From the University of Colorado at Boulder, worry over something that is a natural process that has happened for thousands of years. You gotta love this one: ” Catastrophic lake drainages were 3.5 times more likely to occur during the warmest years than the coldest years.”. Gee, ya think? Or how about this one: “Once the water reaches the ice sheet’s belly that abuts underlying rock, it may turn the ice-bed surface into a Slip ‘N Slide, lubricating the ice sheet’s glide into the ocean.”. Hmm well, the “may” weasel word says that they really don’t know. The Greenland ice sheet is up to 1.8 miles (3 kilometers.) thick in the middle, and that huge weight depresses the underlying crust, which assumes the concave shape of a saucer. So I guess I’m not too worried about it slip-sliding away. And as WUWT has covered before, the warming in Greenland has some issues.
CU-Boulder study shows Greenland may be slip-sliding away due to surface lake melt
Like snow sliding off a roof on a sunny day, the Greenland Ice Sheet may be sliding faster into the ocean due to massive releases of meltwater from surface lakes, according to a new study by the University of Colorado Boulder-based Cooperative Institute for Research in Environmental Sciences.
Such lake drainages may affect sea-level rise, with implications for coastal communities, according to the researchers. “This is the first evidence that Greenland’s ‘supraglacial’ lakes have responded to recent increases in surface meltwater production by draining more frequently, as opposed to growing in size,” says CIRES research associate William Colgan, who co-led the new study with CU-Boulder computer science doctoral student Yu-Li Liang.
During summer, meltwater pools into lakes on the ice sheet’s surface. When the water pressure gets high enough, the ice fractures beneath the lake, forming a vertical drainpipe, and “a huge burst of water quickly pulses through to the bed of the ice sheet,” Colgan said.
The study is being published online today by the journal Remote Sensing of the Environment. The study was funded by the Arctic Sciences Program of the National Science Foundation.
The researchers used satellite images along with innovative feature-recognition software to monitor nearly 1,000 lakes on a Connecticut-sized portion of the ice sheet over a 10-year period. They discovered that as the climate warms, such catastrophic lake drainages are increasing in frequency. Catastrophic lake drainages were 3.5 times more likely to occur during the warmest years than the coldest years.
During a typical catastrophic lake drainage, about 1 million cubic meters of meltwater — which is equivalent to the volume of about 4,000 Olympic swimming pools — funnels to the ice sheet’s underside within a day or two. Once the water reaches the ice sheet’s belly that abuts underlying rock, it may turn the ice-bed surface into a Slip ‘N Slide, lubricating the ice sheet’s glide into the ocean. This would accelerate the sea-level rise associated with climate change.
Alternatively, however, the lake drainages may carve out sub-glacial “sewers” to efficiently route water to the ocean. “This would drain the ice sheet’s water, making less water available for ice-sheet sliding,” Colgan said. That would slow the ice sheet’s migration into the ocean and decelerate sea-level rise.
“Lake drainages are a wild card in terms of whether they enhance or decrease the ice sheet’s slide,” Colgan said. Finding out which scenario is correct is a pressing question for climate models and for communities preparing for sea-level change, he said.
For the study, the researchers developed new feature-recognition software capable of identifying supraglacial lakes in satellite images and determining their size and when they appear and disappear. “Previously, much of this had to be double-checked manually,” Colgan said. “Now we feed the images into the code, and the program can recognize whether a feature is a lake or not, with high confidence and no manual intervention.”
Automating the process was vital since the study looked at more than 9,000 images. The researchers verified the program’s accuracy by manually looking at about 30 percent of the images over 30 percent of the study area. They found that the algorithm — a step-by-step procedure for calculations — correctly detected and tracked 99 percent of supraglacial lakes.
The program could be useful in future studies to determine how lake drainages affect sea-level rise, according to the researchers. CIRES co-authors on the team include Konrad Steffen, Waleed Abdalati, Julienne Stroeve and Nicolas Bayou.
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Don J. Easterbrook says:
April 17, 2012 at 5:13 am
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Thanks for that common sense Don.
…and the opening gala night could feature famous warmists being thrown to the polar bears whilst 10,000 choreographed Emperor penguins do a crazy kindof 70’s smooch to AbbA’s ‘Dancing Queen’ as the marvellous northern lights weave their magic across the polar sky…lovely.
When the ice sheet goes, I want to be on top of it. That’s going to be one heck of a ride on the biggest surfboard ever! Maybe we could direct it over toward the Sahara or something, do some good.
— Sorry, just trying to see the world through Alarmist eyes. It seems to look like it did when I was a teenager.
An earlier study ( http://www.guardian.co.uk/environment/2011/jan/26/greenland-ice-sheet-climate-change ) appears to have ruled out “catastrophic” slippage.
“We have a model of a catastrophic fantasy! More funding, please?
→$$$
Thankyew, thankyew!!!”
Has anyone tried to find out where the water that dissappears down the sink holes re-emerges? Perhaps if they tipped a load of yellow plastic ducks down one there could be a competition to see who’s duck got home first.
CIRES co-authors on the team include Konrad Steffen, Waleed Abdalati, Julienne Stroeve and Nicolas Bayou.
*The* Waleed Abdalati? The Big Kahuna of NASA playing a bit part in a scenario written by a research assistant and a grad student? WUWT?
Further to Don Easterbrook’s comment, the mechanism proposed in this paper is not particularly new in terms of understanding the interactions between sudden inputs of water to the glacier bed(‘catastrophic’ i.e. rapid in this context – for those balking at the termminology) and glacier movement. As Don rightly mentions, there is a complex network of drainage pathways beneath the ice. What matters, during supraglacial lake drainage is the volume of water that reaches the bed vs. the ability of the subglacial drainageways to evacuate this water. In a situation where the volume of water and the rate at which the water reaches the bed (more importantly) are so large that they exceed the capacity of the drainage networks to evacuate the water, subglacial water pressure can increase to the point of localy lifting the ice of its bed and allowing water to effectively spead laterally beyond the margins of the subglacial channel. This happens whether the subglacial channels are in bedrock or sediment (thought the mechanics are slightly different). There is an added complexity in the fact that as the water drains, it also melts the ice and enlarges existing tunnels by ‘eroding’ and melting the ice. At the same time, the ice deforms to fill this gap (but usually at a much slower rate than the water flow). Again, this reinforces the idea that these are short-lived events. When water spreads laterally, the ice is effectively sliding on a layer of water. There have been a number of cases in alpine glaciers, Antarctica, and Greenland that show a localized acceleration of the glacier after lake drainage.
Sea-level would increase (by a minuscule amount for one of these drainage events) if the meltwater reaches the ocean and IF formerly grounded ice moves into the ocean to form a shelf or icebergs. The important things here is that these events are localized and short-lived (transient). The idea that the whole ice sheet is slip-sliding away is beyond fantasy. It is a real travesty that scientific results are written in such a way!
Re: Bill and R Barker
It is a very valid question to ask how much of the lake water actually makes it out of the glacier. Depending on the geometry of the ice and the glacier bed, the meltwater flowing at the base can refreeze to the base of the ice (this is seen in Iceland and recently in Antarctica). Therefore, not all of the lake water necessarily goes to sliding, and not all the water actually reaches the ocean. How much is a big unknown and determined by the local conditions (lake volume, bed topography, etc.)
– R barker
This freezing ice would potentially have an effect on ice core measurements, especially since the isotopic composition of the refrozen water at the base would originate from the surface or from melting of glacier ice. Most ice cores are taken near the summit of the ice sheets where there little to no surface melting and hence little chance of contamination. However, a recent study in Antarctica (profiled on WUWT)
http://wattsupwiththat.com/2011/03/08/east-antarctic-ice-sheet-getting-thicker-from-underneath/
showed that a lot of water (generated by melting at the base of the ice) could flow and refreeze to the base of the ice far into the centre of the ice sheet. Again, the local conditions are critical so it is definitely buyer beware when extrapolating and drawing broad conclusions.
Bloke down the pub says:
April 17, 2012 at 5:47 am
…Perhaps if they tipped a load of yellow plastic ducks down one there could be a competition to see who’s duck got home first.
ROFLMAO. Oh, the visuals!
Brian H got it right. They want more money to keep their gravy train running. Say something scarey and get more money to study the non-issue to death. Those people ,like so many sucking on the agw teat, are pathetic. By the way Anthony, I like your title to this rediculousness.
Don J. Easterbrook says:
April 17, 2012 at 5:13 am
Thanks for some REAL info, Don.
Those “researchers” should be attending ‘Bolder’ U as their computer generated musings
are just a waste of time and money.
Has Boulder U any credibility?
I hope nobody thinks that there is anything new about all this. Here is how A. E. Nordenskiöld describes the Greenland icecap from a visit in july 1870 in approximately the sama area as the current study:
“After the melting of the snow there appears besides a number of inequalities, and the clefts previously covered with a fragile snow-bridge now gape before the wanderer where he goes forward, with their bluish-black abysses, bottomless as far as we can depend on ocular evidence. At some places there are also to be found in the ice extensive shallow depressions, down whose sides innumerable rapid streams flow in beds of azure-blue ice, often of such a volume of water as to form actual rivers. They generally debouch in a lake situated in the middle of the depression. The lake has generally an underground outlet through a grotto-vault of ice several thousands of feet high. At other places a river is to be seen, which has bored itself a hole through the ice-sheet, down which it suddenly disappears with a roar and din which are heard far and wide, and at a little distance from it there is projected from the ice a column of water, which, like a geyser with a large intermittent jet in which the water is mixed with air, rises to a great height.”
Note that this was the first time ever that a scientist penetrated the Greenland Icecap, and that it happened right at the end of the Little Ice Age. Plus ça change, plus c’est la même chose.
One comment on the bowl-shape of the land surface: The land surface of Greenland is depressed below sea level *because* of the weight of the ice sheet. If or when the ice sheet melts, the land surface will rise over a period of several thousand years. The phenomenon of “glacial isostatic rebound” has been very well documented in areas formerly covered by ice. Northern Scandinavia and FInland are probably the best example.
Mike McMillan says:
April 17, 2012 at 3:56 am
“Much of the central axis of Greenland is 200 meters below sea level, with mountains around the periphery…”
Mike – thanks for the comment and the cross sections. Where did you get those, they are great. I’ve added them to my Greenland files. Here’s a map further illustrating your point:
http://commons.wikimedia.org/wiki/File:F1_large2.JPG
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Don J. Easterbrook says:
April 17, 2012 at 5:13 am
“I haven’t crawled around under the Greenland ice sheet but I have crawled around beneath the Iceland ice cap and large alpine glaciers in Alaska…”
Don, thanks for taking time to make an informed, expert comment to lend some reality to the discussion.
One time some years ago, when I was in the military, young adventurous and foolish, I was on duty in Alaska and rode a bike up to a glacier – alone. I ventured out some ways on the glacier having no idea what kind of danger I was exposing myself to. I wandered in far enough that I couldn’t clearly see features from where I came – probably a half mile to a mile. I can still see that place in my minds eye: cold, dry, brilliantly white, quiet but for the wind.
‘Supraglacialslipsialidosis’ – isn’t that when you get a smelly infection above your tonsils and they have to feed you ice cream as it’s the only thing that will slip down?
Zoot Cadillac,
I was being facetious. All is well.
R Barker says:
“What does all the melting and draining do to the ice core measurements?”
It is my guess that all these lakes only form near the coast and than only in summer where the altitude is low enough for the temperature to get just above freezing. But in the centre of the Greenland plateau the altitude is high enough so that the temperature never gets above freezing. It is for that reason that the GISP2 ice core station is situated in the centre of Greenland, because any surface melting would otherwise destroy the information contained in the ice cores.
By the way those subglacial drainage channels aren’t just theory. On Svalbard where glaciers are thinner and the ice is quite cold (and stiff) they sometimes remain open in winter and it is actually possible to penetrate up to several kilometers beneath the glaciers:
Humlum, O et al. 2005: Late-Holocene glacier growth in Svalbard, documented by subglacial relict vegetation and living soil microbes. The Holocene 15(3):396-407
available here: http://epic.awi.de/11679/1/Hum2005a.pdf
They use the c word many times. I used a different c word when I read this nonsense.
Study: The draining of meltwater pools may have a lubricating effect. “Alternatively, however”, it may not.
These budding scientists seem to also have studied their tautological tables and learned how to make unfalsifiable statements—the bedrock of climate science.
The influence of the study co-author and NASA Chief Scientist Waleed Abdalati is undeniable.
I read this post twice to make sure my BSometer was correct – so water drains down a freezing column over 2kms thick. By the time it hits bedrock – if it ever does – it will be a crystal mush which will rapidly freeze. Remember, the temperature of this water will only be just above freezing as it starts its journey. As the water refreezes, it will expand and act as a very effective cement.
OK, there are going to be shear zones within the ice, which will be open, but if water does enter them it will rapidly refreeze. If the supposed problem suggested here was real, it would be in the record of recent (last 8,000 years) changes in ocean levels. Is it there? Answer: No. So like most things to do with ‘climate science’, it is a non-problem, but a scary non-problem.
But this comment says it all: ““Lake drainages are a wild card in terms of whether they enhance or decrease the ice sheet’s slide,” Colgan said. Finding out which scenario is correct is a
pressing question for climate models and for communities preparing for sea-level change.”
The translation is: “Gimme more grant money, and gimme it now!”
As water is more dense than ice under some conditions, there is good likelihood that water is present at the bottom of the glacier anyhow as heat migrates up from the interior of the crust.
Meltwater is an annual reality and to think that it suddenly becomes a lubricant better than normal is fear mongering, Boogeyman in the closet propaganda.
What we should really be worrying about is the obvious number of really stupid and/or dishonest scientists out there and how dangerous they are and can be. I get the feeling that stupid level has been rising as government funds melt in their pockets. Soon we will be over our heads with stupid!
Borehole temperature measurements from NGRIP which reached bedrock show that the glacier is -30C on top, -32C as you get down to 1500 metres and then is actually melting at the bottom of the glacier at 3000 metres down due to the geothermal heat propagating up. The temperature at the bottom is -2.4C but due to the pressure, it is enough for liquid water.
So there is already some liquid water at the bottom of the glacier although the conditions might be slightly different in different locations than NGRIP.
http://www.iceandclimate.nbi.ku.dk/research/flowofice/borehole_logging/
Just noting that models of how temperatures migrate through the glacier is how they have calibrated the isotope measurements in Greenland and what provides the estimate of a decline in temperatures of -20C at the last glacial maximum in Greenland. I think there are significant errors in these borehole thermometry models.
OFF TOPIC
There is yet another biased poll being used for political purposes here http://www.inews880.com/index.aspx
I was wondering if the WUWT crowd would come on and vote for sanity.