Cliff Ollier
School of Earth and Geographical Sciences, The University of
Western Australia, Crawley, WA 6009, Australia.
Colin Pain
Canberra City ACT 2601, Australia.
Global warming alarmists have suggested that the ice sheets of Greenland and Antarctica may collapse, causing disastrous sea level rise. This idea is based on the concept of an ice sheet sliding down an inclined plane on a base lubricated by meltwater, which is itself increasing because of global warming.
In reality the Greenland and Antarctic ice sheets occupy deep basins, and cannot slide down a plane. Furthermore glacial flow depends on stress (including the important yield stress) as well as temperature, and much of the ice sheets are well below melting point.
The accumulation of kilometres of undisturbed ice in cores in Greenland and Antarctica (the same ones that are sometimes used to fuel ideas of global warming) show hundreds of thousands of years of accumulation with no melting or flow. Except around the edges, ice sheets flow at the base, and depend on geothermal heat, not the climate at the surface. It is impossible for the Greenland and Antarctic ice sheets to ‘collapse’.
In these days of alarmist warnings about climate warming, the ice sheets of Greenland and Antarctica have an important role. Many papers have described their melting at the present times, and dire predictions of many metres of sea level rise are common. Christoffersen and Hambrey published a typical paper on the Greenland ice sheet in Geology Today in May, 2006.
Their model, unfortunately, includes neither the main form of the Greenland Ice Sheet, nor an understanding of how glaciers flow. They predict the behaviour of the Ice Sheet based on melting and accumulation rates at the present day, and the concept of an ice sheet sliding down an inclined plane on a base lubricated by meltwater, which is itself increasing because of global warming. The same misconception is present in textbooks such as The Great Ice Age (2000) by R.C.L. Wilson and others, popular magazines such as the June 2007 issue of National Geographic, and other scientific articles such as Bamber et al. (2007), which can be regarded as a typical modelling contribution. The idea of a glacier sliding downhill on a base lubricated by meltwater seemed a good idea when first presented by de Saussure in 1779, but a lot has been learned since then.
In the present paper we shall try to show how the mechanism of glacier flow differs from this simple model, and why it is impossible for the Greenland and Antarctic Ice Sheets to collapse. To understand the relationship between global warming and the breakdown of ice sheets it is necessary to know how ice sheets really work. Ice sheets do not simply grow and melt in response to average global temperature. Anyone with this naïve view would have difficulty in explaining why glaciation has been present in the southern hemisphere for about 30 million years, and in the northern hemisphere for only 3 million years.
Read the complete paper here
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I think the AGWiers underestimate THE POWER OF HYDROGEN BONDS.
When you think that a 10 cm thick ice bridge can support a fully loaded 10 wheels truck, imagine how well the ice of glaciers that have been compressed for millions of years holds itself together because of THE POWER OF HYDROGEN BONDS!
It’s like, when I stick a foot out of my bed, my whole body does not slide down to the floor.
Basic science will trump alarmism if the “pack” doesn’t run off the cliff like a bunch of lemmings, first.
Ollier and Pain should submit their paper for participation in the upcoming Copenhagen conference, even though the odds are that it will be rejected, and they will be “uninvited.”
In fact, I would like to see all the authors of recent papers deviating from the AGW dogma submit them. If most or all are rejected, an international class action suit should be filed against the IPCC.
Very likely an argument would be made that they missed an early submission deadline, in which case they can protest late acceptance of all pro-AGW submissions.
Thrust faults in the earth are a great example of gravity and a descending plane NOT being necessary to cause movement of a semi-rigid (rock moreso than ice) body.
Fluids providing lubrication at the base of a thrust fault will make it easier for the fault to move though. The same can be said for the liquid water at the base of an ice sheet.
The force driving a thrust fault is tectonic forces. That driving force behind glacier movement is the weight of the ice itself. Much like a bowl overfilled with water, the water will settle until it is at it’s lowest point and then any extra will exit over the basin. Same goes for ice, albeit at a much longer time-frame.
As the ice thins, the basin, which is created by the weight of the ice itself, will begin to rebound making it less effective as a basin.
I read that yesterday. There is one area where the ice sheet has regularly “collapsed” and that is a portion of the WAIS. The intervals … somewhere around 100K years, would seem to indicate that it is somewhat in sync with glaciation intervals. The notion being that natural melt at the base due to geothermal heating causes a layer of muddy goo and then some trigger, possibly seismic, causes liquifaction of the underlying material and the glacier rides out on a giant mudslide. This notion comes from study of sediment stratification that would seem to indicate larges flows of material at 100K intervals and alternating periods when parts of the ocean floor are under an ice covered surface and a surface apparently free of ice.
Also, happened to notice that the Wikipedia article on the WAIS includes this:
Footnote 14 points to the Steig paper published in Nature that has been shown to be faulty in its conclusions. Maybe someone with more authority than I would care to correct that portion of the article.
But it is vital for the AGW promotion industry to be free to ’emotionalize’ about threats, espcially if the threats are not real. and since none of the aGW threats are, in fact, real, ’emotionalization’ is even more important.
After all, the mission of AGW promotion, to save us from non-existant threats, is more importnat than any single fact or accurate statment.
Loss is at margins. Central south is growing:
http://img440.imageshack.us/img440/2052/greenlandicesheet.jpg
The global warming doomsday writers claim the
ice sheets are melting catastrophically, and will
cause a sudden rise in sea level of many metres.
Ice sheets are melting catastrophically! I’ve heard few if any people say this. Perhaps they say it could happen in worst case scenarios but not NOW.
I think it would be hard to find statements in IPCC report that claim catastophic melting IS occurring!!!
Volume of ice in Greenland Ice Sheets . . . . 26,000,000+ km3
Average annual melt . . . . 200km3
Melt as % of volume . . . 0.00077%
Years required to melt Greenland Ice sheet at current rate . . . 130,000 years
Repent !
The End is Nigh
There is also a new paper using the most detailed measurements and modeling for the Greenland ice sheet and it shows that the mass balance of the ice sheet is still increasing, not melting.
Total snow accumulation was about 700 GigaTons in 2008 and total melt run-off, ablation and discharge was about 450 GigaTons.
There is a small net loss along the southwest coast and in some small areas in the north, but the vast majority of Greenland is still gaining ice (although the rate of increase is declining).
https://eng.ucmerced.edu/people/rbales/CV/PubsP/120
Here is a cross-section of Greenland from GEUS (the Danish Geological Society) which clearly shows easily 95% of the ice on Greenland exists above sea level and the basin’s edge.
http://www.geus.dk/viden_om/voii/ilulissat-uk/goii03_fig03_large_uk.jpg
Ice will flow and it will flow out of the basin!
A subtle, but very effective, part of the ecotheist’s propaganda about Greenland’s icecaps – particularly when you ignore the geological principles detailed above – is the Mercator projections in hundreds of thousands of classrooms across the countries.
The type of projection – seldom explained and not well-drawn anyway when Antarctica is usually cut-off, but Greenland prominently increased – exaggerates how small Greenland actually is. At 1.6 million km^2, it is the same size as Saudi Arabia, much smaller than Australia.
Yet there is it, seemly bigger than South America – hanging like an icy sword of death over the innocently green rest of the world.
Great read. I learned a lot about ice crystals and glacier flow. Now I am an expert and can make fun of all the people talking about melting ice caps.
More like 2.2 million km^2. But yes, just about the size of Saudi Arabia.
Gee bill google search of ice sheets melting catastrophically returned 307,000 hits.
http://www.technologyreview.com/blog/arxiv/23531/
http://www.encyclopedia.com/doc/1S1-9199807070753092.html
http://climateprogress.org/2009/02/05/antarctic-ice-sheet-collapse-even-more-catastrophic-for-us-coasts/
http://www.answersingenesis.org/home/area/fit/chapter10.asp
http://news.therecord.com/article/292495
That’s nice. It doesn’t mean that it’s going to slide off, though. In fact, if if the ice sheet is similarly secured in the N-S direction, it means that it’s NOT going to slide off. It’d have to tip off, and that’s not going to happen. Sure, it could eventually melt away, or something could happen to otherwise accelerate the rate at which ice leaves the ice sheet, but there doesn’t appear to be any imminent catastrophe, there.
Oh, and also: that’s a cross-section, not the cross-section, so I’m not sure what your point is. There may be more secure containment of the ice sheet, elsewhere.
Finally, the fact that the vertical scale is greatly exaggerated (factor of about 80) makes things appear much less stable than they actually are.
So: your point is what, again?
ak (09:43:31) :
“Here is a cross-section of Greenland from GEUS (the Danish Geological Society) which clearly shows easily 95% of the ice on Greenland exists above sea level and the basin’s edge.”
Nice choice of dramatic scale. Glacier should be about 200km thick if that picture would correspond with reality.
“”” ak (09:25:30) :
Thrust faults in the earth are a great example of gravity and a descending plane NOT being necessary to cause movement of a semi-rigid (rock moreso than ice) body.
Fluids providing lubrication at the base of a thrust fault will make it easier for the fault to move though. The same can be said for the liquid water at the base of an ice sheet.
The force driving a thrust fault is tectonic forces. That driving force behind glacier movement is the weight of the ice itself. Much like a bowl overfilled with water, the water will settle until it is at it’s lowest point and then any extra will exit over the basin. Same goes for ice, albeit at a much longer time-frame.
As the ice thins, the basin, which is created by the weight of the ice itself, will begin to rebound making it less effective as a basin. “””
Lemme see if I have this right; you say that it is the weight of all of that ice (say in Greenland) that will squish the ice to flow out of the basin; but that as the ice thins (from getting squshed out by the great weight of all that ice) the basin bottom will rise; and presumably squish some more ice out.
So now exactly what thickness of ice is stable, so that it isn’t losing ice by basin bottom rebound, nor is it gaining ice thickness, and squishing it over the rim of the basin ?
What is the chance that the present thickness of Greenland ice, is at that stable level so it is neither squishing ice over the rim of the basin, nor having the basin bottom rebound and ejecting the ice. It does seem yo have been there for a good ling time, and not in any great hurry to go some place else.
@NastyWolf – there are TWO scales on the diagram! Or rather, I should say, the ice sheet is only 18km wide! lol
“It’d have to tip off, and that’s not going to happen”
IT COULD…If you believe the previews to the movie 2012
AK …
For the Basin to push back up .. it would occurr in geologic time .. that’s thousands to millions of years.
Thanks for supporting the featured authors position that the Greenland and Anarctic Ice sheets are not going to fall in to the sea and drown us all any time soon.
ak (09:43:31) :
“Here is a cross-section of Greenland from GEUS (the Danish Geological Society) which clearly shows easily 95% of the ice on Greenland exists above sea level and the basin’s edge.”
If you had read the paper, you would know that the only real question is “does the plastic zone of the ice cap extend up beond the high mountains along the coast.
Try reading the material before trying to argue against it.
So, NastyWolf, you wanted them to draw it to scale so that it was 10 inches wide and 1/100 inch thick? And what would that teach us? Better yet, should it be a 10 inch arc representing the actual curvature of the Earth but still 1/100 inch thick?
Or perhaps you’re suggesting that the 600 m tall heights to the West and 1700 m tall heights to the east aren’t going to hold back the glaciers becuase the slope is too low?
I just want to make sure I understand your criticism.
Thanks.
It’s for certain that the given profile doesn’t cross Gunnbjørn Fjeld, for instance, which has a bunch of peaks over 3500m.
“”” ak (09:43:31) :
Here is a cross-section of Greenland from GEUS (the Danish Geological Society) which clearly shows easily 95% of the ice on Greenland exists above sea level and the basin’s edge.
http://www.geus.dk/viden_om/voii/ilulissat-uk/goii03_fig03_large_uk.jpg
Ice will flow and it will flow out of the basin! “””
Well not so fast there; the link above is to a two dimensional vertical plane section; but the Greenland ice mass is actually a three dimensional object.
Your picture creates the fictitious illusion, that that central 3 km thick pile of ice is going to extrude to the left, and all fall off the left edge of the drawing; whereas in fact it is going to spread in three dimensions, to an ever increasing perimeter, so the outward driving pressure keeps falling as the ice approaches the coast.
According to your picture the basin depth at the left end is about 500 metres deep; yet the central bulge is only six times that thickness. That is hardly a highly stressed structure; and I would venture that the bottom of the ice is thoroughly locked to the rock base by the topography of the basin; so the only way for that ice mass to move is by extrusion of the ice itself; and the ice is crystalline; so it is not exactly a fluid; Also the temperature of most of that ice is so far below freezing, even the change in freezing point due to pressure is not going to melt the bulk of that ice; so only at the edges would there be any liquid lubrication flow.
I would venture that any structural analysis of such a monolith would show that it is a robustly stable object; and as fast as ice can get lost from the perimeter, it will be replaced by precipitation; and if in fact temperatures get warmer, that precipitation in the middle of Greenland would be expected to increase, not decrease (see Wentz et al SCIENCE July 7 2007).
Greenland ice sheet collapse is just a red herring; same goes for Antarctica; it hsn’t collapsed in over 700,000 years dsepite going through 8 ice ages and interglacial warm periods.
Oh, crap. Some blogcomments don’t interpret the codes properly.
&uoslash;?