Study shows above ice warming responsible for Larsen-B Ice Shelf collapse, not instability

September 12, 2014 by Bob Yirka report
View of the calving front of the Crane Glacier and open water looking west into the interior drainage system. Water depth here is over 1200 m deep. Credit: Michele Rebesco, 2006.

(Phys.org) —An international team of researchers has concluded that the Larsen-B Ice Shelf collapsed in 2002 because of warmer surface air temperatures, not instability from below, as some have suggested. In their paper published in the journal Science, the team describes how they collected and examined sea floor samples in the area where Larsen-B collapsed and found no evidence of structural damage that could have caused the shelf to collapse—that leaves warmer temperatures from above as the only logical cause.

An ice shelf forms when a glacier slides from land to the sea—because the seawater is near freezing, the ice floats on the surface. But a part of the shelf, very near the shore (the grounding line), does touch the seafloor, and that's where the researchers focused their attention. When Larsen-B suddenly cracked apart into pieces that drifted into the , most experts believed it was because sea had increased to the point where the water could no longer support the ice above it. In this new effort, the researchers looked at the former grounding line of Larsen-B by taking core samples from a ship above it. In so doing, they found that the grounding line hadn't moved in over 12,000 years making it highly unlikely that loss of support from below was the reason for the collapse.

Temperatures from above can cause a collapse when they increase to the point that ice on top of the shelf melts, forming pools of water. Those pools cause the ice beneath them to melt, allowing the water in the pool to seep down, eventually forming crevices. As the crevices grow bigger, they can cause pieces of the shelf to break off in much the same way that cracks on the outlying edges can cause calving to occur. Notably, an breaking off doesn't cause a rise in sea levels because it was already floating on top. Quite often it does lead to a speed up of the glacier flowing into the sea, however, and that does cause sea levels to rise.

Antarctic team discovers mechanism for massive ice shelf collapse
View looking southwest of the seismic reflection system being towed through the water behind the RVIB N. B. Palmer. The Nordensköld Coast is in the background. Credit: Michele Rebesco, 2006.

The researchers believe their findings will help to identify which ice shelves are likely to break apart in the near future, helping to make better estimates on how much sea levels will rise, and when, due to global warming.

Explore further: Research trio offer new explanation for breakup of Larsen B Ice Shelf

More information: Boundary condition of grounding lines prior to collapse, Larsen-B Ice Shelf, Antarctica, Science 12 September 2014: Vol. 345 no. 6202 pp. 1354-1358, DOI: 10.1126/science.1256697

ABSTRACT
Grounding zones, where ice sheets transition between resting on bedrock to full floatation, help regulate ice flow. Exposure of the sea floor by the 2002 Larsen-B Ice Shelf collapse allowed detailed morphologic mapping and sampling of the embayment sea floor. Marine geophysical data collected in 2006 reveal a large, arcuate, complex grounding zone sediment system at the front of Crane Fjord. Radiocarbon-constrained chronologies from marine sediment cores indicate loss of ice contact with the bed at this site about 12,000 years ago. Previous studies and morphologic mapping of the fjord suggest that the Crane Glacier grounding zone was well within the fjord before 2002 and did not retreat further until after the ice shelf collapse. This implies that the 2002 Larsen-B Ice Shelf collapse likely was a response to surface warming rather than to grounding zone instability, strengthening the idea that surface processes controlled the disintegration of the Larsen Ice Shelf.

Press release

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MR166
1.8 / 5 (10) Sep 12, 2014
http://news.natio...erated=1

I know,,,,,"It's just weather",,,,, but if it were a heat wave it would be all over the world news.

How long will it take for this little bit of weather to be linked to global warming or climate change?
Eddy Courant
2.1 / 5 (7) Sep 12, 2014
Hairdryers. It's the only thing that makes any sense.
antigoracle
1.7 / 5 (11) Sep 12, 2014
Yep, it was hot air, never mind that directly below is a very active geothermal region.
Vietvet
4.3 / 5 (11) Sep 12, 2014
Yep, it was hot air, never mind that directly below is a very active geothermal region.


There are indications that there might be geothermal activity in the area of Twaites Glacier but the Larsen ice shelf is 1500 kilometers to the Northwest and has no geothermal activity.

http://www.antarc...lapsing/
SamB
2 / 5 (8) Sep 13, 2014
Don't these researchers have anything better to do? We have much more pressing problems in this world than to wonder what caused an ice shelf to collapse, instability or warm air.. (or maybe warm air caused the instability, eh??).. Give me a break and go help the people fighting Ebola and the insanity called religion that is engulfing our world...
thermodynamics
4.5 / 5 (8) Sep 13, 2014
Don't these researchers have anything better to do? We have much more pressing problems in this world than to wonder what caused an ice shelf to collapse, instability or warm air.. (or maybe warm air caused the instability, eh??).. Give me a break and go help the people fighting Ebola and the insanity called religion that is engulfing our world...


SamB: You don't seem to understand the way you have to combat a complex issue. Let's look at your example of putting these researchers to work solving the ebola issue. Do you know how long it will take to get them ready to be helpful instead of someone in the way?

The first thing that happens when a project falls behind is that management throws dollars and money at it. The result is that it gets further behind because you have to take time of those who know how to do what is needed to train those who don't. That is not to say that we should not be sending gowns and gloves to help those who are there. Continued
thermodynamics
4.5 / 5 (8) Sep 13, 2014
Continued for SamB who might not have ever had to take on a project that needs to gear up.

So, what it takes is proactive effort and predict ahead of time where resources are needed. The result is that no one is really good on making those predictions so things like the Ebola crisis pops up and people can't gear up fast enough to make a difference.

What does that mean for the world? One good example is Anthropogenic Global Warming. The klaxon warnings have been sounded by the scientific establishment. The politicians are not listening. So, by the time you start suggesting we should be diverting effort to lowering CO2, it will take training, repurposing of resources, and resources. It will be more expensive and less effective than if we started now, but it is reactive and that is how we think. You made it clear that is the way you think by stating we could just put these climate scientists to work on Ebola. Reconsider and you can still help influence an early change.
antigoracle
1.7 / 5 (6) Sep 13, 2014
Yep, it was hot air, never mind that directly below is a very active geothermal region.


There are indications that there might be geothermal activity in the area of Twaites Glacier but the Larsen ice shelf is 1500 kilometers to the Northwest and has no geothermal activity.

http://www.antarc...lapsing/

Where there is geothermal activity, there is seismic activity.
MR166
1.6 / 5 (7) Sep 13, 2014
Blaming increased sea ice, unseasonably cold weather (IE Polar Vortex)and climate extremes on CO2 emissions is just one short step or cooling period away from saying that CO2 emissions are creating global cooling!!!

Just saying, to all of you true believers, be prepared for the new research papers and climate models that will inevitably appear when the weather turns prematurely cold,

Vietvet
4.3 / 5 (6) Sep 13, 2014
@anti

"Where there is geothermal activity, there is seismic activity"

True, but that seismic activity is weak and localized.

I found a link just for you, it is simple enough that you might even be able to read and understand it. But then again I'm probably giving you too much credit.

http://volcano.or...-related
antigoracle
1.7 / 5 (6) Sep 13, 2014
In the peak of summer it's still way below freezing, yet the AGW morons would believe that the ice shelf melted enough, from above, to collapse.
Vietvet
4.2 / 5 (5) Sep 13, 2014
In the peak of summer it's still way below freezing, yet the AGW morons would believe that the ice shelf melted enough, from above, to collapse.


Links?

A clue.

While the average summertime temp is -5C, the Larsen A and B ice sheets sit far enough North to develop ice melt ponds at peak temps.

MR166
1.6 / 5 (7) Sep 13, 2014
Huuuum water vapor in the atmosphere is a negative feedback mechanism not positive as claimed. The 97% are wrong yet again.

http://hockeyscht...-in.html

SteveS
4.2 / 5 (5) Sep 14, 2014
In the peak of summer it's still way below freezing, yet the AGW morons would believe that the ice shelf melted enough, from above, to collapse.


See page 5 paragraph starting "Several studies have noted that in addition to higher temperatures"

" satellite imagery shows numerous melt ponds near surface crevasses on the Larsen B ice shelf just before its rapid collapse in 2002"

https://courses.s...2011.pdf

Who's the moron now?
antigoracle
1.6 / 5 (7) Sep 14, 2014
Yes, anything to propagate the CO2 global warming lie. Their ocean warming lie did not pan out, so they just come up with another.
I do not question the existence of melt ponds, but their conclusion that warm air is responsible. A more likely scenario is rain accumulating and then the albedo effect taking over.
Vietvet
4 / 5 (4) Sep 14, 2014
Yes, anything to propagate the CO2 global warming lie. Their ocean warming lie did not pan out, so they just come up with another.
I do not question the existence of melt ponds, but their conclusion that warm air is responsible. A more likely scenario is rain accumulating and then the albedo effect taking over.


You are so damn ignorant. It doesn't rain in Antarctica
http://www.coolan...ions.htm
.

antigoracle
2 / 5 (4) Sep 14, 2014
Rain commonly falls in coastal regions in the summer

http://www.coolan...ther.htm
Vietvet
3 / 5 (2) Sep 14, 2014
Rain commonly falls in coastal regions in the summer

http://www.coolan...ther.htm


Interesting that the site contradicts it self, but rain needs temps above freezing.

http://ww2010.atm.../rs.rxml
antigoracle
1.6 / 5 (7) Sep 15, 2014
Wow!!
So, it's warm enough to melt the ice and create melt-ponds, but not for rain to fall?
Vietvet
4 / 5 (4) Sep 15, 2014
Wow!!
So, it's warm enough to melt the ice and create melt-ponds, but not for rain to fall?


It is warm enough for both, any rain would add to the melt bonds. Glad you agree there are melt ponds on the Larsen ice sheets!
SteveS
4.5 / 5 (8) Sep 15, 2014
I do not question the existence of melt ponds

Yes you do
In the peak of summer it's still way below freezing, yet the AGW morons would believe that the ice shelf melted enough, from above, to collapse.


If you're having problems keeping track of your contributions to this discussion I'll list them for you.

A more likely scenario is rain accumulating and then the albedo effect taking over.

Why more likely? Because you "know" the study is part of the "CO2 global warming lie" therefore anything must be "more likely"?

So your current stand is that it's all a part of a conspiracy

Initially you said it was geothermal activity, then it was due to seismic activity, and then after that you told us that it was too cold to form melt ponds.

So essentially your logic breaks down to "AGW is a conspiracy, therefore it must something else."

Deny much?
antigoracle
1.5 / 5 (8) Sep 15, 2014
Wow steve, that lone neuron you share with your cult members has been busy. Only you in the AGW Cult see conspiracy, when I look at you all I see is stupidity.
Geothermal activity is melting, seismic activity resulted in the sudden breakup of the ice shelf.
Why is it only West Antarctica that this is happening?
SteveS
4.4 / 5 (7) Sep 15, 2014
Geothermal activity is melting, seismic activity resulted in the sudden breakup of the ice shelf.


Do you have any evidence for this? and are you now saying it has nothing to do with "rain accumulating and then the albedo effect taking over."?

A little bit of consistency in your arguments would be helpful.
Vietvet
4.5 / 5 (8) Sep 15, 2014
Wow steve, that lone neuron you share with your cult members has been busy. Only you in the AGW Cult see conspiracy, when I look at you all I see is stupidity.
Geothermal activity is melting, seismic activity resulted in the sudden breakup of the ice shelf.
Why is it only West Antarctica that this is happening?


You must have started hitting the bottle early today with your incoherent comment.

While the potential exist for a volcanic eruption to cause massive melting effecting the Ross ice sheet, you can't provide a single link showing it has occurred recently ( the last 100,000 years).
MR166
1.8 / 5 (5) Sep 15, 2014
Now I know why every event is tied back to AGW and CO2.

http://www.zerohe...d-source
SteveS
4.2 / 5 (5) Sep 16, 2014
Now I know why every event is tied back to AGW and CO2.

http://www.zerohe...d-source


Very sharp, very original. You must be proud of that one.

http://en.wikiped...in's_law
MR166
1.8 / 5 (5) Sep 17, 2014
Well Steve it is comforting to know that I have terminated yet another useless thread.
Vietvet
3.7 / 5 (6) Sep 17, 2014
Well Steve it is comforting to know that I have terminated yet another useless thread.


The only thing "useless" about this thread as been your inane comments.
MR166
2 / 5 (4) Sep 17, 2014
Yup, this administration deserves our full unquestioning support due to their farsighted political agenda and absolutely brilliant foreign policy decisions!

http://market-tic...t=229416
Vietvet
3 / 5 (2) Sep 17, 2014
Yup, this administration deserves our full unquestioning support due to their farsighted political agenda and absolutely brilliant foreign policy decisions!

http://market-tic...t=229416


"In all, 85 Democrats and 71 Republicans voted to deny Obama the authority he sought. The measure passed on the strength of 159 votes from Republicans and 114 from Democrats."
MR166
2.3 / 5 (3) Sep 17, 2014
I see Vet the consequences don't matter just as long as you can blame it on the Republicans.
SteveS
3 / 5 (2) Sep 18, 2014
I see Vet the consequences don't matter just as long as you can blame it on the Republicans.

The way I see it is that Vietvet just provided balance to your off topic, random, and obviously partisan comment, it's almost as if the consequences don't matter to you just as long as you can blame it on the current administration.
Yup, this administration deserves our full unquestioning support due to their farsighted political agenda and absolutely brilliant foreign policy decisions!

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