothing we can do to stop it. On the left here can be seen the elevation of the region, while on the right the various glaciers that will be affected by the melting of the Amundsen Sea region



Several outside experts in Antarctica added their concern.



'It's bad news. It's a game changer,' said Ted Scambos, lead scientist at the National Snow and Ice Data Center.



'We thought we had a while to wait and see. We've started down a process that we always said was the biggest worry and biggest risk from West Antarctica.'

The Rignot study sees eventually 4 feet (1.2 metres) of sea level rise from the melt.



But it could trigger neighboring ice sheet loss that could mean a total of 10 to 12 feet (3.0 to 3.7 metres) of sea level rise, Joughin's study showed.

The findings may also mean that scenarios by the IPCC for sea level rise are too low.



The IPCC said last year that sea levels are likely to rise by between 10 and 32 inches (26 and 82 centimetres) by the late 21st century, after a rise of just seven inches (19 centimetres) since 1900.

'The major ice sheets of this planet will have a larger and larger role in sea level rise in the decades ahead,' said Sridhar Anandakrishnan, professor of geosciences at Pennsylvania State University, who was not involved in the study.

Last week, another study also suggested a part of the far bigger ice sheet in East Antarctica may also be more vulnerable than expected to thaw.



The IPCC says it is at least 95 percent probable that warming is caused by human activities, led by the burning of fossil fuels.

Meanwhile, on May 6, the Obama administration issued a study saying that warming 'once considered an issue for a distant future has moved firmly into the present.'