Fwd: [graffis-l] ANTARCTIC GLACIERS SURGE TO THE OCEAN!

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>Antarctic glaciers surge to ocean

>Posted by: " Mark Graffis " mgraffis mgraffis

>Sun Feb 24, 2008 5:04 pm (PST)

>Antarctic glaciers surge to ocean

>

>By Martin Redfern

>Rothera Research Station, Antarctica

>

>UK scientists working in Antarctica have found some of the clearest

>evidence yet of instabilities in the ice of part of West Antarctica.

>If the trend continues, they say, it could lead to a significant rise in

>global sea level.

>

>The new evidence comes from a group of glaciers covering an area the size

>of Texas, in a remote and seldom visited part of West Antarctica.

>

>The " rivers of ice " have surged sharply in speed towards the ocean.

>

>David Vaughan, of the British Antarctic Survey, explained: " It has been

>called the weak underbelly of the West Antarctic Ice Sheet, and the reason

>for that is that this is the area where the bed beneath the ice sheet dips

>down steepest towards the interior.

>

> " If there is a feedback mechanism to make the ice sheet unstable, it will

>be most unstable in this region. "

>

>There is good reason to be concerned.

>

>Satellite measurements have shown that three huge glaciers here have been

>speeding up for more than a decade.

>

>The biggest of the glaciers, the Pine Island Glacier, is causing the most

>concern.

>

>Inhospitable conditions

>

>Julian Scott has just returned from there. He told the BBC: " This is a

>very important glacier; it's putting more ice into the sea than any other

>glacier in Antarctica.

>

> " It's a couple of kilometres thick, its 30km wide and it's moving at 3.5km

>per year, so it's putting a lot of ice into the ocean. "

>

>It is a very remote and inhospitable region. It was visited briefly in

>1961 by American scientists but no one had returned until this season when

>Julian Scott and Rob Bingham and colleagues from the British Antarctic

>survey spent 97 days camping on the flat, white ice.

>At times, the temperature got down to minus 30C and strong winds made work

>impossible.

>

>At one point, the scientists were confined to their tent continuously for

>eight days.

>

> " The wind really makes the way you feel incredibly colder, so just

>motivating yourself to go out in the wind is a really big deal, " Rob

>Bingham told BBC News.

>

>When the weather improved, the researchers spent most of their time

>driving skidoos across the flat, featureless ice.

>

> " We drove skidoos over it for something like 2,500km each and we didn't

>see a single piece of topography. "

>

>Long drag

>

>Rob Bingham was towing a radar on a 100m-long line and detecting

>reflections from within the ice using a receiver another 100m behind that.

>

>The signals are revealing ancient flow lines in the ice. The hope is to

>reconstruct how it moved in the past.

>

>Julian Scott was performing seismic studies, using pressurised hot water

>to drill holes 20m or so into the ice and place explosive charges in them.

>He used arrays of geophones strung out across the ice to detect

>reflections, looking, among other things, for signs of soft sediments

>beneath the ice that might be lubricating its flow.

>

>He also placed recorders linked to the global positioning system (GPS)

>satellites on the ice to track the glacier's motion, recording its

>position every 10 seconds.

>Throughout the 1990s, according to satellite measurements, the glacier was

>accelerating by around 1% a year. Julian Scott's sensational finding this

>season is that it now seems to have accelerated by 7% in a single season,

>sending more and more ice into the ocean.

>

> " The measurements from last season seem to show an incredible

>acceleration, a rate of up to 7%. That is far greater than the

>accelerations they were getting excited about in the 1990s. "

>

>The reason does not seem to be warming in the surrounding air.

>

>One possible culprit could be a deep ocean current that is channelled onto

>the continental shelf close to the mouth of the glacier. There is not much

>sea ice to protect it from the warm water, which seems to be undercutting

>the ice and lubricating its flow.

>

>Ongoing monitoring

>

>Julian Scott, however, thinks there may be other forces at work as well.

>

>Much higher up the course of the glacier there is evidence of a volcano

>that erupted through the ice about 2,000 years ago and the whole region

>could be volcanically active, releasing geothermal heat to melt the base

>of the ice and help its slide towards the sea.

>

>David Vaughan believes that the risk of a major collapse of this section

>of the West Antarctic ice sheet should be taken seriously.

> " There has been the expectation that this could be a vulnerable area, " he

>said.

>

> " Now we have the data to show that this is the area that is changing. So

>the two things coinciding are actually quite worrying. "

>

>The big question now is whether what has been recorded is an exceptional

>surge or whether it heralds a major collapse of the ice. Julian Scott

>hopes to find out.

>

> " It is extraordinary and we've left a GPS there over winter to see if it

>is going to continue this trend. "

>

>If the glacier does continue to surge and discharge most of it ice into

>the sea, say the researchers, the Pine Island Glacier alone could raise

>global sea level by 25cm.

>

>That might take decades or a century, but neighbouring glaciers are

>accelerating too and if the entire region were to lose its ice, the sea

>would rise by 1.5m worldwide.

>

>Story from BBC NEWS:

>http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/7261171.stm

>

>Published: 2008/02/24 00:24:09 GMT

>

>© BBC MMVIII

>

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