From the University of British Columbia press office:
Greenland ice sheet flow driven by short-term weather extremes, not gradual warming: UBC 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 ice sheet 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 meltwater 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, Greenland 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.
The research was supported by the Canada Research Chairs Program, the Natural Sciences and Engineering Research Council of Canada, and the Canadian Foundation for Climate and Atmospheric Sciences through the Polar Climate Stability Network.
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h/t to Charles the Moderator
PALEOMAP project page on Climate History – http://www.scotese.com/climate.htm
Is there a direct measurement temperature record for Greenland? How many sites over how long?
The Article mentions global warming and Greenland and ice loss in the same article, but does not document how much warming there has been in Greenland (esp in last 15 years, what with this accelerating problem of melting).
from the article:
Is that estimate tied to GRACE?
The (at least) 100 Gigatonnes is net loss – it is not from a model or anything, it comes from direct measurement of the mass using a pair of satellites which detect the variation in the gravitational potential. (and the authors of the article have been careful to quote the lower end of the range for the mass loss)
I’d just like to say that I don’t have a problem with computer models. Yes, I know, many of you are going to have a conniption at this, please, bear with me.
Models do, despite all their bad press, provide us with very good insight into how things might work in the real world.
Everything is simulated these days, chemical interactions for drug discovery, physical properties of new aircraft designs, F1 car materials, manufacturing processes, everything. The difference is that all these things are simulated then tested in the real world to see if the sims stack up.
It seems that its only climate research (and financial services perhaps) where models are taken as gospel and used as evidence and fact without any physical measurements to back them up. With something as complex and chaotic as climate, the chances of the model being correct in the first few iterations (which is where we are at the moment) is very small, as indeed is now becoming blatantly obvious – take Dr Curry’s recent posts at her blog for example – climate models are incomplete and the results should be used in that context.
With the glacier situation, its a relatively well bounded problem that fluid dynamics type models can actually get close to simulating, or at least accurately enough to form a testable theory. From what I understand (I’m sure there are many here who use Fluent, CFX or other CFD apps in their day jobs who can explain better than I), the main challenges with modelling this kind of thing are how you define the boundary layer between liquid and solid and not the physical properties of the materials. I guess all that’s needed now is some empirical measurements to see how well the model stacks up.
“This certainly doesn’t mitigate the issue of global warming.”….
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Ha! I was waiting for that funding plug!
Beyond circular reasoning. Just incredible.
The circles keep intersecting as they cannibalize each other.
Chris
Norfolk, VA, USA
Forget the yearly stuff. Statistically 2010 was normal. Only 3 years since 1958 were outside of 2 sigma for SMB change. Two of those years were positive. Overall change in accumulation is trivial for any of the studies that are 50+ years.
BUSTED!
John Kehr
The Inconvenient Skeptic
Sandy says:
December 8, 2010 at 5:16 pm
There’s Science and there’s Computer Modelling. This isn’t Science.
I agree with Charlie, there are many situations where computer modelling is very useful. But only when the model can be tested against observations. And even then, only when the number of unknown parameters in the model is reasonably small (unlike climate modelling where the number of unknown parameters is huge). Also, it needs to be appreciated that the output of the model is not “data” and that if the model doesn’t agree with the observations, you don’t change the observations (I know, I know, but this is climate science).
You Cancon some people some of the time but you Can’tcon all the people all the time!!
You lose me with the bolded statement above. Wouldn’t a gigatonne of each weigh a gigatonne? Of course the density and volume could/would be different but that’s another matter.
Just wondering.
I hope “Sandy” isn’t the one I know from VIU, she’s in enough legal trouble from me over her pretentiousness and her condescending attitude toward men.
Job loss soon.
dwright, 9:45 PST
has been attributed to accelerated glacier flow towards ocean outlets.
which prior to CAGW turning the world upside down would have been a sign of glacier growth
I’m trying to understand the process so please stop me if I have it wrong:
* Observe an event
* Nature is too complex to understand, so build a model
* Design model to replicate observed but not well understood phenomena – accept rounding errors and playing dice as God does as unavoidable necessity – confidence level remains high, hell why should it not.
* Use model rather than observations to understand natural phenomena. Confidence level surges as results validate prediction to 3 decimal places.
* Write up a paper that actually says the above or worse and use peer review speak so peer pals won’t be put off by injecting language of commoners into the puddin’.
* Wait for Nobel prize in science fiction
Let’s look at the past:
and
mitchell44;
fun post but — what weighs more? A kilo of water or a kilo of ice?
Think carefully and slowly, now ….
Just to be more explicit, mitchell44, “What weighs more, a kilogram of water or a kilogram of ice?” “… a ton of water, or a ton of ice?” Etc.
Ted Gray says:
December 8, 2010 at 3:11 pm
OT – I THINK THIS IS IMPORTANT!
RUSSIAN PM PUTIN OFFERS FIREWOOD TO GERMANY
You’re right Ted. I’ve been living in Germany for years and I bought some firewood from…Russia, serious!
I wonder how much ice was on greenland just before the LIA set in? Does anyone know of a sea level peak at this time?
Never soon. Those people got the legal right to call themselves “scientists” by means of political decisions including laws set up to “produce” more people working in the area of science. This can’t and didn’t work. What was produced is a horde of numbs hindering the Really Qualified to perform their duty.
IMO this leads to the relatively desinterest[sp?] by the RQ to fight against the flood of nonsense. They know they can’t win.
OTOH the “other” party knows that they can’t compete with RQ. They hate this fact and react like naughty children but politically correct which helps the politicans responsible for the “production” laws to claim those laws to be successful.
Nice dilemma.
At a quick reading, this paper seems to me to be the beginning of a search for an exit strategy from the CAGW horsepucky. If it is, it must be a new use for computer modelling in climate science.
@Alfred Ledner Gray
‘OT – I THINK THIS IS IMPORTANT!
RUSSIAN PM PUTIN OFFERS FIREWOOD TO GERMANY’
Funny, I believe it was Germany based E-on energy corporation that got a contract to build 5000 MW worth of nuclear power plant in England. But Germany is dependent on gas, or now firewood, from Russia. That’s hilarious. :-()
But isn’t weather controlled by global climate change? So Mann-made global warming changes the climate which changes the weather. So we still need to ruin everyones economy and go back to 18th century agrarian style of living.
/sarc off
I note the droll comments and the insight that “this new study” is a computer model, not empirical.
I also note NASA claims to know by some secret method of altimetry and gravity sensors in space how much ice is melting away from Greenland, and that almost all studies of glacier movement in Greenland are focused on melting rather than growing glaciers as a function of available academic funding.
I would like to note that while Europe does have a little bit of firewood left, Greenland has none. Therefore I would like to ask Prime Minister Putin to worry a little more about the Greenlanders and a little less about the Germans, who in a pinch have been known to find all manner of things to use as fuel.
Thank you.
No problem the next Ice Age is coming
http://hetuurvandewaarheid.wordpress.com/2010/11/19/geen-global-warming-maar-een-ijstijd-komt-eraan-2/#comment-162
UBC … my alma mater.
Three things that made me cringe:
“created computer model” — here we go.
“does not mitigate the global warming” — the obligatory statement to stay in the good graces of the CAWG camp.
“loss of ice that worries us” — we should be emotionally detached from the subject of scientific study. Science seeks truth. Not emotion. Leave your emotional baggage at the lab door, please, professor.
I’m curious–is it even possible to measure 0.14 or 0.28 mm per year sea level rise? Does whatever measurement there is get lost in the error range? Please explain to me, someone, how this actual measurement can be accomplished?