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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Does anyone know the temperature at the interface of the rock and and the bottom of the ice sheet?
“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”
That would be 250 cubic meter of water per Olympic swimming pool.
“Olympic size pools measure: 50 metres long, 25 metres wide, and a minimum of 2 metres deep.”
http://wiki.answers.com/Q/How_much_water_does_an_Olympic_sized_swimming_pool_hold
That’s a minimum of 2,500 cubic meters.
What’s an order of magnitude amongst friends. Did they use a GCM to compute that?
And that very cold meltwater could also fall 3klms into much colder regions to refreeze and grout things back together even tighter.
Is it possible that the water that is near its freezing point could re-freeze as it is cooled passing through a mile of ice and then act as a glue to cement the ice sheet to the rock? This seems like a 3rd possibility in addition to the slip-n-slide or the “sewer” idea.
Now I am terrified that umteen million cubic miles of ice is about to slide off into the ocean. I cannot sleep tonight as billions of souls will perish in with the rising of the seas. Then I keep reading and they say maybe the opposite is true, then I feel better.
Perhaps nothing is happening that is not normal, maybe a good plumber needs to access the situation.
Interesting. Once the hand-wringing and doom starts from the usual suspects perhaps we could distract them for a moment with some news that ought to cheer them up. It’s not as bad as we thought.
Himalayan glaciers actually GAINING ice, space scans show
From the abstract:
It is unclear whether this [increased surface meltwater production] will ultimately increase or decrease the basal sliding sensitivity of interior regions of the Greenland Ice Sheet.
Slightly off topic, a question about Arctic sea ice: am I the only one to notice that the Hansen data (Arctic Roos) have not been updated since April 5, twelve days ago ?! Satellite problems? Can anyone comment on this?
The Connecticut-sized area is near Jacobshaven, where the ice sheet is thin.
The Greenland ice sheet covers an area of ~122 Connecticuts.
The Greenland ice sheet has a volume of 10.4 trillion olympic-sized swimming pools.
The “catastrophic lake drainages” may either destabilize or stabilize the Greenland ice sheet.
Why did these grad students merit a Eureka Alert?
Um… the water can’t lubricate an ice sheet’s slide unless the water gets actually underneath the main bulk of the ice. Simply having some flowing water around the bottom is not the same as lubricating it for motion.
Either someone doesn’t understand ice or they are counting on the reader not understanding ice, or “cold” in general… if the first, why are they pontificating about it, if the second, what’s their scam?
Much of the central axis of Greenland is 200 feet below sea level, with mountains around the periphery. With enough warming before the next ice age, we may get Lake Greenland, but she’s not gonna slide nowhere.
map –
http://i44.tinypic.com/r10nd0.jpg
cross-section –
http://i41.tinypic.com/r045n6.jpg
Lakes were monitored over a 10-year period and “as the climate warms.” Seems like an awfully short period of time to define a climatic warming trend. Also the lake drainage is described as catastrophic. I find it a stretch to define a natural event that apparently harms no one and happens rather frequently as “catastrophic.” When people are killed or massive property damage happens, then draining of one of these lakes might be catastrophic. Why lakes and not pools of melt water?
Actually, I meant central Greenland is 200 meters below sea level, not 200 feet.. I always have trouble converting feet to Olympic swimming pools.
I’m betting the house on subterranean sewers. Since Greenland has undergone numerous periods in which it was warmer in the past than now (and didn’t slide slide away from inside it’s bowl), one should be able to safely say that the future holds similar results. What I find interesting is that I made this simple deduction at 7am while sipping coffee for a minute or two. Are we to conclude that these researchers over several years of study considered “slip and slide” and “sewers” under the context of our temperature past and concluded that the “slip and slide’ best represented the evidence?? What a sad scientific discipline climate science has become.
I think we need to do some research into how many climate related papers start out with an alarmist argument, then conclude, after much modelling, that it is all a mystery but we need to do further research because we ‘know’ it is all bad just not how much.
The sad thing is that this attitude is spreading out into other disciplines.
ZootCadillac says:
April 17, 2012 at 3:33 am
How can that be? The Himalayas will have melted by 2035, or 2305, or 2350, 0r 2503, or 2530. Take your pick. Unless the Himalayas are hit with a massive drought the likes of which have not been seen in our historical record, I not going to lose any sleep over snow and ice melt at 20-30km up now or ever.
What does all the melting and draining do to the ice core measurements?
Is “catastrophic” the new “wicked”? Hyperbole drives me nuts unless it involves a joke.
Unfortunately the article and review are both behind a paywall at Nature Geosciences so I don’t know the details. However the article at El Reg states:
Something about not shooting messengers.
The funny this is that the song “Slip Sliding” is a rather appropriate theme song for CAGW and CAGW modeling: “You know the nearer your destination/ the more your slip sliding away”
I like the way these events are described as ‘catastrophic’ lake drainages.
Catastrophe
An event causing great and often sudden damage or suffering.
The denouement of a drama, esp. a classical tragedy.
The only thing slippery about this study is the use of the English Language!
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. What I saw was pretty amazing–lots of shearing within the base of the ice and many subglacial drainage tunnels. What I came away with was a fuller appreciation of what we already knew from borehole deformation–glaciers are not brittle masses of ice sliding along on their base like a brick; a good deal of the movement of ice is by basal shearing within the ice itself. The area under a glacier whose base is not frozen to the underlying rock is already wet, with abundant evidence of plenty of meltwater. But the meltwater isn’t distributed as a flowing film between the ice and rock–it is concentrated in numerous subglacial channels that don’t really affect basal sliding that much. So adding more water doesn’t really decrease the coefficient of friction between the ice and its base very much because it is already wet there. So how likely is it that drainage of supraglacial lakes is going to cause the Greenland ice sheet to ‘slide into the sea’? This is a geofantasy that could only be imagined by a computer model that has never seen a real glacier.
Another aspect of this geofantasy is if melting of surface ice (which is a perfectly natural process that is not unique to the present), why hasn’t the ice sheet slid into the ocean before. We know from the Greenland ice cores that for all but the last few thousand years,, the climate for the past 10,000 years has been warmer than present. So during all of that time, why don’t we see any evidence at all of the phenomena these authors are postulating? Most likely because it hasn’t happened before. If there is no evidence that this has never happened in the past, why should we worry about it happening now in a climate that isn’t even as warm as most of the past ten millenia?
There really is a lot of chaff in the scientific world these days, lucky they don’t influence Goverment policy in anyway.
I assume the scientist are vrying for Disney Land Ice World a heater and you got a water park.
A floating ice scultpure of Mike Mann’s pointy head? Could tow it slowly down to Iceland and hold the next winter olympics on it… the IPCC could maybe sponsor the ice hockey comp??
Does no one in the press understand about friction and mass?