From the University of Colorado at Boulder Water flowing through ice sheets accelerates warming, could speed up ice flow
Caption: Standing melt water in Greenland crevasses can carry warmth to the ice sheet’s interior, accelerating the thermal response of the ice sheet to climate change.
Credit: Image courtesy Konrad Steffen, CIRES
Melt water flowing through ice sheets via crevasses, fractures and large drains called moulins can carry warmth into ice sheet interiors, greatly accelerating the thermal response of an ice sheet to climate change, according to a new study involving the University of Colorado at Boulder.
The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models. Ice flows more readily as it warms, so a warming climate can increase ice flows on ice sheets much faster than previously thought, said the study authors.
“We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years, ” said lead author Thomas Phillips, a research scientist with Cooperative Institute for Research in Environmental Sciences. CIRES is a joint institute between CU-Boulder and the National Oceanic and Atmospheric Administration.
Phillips, along with CU-Boulder civil, environmental and architectural engineering Professor Harihar Rajaram and CIRES Director Konrad Steffen described their results in a paper published online this week in Geophysical Research Letters.
Conventional thermal models of ice sheets do not factor in the presence of water within the ice sheet as a warming agent, but instead use models that primarily consider ice-sheet heating by warmer air on the ice sheet surface. In water’s absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.
But the Greenland ice sheet is not one solid, smooth mass of ice. As the ice flows towards the coast, grating on bedrock, crevasses and new fractures form in the upper 100 feet of the ice sheet. Melt water flowing through these openings can create “ice caves” and networks of “pipes” that can carry water through the ice and spreading warmth, the authors concluded.
To quantify the influence of melt water, the scientists modeled what would happen to the ice sheet temperature if water flowed through it for eight weeks every summer — about the length of the active melt season. The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades depending on the spacing of crevasses and other “pipes” that bring warmer water into the ice sheet in summer.
“The key difference between our model and previous models is that we include heat exchange between water flowing through the ice sheet and the ice,” said Rajaram.
Several factors contributed to the warming and resulting acceleration of ice flow, including the fact that flowing water into the ice sheets can stay in liquid form even through the winter, slowing seasonal cooling. In addition, warmer ice sheets are more susceptible to increases of water flow, including the basal lubrication of ice that allows ice to flow more readily on bedrock.
A third factor is melt water cascading downward into the ice, which warms the surrounding ice. In this process the water can refreeze, creating additional cracks in the more vulnerable warm ice, according to the study.
Taken together, the interactions between water, temperature, and ice velocity spell even more rapid changes to ice sheets in a changing climate than currently anticipated, the authors concluded. After comparing observed temperature profiles from Greenland with the new model described in the paper, the authors concluded the observations were unexplainable unless they accounted for warming.
“The fact that the ice temperatures warm rather quickly is really the key piece that’s been overlooked in models currently being used to determine how Greenland responds to climate warming,” Steffen said. “However, this process is not the ‘death knell’ for the ice sheet. Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.
This study was funded by NASA’s Cryosphere Science Program.
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Let’s see….
Melt water from the ice sheet surface flows through cracks and fissures, taking heat with it. Greenland ice sheet is really really big so that’s a lot of energy. Multiply by all the glaciers in the world subject to the same process… tons of energy that the models didn’t previously account for.
Someone want to call Trenberth and tell him the missing heat has been found? If he says the amount is wrong they can just adjust the model and PRESTO! problem fixed.
If they are claiming Global temperature’s are rising from the greenhouse effect, Greenland,the Arctic and west Antarctic are loosing so much ice mass, how on Earth can they validate their model outcome while Sea levels are not in lockstep?,In a decade or so they will worm their way out by saying their failed lounge chair so-called “studies” were only “scenarios”
Wait up!!”NEW STUDY” shows sea floor is collapsing under the weight of the excess melt-water as the result of DAGW is putting more pressure on the Earths molten core,causing the increase in Volcanic activity.
Now it’s all making sense
RE: pRadio : (November 5, 2010 at 4:25 am )
“Typical, keep changing the Model until you get the answer you want!”
That sounds like a “Spiral Development Process” except, in that case, you keep changing your software in a converging trial and error process until it works properly.
http://en.wikipedia.org/wiki/Spiral_model
Does the water in the crevasses really appear that blue? If so, anyone know why?
“Does the water in the crevasses really appear that blue? If so, anyone know why?”
Water is blue and therefore ice is blue.
“Does the water in the crevasses really appear that blue? If so, anyone know why?”
Yes it does. In an ordinary lake the light is reflected from the bottom, in a supraglacial lake most of the light has gone some distance down into the ice before being scattered/reflected back. Old glacier ice (“blue ice”) absorbs light preferentially in the red part of the spectrum, so the upcoming light is already rather strongly bluish before passing through the water.
Thanks! I’m always amazed when some groups blather on about current melt, then you check the (unhomogenized) thermometers or sattelites and see that it’s below freezing and the temperature has hardly changed or gotten colder. Once again, the emphasis is on misinforming the public. All for a good cause.
I’m with a jones and perhaps others, I did not read all entries above. This is too silly. If the air can’t heat the ice rapidly, what heats the water rapidly that melts the ice rapidly?
In water’s absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.
The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models.
“We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years…
The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades…
Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.
For Pete’s sake, will you make up your minds? Is it millenia or decades?
-The little surface water we see in the photo has to warm 3km thick ice? Meanwhile, sealevel is falling back to the 20cm line first reached in 2002 and G-land ice sheet is under well below -20C air from end to end – probably the cracks are well sealed at least for now. Indeed, wouldn’t a 3000m thick ice sheet tend to freeze the water pretty fast before it got too far – what are the mass balances between ice and water we are talking about:
http://sealevel.colorado.edu/current/sl_noib_global.jpg
Did the computer data find a WWII airplane buried under 25 stories of “global warming”?
http://p38assn.org/glacier-girl.htm
Didn’t Hansen trot this out earlier in the decade–around 2005 or so–as a means for claiming that the glaciologists were underestimating how fast the Greenland ice sheet would melt? I believe the claim was that “moulins” filled with melt water would simply lubricate the way for the entire upper part of the Greenland ice sheet to slide off into the ocean.
Then, new data emerged 1-2 years later saying that, yes, the flow rate TEMPORARILY increased, but then the ice bogged down again. Unfortunately, I don’t remember the papers–but I think this was commented on, both the initial Hansen claims and the refutation, on WUWT at the time.
Too many graduates chasing not so much funding. Causes ice to melt more rapidly, clouds to cause globl warming, temps to change magically etc.
1) NASA funded
2) model
3) …well, who cares?
————————————————————————————-
In water’s absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.
The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models.
“We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years…
The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades…
Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.
————————————————————————————-
How long have they been reading these temperatures??
john r
Eskers, anyone?
https://www.dmr.nd.gov/ndgs/ndnotes/Eskers/Eskers.asp
~ ~ ~
As no one has said it yet, I will. Water is not blue. And, also, Earth is often called the “blue planet” because of its atmosphere, not its water.
There are no figures or working shown to say how they arrived at the conclusions they have drawn. A viable and reasonable energy budget would lend some credibility to their argument.
Though to do that would mean they have to put their pots on the wall to be shot at.
john r
Just so I can get a handle on things , how cold is the average ice in a glacier – equivalent to my domestic freezer at minus 14 C ? Any water trickling onto a six pint container of frozen milk freezes almost immediately when the carton it is in the sink defrosting , I cant see how water would behave any differently trickling down a few thousand feet of similar temperature glacial ice . Unless it starts its run at boiling point !!
Steve Keohane (November 5, 2010 at 8:32 am):
“I’m with a jones and perhaps others, I did not read all entries above. This is too silly. If the air can’t heat the ice rapidly, what heats the water rapidly that melts the ice rapidly?”
Presumably it’s sunshine. Snow, or glacial ice, reflects the majority of the sunlight falling on it (that is, it has a high albedo). Water absorbs more of the sunlight (has low albedo).
Just another piece form the “cabinet of triviality”.
so they are fixing their wrong models, so that they now will be even more wrong.
A very fine theory.
One slight problem – Greenland’s temps have not increased since around 1940 so where is the heat that is generating the extra melting?
Nothing to see, move along.
@Paul H
> One slight problem – Greenland’s temps have not increased since around
> 1940 so where is the heat that is generating the extra melting?
No problem. The heat that causes melting does not raise the temperature.
That’s why it’s called “latent heat”.
http://en.wikipedia.org/wiki/Latent_heat
You get it back when the water freezes again. (Hmm, I wonder if the CAGW gang considered this ‘hidden’ heat in their prognostications?)
They think they have found some of the “lost heat” but haven’t a clue as to how much. We need more money to do the research.