Greenland ice sheet flow driven by short-term weather extremes, not gradual warming: research

Sudden changes in the volume of meltwater contribute more to the acceleration – and eventual loss – of the Greenland ice sheet than the gradual increase of temperature, according to a University of British Columbia study.

The consists of layers of compressed snow and covers roughly 80 per cent of the surface of Greenland. Since the 1990s, it has been documented to be losing approximately 100 billion tonnes of ice per year – a process that most scientists agree is accelerating, but has been poorly understood. Some of the loss has been attributed to accelerated glacier flow towards ocean outlets.

Now a new study, to be published tomorrow in the journal Nature, shows that a steady meltwater supply from gradual warming may in fact slow down glacier flow, while sudden water input could cause glaciers to speed up and spread, resulting in increased melt.

"The conventional view has been that meltwater permeates the ice from the surface and pools under the base of the ice sheet," says Christian Schoof, an assistant professor at UBC's Department of Earth and Ocean Sciences and the study's author. "This water then serves as a lubricant between the glacier and the earth underneath it, allowing the glacier to shift to lower, warmer altitudes where more melt would occur."

Noting observations that during heavy rainfall, higher water pressure is required to force drainage along the base of the ice, Schoof created computer models that account for the complex fluid dynamics occurring at the interface of glacier and bedrock. He found that a steady supply of is well accommodated and drained through water channels that form under the glacier.

"Sudden water input caused by short term extremes – such as massive rain storms or the draining of a surface lake – however, cannot easily be accommodated by existing channels. This allows it to pool and lubricate the bottom of the glaciers and accelerate ice loss," says Schoof, who holds a Canada Research Chair in Global Process Modeling.

"This certainly doesn't mitigate the issue of global warming, but it does mean that we need to expand our understanding of what's behind the massive ice loss we're worried about," says Schoof.

A steady increase of temperature and short-term extreme weather conditions have both been attributed to global climate change. According to the European Environment Agency, ice loss from the Greenland ice sheet has contributed to global sea-level rise at 0.14 to 0.28 millimetres per year between 1993 and 2003.

"This study provides an elegant solution to one of the two key ice sheet instability problems identified by the Intergovernmental Panel on Climate Change in their 2007 assessment report," says Prof. Andrew Shepherd, an expert on using satellites to study physical processes of Earth's climate, based at the University of Leeds, the U.K.

"It turns out that, contrary to popular belief, ice sheet flow might not be accelerated by increased melting after all," says Shepherd, who was not involved in the research or peer review of the paper.

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Citation: Greenland ice sheet flow driven by short-term weather extremes, not gradual warming: research (2010, December 8) retrieved 18 September 2019 from
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Dec 08, 2010
Well, THAT's inconvenient.

Dec 08, 2010
Whoever writes these headlines for PhysOrg must be doing so just to generate controversy, in order to drive web hits. Very much against the spirit of the original research.

Dec 08, 2010
Well, THAT's inconvenient.

Yep. For those who seize on evidence that supports their bias, and rejects all data that doesn't, anything about climate warming is bound to be inconvenient to someone.

Dec 08, 2010
I smell the blood of a troll or two. Forget it guys, it's OVER! AGW is in its death throes. The only way to influence things is to do dirty deals behind closed doors, which is now the climate change racketeer's weapon of choice.
It is true that these scum will be the most difficult to deal with, but they can FORGET popular support. That has gone forever - here's to the wisdom of crowds!

Dec 08, 2010
Uh-oh. Professor Schoof, I think you can kiss the possibility of you getting another dime in grant money bye-bye. The imminent melting of the Greenland ice sheets is one of the cornerstones of AGW.

Maybe you can get back in the good graces of the grantors if you can find some historical records that prove it was called "Greenland" because it was discovered by Eric the Green. And prove that there wasn't a Medieval Warming Period where for several hundred years it was warmer than it is today, and people farmed and raised livestock there. And that there were no vineyards in England at the same time.

Oops, looks like you'll have to get William Connolley to edit that out of wikipedia like he did when he fudged those other 5,000 wiki-pages to make them all favorable to AGW.

Oh, wait...too late.

Looks like wikipedia has gone all denialist and banned him from ever editing on their site again because of his blatant bias in favor of AGW.

Dec 09, 2010
Wow - now it appears that denialists can't understand what they read. What was said in the summary is:

"It turns out that, contrary to popular belief, Greenland ice sheet flow might not be accelerated by increased melting after all,"

Let me explain that since those who have commented don't have the ability to parse the sentence.

First: They are talking about the flow of the ice, not the water. The reason that is important is that bulk ice flow moves ice toward locations where it will calve and melt in the ocean.

Second, they are talking about the ice flow "might not be accelerated by increased melting" which means that the two events are coupled but not mutually causal.

They are not commenting on the rate of melting (which is well documented to be increasing). They are stating that the increased melting will not accelerate the flow of ice to the ocean (by their models).


Dec 09, 2010
Continued: In summary, melting is increasing by every monitoring means available. However, this model says that the accelerated melting will not increase the motion of the ice sheets to the ocean.

Now let me point out one other interesting thing.

jscroft, cremmy, and geokstr are talking about this being the death knell for the AGCC group. It seems very interesting to me that these same folks have been quick to point out that the models are useless. So, now that their mis-reading of the article seems to bolster their view that the ice sheets are not melting as fast, they are ready to consider the models they denounce as gospel.

Let me summarize. This is one of many models. These modelers explains it is improving at every release. The people who say modeling is useless and wrong are jumping on this model as being gospel. And no matter what the accuracy of the model, those commenting on the perception that this indicates the ice sheets are not melting are just wrong.

Dec 09, 2010
Oh no, what ever will we do? the ocean is rising by the alarming rate of 1.4 to 2.8 millimeters per decade.

Wow. These numbers only come to ~0.5 to ~1 inch per century, not the 1 meter per century commonly reported by CNN and other media outlets.

What happened? Did the alarmists finally realize nobody is buying this BS anyway?

At a rate of 1 inch per century, we're in great shape, because a few decades from now we are all going to be on mostly solar and nuclear anyway. The majority of oil reserves will run out in a few decades anyway; long, long before any irreversible environmental damage would ever be done.

Dec 09, 2010
@thermodynamics: You give me far too much credit. What you're interpreting as a flawed logical argument is really nothing more than unrestrained mockery. Now excuse me... I have to go shovel some more snow before my roof collapses.

Dec 09, 2010
Thermo is right. This guy's model isn't suggesting any change in the view that Greenland is melting and that the melting is accelerating. He's just trying to explain the mechanics of why the melting is accelerating, and he's saying that fluid dynamics models suggest something different than what most other people seem to think. He could even be wrong, or could be missing some critical factor in his model. This is just a starting point, and I would guess that he will now attempt to get field observations going to either prove or disprove his theory. That's how science is done. Don't get carried away and jump to conclusions.

If this guy's research really did say anything negative about global warming do you think it would have been published on this site?

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