WUWT readers may remember this article:
Watch the Wilkins ice shelf collapse in time lapse animation – looks like ‘current’ events to me where mechanisms other than melt were discussed. It was pointed out that this photo appeared to be showing a stress crack, like the sort you’d get from a wave. Melt makes rounded irregular edges, not sharp straight line ones.
http://www.ogleearth.com/wissm.jpg
Now there’s a study from Scripps that suggests that long period waves could be a big factor.
Antarctic Ice Shelf Collapse Possibly Triggered by Ocean Waves, Scripps-led Study Finds
Extremely long waves could have initiated 2008 collapse events
Scripps Institution of Oceanography / University of California, San Diego
Depicting a cause-and-effect scenario that spans thousands of miles, a scientist at Scripps Institution of Oceanography at UC San Diego and his collaborators discovered that ocean waves originating along the Pacific coasts of North and South America impact Antarctic ice shelves and could play a role in their catastrophic collapse.
Image: Joe Harrigan
Peter Bromirski of Scripps Oceanography is the lead scientist in a new study published in the journal Geophysical Research Letters that describes how storms over the North Pacific Ocean may be transferring enough wave energy to destabilize Antarctic ice shelves. The California Department of Boating and Waterways and the National Science Foundation supported the study.
According to Bromirski, storm-driven ocean swells travel across the Pacific Ocean and break along the coastlines of North and South America, where they are transformed into very long-period ocean waves called “infragravity waves” that travel vast distances to Antarctica.
Bromirski, along with coauthors Olga Sergienko of Princeton University and Douglas MacAyeal of the University of Chicago, propose that the southbound travelling infragravity waves “may be a key mechanical agent that contributes to the production and/or expansion of the pre-existing crevasse fields on ice shelves,” and that the infragravity waves also may provide the trigger necessary to initiate the collapse process.
Peter Bromirski
The researchers used seismic data collected on the Ross Ice Shelf to identify signals generated by infragravity waves that originated along the Northern California and British Columbia coasts, and modeled how much stress an ice shelf suffers in response to infragravity wave impacts. Bromirski said only recently has technology advanced to allow scientists to deploy seismometers for the extended periods on the ice shelf needed to capture such signals.
The study found that each of the Wilkins Ice Shelf breakup events in 2008 coincided with the estimated arrival of infragravity waves. The authors note that such waves could affect ice shelf stability by opening crevasses, reducing ice integrity through fracturing and initiating a collapse. “(Infragravity waves) may produce ice-shelf fractures that enable abrupt disintegration of ice shelves that are also affected by strong surface melting,” the authors note in the paper.
Whether increased infragravity wave frequency and energy induced by heightened storm intensity associated with climate change ultimately contribute to or trigger ice shelf collapse is an open question at this point, said Bromirski. More data from Antarctica are needed to make such a connection, he said.
In separate research published last year, Bromirski and Peter Gerstoft of Scripps Oceanography showed that infragravity waves along the West Coast also generate a curious “hum”-subsonic noise too low for humans to hear (see Scripps explorations story Earth Sounds from Central America).
h/t to Dr. Richard North
Why are anti-AGW believers seeing papers they like now?
Is it because Jones is not sitting in his ‘chair” now, or is it because others are concerned about the possibility they might be removed from their own ‘chair’ if the shenanigans continue?
Maybe it is just a coincidence. I dunno.
Robert you would explain then why every paper ever reported on before Copenhagen was alarmist?
As for non-believer, it ain’t a faith Bob. It’s science.
I wasn’t able to open the BBC link but this was up on NewsBusters.org, Phil Jones and the BBC.
http://newsbusters.org/blogs/noel-sheppard/2010/02/13/climategate-scientist-says-g-warming-debate-not-over-discusses-hide-d
“ocean waves originating along the Pacific coasts of North and South America impact Antarctic ice shelves and could play a role in their catastrophic collapse.”
By what measure was the breaking off of part of the shelf a “catastrophe”.
Is there a list somewhere of the damages caused?
Beyond parody.
“Carbon dioxide is “essentially harmless” to human beings and good for plants. So now will you stop worrying about global warming? Utah’s House of Representatives apparently has at least. Officially the most Republican state in America, its political masters have adopted a resolution condemning “climate alarmists”, and disputing any scientific basis for global warming.
The measure, which passed by 56-17, has no legal force, though it was predictably claimed by climate change sceptics as a great victory in the wake of the controversy caused by a mistake over Himalayan glaciers in the UN’s landmark report on global warming.”
Utah Legislates Against ‘Climate Alarmists’: Just a Ruse to Control Population
http://www.infowars.com/utah-legislates-against-climate-alarmists-just-a-ruse-to-control-population/
Robert (16:06:46) :
Now, just because the world stopped warming 10 years ago and has been cooling the last 2 years rapidly doesn’t mean that we all have confirmation bias.
Nobody is saying that since the world is cooling rapidly that we will now enter an Ice Age faster than previously imagined (quick, pass AGC legislation and tax/ban the crud out of refrigerants). Hansen, Schneider and others already blew that trumpet in the 70’s, and look what happened.
Nobody is screaming that the Sea Level will drop catastrophically and high-center the ports of the world.
Nobody is shouting the dire consequences of glaciers running down the Mississippi and the Nile, or running frantically down the street with “The world will end with NY buried under a mile of ice.
What we are saying is that AGW isn’t happening, and the world’s weather is confirming it week after week, month after month, year after year.
That’s not bias, that’s what’s for dinner.
I’m curious: has anyone measured the elevation of the separated portions of the ice sheet and compared it with the intact portion? If there is no difference, then the wave theory is persuasive. If it’s lower, then what: lower sea level? If it’s higher, then maybe there’s some rise in sea level.
The measurement shouldn’t be a problem.
“Whether increased infragravity wave frequency and energy induced by heightened storm intensity associated with climate change ultimately contribute to or trigger ice shelf collapse is an open question at this point, said Bromirski. More data from Antarctica are needed to make such a connection, he said.”
or to put it another way:
“I’ve inserted the obligatory possible link to climate change. Now can I have some more grant money for further studies.”
I actually thought about this possibility when I read the article on the ice breaking off but then shrugged it off as not possible.
Now, just because the world stopped warming 10 years ago and has been cooling the last 2 years rapidly doesn’t mean that we all have confirmation bias.
Two years later and still waiting for the “not warming/cooling” confirmation …
http://tamino.wordpress.com/2008/01/31/you-bet/
Whilst reading the article, I was wondering when the de riguer AGW reference would come. I was not disappointed. Surely it must now rank up there with “do not try this at home – this …..(study) is performed by highly trained …. (prp scientists)”.
In my simple world of civil engineering, ice would be up there with “brittle” materials like concrete that crack due to low tensile strength. Throw in some cyclic loading and we have fatigue failure. So where is the cause of the tensile stress? Well, we do have that (possibly AGW enhanced) wave action. Complicate it with buoyancy effects due to ice thickness, daily tidal effects, freeze thaw cycles (change in loading), grounding, wind loading and a temperature difference between the sea below to air above. Throw in some glacier action causing lateral loading and I see a very complicated dynamic system. Is it “new” ice, old ice, (rotten ice ;))? Are there residual flaws or fault lines in the ice shelf from some geophysical effect?
Call me a skeptic but I just don’t see this event as some kind of “Big Wednesday” of infragravity waves.
This alarming title is begging for an illustration of the propagation of these long period ‘infragravity waves. Without this it is difficult to discuss in any detail how these waves arrive at the break-up site and produce such fractures.
Where I live – In Western Australia – we see a lot of these infra-gravity waves going past. But in the opposite direction, from Antarctica Northwards. We have very large swell here that can exceed 10 metres (30 feet) at some locations off the coast. I know because it was my job to measure it with directional wave buoys for a number of years.
The source of these waves are the very deep depressions circling the Antarctic continent. I would have thought that these massive wave generators near to Antarctica would have a much greater effect on the Antarctic shoreline than generators half way around the world.
Good stuff. We’ve been in Antartica permenantly since the 50s? And satellite coverage since the 70’s? Part of the problem here, as in much else about climatology, is the hubris of jumping to the conclusion that just because its the first time *we’ve been there to see it*, it must be new.
Otoh, to say that these infragravity waves could very well be the trigger, says nothing about what makes ice shelves vulnerable to these triggers in the first place. Could be a natural aging process. . . could be due to thinning of the shelf due to global warming. I don’t see any particular reason to favor one theory over the other right now.
Noodlehead (16:46:55):
“Why are anti-AGW believers…”
Please. The proper term is “skeptics.” Scientific skeptics, if you prefer. As in, skeptical of the unproven CAGW conjecture. Thanx.
[snip]
“Deniers” is not acceptable here. ~dbs, mod.]
Ron Broberg (17:51:22) :
If it’s proof you want, just listen to what people are griping about.
They’re mostly griping about the cold.
Why miss out on one of life greatest pleasures?
If it’s not cold enough for you, move to where it is, then you can enjoy griping about how cold it is.
You don’t hear Gore griping about how hot it is. He’s too busy buying up beachfront properties while scaring everyone else into selling.
Better yet, if you are still convinced that AGW is the way to go, ask your Real Estate Broker if the Yukon is right for you. Get it while it’s hot.
Who would have thought that long period ocean waves could fracture ice shelves? Of course the authors have to genuflect to the AGW consensus with the gratuitous “ice shelves that are also affected by strong surface melting”.
“[Infragravity waves] may produce ice-shelf fractures that enable abrupt disintegration of ice shelves that are also affected by strong surface melting,” the authors note in the paper.
“Surface melting” my foot. Those icebergs in the top image are 600 feet thick. Any “surface” melting is occurring 70 feet above sea level, and doing so despite the temperatures so low that the salt water is freezing down on the sea surface. Not likely.
In the Wilkins breakup animation, note that the time between when we first see the green highlighted ice, through it’s compression of the shelf, to its final departure out to sea, is Two Weeks. That is one heavy swell, very “infra” indeed.
It isn’t hard to imagine how much the sea level steadily rose during those weeks, and how much stress that put on the 600 ft thick, brittle ice shelf floating on it.
It would be interesting to see the Jason sea level data for that area, if it’s available.
Surprised there wasn’t a mention of tsumanis and their added stress. They involve the whole column of water. Even small ones would do some damage, or weakening. That Sumatra quake created a pretty nasty one a few years ago. Even that Samoa one recently had to have some effect on those ice shelves.
Didn’t WUWT have something about cracks and Ice shelves a while back? Something about tidal influences and waves…. Can’t remember now.
Looks like us unruly mob are way ahead of them… But it is good to see it scientifically confirmed in a new paper.
Wonders never cease….
For more information regarding the Wilkins Ice Shelf break up I posted an article on this subject last July at http://webdiary.com.au/cms/?q=node/2971, which covers some of the issues raised in this blog and elsewhere.
Robert — Confirmation bias is so interesting. When anti-AGW believers don’t see papers they like, it’s evidence of censorship. When they do, it’s evidence that censorship is breaking down and failing.
You have this backwards.
Essentially what you’re seeing the skeptics happy about is that there seems to be a growing movement toward some rationality.
As the AGW crowd would have it, “climate change” means that there are warmer winters with less snow. Or there are cooler winters with lots of snow. Essentially, what they’re claiming belongs more in the realm of a belief system. If it’s not falsifiable, it’s not a real hypothesis, much less a theory.
A theory, meanwhile, makes predictions. If the theory is that we’re going to have warmer snow free winters in the US, having the opposite happens falsifies the prediction. If the prediction is to have colder snowier winters, a warmer, snow free winter falsifies the prediction. Saying “we’ll have warmer winters except when we don’t” is simply nonsense. It’s certainly not science, and any child could make this same prediction.
As a result sketpics see papers that seek to attribute falsifiable theory to physical phenomenae and cheer accordingly. Ice shelves break because of warming (how? We’re not sure, we’ll get back to you) except when they don’t isn’t falsifiable. Attribution of ice shelf breakage due to the action of oceanic wave systems IS falsifiable.
If you can’t falsify it, it ain’t a theory. It’s painfully simple.
And sure, skeptics do see evidence of censorship and tampering and politically motivated cheerleading when there’s a thousand unfalsifiable claims made for AGW — (e.g. http://www.numberwatch.co.uk/warmlist.htm or http://www.businessandmedia.org/articles/2008/20080206170159.aspx)
Ian Read (20:45:29) :
For more information regarding the Wilkins Ice Shelf break up I posted an article on this subject last July at http://webdiary.com.au/cms/?q=node/2971, which covers some of the issues raised in this blog and elsewhere.
Nice takedown, Ian. Even without any special knowledge of ice shelves, my first question would be and was, “why wouldn’t an ice shelf fracture?” Why would anyone presume they go for very long periods without breaking?
Robert: “Confirmation bias is so interesting. When anti-AGW believers don’t see papers they like, it’s evidence of censorship. When they do, it’s evidence that censorship is breaking down and failing.”
I would have thought continued belief in CO2 AGW doctrine a much better and more interesting example of “confirmation bias”, especially the delusional kind where it is instead alleged that the non-delusional have a bias.