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
Ray: “When you think that a 10 cm thick ice bridge can support a fully loaded 10 wheels truck”
Somehow, I don’t think that civil engineering is your strong point.
@Slartibartfast No problem with the word ‘basin’, just the ‘deep’ modifier used. 😉
@ginckgo Also interesting is that they bemoan textbooks for propagating the idea of glaciers sliding down an inclined plane as incorrect, so do they offer a more appropriate diagram? No. In fact, their figures 2 and 3 depict that same exact process!
Okay, I found the book they criticized on the first page, The Great Ice Age (2000) by R.C.L. Wilson, on google. Not sure which version the authors of this ‘paper’ read, but the figure showing the ‘misconception’ of glaciers sliding down a plane is clearly labeled ‘Valley Glacier’. They even have an ‘Ice Cap’ laying on a level surface.
You be the judge.
http://books.google.com/books?id=M4Nq7BBVfngC&lpg=PA253&ots=mt5hKPO5nw&dq=The%20Great%20Ice%20Age%20(2000)%20by%20R.C.L.%20Wilson&pg=PA52#v=onepage&q=The%20Great%20Ice%20Age%20(2000)%20by%20R.C.L.%20Wilson&f=false
The authors do themselves a great disservice by not clearly distinguishing between mountain and continental glaciers from the very outset, and resorting to a bait and switch argument. :/
Vincent (05:36:35) :
My own research shows that Greenland ice is only resisting the centrifugal force of the earths rotation due to the frozen ice at the base that sticks it to the bedrock. In 95 months the friction of that base ice will give way and the whole ice sheet will travel tangentally across the globe like a hammer being released by an Olympic thrower. This ice sheet will travel into the stratosphere on a parabolic trajectory finally returning to earth in the Gulf of Mexico.
—–
What!
No, no, no. You’re wrong. Simply dead wrong. We’ve discussed this before, but this time I can’t let your math error continue.
The Greenland Ice cannot fall back into the Gulf of Mexico – the earth’s rotation, plus the original latitude of the centroid of Greenland’s icecap at just above 72 degrees means that the impact point is west of Greenland.
Never southwest.
Yes, I concede you have the basic physics right. Melted water from the minus 30 degree surface goes down 3 km through the icecap, pools underneath the icecap on the parabolically smooth landmass under the icecap, then creates a slippery “tipping point” sloped ramp caoting the 2.2 million sq km under the ice. We “all” know that.
But you have never – in any calculation! – accounted for the southerly acceleration needed to land the icecap in the Gulf. It goes up, pauses under gravity at its peak height while the earth underneath rotates at just at 1000 mph (at the equator mind you!). Then the icecap falls back – but at the same latitude.
It will land approximately mid-Canada – depending on how much you assume for aerodynamic braking through the atmosphere compared to the lift as it flies “sideways” with both a rounded upper and lower surface. I must admit, the amount of net lift vs the changing “angle of attack” of the bottom surface may be endlessly debatable without wind-tunnel testing.
But not the Gulf of Mexico. No. There simply can be no acceleration to the south.
Ray & Larryoldtimer
As for the strength of 10 cm thick ice, according to the standards of the Soviet Army it is sufficient (with peacetime safety margins) for a wheeled vehicle weighing 1550 lbs or a tracked vehicle weighing 2700 lbs. According to the Swedish Army it is safe for a wheeled vehicle weighing 2200 lbs, with the proviso that this only applies to solid, cold winter ice, not spring ice.
It would have to be a very light truck!
I presume the Antarctic Peninsula fits into the “Except around the edges” exception. The given arguments wouldn’t apply, since the AP is narrow and ‘highly mountainous’.
But how do marine-based ice sheets fit into their arguments?
The West Antarctic Ice Sheet (WAIS) is…classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves…
Polar ice experts from the U.S. and U.K….in March, 2007…discussed a new hypothesis that explains the observed increased melting of the West Antarctic Ice Sheet. They proposed that changes in air circulation patterns have led to increased upwelling of warm, deep ocean water along the coast of Antarctica and that this warm water has increased melting of floating ice shelves at the edge of the ice sheet. An ocean model has shown how changes in winds can help channel the water along deep troughs on the sea floor, toward the ice shelves of outlet glaciers. The exact cause of the changes in circulating patterns is not known and they may be due to natural variability. However, the connection between the atmosphere and upwelling of deep ocean water provides a mechanism by which human induced climate change could cause an accelerated loss of ice from WAIS. Recently published data collected from satellites support this hypothesis, suggestin that the west Antarctic ice sheet is beginning to show signs of instability. Wikipedia
…..Pine Island Glacier (which drains about 10% of WAIS):
One of Antarctica’s greatest glaciers is thinning so quickly it could disappear within 100 years…jeopardising a volume of ice that could raise global sea levels by around 25 cm.
…the rate at which the glacier is thinning has accelerated and spread inland…the central ‘trunk’ of the glacier lost four times as much ice in 2006 than it did in 1995…
“As the glacier thinning speeds up, more and more ice is lost to the oceans and the supply of snowfall just cannot keep pace.”
Sea water in this region is about 0.5 degree Centigrade warmer than scientists think it should be…And because Pine Island Glacier flows straight into the sea, its much more vulnerable to changes in water temperature than most other Antarctic glaciers which are buttressed by ((larger??)) floating ice shelves.
“We know that warm water is the most likely candidate for the cause of Pine Island Glacier thinning. What we need now is for oceanographers to tell us why the ocean temperature is so high…”
Some researchers suggest that warm water at the coastal end of the glacier may be melting the underside of the glacier’s floating ice shelf at an unsustainable rate. They say that this may have ultimately led to accelerated thinning inland.
“This is perhaps the greatest signal of change in the cryosphere today…”
The underlying danger is that most of the West Antarctic Ice Sheet lies on bedrock that rests well below sea level. If the Pine Island Glacier continues to thin and retreat it will eventually become afloat, leading to drawdown of ice from the deep interior of Antarctica. Planet Earth online, 14 Aug, 2009
“”” Robert A Cook PE (12:03:24) :
Vincent (05:36:35) :
Yes, I concede you have the basic physics right. Melted water from the minus 30 degree surface goes down 3 km through the icecap, pools underneath the icecap on the parabolically smooth landmass under the icecap, then creates a slippery “tipping point” sloped ramp caoting the 2.2 million sq km under the ice. We “all” know that. “””
Would you care to explain the physics (which you assert you both have correct (right)) that causes water ice at -30 deg (C ?) to “melt” into water.
There are no physical conditions anywhere on earth, where ice exists, which permit the melting of ice at -30 deg C; or for that matter at -30 deg F if you wish to try and weasel out of it that way.
So you both agree on the Physics; so enlighten us all; what is that Physics ?
George
“”” LarryOldtimer (09:50:30) :
Ray: “When you think that a 10 cm thick ice bridge can support a fully loaded 10 wheels truck”
Somehow, I don’t think that civil engineering is your strong point. “””
Well I would agree with that; having designed a road bridge with a wooden deck and structural steel I-beam supports on a concrete base, that WAS capable of carrying a mythical 20 ton 10 wheeler H-20 truck; a truck which you can’t legally drive on any piece of US highway to get to my bridge. A District Civil engineer assured me my design was sound; in fact it could support an A-1 Abrams tank, carrying an identical tank on top of it. But the diustrict still wouldn’t allow me to build it without paying off all their parasites; so they have to make do with a “repaired” all wooden bridge, which I won’t guarantee to them is capable of supporting more than a 4000 pound vehicle of any kind.
Now as I understand ice, it is similar to concrete and has very little tensile structural strength; which means it also has no flexural strength; so drive your truck on 4 inches of ice on your own time and property.
You can learn something, by noting that the average pressure on the carrying surface cannot exceed the air pressure in the tires (maybe 150 psi max), plus whatever flexural rigidity rubber tires have which isn’t a heck of a lot. Typical 18 wheeler tires are rated for 125 psi (cold pressure) maximum, so my 150 would be close to the road point pressure limit.
Reminds me of a debate either here or on CA in respect of the Greenland ice sheet and the extent to which it could be affected by solar irradiance . One particularly amusing post about someone not wanting to try and calculate how much it would take to make the water flow uphill sticks in the mind.
Maybe this was humouralizing. It made me laugh anyway.
George E. Smith (15:33:12) :
“”” Robert A Cook PE (12:03:24) :
Vincent (05:36:35) :
Yes, I concede you have the basic physics right. Melted water from the minus 30 degree surface goes down 3 km through the icecap, pools underneath the icecap on the parabolically smooth landmass under the icecap, then creates a slippery “tipping point” sloped ramp caoting the 2.2 million sq km under the ice. We “all” know that. “””
Would you care to explain the physics (which you assert you both have correct (right)) that causes water ice at -30 deg (C ?) to “melt” into water.
===
Yes, you caught me in that slight (but really very trivial) exaggeration. I apoligize, I should have kept to Hansen’s highest level of accuracy. The surface melt water from today’s +.23 degree C increase in temperature is really at only -26.3 K; and it only flows down through an average 0f 2682 meters of ice before creating the meltwater under all that ice that will cause the Greenland ice cap to go sliding up into space.
But it will fall down on mid-Canada. Not Vincent’s totally absurd Gulf of Mexico projection.
I really, really hope that you are saying this tongue-in-cheek. This is not even wrong.
I mean, assuming you are serious, what force balance could possibly result in a chunk of matter massing a couple of trillion metric tons being launched into space at sometime in the future, but not now? And not only not now with the ice cap, not now with the humans and various animals that currently inhabit that part of the world?
Ok, so I was short a few orders of magnitude in the mass department. Still, the larger question stands.
Hey what’s a few gigatonnes between friends?
Kindest Regards
Vincent and Robert,
Surely, the sudden negative pressure created by the departing ice would suck out both north poles ( the True and the Magnetic) and their acceleration could propel them far to the south. Ice may have more to do with polarity switcheroos than the models suggest.
Robert A Cook PE & Vincent:
Fascinating new scientific findings you’ve got there. Now that we’ve established you got the basic physics right, I think you need to hurry up and include an attribution study in time to have your research ready for Copenhagen.
What’s “driving” this sudden ejection of the Greenland ice sheet into the stratosphere and subsequent landing in Canada? Are you suggesting natural causation or is it mainly caused by the evil ways of mankind? What about time scales, you need to show catastrophic impact by the end of the century, you know.
Also, don’t forget about probabilities. This is climate science, so never mind statistical significance. Just pull some wild-ass guess out of your butt end. Shall we say 90% probably most likely due to man-made climate change?
If you can get your study together for Copenhagen in December, you will certainly compete with Rahmstorf, Mann, et. al. for most catastrophic non-science in show.
Slartibartfast (20:23:01) : “I mean, assuming you are serious. . .”
LOL!
JAN (01:40:59): “Are you suggesting natural causation or is it mainly caused by the evil ways of mankind? ”
Answer: Evil ways, evil ways!
Thanks all for playing along with a little light hearted fun!
PS, I was wrong about Gulf of Mexico – Canada definately. Sorry Candadians.
Vincent (06:28:48) :
Slartibartfast (20:23:01) : “I mean, assuming you are serious. . .”
LOL!
JAN (01:40:59): “Are you suggesting natural causation or is it mainly caused by the evil ways of mankind? ”
Answer: Evil ways, evil ways!
Thanks all for playing along with a little light hearted fun!
***
Light hearted fun? I’ve just managed to get a large grant to study this effect so you’d better all keep up the pretence…
tonyb
TonyB, you’re not a grant foster, are you?
Oh, thank God.
JAN (12:12:17) :
TonyB, you’re not a grant foster, are you?
—
Neigh, neigh m’lord Jan.
I saw TonyB at the mall today as he’d hurried right around the optical shop, skipping both breakfast and lunch in the hopes of getting his account serviced in time downtown:
If I’d had not seen him run right over EM Smith in his haste, I’d never have known he was a faster Foster Grant granted faster.
Robert A Cook PE (18:09:40):
That’s a relief then. If he were to be a grant foster, I am convinced his study would show that by assuming an oversimplified two box model unsupported by the physical world, and possibly in conflict with 2LOT, the ejection of the Greenland ice sheet would be granted by 2100.
And then Lucia at the Blackboard http://rankexploits.com/musings/2009/two-box-models-the-2nd-law-of-thermodynamics/ would have to come over and kick his butt.
Jan and Robert
With the amount we’re paying in the UK in ‘environmental taxes’ of one sort or another we have to grab any grants we can 🙂
Unfortunately to date I’ve never managed to get a grant in my life, but it seems to me that recent threads here highlighting various areas of research open up lots of possibilities.
Greenland seems a bit cold but perhaps I could grab a grant to study the effects of ice and snow on high level slopes during the forthcoming skiing season in the Alps? I’ll need a luxurious chalet as a base of course…
tonyb
TonyB (03:20:33) “perhaps I could grab a grant to study the effects of ice and snow on high level slopes during the forthcoming skiing season in the Alps? I’ll need a luxurious chalet as a base of course…”
Perhaps you should become a medical consultant of some sort. I am always bumping into doctors or dentists attending conferences during ski season in the Alps. It seems possible to claim some sort of tax benefit for attending such conferences whilst missing some of the more boring seminars!
Regards