Claim: New model for gauging ice sheet movement may improve sea-level-rise predictions

From the UNIVERSITY OF KANSAS

LAWRENCE — A just-published paper in Science changes the formula scientists should use when estimating the speed of huge ice sheets in Greenland and Antarctica that flow into the ocean and drive mounting sea levels around the globe.

The change in the formula for predicting ice flow — or basal sliding — reduces “the largest uncertainty” in predicting future sea-level rise. It was prompted by analyzing data from 140 glaciers in Greenland.

University of Kansas researchers Leigh Stearns, associate professor of geology and research scientist at the Center for Remote Sensing of Ice Sheets, and Cornelis van der Veen, professor of geography, discovered friction — or “basal drag” — between ice sheets and the hard bed underneath has no influence on how fast glaciers flow.

This finding throws out a notion that has colored estimates of glacier speed for decades.

“Basal sliding is one of the most important things we try to measure in glaciology and one of the hardest to measure,” said Stearns. “Our paper says the parameter most used in ice sheet models is incorrect — the Weertman model — developed in the 1950s based on a theoretical framework that how fast ice moves at the bed is based on friction and the amount of water at the bed. We’re saying that friction doesn’t matter.”

Instead, the KU researchers found subglacial water pressure, the water pressure between the bottom of the ice sheet and the hard bed underneath, controls the speed of the ice flow.

Red polygons show the 140 marine-terminating glaciers analyzed. Jakobshavn Isbræ, Kangerdlugssuaq Glacier and Helheim Glacier are circled in blue. CREDIT University of Kansas

Part of their work included an analysis of decades-old studies of water pressure underneath mountain glaciers, which “have been largely overlooked by the glaciological community.” Stearns and van der Veen paired the mountain-glacier results with the recent observations on surface velocity from the outlet glaciers in Greenland.

“We can calculate the friction at the bed of glaciers by investigating spatial patterns of surface velocity. Surprisingly, we found that the two are not at all correlated. Pressure is different and much harder to measure. We know what the pressure at the terminus is because the glacier is floating there, and we can calculate up-flow pressure based on ice thickness. It’s not a perfect estimate, but it gives us a good first approximation. If we could, we’d love to put boreholes into all 140 glaciers around Greenland and measure water pressure directly, but that’s not practical.”

Stearns and van der Veen found the relationship between subglacial water pressure in Greenland’s outlet glaciers lined up with measurements taken from the mountain glaciers in the 1980s, implying the processes for sliding variations are also similar.

“The simplified sliding relation can appropriately reproduce spatial patterns of ice velocity,” the KU researchers said. “This is in stark contrast to current modeling techniques, which involve tuning the sliding parameter in order to match observed velocities.”

“Models that are used to predict sea-level change are inexact because we can’t directly measure processes happening at the bed,” Stearns said. “Current models using Weertman solutions require tuning to match observations. It’s an imperfect way of doing what has to be done to come up with estimates. It has a lot of knobs. With this new parameter, we’re trying to reduce the amount of tuning needed.”

Even though “people were waiting for someone to challenge Weertman, people knew it needed to be improved,” Stearns said she worried about causing upset with scientists who’d relied on the older model for earlier research.

“I was a little nervous,” she said. “I was anxious because it negates what people have been using for a while. It calls into question the model they’re using. But the reaction has been positive so far. People have been encouraging of a new systematic approach to a sliding law.”

Stearns has too much humility to dub her new formula the “Stearns model,” even though it improves and replaces the less accurate “Weertman model,” named after the scientist who devised it.

She stressed her revised formula is part of the self-correcting nature of scientific inquiry and shouldn’t shed doubt on climate science or the inexorable rise of sea levels around the world as more ice from Greenland and Antarctica melts into the ocean.

“I hope it helps people believe in our projections,” she said. “This is based more on physical processes and less on things you have to tune for any reason. Anything that’s improving how we model ice sheets in the future is a good thing — how are ice sheets responding to climate change? With these model improvements, we’re getting a step closer to a really accurate understanding.”

###

The paper: http://science.sciencemag.org/content/early/2018/06/06/science.aat2217

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78 thoughts on “Claim: New model for gauging ice sheet movement may improve sea-level-rise predictions

    • It’s all about not getting a knife in your back in the dead of night. Look at Soon, Baliunas, Lindzen, Curry, Ridd, and any number of others.

  1. We can calculate the friction at the bed of glaciers by investigating spatial patterns of surface velocity. Surprisingly, we found that the two are not at all correlated.

    That makes no sense. If friction and the spacial patterns of surface velocity are not correlated, then we cannot the friction by investigating the spacial patterns of surface velocity.

    • That’s how I’m seeing it too.

      They use the spatial patterns of surface velocity to calculate friction.

      They USE velocity to calculate friction.

      This means that there MUST be a mathematical relationship between velocity and friction. If there is a mathematical relationship between velocity and friction, then there MUST be a correlation between velocity and friction.

      They USE a correlation, only to arrive at a conclusion that the correlation that they use does NOT exist.

      Am I reasoning this right ?

    • The article states “We’re saying that friction doesn’t matter.” it’s the waterpressure which drives the speed of the glacier.
      So i guess they give up on trying to guesstimate the friction and move to a new model that doesn’t use it.

      Could be science or even progress if not for the kowtowing to the AGW funding machine.

      • I think it is convenient too that a variable has been chosen that is impractical to actually measure.

        So, they use velocity to calculate friction, trash the significance of friction, and somehow assign pressure (which is impractical to actually measure) as the new variable upon which glacier movement is predicated.

        So, is pressure modeled ? How is pressure determined, if it is impractical to actually measure it? Models would, thus, now emphasize a new variable that I guess, itself, is modeled.

        “Models all the way down”, as someone wrote earlier, … because obtaining actual measurements is just too impractical.

        Is anybody else realizing how utterly absurd this appears?

        Reality is too impractical to ascertain ?! So, we base our approach to living in reality on a plan NOT based in reality ?!

        Maybe I’m being too harsh ?

  2. “… shouldn’t shed doubt on climate science or the inexorable rise of sea levels around the world …” SEE! I haven’t rocked the boat guys. I’m onside. Really.

    I weary of all these ‘new’ findings that don’t expose AGW for the shambles it is. It’s my money they are ‘spending’. I wanna, I wanna see, I wanna see blood and gore and guts and veins in my teeth …

    • “I weary of all these ‘new’ findings”.

      It must be incredibly tiring for you with all this evidence piling up.
      Try the other end of the telescope.

      • You zazove, very obviously, have no idea what constitutes evidence.

        Evidence: noun 1. the available body of facts or information indicating whether a belief or proposition is true or valid.

        Models are not evidence. Models are not facts. Correlations are not either.

        If you had any evidence we could all go home and quit wasting our time and treasure on this belief system’s guesswork because it would have then gravitated from a guess/conjecture/proposition to a hypothesis, which demands some evidence. Your side has none. 0. Zip.

        I do so wish you would stop acting as if you are right but, amongst other things that is what trolls do.

        • In zazove’s world, if this year is warmer than last it’s proof that CAGW is real.
          If it’s cooler than last year, that’s just weather.

      • All the new evidence is reinforcing that fact that the alarmists are perpetrating a sc@m on the rest of the world.

    • You have to have a model so lets call it the Chris4692 model and here let me write your climate mode code for you so you can be a proper climate scientist

      double Chris4692_Sea_Rise (double temp){
      return 0.0;
      }

      There all done you are now pro

  3. “I hope it helps people believe in our projections,” …nope, not one little bit

    …fool me twice

  4. “We know what the pressure at the terminus is because the glacier is floating there”

    That is a rather doubtful statement. The pressure can’t be lower than the water pressure in the ocean at the base of the ice, but it can definitely be higher. As a matter the existence of subglacial river proves that it is higher.

    Also note that much of the Greenland ice-cap is cold-based, i e frozen to the bedrock underneath, with no water film and thus no water pressure.

    • Yes, while some glaciers have liquid water at the base, not all do. Additionally, there are different kinds of ‘friction.’ If the bedrock is flat, then one is dealing with the classical friction that operates at the microscope level. However, if the bedrock is highly irregular, with high relief, then the ice encounters a buttressing opposition that may require the ice to shear over the ridges and the effective friction will the the resistance to shearing, which probably varies with temperature, thickness of the ice, and the angle of shearing. I don’t think that this publication settles the science. It leaves a lot of questions unanswered.

  5. The new model is based on the same, flawed assumptions, which will produce wronger than wrong results, but hey, it’s new, so that’s a good thing, right?

  6. Has any one of these so called scientists ever left the building? Have they ever seen an ice sheet other than on the Television? Is science just about sitting in front of a computer and jiggling with data? How many times can you analyze, re-analyze, re-re-analyze the same data with your swishy new computer before someone says get off your ass and go out and collect some new data?

  7. “Current models using Weertman solutions require tuning to match observations. It’s an imperfect way of doing what has to be done to come up with estimates. It has a lot of knobs. With this new parameter, we’re trying to reduce the amount of tuning needed.”

    That’s very positive and has a lot of positive implications for how climate science should be conducted, in contrast to how it currently is being conducted.

    Please call off the attack dogs.

  8. We have these things called tide gauges all over the world so we need more precision on glacier ice flow rates because?

  9. The ‘non-friction’ theory doesn’t make much sense. A glacier is ice, a LOT of it, standing a non-smooth bed of rock (I presume). Water, under pressure, can exist in between the ice and the rock. If water pressure builds, or ice melts due to geothermal heat from the earth’s interior and more liquid water appears, pockets of water will appear. If enough water collects, the glacier WILL float on the layer of pressurized water. If it floats ‘high’ enough the solid ice will not touch the bed rock at any point. The glacier will still not move until and unless there is a slope in the valley or terrain. So, the rate of movement is controlled by the force imposed by gravity down the ‘hill’ and the ‘drag’ caused by the ability of the ice to ‘flow’ around the high points in the glacier bed. In effect, the ‘friction’ is caused by the limits of the ice in flowing around an obstruction.

    • Yes, that occurred to me too. They seem to be treating friction not as some form of simple Coulomb friction which is not dependent on velocity of sliding but as a viscous drag which increases with velocity. I would expect that in fact the bottom of the glacier would be mechanically interlocked with rocks in its bed and the velocity would depend on the mechanics of the breaking of the interlocks. In some cases the rocks themselves would give way but mostly it would be the ice which variously melts, fractures and reforms. Presumably the rate at which this occurs is dependent on the both the physical characteristics of the ice and the principal stresses generated. Characterizing this as ‘friction’ is a misuse of the language.

      • It should be noted that each ice age removes essentially all loose material and a fair amount of solid rock from the ice-covered areas. On the order of several hundred meters of rock has been eroded during the Pleistocene.
        It would seem that this is rather strong evidence that there is friction between the ice and the bed.

        • Not to mention the glacial grooves gouged out of coherent bedrock, analogous to a lathe tool cutting metal, indicating the expenditure of considerable work.

        • Whatever it is, it is not Coulomb friction. The nearest analogy is the action of a saw when cutting: the interlocking of teeth with the material being cut. The mechanical properties of the material being cut are more significant than simple friction between surfaces.

    • NW sage

      There is an aspect of Greenland’s glaciers that must be considered in this discussion: the bowl-shaped interior is such that glaciers around the periphery are forced uphill by the higher pile of ice in the centre. The glaciers are pushed uphill and over the ‘lip’ and then the fall down the other side by gravity.

      The forcing of glaciers uphill should give everyone pause to consider that the ‘classic’ view of how glaciers move is not universal, particularly in Greenland. What role water plays in these peculiar movements is anyone’s guess.

      • It is also possible that instead of the ice moving uphill, it is stagnant inside the encircling ring of mountains and the ice shears over the underlying ice, with a relatively low gradient.

    • How smooth the bed is depends a lot on how old and heavy the glacier is. All that ice can polish rock fairly quickly in geological terms.

    • There are two components to the glacier’s movement. There is down-slope movement induced by the slope of the bedrock, and a tendency to spread under its own weight like a ball of Silly Putty sitting on the floor.

    • NW Sage,

      On the contrary, I think this makes sense for the exact reasons you describe. A hydro-static interface between the glaciers (note: I assume it’s not the ice sheet in general) and whatever substrate the glacier is riding on renders calculations for glacier flow based on friction meaningless. This is precisely why the previous models had to rely on parameterization. That there is sufficient incline to induce movement in the glacier is apparent in the many excellent diagrams and radar cross sections on the subject:

      http://blogs.ei.columbia.edu/wp-content/uploads/2015/05/greenland-ice-sheet-graphic.jpg

      Dave Middleton, in his recent post, also included some excellent graphics and commentary…though glacier flow was not precisely the point of his commentary, it does provided some meaningful context: https://wattsupwiththat.com/2018/03/22/a-geological-perspective-of-the-greenland-ice-sheet/

      Finally, it’s not clear to me why there’s so much negativity regarding this research. This scientist has done EXACTLY what we want our scientists to do. Namely, eschew the faulty approach of previous science, and look for a new, better explanation for observed phenomena. That she has upended a previous theory with a better understanding is excellent, and nothing to be derogatory about. (Note, NW, I’m not suggesting you were derogatory, but rather am taking this opportunity to address the many other posts which were.)

      What’s most telling to me, and what I think, perhaps, is being missed by everyone, is that the scientist affirmed something we’ve been saying repeatedly. Namely, that parameterization is a faulty method for modeling. And does not achieve accurate results. This is exactly correct, and is the reason for the imprecision embedded in the many GSMs (or, ESMs). Literally, she just affirmed one of “our” major complaints. We should be congratulating her for this.

      Instead, there are a gazillion knee-jerk reactions which only serve to confirm the worst caricatures of the climate alarmist crowd that we’re just a bunch of “deniers”.

      Respectfully,

      rip

  10. … discovered friction — or “basal drag” — between ice sheets and the hard bed underneath has no influence on how fast glaciers flow.

    Forgive me, if I’m being stupid, but wouldn’t such a “discovery” imply that a fundamental law of physics, all of a sudden, does not apply to glaciers ?

    Maybe the discovery is that there is some problem with definitions that leads to what, to me, seems like a wild claim. But, again, maybe I’ve got a big gap in my understanding here.

    • RK,

      I take it to mean there are other factors influencing flow rate, rather than friction. That there exists a thin film of water between the glacier and substrate isn’t really surprising. That this film renders previous calculations (based on coeffficient of friction between ice and rock) inaccurate, is likewise, unsurprising.

      So we now have an approach based on pressure, rather than friction, which leads to actual calculation rather than parameterization. Good. That’s how modeling is done properly.

      rip

  11. I would have thought the amount of water upon which the glacier is floating would effect the FRICTION as it essentially determines how much hard ice is in contact with hard rock.
    Any child knows that a dry slip and slide isn’t very slippery.

    • Again, that’s what I was thinking.

      The water is like a lubricant and a gap filler on the rough bed. Water can CHANGE friction dramatically, NOT eliminate friction from consideration altogether.

      Maybe a better line would be … It’s Not Your Daddy’s Friction

      … but it’s STILL friction. It’s still there.

    • In the past we utilized knowledge about friction to ensure we had ‘safe’ highway/roadway stopping sight distances given a certain speed … recognize the need, slam on the brakes, come to an eventual stop.

      Now this lady comes along and tells us about hydro-planing. Since hydro-planing almost eliminates the tire/surface friction (when there is a lot water on the road), the concept of friction being a controlling factor is possibly wrong. We need to notify AASHTO immediately.

      (OK, the more I’ve thought about it, maybe the concept of friction is not really wrong. Maybe the friction factor just changes, depending on surface conditions. Maybe friction is still a thing … regardless of the object type & surface materials. Maybe the coefficient of friction is variable, depending on materials/temperature/speed/etc. Maybe this lady, and her helpers are the ones that are wrong.)

    • Technically, the ice isn’t floating. Remember water isn’t compressible. It’s quite possible for an entire glacier to ride upon a thin layer of water.

    • So, I’m speculating that different glaciers might have very different interfaces between what might be considered the “base” and the “surface” upon which the base rests.

      Okay, lots of pebbles and dirt can be mixed in the base ice for some cases, and maybe, for other cases, less pebbles and dirt are mixed in the base ice. Still, I do not see forgetting about friction in one instance as a consistent way to look at sliding in all instances.

      Again, how is water pressure in less “dirty” base ice even figured? — I’m not paying for the article to read it — people making these claims need to make their details accessible to anybody and stop holding it hostage behind pay-to-read. All this does is keep the inbreeding of possible errors insured.

  12. “If we could, we’d love to put boreholes into all 140 glaciers around Greenland and measure water pressure directly, but that’s not practical.”

    In other words, there is very little or no real measurements to back up their claims? But they seem awfully sure they are 100% right. Geesh.

      • Probably long enough to reach the bottom. There have been a number of successful drillings to reach bedrock in both Greenland and Antarctica. But, you can’t expect the hole to remain open over a number of years for re-visits. But then, it doesn’t all close at the same rate, so it might be possible to recondition holes if necesary.

  13. Somehow, an old quip came to mind:
    “The essence of duplicity rests upon apparent frankness.”
    I thought it was by Alexander Pope. Could not verify that but it is a good one.
    Bob Hoye

    • Bob: A new quip, if I may- the essence of duplicity rests upon whether Bill is speaking, or Hillary.

      I know. A bit forced, but I had to say it.

  14. I had understood that glaciers move by creep and do not ‘slide’, and that the characteristic marks one sees on glaciated terrains are caused by sediment trapped within the ice, like sandpaper?

  15. From Kansas and they haven’t read any road signs ?
    ” SLIPPERY WHEN WET ! ”
    Maybe they don’t drive ?

  16. re “If we could, we’d love to put boreholes into all 140 glaciers around Greenland…” That right there will probably accelerate those glaciers’s progress to the ocean. Leave them glaciers alone!

  17. If this is such important research for understanding the coming catastrophe of sea level rise then why wouldn’t drilling boreholes in a good sampling of the glaciers to test their new hypothesis be extremely important. Of course such measurement just might prove their hypothesis or is it their new model wrong.

  18. So, reading this, it indicates that modeling glacier movements is based upon a measurement that they likely are never going to make in most places. So what they will do is simply make up water pressure numbers to create the “futures” that make them the most money?

  19. This is nothing new and will not ‘replace’ previous basal ice parameters. Sliding of basal ice has always been a function of friction vs driving force. Friction is governed by bed roughness, normal force, and slope minus any hydraulic lift due to basal water pressure. All of those factors remain valid today and cannot be disregarded.

    • Oh, but in GREENLAND, we CAN do something different == we can ignore friction — that way maybe we can make the ice slide faster in the models there, to predict even GREATER sea-level rise. Trashing friction might not be right, but it’s for the right reason. (^_^)

  20. Whatever isostatic correction is made for Antarctic ice gain and loss over the Holocene, and the response of the landmass to these changes, must be a difficult task requiring knowledge of what happened in Antarctica over the Holocene.

    For instance, Weaver et al 2003:

    http://home.sandiego.edu/~sgray/MARS350/deglaciation.pdf

    show that 14,600 years ago there was a huge ice sheet collapse in Antarctica, which by then had been steadily warming under obliquity forcing for about 5000 years. This gave rise to what is called Meltwater Pulse 1A (MPW 1a), which caused 20m of sea level rise in about 500 years, and initiated the Bolling-Allerød D-O-like warm spike (followed in reaction by the Younger Dryas).

    So clearly around Holocene inception there was a big loss of land ice from Antarctica. However over the course of the Holocene the warmer moist atmosphere caused more snow, so at some point Antarctic land ice loss (as evidenced by mwp 1a) would have reversed to ice gain from all that snow.

    Presumably the Antarctic land mass responded to more ice by being pushed down and to less ice by springing back up. If one wants to make an isostatic correction for Antarctica one needs to know reasonably accurately the history of land ice loss then gain over the whole Holocene inception and Holocene. I’m not sure that the state of this knowledge is good enough to allow this. This all adds a significant question mark to Antarctic isostatic adjustment, which is unfortunate in regard to both Antarctic ice volume changes and sea level, which require this adjustment to be very accurate since both metrics are in fact little more than derived factors of isostatic adjustments.

    • That theory is more or less dead. The problem with deriving MWP-1A from Antarctica is that an “ice collapse” would have left fresh abandoned end moraines on nunataks higher than the present ice-levels.
      There isn’t any. Such higher moraines that do exist are almost invariably very old, even Pliocene or Miocene. The current Antarctic ice is about as thick as it has ever been in the Pleistocene. What happened at the end of the last ice age in Antarctica is that rising sea-levels caused flat, marginal marine-based ice sheets to retreat (an ice-front in deeper water than c. 500 meters is mechanically unstable).

      • What happened at the end of the last ice age in Antarctica is that rising sea-levels caused flat, marginal marine-based ice sheets to retreat (an ice-front in deeper water than c. 500 meters is mechanically unstable).

        And this caused a melt-water pulse?
        If the rising sea levels caused, rather than were caused by, Antarctic melt, the result is the same – a pulse of meltwater that indirectly caused the excursion of the AMOC giving rise to the Bolling-Alerod. (I had wondered why a catastrophic melt event would make sea levels rise over 500 years – one would expect a shorter timescale. Thus your explanation is more plausible.)

  21. Let me apply a little common sense to the climate change argument. Please point out where common sense fails me.

    Stipulated that the dire results of climate change will take place in the next 50 to 100 years. (Note that this is AFTER the death of most of the “scientists” doing the research so there will be no opportunity to publicly embarrass them.)

    1. “We” have known about these dire consequences for several decades even though “we” are only now able to predict them with precision.

    2. Much of civilization’s buildings and infrastructure have been built or rebuilt in those decades. World Population 1975 4.1 Billion vs 2015 7.4 Billion

    So, which idiots have either rebuilt in the EXACT same locations that were destroyed by climate change, or built new structures withOUT taking into consideration the “dire results” of climate change?

    Seems like common sense would have led all these “brilliant” scientists, city planners, architects and engineers to:
    1. Move their projects out of the “danger zones” such as the coast and flood zones.
    2. Designed their projects so that even a massive 1 or 2 foot rise in water levels wouldn’t affect them.
    3. Would have advised AGAINST even doing the projects in an effort to reduce the SIZE of the human population to counter climate change by making life unpleasant.

    Yet, here they are, building structures that will be destroyed by the inevitable change in climate.

    Have I missed something? Has common sense failed me?

    • I suspect that one reason the cliffs, low-lying coasts, and flood plains are getting built up is that older, and wiser generations avoided obviously dangerous places. Then, people with more dollars than cents, and greedy developers, built on the land formerly rejected because it was available and relatively cheap. The real tragedy is that the people making unwise decisions about where to live, expect everyone else to bail them out when their homes get destroyed.

  22. It would be nice if they had some experimental data to validate their model.
    As I recall from freshman physics, and geology 101; we spent a lot of time on friction, and slip/slump/slide.
    I don’t see how friction or fundamental geology would not apply to glaciers, and their propensity to move or not.

  23. God, have we had it up to here with rattling tins for more funding of climate models, or what? Climate is chaos. Chaos is climate. Chaos is unpredictable. Live with it and keep your hands off our wallets.

  24. Here’s an example of the mindset of climate modellers nowadays. Remember the legendary John Daly, intrepid climate sceptic? Sea levels were his specialty. Some years ago a “peer reviewed” paper, awash with data and fancy analyses, produced a graph showing the trend in sea levels (rising, of course) from historical times to some scary point in the future. But the historical part mismatched cold hard measurements, that Daly had reported, by a country mile. When I pointed this out on the publisher’s website, the authors’ answer was that Daly’s data were clearly invalid outliers and therefore disregarded. It’s so long ago that I can’t remember essential details of the paper but maybe readers can help.

    Another example in a related vein is a report, maybe about 2 years ago, of widespread famine caused by global warming, diametrically opposed to the observed reality to the contrary. Only after the report had been brandished and broadcast widely by the MSM did it sink in that the report was based on modelling! Again, just lazy about googling I suppose, but can’t recall the details.

  25. If we could, we’d love to put boreholes into all 140 glaciers around Greenland and measure water pressure directly, but that’s not practical.”

    Well, practical they could bore holes in ice cubes.

    Practical. Studies or not, same outcome.

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