‘Hidden plumbing’ helps slow Greenland ice flow
Hotter summers may not be as catastrophic for the Greenland ice sheet as previously feared and may actually slow down the flow of glaciers, according to new research.
A letter published in Nature on 27 January explains how increased melting in warmer years causes the internal drainage system of the ice sheet to ‘adapt’ and accommodate more melt-water, without speeding up the flow of ice toward the oceans. The findings have important implications for future assessments of global sea level rise.
The Greenland ice sheet covers roughly 80% of the surface of the island and contains enough water to raise sea levels by 7 metres if it were to melt completely. Rising temperatures in the Arctic in recent years have caused the ice sheet to shrink, prompting fears that it may be close to a ‘tipping point’ of no return.
Some of the ice loss has been attributed to the speed-up of glaciers due to increased surface melting. Each summer, warmer temperatures cause ice at the surface of the sheet to melt. This water then runs down a series of channels to the base of the glacier where it acts as a lubricant, allowing the ice sheet to flow rapidly across the bedrock toward the sea.
Summertime acceleration of ice flow has proved difficult for scientists to model, leading to uncertainties in projections of future sea level rise.
“It had been thought that more surface melting would cause the ice sheet to speed up and retreat faster, but our study suggests that the opposite could in fact be true,” said Professor Andrew Shepherd from the University of Leeds School of Earth and Environment, who led the study.
“If that’s the case, increases in surface melting expected over the 21st century may have no affect on the rate of ice loss through flow. However, this doesn’t mean that the ice sheet is safe from climate change, because the impact of ocean-driven melting remains uncertain.”
The researchers used satellite observations of six landlocked glaciers in south-west Greenland, acquired by the European Space Agency, to study how ice flow develops in years of markedly different melting.
Although the initial speed-up of ice was similar in all years, slowdown occurred sooner in the warmest ones. The authors suggest that in these years the abundance of melt-water triggers an early switch in the plumbing at the base of the ice, causing a pressure drop that leads to reduced ice speeds.
This behaviour is similar to that of mountain glaciers, where the summertime speed-up of ice reduces once melt-water can drain efficiently.
Study co-author Dr Edward Hanna from the University of Sheffield added: “This work also underlines the usefulness of modern gridded climate datasets and melt-model simulations for exploring seasonal and year-to-year variations in Greenland ice sheet dynamics and their relationship with the global climate system.”
The study was funded by the Natural Environment Research Council’s National Centre for Earth Observation, the Philip Leverhulme Trust, and by the European Commission Ice2Sea project.
For more information
The Letter entitled ‘Melt-induced speed-up of Greenland ice-sheet offset by efficient subglacial drainage’ by Aud Venke Sundal, Andrew Shepherd, Peter Nienow, Edward Hanna, Steven Palmer & Philippe Huybrechts is published in Nature on 27 January 2011 [doi:10.1038/nature09740].
Contact Hannah Isom in the University of Leeds press office on 0113 343 5764 or email h.isom@leeds.ac.uk.
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See also:
Upcoming paper in Nature – Greenland ice sheet melt: “it’s weather, not climate”
Greenland Ground Zero for Global Soot Warming
h/t to Steve Milloy
I’m so glad the science is settled …
“may have no affect”
effect is the noun
Well, that`s a cheerful bit of news.
As the props and supports drop away from from the catastrophists case, i can`t help but wonder, just how much time will pass before they, and the absurd edifice they have built collapses and vanishes up their own fundament.
Not soon enough i suspect.
The Greenland ice sheet covers roughly 80% of the surface of the island and contains enough water to raise sea levels by 7 metres if it were to melt completely.
+++++++++++++++++++++++++++++++++++++++++++++++++++
Hmm, 7 metres………that’s a lot!
Be prepared for a whole raft of such, “it might not be as bad as we thought” reports over the next few years.
It’s a face-saving exercise.
The article implies a thirty percent reduction of the ice would increase global sea levels by about 2.3 metres.
1000 years ago there was a third less ice.
There was no perceptible rise in global sea levels.
This was during a time when human population was much lower and water use was lower too.
So if the ice melted by a third again when water use is an order of magnitude much higher today we should not see flooding.
That probably explains why the Greenland ice sheet is still there after thousands of years, surviving the high temperatures of medieval and roman warm periods. Simples!
Summer temperatures in Greenland have been relatively constant, varying between from + 5 to 7 degrees C) during last 100 years. It is the winters that got much warmer (from -9 to -5 C) consequently less ice generated.
http://www.vukcevic.talktalk.net/LFC10.htm
Heat From Earth’s Magma Contributing To Melting Of Greenland Ice
http://www.sciencedaily.com/releases/2007/12/071212103004.htm
It’s an old article but, I think it is A contributing factor . . . .
It’s also why I think contributing scientists are important, . . . . they can at least warn you as when it might be a real good idea to “run like the devil himself is after you!”
And once again, it’s why I say . . . any and all knowledge can be used to abuse.
If the Greenland ice sheet melted every time the climate went through a warming cycle, historical records would show seacoast towns getting regularly submerged. But history shows an amazingly steady sea level. The article explains why:
Another warmist Whack-A-Mole theory gets whacked. Greenland isn’t gonna melt.
“Summertime acceleration of ice flow has proved difficult for scientists to model, leading to uncertainties in projections of future sea level rise.”
Says everything you need to know about climate science in general. Models.
Do these people ever get out of the office these days and do real every day physical
science? Rubbish in, Rubbish out.
Oh I see. Instead of the glacier floating on a lubricating sheet of water, the increasing water flow as spring progresses cuts dendritic channels through the ice (and perhaps the basal rock rubble and dirt), re-grounding the glacier.
Yet glaciers still from time to time speed up. Seems like glaciologists have more basic research to do. Tying “global warming” to glacier research is just t0day’s hook to keep the research funding flowing.
This is so confusing. I just read today that Britain is in for more freezing winters if Arctic melting continues
http://www.dailymail.co.uk/sciencetech/article-1350620/UK-weather-Regular-big-freeze-winters-Arctic-continues-warm-up.html
Well when the floating arctic ice melts, it does expose sea water to the oblique radiation from the summer sun, which will allow solar energy to reach into the Artic Ocean depths and increase water temperatures (which often are warmer on the surface, having come from the tropics) But that should also allow for a significant increase in evaporation from those heated waters; which inevitably will lead to greater snow falls; and quite likely on the surrounding lands (there’s more land north of +60 deg, than there is water) And having all that snow and ice growing on the lands surrounding the arctic ocean, is likely to increase the earth albedo, more than is lost from the floating ice; those vast land areas see more sunlight than the Arctic ocean does.
So I wouldn’t be in any hurry to predict a snowballing loss of albedo, when the floating sea ice melts; all that open cold water will also take up more CO2 from the atmosphere.
Since the ice has been there for 420,000 years (from the ice core record) with several time frames of higher temps, ( http://muller.lbl.gov/pages/iceagebook/Image5.gif ) why will it all go this time?
BREAKING NEWS : “Ice sheet dynamics are complex.”
COMING NEXT : “Man discovers the Wheel.”
It’s as if every week / month we find evidence of why there won’t be catastrophic positive feedback runaway global warming. And here I was being told about lubrication and tipping points. I’m beginning to warm to the Gaia hypothesis. ;O)
http://dx.doi.org/10.1016/0033-5894(74)90038-6
I can’t take any more good news…………………..
…I’m totally into the whole doom and gloom thing.
Al Gore ……. says
——–
1000 years ago there was a third less ice.
There was no perceptible rise in global sea levels.
——–
What part of the law of conservation of mass and the concept of density don’t you understand?
Do this experiment. Fill a glass of water to the brim. Hold it over your lap. Drop in an ice cube. Predicted outcome: you wet your pants.
Al Gore’s Holy Hologram says:
January 26, 2011 at 12:44 pm
“The article implies a thirty percent reduction of the ice would increase global sea levels by about 2.3 metres.”
Very good. That means I can eat more beef!!!
Maybe what the Warmists are seeing is just part of a cycle. It’s been warmer before I think.
I think Greenland survived the following, but please correct me if I’m wrong:
http://dx.doi.org/10.1016/j.quascirev.2010.08.016
http://adsabs.harvard.edu/abs/2007AGUFMPP11A0203F
http://geology.geoscienceworld.org/cgi/content/abstract/21/3/227
I was debating the Arctic Report Card (ARC) with a glaciologist from SkS last fall. He was pretty much pulling a chicken little by saying the sky was falling because the last 5 years were such absolute dramatic proof that the sky was falling based on the Surface Mass Balance.
So I ran an analysis using the actual numbers from the and the numbers in the report proved that nothing significant is happening. I did the same for another peer-reviewed journal article and found different numbers, but the same result.
All the studies show it has lost mass in the last 10 years, but they also show that there is nothing statistically unusual about the last 10 years.
My write-up over the debate is here:
http://theinconvenientskeptic.com/2010/12/mass-accumulation-of-greenlands-ice-sheets/
Of course this quoted headline, “Hotter summers may not be as catastrophic for the Greenland ice sheet,” does not appear in the article. (The article is here: http://www.nature.com/nature/journal/v469/n7331/full/nature09740.html ; a sub. may be required.)
The issue is this. Glaciers are melting. As the melt water drains to the land/ice surface there is concern that this will lubricate the ice and enhance the sliding of the sea sheer toward to sea. This article claims to show (and the claim seem credible) that higher rates of melting can lead the melt water to carve out channels to the sea and because of these channels the friction between the ice and land can be higher than with low melting — but, I would add, certainly higher than with no melting! With higher temps the glaciers will melt and sea level will rise, but this work means the time it takes to rise the sea levels will be longer, although a lot more work needs to be done before good quantitative models can be constructed.
REPLY: The quote is from the press release – Anthony
Won’t Greenland take nearly 10,000 years to completely melt at it’s current pace?
Not sure how that breaks down say in 200 year increments (sea rise vs melt) but I’m sure it’s slow enough that New York and other cities can deal with the problem at a much later date…
However, this doesn’t mean that the ice sheet is safe from climate change, because the impact of ocean-driven melting remains uncertain.”
Lol. Mmmmmphh errrrrrr….. It doesn’t mean we admit to being wrong, or hyping disaster… It just means we might do so eventually. We still Get grants and publicity from hyping apocalypsis, so you should expect that to continue for some time…