Meltwater seeping beneath Arctic glaciers puts thickest and fastest at risk of sudden collapse
UNIVERSITY OF CALIFORNIA – BERKELEY
As climate change warms the planet, glaciers are melting faster, and scientists fear that many will collapse by the end of the century, drastically raising sea level and inundating coastal cities and island nations.
A University of California, Berkeley, scientist has now created an improved model of glacial movement that could help pinpoint those glaciers in the Arctic and Antarctic most likely to rapidly slide downhill and fall into the ocean.
The new model, published last week in the journal The Cryosphere, incorporates the effects of meltwater that percolates to the base of a glacier and lubricates its downhill flow. The new physical model predicts that the most vulnerable glaciers are the thickest ones that have a history of faster flow, even when that rapid flow is periodic.
“The model suggests that thick and fast-flowing glaciers are more sensitive to lubrication than thin and slow glaciers,” said Whyjay Zheng, a postdoctoral fellow in the UC Berkeley Department of Statistics. “The data from Greenland glaciers support this new finding, indicating that those fast and thick glacier beasts might be more unstable than we thought under global warming.”
Zheng built the new model to incorporate a mechanism that has taken on more importance with global warming: meltwater penetrating to the bottom of glaciers and lubricating their downhill movement over bedrock. The Arctic and Antarctic have warmed more than the rest of the world — in March, the Antarctic saw record high temperatures of 70 degrees Fahrenheit above normal, while some parts of the Arctic were more than 60 degrees warmer than average. The warmer weather causes meltwater lakes to form on many glaciers, in particular those in Greenland. The lakes can punch through to the bottom of glaciers by a process called hydrofracture or drain to the bottom through crevasses nearby.
Glaciologists have already seen that the speedup and slowdown of glaciers are related to what’s happening at the front of the glaciers, where the ice merges into the ocean and meets warmer water. Observations show that for many such marine-terminating glaciers, when the fronts melt, or calve, into the ocean, the remaining glaciers tend to speed up. When the fronts advance into the ocean, the glaciers slow. As a result, the focus has been primarily on what’s happening at the glacial terminus.
But basal lubrication by meltwater appears to be creating a feedback loop that accelerates glaciers that have already sped up for other reasons, such as changes at the terminus.
“In Greenland, the glacier’s speed seems to be mostly controlled by the terminus position: If the terminus is retreating, then the glacier will speed up; if the terminus is advancing, the glacier will slow down,” Zheng said. “People think this is probably the primary reason why the Greenland glaciers can speed up or slow down. But now, we are starting to think there’s another and maybe quicker way to make glaciers slow down or speed up — basal lubrication.”
So Zheng set out to modify the common perturbation model of glacier flow to take meltwater lubrication into account, using standard equations of fluid flow.
He tested the predictions of the model against glaciers in Greenland, which is part of Denmark, and in Svalbard, a Norwegian archipelago. The prediction that thicker, faster-moving glaciers are more prone to thinning and discharge into the ocean fit with observations of glacier flow over a 20-year period, from 1998 to 2018.
“Basal lubrication creates a positive feedback loop,” Zheng said. “The faster glaciers are more likely to respond faster to basal lubrication, and the following speedup makes them more prone to future lubrications. For example, if a glacier is flowing 3 kilometers per year, and basal lubrication suddenly happens, it will react so fast that you can see the fluctuation of the speed, probably just a few days later, compared to another glacier that would be flowing at 100 meters per year.”
The implication is that thick, fast-moving glaciers around the Arctic and Antarctic should be monitored frequently, just as glaciers are now monitored for changes at the terminus, to anticipate discharges of large icebergs into the ocean that could impact sea level. Better ways of measuring basal lubrication are also needed, Zheng said.
“If the glacier has a potential to be disrupted in a short time and drain a lot of the ice into the ocean, perhaps within a year or two, that could be something we have to worry about,” he said.
Zheng, whose background is in geophysics, planetary science and remote sensing, first got interested in the basal lubrication of glaciers after studying an ice cap in the Siberian Arctic — the Vavilov Ice Cap on the Russian island of Severnaya Zemlya — that suddenly collapsed over a period a few years, at one point in 2015 speeding up to 9 kilometers per year. After analyzing the event, he determined that the stationary ice cap transitioned to an ice stream — a rapidly flowing glacier — in such a short amount of time because of basal lubrication and the advance of the terminus into the ocean, which reduced friction at the front of the glacier that was holding the glacier back. About 11% of the ice cap flowed into the ocean between 2013 and 2019.
“This is the first time we saw such a gigantic collapse of an ice cap,” he said. “Once it started to speed up, it maintained its speed for a long time. We think one of the most likely reasons is that it created a lot of crevasses on the surface, and those crevasses are pipelines for the surface meltwater to go down into the bottom of the glacier. Now, water comes down more easily and effectively reduces the friction, so the glacier can keep sliding fast, and even faster if the climate gets further warmed up.”
Zheng plans to test the new model on some of the marine-terminating glaciers in Antarctica. Meanwhile, through a new online platform called Jupyter Book, anyone can run Zheng’s data through the model equations and Python code to reproduce his results — a publishing standard he hopes will become commonplace for big data research in the future.
The work was partially supported by the Jupyter meets the Earth project, which is funded by the National Science Foundation’s EarthCube program (1928406, 1928374).
METHOD OF RESEARCH
SUBJECT OF RESEARCH
Glacier geometry and flow speed determine how Arctic marine-terminating glaciers respond to lubricated beds
ARTICLE PUBLICATION DATE
So there is obviously evidence in the geological records that this sudden sea level rise happened before during previous warm periods?
Bingo! Just because you observe something for the first time does not mean it hasn’t happened before.
They aren’t even observing it, they are speculating that it could possibly, maybe, might happen.
According to what? Models, of course!
And more research will be needed- funded by The Church of the Perpetual Climate
Exactly what I noticed – model shows glaciers can ‘suddenly’ speed up so we need more monitoring stations to … watch it happen …so we can… do nothing about it!
If we continue coming out of the ice age, those glaciers are doomed (glaciation in the poles is a relatively new thing, <35 million years in the south and about half that in the north) and will 'suddenly collapse' – which is climate scientist-speak for "panic! Hurry! Emergency! We only have 700 years to run to high ground"
More likely that the world is heading back into glaciation – temperature trend of the last 10,000 years is not reassuring – and so glacial lubrication is trivia. Future generations will laugh at us how we threw away our hard earned advances in civilization because governments heeded misanthropic scammers.
“The Church of the Perpetual Climate Gravy Train”. I like that, I’ll use it when I can. With your permission, of course. Or not.
The warmer weather causes meltwater lakes to form on many glaciers, in particular those in Greenland.
“If the glacier has a potential to be disrupted in a short time and drain a lot of the ice into the ocean,
The implication of the paper is that water seeping to the base of the glacier is a new phenomenon.
If you Google “How do ice skates work?” you will find out that the weight of the skater on the thin blade of the skate causes a film of water to form between the ice and the blade. One could assume that the same forces apply to the weight of a glacier which would also form a film of water on which it will slide. Will more water make it slide faster? Why would it? Where is the actual lab experiments showing this to be true?
Besides that, Greenland is bowl shaped with the center bed rock below sea level. The flow at the bed rock level toward the ocean would be up hill.
Good points you make.
Also, IIRC, that record high temperature “in March, the Antarctic saw record high temperatures of 70 degrees Fahrenheit above normal” was modelled, not actually measured. Geoff S
The paper specifically refers to “marine-terminating glaciers”. The ones that flow into the oceans. There are 141 of these on Greenland, creating a total of 187 ocean outlet basins when branches are taken into account (see section 3.1 of the paper).
You mean like rivers, where extra rainfall causes greater flows.
Is that what you are trying to say?
Glaciers are frozen rivers. A lot of these silly comments could be avoided if people would just take a few moments to skim through the paper in question before attempting to critique it.
You seem to not have the remotest understanding of what glaciers are.
No they are not frozen solid, they are always moving.
They respond to push as well as other natural forces.
Try not to show so much ignorance.
Those “marine-terminating glaciers” are likely being sourced in the interior by the very thick ice in the center of the bowl. Therefore, the ice is probably shearing over the lip of the bowl, and any water reaching bedrock either pools inside the bowl, or finds an outlet through joints and faults in the bedrock.
It is my personal experience in Greenland, while supervising the final closure survey of the plastic deformation of the ice in a tunnel driven by the US Army, that surface melt-waters flow well above the bedrock in the “marine-terminating glaciers” and therefore do not act in the manner speculated.
Were the surface meltwater to reach bedrock near the coast, the speed up would be expected to create tension fractures as the faster ice downslope pulls away from the upslope ice. Is there evidence for that? How would one differentiate that from a speed up resulting from an increase in slope caused by topography?
Water flowing up hill is the effect of Green gravity. It’s also why unicorns can fly!
No one is claiming these glaciers are flowing uphill. The paper specifically states that it concerns “Marine-terminating glaciers”. Those are the very first words in the introduction. You would think that self-described skeptical people would read into the paper at least that far before commenting on it, but there we are.
Did I specifically claim that glaciers flowed uphill? Take some of your
own advice, please!
No one is claiming these glaciers are flowing uphill.
After a short Google search on “Greenland cross section” images:
“Besides that, Greenland is bowl shaped with the centre bed rock below sea level. The flow at the bed rock level toward the ocean would be uphill.” All true except for a few little spoilers; there is no actual ‘flow at the bedrock level’ – the ice at the very, very bottom of the bowl, bedrock level, is very old ice from the previous interglacial, the ice filling the rest of the bowl is old ice from the last glaciation and the ice above the rim of the bowl is newer ice from this interglacial. The flow occurs at rim level, between the newer ice on top and the old ice on the bottom, and the flow is virtually horizontal; the weight of new ice pressing down forces the flow outwards (like toothpaste out of a tube) where it calves into the sea. The implication is that, under enormous pressure, solid ice behaves like a thick liquid.
Zheng built the new model to incorporate a mechanism that … meltwater penetrating to the bottom of glaciers and lubricating their downhill movement over bedrock. … in particular those in Greenland.
Richard Page says: Greenland is bowl shaped The flow at the bed rock level would be uphill.” there is no actual ‘flow at the bedrock level
Thank you for pointing that one out. The every day analogy for that is pancake batter spreading out from the center.
But the so-called mainstream media wants to claim differently:
The claimed lubrication from surface melt water and the melting of the grounding line by warm deep ocean water is a theme repeated over and over and over again in popular press stories. These stories imply that both of these phenomena are new and true. The image above claims the ice was stable in the 1960-1990s.
I very much doubt that the speed of glaciers is modulated by surface melt water finding its way to the bed rock providing extra lubrication.
A trip back in time in Dr. Brown’s DeLorean would probably show that the surface melt water and water temperature at the grounding line would be very much like it is today. The case would have to be made why it wouldn’t be, and it would take more than some vague reference to atmospheric CO2 and Climate Change.
I can assure you that when I was in Greenland in 1966, the glacier near Camp Tuto (near Thule AFB) was not stable. It was moving internally, had Summer meltwater streams, and had built up a thin moraine at the snout, indicating recession.
“A trip back in time in Dr. Brown’s DeLorean would probably show that the surface melt water and water temperature at the grounding line would be very much like it is today.”
Oh I don’t think you need to go that far – if you think about it, all you have to do is date the Greenland ice immediately above and below the rim. If the ice above the rim is markedly younger than the ice below it, then you’ve got a good indication that the ice is constantly being replaced and calved – if it wasn’t then the ice above the rim and the ice below the rim would show a similar age.
Steve Case —
I cannot see how a pool of water like that illustrated can contain enough spare energy to melt its way down to the base and then lubricate the underside. Surely it is lost by freezing before the meltwater passes all the way through ice at below freezing. Geoff S
Yeah but in a model, all kinds of things can happen.
Well, according to the article it punches through, no melting required.
Ah, that explains it. It works like a tunnel diode. Amazing. Semiconductor physics in the glacier world!
The paper describes how the formation of supraglacial lakes in the Greenland Ice Sheet have opened up new moulins that can last for years, contributing to long-lived speedups. These speed ups themselves seem also to have created more crevassed surfaces, allowing water from the surface to route to the base by gravity. It’s all referenced in the introduction.
Did you know that the area of Greenland ice is only fractionally down from its highest extent in 8000+ years.
Nothing out of the ordinary is happening, except there is still a whole lot of ice in Greenland.
Stop your idiotic panicking.
Who’s panicking? I was just letting Geoff know that the thing he had an issue understanding is addressed in the very introduction of the paper he apparently didn’t bother to read.
You are trying to push/support the farce of AGW..
… stop being an ignorant twerp.
Seem you didn’t even read the first BS paragraph……
“As climate change warms the planet, glaciers are melting faster, and scientists fear that many will collapse by the end of the century, drastically raising sea level and inundating coastal cities and island nations.”
The first statement is high farce.. and it just continues from there..
… and silly little boys like you, just lap it up..
Seems that there is not much about climate in the actual paper.
All the climate crap has been added in the comment at phys.org….. where the text of this thread comes from.
TFN, No, no issue, I read the paper before commenting.
Much relies on descriptions of meltwater lakes suddenly releasing large volumes of warmish waters that end up under the glacier. This does not seem an event that can be related to climate change. If anything, it reflects the long odds that now and then a deep crevasse will open by chance under a meltwater pool. Geoff S
Since 2002 the Greenland ice sheet has lost ~5,000 GT.
PODACC-JPL Greenland Ice Sheet Mass loss from GRACE and GRACE-FO.png
It would seem that gravity would close these cravasses before water could reach the base. The pressure from the surface to the bottom of a
“bowl” would tend to close them by pushing the sides together.
Those crevasses are typically less than 60m deep, because beyond that the plastic deformation closes them up. Any warm water from the surface may extend the crevasse depth by melting. However, I expect that to be short-lived both because the water will be cooled from melting the ice, and the ice will tend to close the open voids below 60m from plastic flow, thus squeezing the water out that hasn’t refrozen.
Unless the ice-bedrock contact is already near the melting point, there is little hope that warming of a fraction of a degree is going to result in melting.
My recollection is that when working in the ice tunnel in the snout of the glacier at Camp Tuto, in an environment where ambient air frequently found its way in during the Summer, the tunnel temperature was about 5 deg F below freezing (i.e. 27 deg F).
But heat is gained as a result of the loss of potential energy.
Geoff S — The process is called hydrofracture. This allows water to penetrate ice before it refreezes in the ice. Totally different from melting the pool’s bottom.
What’s for sure is that climate models’ credibility tipping point has been reached years ago and that they are actually collapsing, the laters being each time worse than the formers.
Modeling is the secret weapon The Team™ is using to win the Climate Wars,
by creating stupider & stupider models, hoping we’ll eventually crack by
seeing just how stupid they can be. It’s the excessive extremism of Monty
Python come to life:
Who cares. The evidence is that glaciers melt and reform all the time. The glaciers we see today are the product of the little ice age that ended circa 1850. It’s warmer now – thank God!
Another study and another duff model…
More modelling nonsense, but the
will be along shortly to explain how this is actual evidence..
More modelling nonsense …
because they’ve used Lego instead of Plasticine !
Why do they always use the term “collapse’?
I’ve seen glaciers melting and calving but I have yet to see one collapse.
What do the mean by collapse?
I think “collapse” is the magical word climate research grifters use to open
the door to even more funding.
“Collapse” sounds so much more scary than “melting gradually over thousands of years”.
I am not fond of the word “collapse” either. I would use “dynamic thinning”, or for plain text, “stretching of glacier ice.”
Some of the assertions and logic this article describes do not seem to make logical sense and some sound flat out wrong.
I am not sure if this guy does a very good job of distinguishing cause from effect, or particular circumstances from general rules and principles.
Have not had coffee yet, but several things said in this article need to be picked apart.
I see no mention of rates of accumulation of the ice and how that affects what happens downstream, nor do I see any mention of the lag time between increased or decreased accumulation in the accumulation zone, and when the effect of those changes is manifested downstream with regard to terminus advance or retreat in the ablation zone.
Lag times are all-important when it comes to understanding glaciers.
Nothing that happens for a short time has much effect on a glacier, and long term variations in conditions take a considerable amount of time to be manifest as changes in the behavior or other particulars of the ice mass as a whole.
Glacial advance and retreat is not a simple matter of temperature.
For one thing, it can be getting warmer but with increased precip, or getting colder with decreased precip. It can be getting colder at one time of the year or the diurnal cycle, at the same time the opposite is happening at another time of year or the diurnal cycle.
The air can be getting moister or less moist, affecting ablation by sublimation.
And as mentioned, there is a big difference between water forming a pond on a surface of ice and the water being able to get to the bottom as a liquid.
What is the temp of the ice at various depths? It is rarely right near the melting point, and in fact is often very far below the melting temp.
And right at the beginning, the article starts off talking about unusual warmth at both poles, but said nothing about the duration or aerial extend of such excursions from normal temp.
A few years ago, there was a report of “record high temp in Antarctica”, but it said nothing about where, or for how long, or over how wide an area. Turned out it was one small spot way out on the West Antarctic Peninsula, for a few hours, caused by a downslope compressional wind, over a part of Antarctica that is close to South America…far from the pole and sticking way out into the ocean.
IOW, it had nothing to do with average temps in Antarctica, or even the temp over the polar ice sheet, nor was it anything which cause possibly cause a wide effect or any melting beyond a thin layer that then quickly refroze, more solid than ever.
March at the poles is a time when the Sun is barely above the horizon, and at one pole the long six months of night is starting, and at the other, ice is near a max and the ice itself is frigidly cold…far below the melting point.
It never said any ponds of melt formed, but merely juxtaposed a general observation that this can happen at times, with the part about some warmer than average temps.
It also implied that average and normal are equivalent terms, but they are not.
Excursions far from average are exactly normal for this time of year, and typically followed by the opposite excursion. In fact, whenever air moves north, some other air is moving south, and vice versa.
More alarmist BS is mixed in with dubious reasoning from a biased and likely untrustworthy modeler.
I am seeing a huge spike in over the top alarmist nonsense lately, across a wide swath of media sources.
But everpresent right at the surface of all of it is constant reference to “climate change”, “global warming”, etc…as if we are in the midst of some huge and widespread and prolonged and steady rise in temps everywhere, all the time.
In fact nothing like that is going on, anywhere.
Sea ice in the Arctic is near long term averages in both volume and extent, which represents a big increase over most the last 15 years.
UAH TLT graph shows GAT is very close to the values seen at the beginning of the record, and the big red line showing the long term average (the smoothed value), is currently decreasing. We could be about to see a prolonged period of below mean TLT temps.
We are being massively gaslit.
Warmer would be better, but we may be in the verge of dangerous, costly, and ill-timed global cooling.
And so of course the alarmists choose now to ramp up the volume of the lies and BS to a howling roar.
Personally, I am sickened by it all.
These rotten lying SOBs want to impoverish everyone, and have no regard for the truth or how the things they say affect people, our mental status, our lives, our economy, or our finances.
They are really nasty rotten awful people, bad scientists, greedy self-serving ideologues…
And they are wrong.
Moulin formation during supraglacial lake drainage has been frequently observed and is well documented, e.g. here, here and here.
Yep, its a totally natural phenomenon.
Thanks for showing us that.
Natural yes, and more likely to occur in a warming atmosphere. In any case, it’s a phenomenon that explains one method of how liquid water can route to the base of a glacier. It doesn’t always just sit on the surface in superglacial pools.
Just because water forms a pool and makes it’s way down into an ice sheet or glacier, does not mean it will make it to the bottom as a liquid, or that if it does, it will not refreeze.
Sure…it CAN do so, but it is not a given.
Any more than it is a given that some melting caused by a warmer than average period means lakes will form, or that a lake once formed will find a crack.
I am wondering what part of my comment, or what part of what you quoted, gave some indication that I am unaware of the processes you mention?
Like groundwater, the ice within a glacier or ice sheet is going to be at the average temperature of the air.
Ice is a poor conductor of heat, and has tremendous thermal mass.
And the melt sitting on the surface is going to be barely above freezing, given that it is in contact with ice.
The way this article is written is contrived to imply facts not in evidence…that ice at the poles is melting rapidly and making its way quickly to the bottom and lubricating the glacier/surface interface, causing the mass of ice to speed up.
In fact nothing presented gave any evidence or reason to think any of that has or is occurring.
It is a contrived narrative, ungrounded from factual information.
That’s true, some morains just deliver the water into the belly of the glacier. However, at least one of the links I posted above describes incidents where the water was observed to access the base of the glacier rapidly, e.g.:
So it does happen and it has been observed and documented. What the author of this paper has done is hypothesise that increased basal lubrication may be the mechanism that explains the observation that some ocean-terminating Arctic glaciers are advancing more quickly than observed ocean interaction at their terminus suggests they should be.
To test this, he sets out a clear mathematical model of how the various physical processes would be expected to react, used this to make predictions of flow rates then compared these to observational data for over 100 glaciers. He found a good correlation, as stated in the conclusion. This is evidence supporting the hypothesis, whether we care to accept it or not.
So, absolutely nothing to do with anything humans have done..
Wouldn’t you agree.
Just a totally natural process
You do know that the Greenland Ice sheet is only a tiny amount down from its highest extent in some 8000+ years, don’t you.?
And using climate models in the pretense they can predict the future.
A total joke/farce, as I’m sure you would agree.
Kudos to Zig Zag Wanderer for giving the best synopsis of this study:
April 29, 2022 2:25 am
They aren’t even observing it, they are speculating that it could possibly, maybe, might happen. According to what? Models, of course!
I might add the researcher may also be looking for fame & possibly
more funding. If you had read the article closely, you may have come
to a similar conclusion & spared yourself a lot of aggravation!
There are glaciers that are frozen to the ground under them, and those that have a layer of melt under them.
This has been well known for many decades, long before I took any classes in glaciology or hydrology.
It has to do with the temperature of the ice.
The difference results in two entirely different modes of glacial advance.
The whole thing can slide, or it can move by plastic deformation.
When accumulation increases for a sustained period of time, a glacier will often become thicker and thus heavier and pressure can melt the interface with the ground.
What we seem to have with this paper is someone who is not very knowledgeable of the subject just acting like little is known about the behavior of glaciers, and figuring they would just rewrite the textbooks starting with CAGW gospel as the basis of the “science”.
Anyone can look up any online glaciology text, or just look at Wikipedia and read the articles there, and then read the references at the bottom of the page.
Glacial surge is not a newly discovered phenomenon.
Neither is meltwater making it’s way into the interior of a glacier.
This article does not even seem to differentiate between alpine and continental glaciers. The one he describes in some detail is a subtype called an “ice cap”.
On the islands where what he describes tales place, are dozens of glaciers and ice caps.
Only this one has done what it is doing, so it is hard to make the logical case that it is because of “global warming”.
The article also bizarrely claims:
““In Greenland, the glacier’s speed seems to be mostly controlled by the terminus position: If the terminus is retreating, then the glacier will speed up; if the terminus is advancing, the glacier will slow down,” Zheng said. “People think this is probably the primary reason why the Greenland glaciers can speed up or slow down.”
Maybe “people think this” who have recently graduated with Climate Science™ degrees, or who like this guy just decided he is gonna rewrite the book on how and why glaciers do what they do, but it is not what everyone trained in this subject for most of the 20th century ever thought…or knew.
The speed is not determined by the position of the terminus, the position of the terminus is determined by the balance between accumulation and ablation.
This part is just wrong: “If the terminus is retreating, then the glacier will speed up; if the terminus is advancing, the glacier will slow down”.
I do not think one even needs to know anything about glaciers to realize this makes no sense and is not what glaciers do.
When glaciers move faster, for any reason, the terminus will advance until a new equilibrium is reached.
How would a terminus retreating make a glacier move faster?
This does not make any sense, and is factually wrong.
And the reverse is just as wrong and probably more obviously so: If the terminus of a glacier is advancing, how would that mean the glacier is moving slower, let alone cause it?
One big problem with the approach this guy seems to be taking is that he wants to make a model and use it to describe glaciers, instead of doing extensive observations and learning more about the various mechanisms and how various factors interact to make every glacier on Earth have constantly varying behavior and all be somewhat different in how they respond to local conditions.
“When a glacier is experiencing an accumulation input by precipitation (snow or refreezing rain) that exceeds the output by ablation, the glacier shows a positive glacier mass balance and will advance. Conversely, if the loss of volume (from evaporation, sublimation, melting, and calving) exceeds the accumulation, the glacier shows a negative glacier mass balance and the glacier will melt back. During times in which the volume input to the glacier by precipitation is equivalent to the ice volume lost from calving, evaporation, and melting, the glacier has a steady-state condition.
Some glaciers show periods where the glacier is advancing at an extreme rate, that is typically 100 times faster than what is considered normal, it is referred to as a surging glacier. Surge periods may occur at an interval of 10 to 15 years, e.g. on Svalbard. This is caused mainly due to a long lasting accumulation period on subpolar glaciers frozen to the ground in the accumulation area. When the stress due to the additional volume in the accumulation area increases, the pressure melting point of the ice at its base may be reached, the basal glacier ice will melt and the glacier will surge on a film of meltwater.”
Glaciology – Wikipedia
“The top 50 m (160 ft) of a glacier are rigid because they are under low pressure. This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in the fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in the ice, called seracs.
Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from the stagnant ice above, forming a bergschrund. Bergschrunds resemble crevasses but are singular features at a glacier’s margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges.
Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of a glacier via moulins. Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier’s surface.”
“A few glaciers have periods of very rapid advancement called surges. These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock, the pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical “tipping point”. Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier.”
Glacier – Wikipedia
“in a warming atmosphere.” ????
The Arctic atmosphere has been cooling since the 2015 El Nino spike
Apart from that spike, all gone now, there has been no Arctic warming this century.
So stop your nonsense statements,.
No, it’s conjectured by a model, not explained.
Actually, more likely to occur with reduced cloudiness because the sun is more effective at heating and melting ice than the air is.
I don’t suppose it ever occurred to you and the other frickin’ geniuses writing this paper that the lubricating water under the glacier might not be anything to do with rising temperatures, but might instead be due to the incredible pressure from the sheer weight of ice pressing down on the underlying surface? Has anyone investigated that possibility?
This is what you get when “scientists” use the mean of a distribution and never look at the Standard Deviation of that distribution. There is only one number and that is the calculated mean. I doubt if any could even tell you if the distribution used is normal or skewed.
Too many climate scientists are all too willing to call the excursions you mention “NOISE” and thereby rationalize ignoring the true Standard Deviation.
Since “climate change” (as in human CO2 caused) is a fantasy.
Everything that follows from it is a load of Mills and Boon crap. !
As soon as I saw the word model I stopped readying.
Be aware that the text in the body of the main post, has very little to do with the content of the actual paper..
The paper has been massively distorted by some clown at U Berkley.
Then you’ll miss the analysis done for real data from Greenland and Svalbard.
And yet glaciers are doing exactly what they have always done. Funny how that works.
I wonder what conclusions you could draw from investigating the weight of ice exerting pressure on the underlying surface and how the ice would behave under those conditions? Not temperature, but pressure from the weight of ice?
Basically, what has happened here is that some clown from U Berkley has written a twisted opinion piece about Zheng’s paper.
They have added in a whole heap of climate BS that was not in the actual paper.
Shows how much phys.org has become nothing more than a propaganda rag.
Scientists who should know better still persist in calling an examination of the output of computer models a ‘study’. It is not a study. Its an exercise in computer modelling. It might or might not be useful and informative, but it is not a study. Its a modeling exercise.
The paper does not do computer modeling. All the data are from real glaciers in Greenland and Svalbard.
“…scientists fear that many will collapse by the end of the century…”
This is a good fear to have and push onto the media to justify your paycheck.
Flash news: Berkeley “scientist” mesmerized by the melting ice in his gin and tonic creates model predicting the collapse of arctic glaciers, applies for and receives generous grant, publishes useless article and then fixes another drink.
But he failed to notice that the melting ice didn’t raise the level of the G&T.
“Lubrication” is a bullshit made up phenomenon. Glaciers move faster only due to having more ice “upstream” – it’s simple physics, gravity is what causes all glaciers to move. Meltwater does not flow down through solid idea, because ice is a plastic impermeable semi-solid – if there is any meltwater it is generated at the surface where it either flows downhill, like all other water, or if it cannot flow due to surface obstructions, it will simply collect and refreeze most of the time.
As usual, the warmunists confuse and conflate cause with effect.
Ice is an impermeable plastic semi-solid. Any cracks that exist that could transmit meltwater quickly close up and seal off with pressure at depth within the ice column.
Any meltwater that appears at the base of the ice column at depth is strictly due to frictional heating between the moving ice over the stationary ground surface. The faster the glacier moves, the more friction, the more frictional heating, and therefore the more meltwater at the interface. But that has nothing to do with meltwater at the surface due to “climate change”.
This is elemental physics, but of course the warmunists are all science deniers
at their core – they depend entirely upon scientific ignorance to make their bullshit case..
You also have to realise that most of Greenland lies over an extension of the very active Icelandic volcanic sac.
Glaciers move by plastic deformation AND basal sliding, Duane. For example, plastic deformation cannot explain the seasonal speed flucuations at Jakobshavn Isbræ because there isn’t more ice upstream in the summer. Basal sliding is the most reasonable way to attribute high flowing speed in the summer.
Video games. Scary, scary video games.
We are paying these doofuses. to code and play video games.
Wouldn’t want to go out a look at real glaciers. That would be cold, wet, and grimy work. No stay home and play video games.
No, that METHOD OF RESEARCH is wrong. The paper does not simulate anything. All the data are from real glaciers in Greenland and Svalbard.
“Models”. Meh. The fear of sea level rise is why the elite are buying more oceanfront property. Right?
If the leaders of the cult are buying up said property, I don’t think we have much to worry about in regards to catastrophic global warming.