One of the largest glaciers in Antarctica is thinning four times faster than it was 10 years ago, according to research seen by the BBC.
By David Shukman Science and environment correspondent, BBC News Page last updated at 21:19 GMT, Thursday, 13 August 2009 22:19 UK
One of the largest glaciers in Antarctica is thinning four times faster than it was 10 years ago, according to research seen by the BBC.
A study of satellite measurements of Pine Island glacier in west Antarctica reveals the surface of the ice is now dropping at a rate of up to 16m a year.
Since 1994, the glacier has lowered by as much as 90m, which has serious implications for sea-level rise.
The work by British scientists appears in Geophysical Research Letters.
The team was led by Professor Duncan Wingham of University College London (UCL).
Calculations based on the rate of melting 15 years ago had suggested the glacier would last for 600 years. But the new data points to a lifespan for the vast ice stream of only another 100 years.
The rate of loss is fastest in the centre of the glacier and the concern is that if the process continues, the glacier may break up and start to affect the ice sheet further inland.
One of the authors, Professor Andrew Shepherd of Leeds University, said that the melting from the centre of the glacier would add about 3cm to global sea level.
"But the ice trapped behind it is about 20-30cm of sea level rise and as soon as we destabilise or remove the middle of the glacier we don't know really know what's going to happen to the ice behind it," he told BBC News.
"This is unprecedented in this area of Antarctica. We've known that it's been out of balance for some time, but nothing in the natural world is lost at an accelerating exponential rate like this glacier."
The highlighted area shows a dense concentration of crevasses along one edge of the glacier. Large numbers of deep crevasses are a sign that parts of the glacier are moving rapidly.
Pine Island glacier has been the subject of an intense research effort in recent years amid fears that its collapse could lead to a rapid disintegration of the West Antarctic ice sheet.
Five years ago, I joined a flight by the Chilean Navy and Nasa to survey Pine Island glacier with radar and laser equipment.
The 11-hour round-trip from Punta Arenas included a series of low-level passes over the massive ice stream which is 20 miles wide and in places more than one mile thick.
Back then, the researchers on board were concerned at the speed of change they were detecting. This latest study of the satellite data will add to the alarm among polar specialists.
This comes as scientists in the Arctic are finding evidence of dramatic change. Researchers on board a Greenpeace vessel have been studying the northwestern part of Greenland.
One of those taking part, Professor Jason Box of Ohio State University, has been surprised by how little sea ice they encountered in the Nares Strait between Greenland and Canada.
He has also set up time lapse cameras to monitor the massive Petermann glacier. Huge new cracks have been observed and it's expected that a major part of it could break off imminently.
Professor Box told BBC News: "The science community has been surprised by how sensitive these large glaciers are to climate warming. First it was the glaciers in south Greenland and now as we move further north in Greenland we find retreat at major glaciers. It's like removing a cork from a bottle."
Ice cave or englacial melt channel. Meltwater flowing within the glacier ice formed this cave. Belcher Glacier, Devon Island, Nunavut, Canada. (Credit: Angus Duncan)
By John D. Cox April 22, 2011
Withering in the warm temperatures, melting ice of the glaciers on thousands of Canadian Arctic islands off the coast of northwestern Greenland seems to be literally racing to the sea – contributing unexpectedly large volumes to global sea level rise.
A six-year study led by University of Michigan researcher Alex Gardner – just published in the journal Nature [ http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10089.html ] – estimates that between 2004 and 2009 the islands of the Canadian Arctic Archipelago shed enough water to fill Lake Erie three-quarters full and added a millimeter to the height of the world’s oceans.
Gardner says he was as surprised as anyone that the region was adding so much water to the sea. “Now we realize that outside of Antarctica and Greenland, it was the largest contributor for the years 2007 through 2009,” he said in a University of Michigan release. “This area is highly sensitive and if temperatures continue to increase, we will see much more melting.”
While six years is too short a period to establish a trend, Gardner noted, the pace of the melting accelerated dramatically during the study – at a time when temperatures rose just one degree.
In the first three years, from 2004 to 2006, the region lost seven cubic miles of water per year, on average. In the following three years, through 2009, when average air temperature was one degree Celsius warmer, the melt water volume jumped to 22 cubic miles of water per year.
“This is a big response to a small change in climate,” observes Gardner. “If the warming continues and we start to see similar responses in other glaciated regions, I would say it’s worrisome, but right now we just don’t know if it will continue.”
The study was based on satellite-borne measures of changes in elevation and gravity field that detects mass loss as well as computer-based modeling techniques.
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