Study finds warm ocean currents cause majority of ice loss from Antarctica

Apr 25, 2012
This images shows the circulation of ocean currents around the western Antarctic ice shelves. The shelves are indicated by the rainbow color; red is thicker (greater than 550 meters), while blue is thinner (less than 200 meters). Credit: NASA/Goddard CGI Lab

Reporting this week in the journal Nature, an international team of scientists led by British Antarctic Survey (BAS) has established that warm ocean currents are the dominant cause of recent ice loss from Antarctica. New techniques have been used to differentiate, for the first time, between the two known causes of melting ice shelves - warm ocean currents attacking the underside, and warm air melting from above. This finding brings scientists a step closer to providing reliable projections of future sea-level rise.

Researchers used 4.5 million measurements made by a laser instrument mounted on NASA's ICESat satellite to map the changing thickness of almost all the shelves around Antarctica, revealing the pattern of ice-shelf melt across the continent. Of the 54 ice shelves mapped, 20 are being melted by currents, most of which are in .

In every case, the inland glaciers that flow down to the coast and feed into these thinning ice shelves have accelerated, draining more ice into the sea and contributing to sea level rise.

Lead author Dr Hamish Pritchard from , which is part of the UK's Natural Environment Research Council (NERC), said:

"In most places in Antarctica, we can't explain the ice-shelf thinning through melting of snow at the surface, so it has to be driven by warm ocean currents melting them from below.

"We've looked all around the Antarctic coast and we see a clear pattern: in all the cases where ice shelves are being melted by the ocean, the inland glaciers are speeding up. It's this glacier acceleration that's responsible for most of the increase in ice loss from the continent and this is contributing to sea-level rise."

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This animation shows the circulation of ocean currents around the western Antarctic ice shelves. The shelves are indicated by the rainbow color; red is thicker (greater than 550 meters), while blue is thinner (less than 200 meters). Credit: NASA/Goddard CGI Lab

"What's really interesting is just how sensitive these glaciers seem to be. Some ice shelves are thinning by a few metres a year and, in response, the glaciers drain billions of tons of ice into the sea. This supports the idea that are important in slowing down the glaciers that feed them, controlling the loss of ice from the Antarctic . It means that we can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt - the oceans can do all the work from below.

"But this does raise the question of why this is happening now. We think that it's linked to changes in wind patterns. Studies have shown that Antarctic winds have changed because of changes in climate, and that this has affected the strength and direction of . As a result warm water is funnelled beneath the floating ice. These studies and our new results therefore suggest that Antarctica's are responding rapidly to a changing climate."

A different picture is seen on the eastern Antarctic Peninsula (the long stretch of land pointing towards South America). Here, the ice-shelf thinning found by this study can be explained by warm summer winds directly melting the snow on the ice-shelf surfaces. Both patterns, of widespread ocean-driven melting and this summer melting on the Antarctic Peninsula, can therefore be attributed to Antarctica's changing wind patterns.

This research is part of international efforts to improve understanding of the interactions between ice and climate in order to improve the reliability of projections. Professor David Vaughan is the leader of ice2sea - a major EU-funded FP7 programme. He said,

"This study shows very clearly why the Antarctic ice sheet is currently losing ice, which is a major advance. But the real significance is that it also shows the key to predicting how the ice sheet will change in the future is in understanding the oceans. Perhaps we should not only be looking to the skies above Antarctica, but also into the surrounding oceans."

The study was carried out by an international team from British Antarctic Survey, Utrecht University, Scripps Institution of Oceanography and Earth & Space Research in Corvallis, Oregon. NASA's ICESat – Ice, Cloud and Land Elevation Satellite – measurements were collected during the period 2003 – 2008 to detect changes in ice-shelf thickness through time.

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More information: Antarctic ice sheet loss driven by basal melting of ice shelves: H.D Pritchard, S.R.M Ligtenberg, H.A Fricker, D.G Vaughan, M.R van den Broeke, L. Padman is published this week in the journal Nature.

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User comments : 13

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NotParker
1.4 / 5 (19) Apr 25, 2012
"In every case, the inland glaciers that flow down to the coast"

That means those glaciers are growing. If they were shrinking they would be retreating, not flowing down to the coast.
Ojorf
5 / 5 (9) Apr 26, 2012
"In every case, the inland glaciers that flow down to the coast"

That means those glaciers are growing. If they were shrinking they would be retreating, not flowing down to the coast.


Read the article, it is explained.
Vendicar_Decarian
1.1 / 5 (46) Apr 26, 2012
Yes, in the same way that ice cubes "grow" when they melt.

"That means those glaciers are growing." - ParkerTard

Poor ParkerTard. He never misses an opportunity to lie or distort in order to support his Conservative Political Ideology.
SincerelyTwo
3.9 / 5 (7) Apr 26, 2012
There's something wrong with NotParker ...
kaasinees
3.1 / 5 (8) Apr 26, 2012
There's something wrong with NotParker ...

Hes indoctrinated by religion/politics etc.
Hes an alien that wants to convert our environment.
He gets payd a lot of money to make these stupid posts.
He got a brain infection from a virus or a bacteria or a toxin like fluoride maybe?

Take your pick...
NotParker
1.4 / 5 (9) Apr 26, 2012
"In every case, the inland glaciers that flow down to the coast and feed into these thinning ice shelves have accelerated, draining more ice into the sea and contributing to sea level rise."

They claim the ice is thinning from below. How can a laser coming from a satellite see the underside of the sea ice?

It can't.

If the ice is thinning (it isn't but I am just using their argument) and the thinner ice is being replenished by even more ice that is growing and flowing down to the sea, why would it affect sea level?

Floating sea is already in the ocean and would have no effect if it melted.

Glaciers that melt retreat inland because they melt from the coast which is the warmest part. They only grow and flow downwards if more ice is created in the colder interior.

Sea Ice in Antarctica has been growing for 30 years.

http://arctic.atm...ctic.png
NotParker
1.4 / 5 (9) Apr 26, 2012
"draining more ice into the sea"

The interior glaciers are growing. More ice means growth.

How do lasers shot from a satellite see how thick a snow covered ice sheet is?
NotParker
1.4 / 5 (9) Apr 26, 2012
"in all the cases where ice shelves are being melted by the ocean, the inland glaciers are speeding up. It's this glacier acceleration ... "

Ok. Glaciers are accelerating and speeding up and growing. Got it.

" .... that's responsible for most of the increase in ice loss from the continent ... "

Wait! I thought they were using the magical laser from the satellite to measure the thickness of the sea ice not ice on the continent!

"... and this is contributing to sea-level rise."

But growing interior glaciers mean more ice on the continent and less ice in the ocean.

Antarctic Sea Ice is growing and has been for 30 years.

http://arctic.atm...ctic.png

I wonder if the authors of this paper were on drugs?
NotParker
1.4 / 5 (9) Apr 26, 2012
"In most places in Antarctica, we can't explain the ice-shelf thinning through melting of snow at the surface, so it has to be ....

What thinning? Sea Ice in Antarctica is growing.

And Sea Level rise is slowing down.

http://notrickszo...eration/

And just because you can't think up an explanation for the imaginary thinning, doesn't mean you should just make stuff up about invisible, unseen, undocumented imaginary underwater melting in sea water that is below freezing almost all of the time.

rubberman
4.5 / 5 (8) Apr 26, 2012
OK...NotParker has got to be a Vendicar sock puppet he put on here to serve up these non scientific tater balls for us to bash out of the park....that is the only way I can explain the stuff he posts.

"What thinning? Sea Ice in Antarctica is growing."

It is the beginning of winter in the coldest place on earth...if sea ice wasn't growing I would hate to see what the rest of the planet looked like.

"How do lasers shot from a satellite see how thick a snow covered ice sheet is?"

I was curious about this so I googled it...you can too. Otherwise you can continue to think it is magic...or, not real. Cheers
NotParker
1.5 / 5 (8) Apr 26, 2012

"What thinning? Sea Ice in Antarctica is growing."

It is the beginning of winter in the coldest place on earth...if sea ice wasn't growing I would hate to see what the rest of the planet looked like.



Its been growing for 30 years, not just this season.

http://arctic.atm...ctic.png


"How do lasers shot from a satellite see how thick a snow covered ice sheet is?"

I was curious about this so I googled it...you can too. Otherwise you can continue to think it is magic...or, not real. Cheers


And of course your somehow forgot to post the reference.

rubberman
4.3 / 5 (6) Apr 26, 2012


"How do lasers shot from a satellite see how thick a snow covered ice sheet is?"

I was curious about this so I googled it...you can too. Otherwise you can continue to think it is magic...or, not real. Cheers


And of course your somehow forgot to post the reference.



I didn't forget, I'm not your babysitter. If you really care to learn you can find it 15 seconds by a google search combining the name of the satelite and the function it is being used for.
NotParker
1.6 / 5 (7) Apr 26, 2012
If you really care to learn you can find it 15 seconds by a google search combining the name of the satelite and the function it is being used for.


Its dead. The last of its 3 lasers died several years ago. And they only measured topography.

Those lasers could not measure ice thickness.

I was hoping you would have the courage to mention that. My mistake.

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