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
One single meteor smashing in the ocean would cause more damage instantly than any catastrophic melting of all ice bodies of earth, even if it melted over a few years… which obviously will never happened. So, where should we put money to save the earth?
@Slartibartfast, I never said anything about sliding, only flowing. That’s how ice behaves. It’s talked about in the linked paper, and in many Glacialogy textbooks. Not knowing that would logically lead to your second question about containment. Ice simply flows around the mountains.
But just to entertain the idea that it is a single cross-section… well, it makes sense since I only linked one image. Regardless, if I were trying to ‘tip the scales’ in my favor, I would not have put a large mountain range in the east, but that’s just where this cross-section was taken. Fact is, it is the only cross-section I could find 🙂
Sadly, it has now become necessary to publish papers simply to re-emphasize basic science, refute complete and utter nonsense and remind everyone about the facts.
It indicates the incredible power of the propaganda that Ecofascists wield in our schools, in the fields and in the streets, in the hills and on the beaches, striking at the very heart of our industrial civilization. Many old and famous Institutions have fallen or may fall into the grip of the AGW and all the odious apparatus of Ecofascist rule.
This image shows surface velocities of ice in Antarctica (mostly, it doesn’t take into account up and down movement) and shows that the ice flow does not move as a uniform block (for those still clinging to the ‘sliding’ canard) and will speed up closer to the margins due to lessening bounding ice on one side.
http://en.wikipedia.org/wiki/File:Antarctica_glacier_flow_rate.jpg
from: http://en.wikipedia.org/wiki/Ice_sheet_dynamics
I agree with the author in the general point that most of the population may not have a strong grasp of the actual mechanisms of glacier behaviour, but only addressing the negligible aspect of glacial movement against bedrock is not doing much for educating that population.
How do gwrs. explain that glaciers keep advancing upwards from its basins?; the only explanation is that they are growing up, as in antarctica. The well known , and previously explained here in WUWT, phenomenon of the “ice cube dispenser machine”.
@Slartibartfast, @NastyWolf, my apologies… I misread your comments about the exagerated scale as non-existent scale. It’s common in geology to exaggerate the vertical axis – it would be kind of hard to view an image that is 10 million pixels wide 🙂
I’ve linked to an image which shows actual values for the speed of glacial movement at the surface. While, it may take a 100 years for ice at the middle to flow to the edge, it is still moving and doesn’t rely on basal flow.
This paper explains what was already explained, in detail, by Ian Plimer in his book “Heaven and Earth”.
You gotta love that GISS page (sometimes):
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=431043600000&data_set=1&num_neighbors=1
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=431042500000&data_set=1&num_neighbors=1
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=620040130000&data_set=1&num_neighbors=1
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=620040630003&data_set=1&num_neighbors=1
Where´s the unprecedent warming causing ice collapse, bunnyfvcks?
crosspatch (09:26:44) :
Those recurring collapses of the WAIS are an AGW factoid. There is no credible evidence for them, no sudden d18O jumps, no IRD layers in the Southern Ocean, no abrupt sea-level rises anywhere.
On the other hand there is now strong evidence that the WAIS has not been much smaller than at present since MIS 31, about 1,07 million years ago. During this exceptionally warm interglacial it was apparently at least much reduced, and temperatures in the Ross Sea significantly warmer than at present (see for example Wilson, G. S., et al. 2007. Preliminary chronostratigraphy for the upper 700 m (late Miocene-Pleistocene) of the AND-1B drillcore recovered from beneath the McMurdo Ice Shelf, Antarctica. USGS Open-File Report 2007-1047, http://pubs.usgs.gov/of/2007/1047/ and references therein).
ak (09:25:30) :
That is an absurd comparison. Movements on faults are driven by tectonic forces. There are no tectonics in ice-sheets, they are moved exclusively by gravitation. Also while the basin will undoubtedly rebound if the ice-sheet thins, it will not disappear since there are mountain-chains (up to 3700 meters high) around most of Greenland. This rather unusual configuration which is due to the way the north Atlantic opened is probably the main reason Greenlands ice-sheet is so uniquely stable compared to the Scandinavian and Laurentian ice-sheet. Furthe it is not at all clear that the ice will become thinner as it retreats. Once it has retreated far enough that it can no longer calve into the sea, it can only lose mass by peripheral melting which is a much slower process. This means that the ice-dome becomes steeper and higher. There is evidence that the northern dome of the Greenland Ice was actually a few hundred meters higher during the last interglacial, when the ice area was reduced.
ak (09:43:31) :
And that image you link to is somewhat misleading since the vertical scale is exaggerated about 35 times. The ice cap is actually very very flat. The map on page 10 of:
http://www.geus.dk/publications/bull/nr14/nr14_p01-13_A1b.pdf
gives a much better picture of the subglacial topography. As you can see there, it is only a very small part of the Greenland ice that could even theoretically “slide into the sea”. Also if these remarkable ice-slides are possible, why didn’t they happen in Scandinavia during the last deglaciation, where the ice retreated up-slope and there were handy seas to slide into on both sides of the divide?
In short the ice will indeed flow, but very slowly, like it always does, and it definitely won’t flow uphill!
Fred from Canuckistan . . .
Well, yes. The end will be nigh……..eventually. Maybe. Possibly, but not just yet.
As much as I’d like the world to not see another Ice Age while humans exist it looks like we can expect one in a few thousand years if not sooner. If you look at the climate record it seems overdue. So it isn’t reasonable to talk about 130,000 years of melting. This melting happens only a small fraction of the time.
If you believe more CO2 is a problem, don’t worry too much about that. We won’t be able to keep enough CO2 in the air to prevent the next Ice Age and once the oceans cool they will suck up CO2 rapidly. And when we get into an Ice Age we stay in it for a long long time.
Our money might be better spent on figuring how to breed hairy children with massive brows. When the time comes, they will appreciate it.
AK-
if the ice is a couple hundred thousand years old, and it has not slid off yet, why would it do so now? temperatures were much warmer in greenland during the medieval period, the roman period, and from there almost always at at least a degree warmer all the way back to the Holocene climate optimum which was 2-3 degrees C warmer than the present and lasted 3000 years.
what’s so magic about now that suddenly the ice will alter behavior? might it shrink from 1850 to now, sure. in 1850, the little ice age was ending. that was the coldest period in the last 9000 years. but it’s not even as warm on greenland now as it was when the vikings settled there. i don’t recall the vikings getting pushed into the sea by a sliding ice sheet. i recall them getting frozen out by expanding glaciers and dropping temperatures that made the settlement untenable.
if you’re going to claim: “this time is different” and this warming will do what others didn’t, you’re going to need to show us WHY it’s different.
@Deanster I didn’t use timescales, because I felt like most people would know what they are, but good point. Yes, I agree with the author that there won’t be a big “kerplunk” episode anytime soon – continental glaciers falling into the sea! :/
@Jeff in Ctown, see my later comments (updates around here are slow – why isn’t this a forum?) specifically (“I agree with the author in the general point that most of the population may not have a strong grasp of the actual mechanisms of glacier behaviour, but only addressing the negligible aspect of glacial movement against bedrock is not doing much for educating that population.”)
@george E. Smith Yes, it’s 3-dimensional in reality and that movement can be clearly seen in the Antarctic image I linked to. I can’t find a similar velocity map for Greenland. And ice, even in it’s crystalline form, will not act as a solid body.
@tty Good comments. I’m kind of at a loss about these ice slides everyone is talking about. There is no evidence for them happening before, but everyone is happy to argue against them! 🙂
John G. Bell (11:54:08) :
Priceless. . .
Interesting paper in nature
“Most high-resolution climate reconstructions for the past millennia have focused on Northern Hemisphere land records. Ocean reconstructions have to date been rare and, critically, have missed the most recent centuries, preventing a comparison with the observational records. A new reconstruction of sea surface temperatures for the Indo-Pacific warm pool now provides a decadally resolved record that spans the last two millennia and overlaps the instrumental record, enabling both a direct calibration of proxy data to the instrumental record and an evaluation of past changes in the context of twentieth century trends. The data show that while recent decades have been anomalously warm, they are statistically indistinguishable from temperatures prevailing during the Medieval Warm Period from around AD 1000 to AD 1250 ”
http://www.nature.com/nature/journal/v460/n7259/edsumm/e090827-06.html
Ubiquitous “global MWP” is against the “party line”
Oh, sure ice flows. It flows because it’s continually being weighed down by new snowfall, as well as by its own upper layers. If you know this, then you know that ice flows all of the time, and that all warmer weather might do is cause it to melt a bit faster.
If basal flow is irrelevant, why show the cross-section?
I made the comment about cross-section location because I was confused as to what your point was, and now I’m even more confused. Is the shape of the terrain under the ice sheet important, or not important, in your opinion?
I’m not trying to be difficult; I am simply attempting to understand what it is you’re trying to say, and how it relates to the main post.
Thanks in advance!
“Those recurring collapses of the WAIS are an AGW factoid.”
The paper I read (and can not locate, though I admit I am busy with other things right now and haven’t looked with any diligence) wasn’t a “warmest” paper at all. On the contrary, the conclusion was that “collapse” of the sheet in that specific area was a normal cyclical event unrelated to “global warming”. The notion being that either seismic activity or possibly geothermal/volcanic conditions combined with the natural slope of that specific area would be enough to explain it and it wouldn’t be associated with climate change except possibly in periods when the glacial mass might be better optimized for the failure to occur, which might be related to long-term climate changes. These changes would be regular cyclical changes and not anything induced by humans.
If you’ve ever seen my younger brother, well…success!
John G. Bell (11:54:08) :
Not at all unlike the Big Earthquake California or the Mississippi expects.
Or the next supervolcano.
Or when the next asteroid or comet comes sailing stright for the planet.
The attention span is the same or less than the surveillance that currently missed the impact on Jupiter.
Another overdue event.
47 days and counting.
So, while attention is focused on a ‘fake out’ emergency, things that are really happening or overdue to happen go unnoticed.
Warming alarmists can be certain Greenland and Antarctic ice sheets will evaporate – in 1,000,000,000 years when our sun becomes a red giant and consumes the earth. ‘Till then, we can probably keep ahead of sea levels rising at 2-3 mm/year for much less cost than “controlling climate”.
What they have forgotten is that:
Relax, enjoy, and lets work on really serious issues like providing alternative fuels to accommodate the rapid decline in global oil exports after peak oil.
This paper does not include the phrase “an area roughly the size of Manhattan”. Therefore it is not science.
I’m off to watch Independence Day and The Day After Tomorrow before my house burns down from global warming.
So much theorizing of the anthropogenic global warming crowd is based on wishful thinking. What wish? The age old wish to be judged from on high. The story of Noah, passover, and apocalyptic doomsday (to name a few) are all inescapable features of our civilization, always on ready to seduce the uneducated and unthinking mind into making grave judgment on one’s fellow man. But this is the simpleminded outlook. The only known place of judgment in the universe is in the mind of humans. So it is naive to attempt blanket condemnation of modern man as so many current environmentalists do. The task of environmentalism will never be so simple. It will always take difficult and honest inquiry. This post on mechanisms of continental glaciers is a great addition to the inquiry.
Ray (09:12:14) :
When you think that a 10 cm thick ice bridge can support a fully loaded 10 wheels truck […]
First off, you don’t state the length and width of the ice bridge, but irrespective, I don’t think anyone in their right mind would drive a loaded truck over a 10 cm thick ice bridge.
By comparision, I understand that the ice road in the Canadian North, which is floating, is typically 3 ft thick.
Cliff Ollier and Colin Pain are heroes. Simply presenting sound information to confound the alarmists. Well done.
@Slartibartfast The author talks about “deep basins” in which this ice resides. Showing a cross-section of these “deep basins” shows that they really aren’t that deep. The ice isn’t filling in the basin with the basin edge acting as a physical barrier, rather it is sitting atop a very slight (given the scales) depression and the ice can flow over or around the edge easily.
His wording conjured up the idea of a deep bowl filled to the top with ice-cubes versus a plate with the same amount of ice sitting on top, which would be closer to reality.
Just to be clear, IMO, ice flow is far more important to continental glacial movement than basal conditions (except at the very edges of the sheet).