Study: Greenland ice sheet moving slower now than in the last 9000 years

From the UNIVERSITY OF TEXAS AT AUSTIN and the “must add a global warming caveat to prevent backlash” department:

Greenland's average ice speed over the last nine thousand years (left), its current speed (center) and the difference between them (right). Blues (negative values) signify lower speeds today as compared to the nine-thousand-year average. CREDIT Joseph A. MacGregor

Greenland’s average ice speed over the last nine thousand years (left), its current speed (center) and the difference between them (right). Blues (negative values) signify lower speeds today as compared to the nine-thousand-year average. CREDIT Joseph A. MacGregor

Scientists map movement of Greenland Ice during past 9,000 years

Scientists have created the first map that shows how the Greenland Ice Sheet has moved over time, revealing that ice in the interior is moving more slowly toward the edges than it has, on average, during the past 9,000 years.

The findings, which researchers said don’t change the fact that the ice sheet is losing mass overall and contributing to sea level rise, are published in the Feb. 5 issue of Science. Along Greenland’s periphery, many glaciers are rapidly thinning. However, the vast interior of Greenland is slowly thickening, a process the new study clarifies.

“Scientists are very interested in understanding how ice sheets flow and how that flow may have been different in the past. Our paleo-velocity map for Greenland allows us to assess the flow of the ice sheet right now in the context of the last several thousand years,” said lead author Joe MacGregor of The University of Texas at Austin’s Institute for Geophysics (UTIG), a research unit of the Jackson School of Geosciences.

The study builds on earlier UTIG-led research that developed a database of the many layers within Greenland’s ice sheet. Using this database, the scientists determined the flow pattern for the past 9,000 years — in effect creating a “paleo-velocity” map.

In comparing the paleo-velocity map with modern flow rates, researchers found that the ice sheet’s interior is moving more slowly now than during most of the Holocene, a geological period that began about 11,700 years ago and runs to the present.

“Like many others, I had in mind the ongoing dramatic retreat and speedup along the edges of the ice sheet, so I’d assumed that the interior was faster now too. But it wasn’t,” said MacGregor.

The authors identified three causes for this deceleration. First is that snowfall rates were generally higher during the past 9,000 years, second is the slow stiffening of the ice sheet over time, and third is the collapse of an “ice bridge” that used to connect Greenland’s ice to that on nearby Ellesmere Island. Of most interest were the last two.

“The ice that formed from snow that fell in Greenland during the last ice age is about three times softer than the ice being formed today,” according to William Colgan of York University’s Lassonde School of Engineering, a co-author of the study.

Because of this difference, the ice sheet is slowly becoming stiffer. As a consequence, the ice sheet is flowing more slowly and getting thicker over time. This effect is most important in southern Greenland, where higher snowfall rates have led to rapid replacement of ice from the last glacial period with more modern Holocene ice.

“But that didn’t explain what was happening elsewhere in Greenland, particularly the northwest, where there isn’t as much snowfall, so the stiffening effect isn’t as important,” said MacGregor.

The explanation of deceleration in the northwest lies in the collapse 10,000 years ago of an “ice bridge” across Nares Strait, which used to connect Greenland’s ice to that on Ellesmere Island. The collapse of the ice bridge at the end of the last ice age led to acceleration in the northwest, but the ice sheet has since returned to a slower pace.

These changes, which started thousands of years ago, affect our understanding of the changing Greenland Ice Sheet even today. Scientists often use GPS and altimeters aboard satellites to measure the elevation of the ice surface and study how much mass is being lost or gained across the ice sheet. When correcting for other known effects on the surface elevation, any leftover thickening is assumed to be due to increasing snowfall, but this study shows that may not be the case.

“We’re saying that recent increases in snowfall do not necessarily explain present-day interior thickening,” said Colgan. “If you’re using a satellite altimeter to figure out how much mass Greenland is losing, you’re going to get the answer slightly wrong unless you account for these very long-term signals that are evident in its interior.”


71 thoughts on “Study: Greenland ice sheet moving slower now than in the last 9000 years

      • Tree rings somewhere; possibly.
        Not necessarily as close as Siberia.
        Think also squid casings . . . .

    • Arguments from ignorance are not valid. Just because you don’t get it doesn’t mean the authors are incorrect. I’m sure the research is valid and I will take their word on it for now. So what it means is less ice is forming and it’s now warmer than when we crept out of the last ice age. Sounds logical and believable. So what’s the beef?

      • Science is not like religion. You need to read the work critically before believing it. The disbelief comes from blatantly shoddy science rife in anything associated with AGW.
        From what I can gather, they model the dielectric constant of deep layers of ice using radar signals, then model thickness and then model flow in order to …
        “If you’re using a satellite altimeter to figure out how much mass Greenland is losing, you’re going to get the answer slightly wrong unless you account for these very long-term signals that are evident in its interior.”

    • They measured the velocity for a few months then built a computer model to extrapolate back 9000 years. The model also proved beyond a doubt that dogs are better than cats and Sasquatch died out because of climate change.

      • @ Proud Skeptic @ 4.49 pm, B… bu…. but , but those models (in my case anyways) make things move one heck of a lot faster, ( blood flow especially and not in the north or south, right around the equator).

    • Easy.
      First develop “faster Then Light Drive” next fly out 9.000 Light years, and turn a real good telescope on the earth.
      If that is to difficult then plan “B”
      Next question?

      • Mike the Morlock
        February 5, 2016 at 8:12 pm
        First develop “faster Then Light Drive” next fly out 9.000 Light years, and turn a real good telescope on the earth.
        If that is to difficult then plan “B”
        Next question?
        Very good, but doesn’t answer the question exactly – which was “how ON EARTH could……..”
        🙂 🙂

  1. How many of these studies that find nothing happening (but it could happen if warming increases as models suggest) are we going to see?

  2. This could mean that Greenland is indicating that despite of the highest global temperature since yesterday we already on our way to next ice age.

      • Not much will happen while Iceland, Kamchatka and Aleutian are popping off and pushing polar jet stream into meridional flow. When they slow down, and the jet stream gets stuck more and more often in the zonal flow my graph says “it’s time to migrate to the south”.

      • This is true but stupid. When I studied geology a very long time ago, vukcevic would have been correct. We called the glacial period the ice age. For some reason we are moving toward everything being homogenized.

  3. All Ice Ages present themselves at the Hudson Bay. That is, once that huge body of water in Canada stays frozen in summer, soon enough giant glaciers will cover most of Canada, parts of the US and much of Europe while Siberia remains basically glacier-free as does half of Alaska.
    Watching other places like Antarctica or Greenland or Alaska for glaciation is useless.As far as ice melting goes, we still don’t see this matching the height of the Medieval Warm Era.

  4. “database of the many layers in Greenland’s ice sheet.”
    Without at least a brief explanation of the methodology, the reader has no idea whether the conclusions are valid.

      • The conclusion is written first. The methods, “results” and even the rules of logic used are fabricated to support the pre-dictated conclusion.

  5. Without having seen the data and all of the assumptions that must be built into their analyses , it’s premature to judge their conclusions. However, some questions are certainly appropriate. For example, how did they get ice velocity out of ‘softer snow?’ I don’t know any physical basis to make such a connection. How can they make a detailed ice velocity map from a handful of boreholes? What is the basis for calculating velocity in areas hundreds of miles from the nearest borehole? Computer models? We know what those do–garbage in, garbage out.

      • Where did you get the idea that the planes hadn’t moved? They were located with the aid of an understanding of the ice movement since that time.

      • In the Arctic area, geomagnetic storms are frequent events, inducing electric currents in large metal objects (e.g. aircraft frame), raising their temperature fractionally. If this is sufficient enough to promote slow sinking through the arctic ice I could not say with any degree of certainty.

      • Phil How far did the Plane’s move from the original spot. They were only 10 miles from the coast when they landed. They should be in the Sea by now. Thanks

      • If I remember correctly the estimate is that the planes had moved 3 miles from the time of the landing to the time of recovery. The rescue team walked in and they all walked out, so they probably had a pretty good idea where the planes originally landed.

      • And that ” lost squadron ” WAS 260 feet deep in the ice. Far as I know they were full of ice not air, or they would have been crushed to scrap metal so they likely did not do the melt and refreeze under pressure thing, so they didn’t sink. They must have had more than 260 feet of snow deposited on them in the sixty some odd years before they were discovered.
        That’s an awful lot of Greenland ice melting to explain.
        The P-38 they got out was taken apart and lifted out of the hole piece by piece.

      • I made a similar point some months ago when referring to a newspaper article on the finding of these planes. It suggests that Greenland was either warmer all those years ago when these planes came down and/or that there has been a vast amount of snow during the intervening years.
        The historical data pertaining to Greenland does nothing to support the AGM meme.

      • 2 richard verney, 5.56 pm feb 5. A local mountain ( about 50 degrees North gets about 30 ft of snowfall a year ( and then melts). If on Greenland they get the same amount per year that could amount to 2100 ft of snow. if it does not melt annually but gets compressed could that lead to 260 ft of ice?

      • Those planes did not exactly crash on Greenland. There was a whole squadron of P-38s and I don’t remember how many B-17s, but they basically landed on Greenland, when they encountered extreme weather on their way to England. And they got snowed in before they could get off again. So they were pretty much intact when they got buried. I can see how the B-17 might crush, although it is odd that with those side fuselage slots for the 50 mm Brownings, they didn’t fill up with snow first.

      • Apparently the B-17 was the first to be exposed and they were very disappointed to find it crushed. After thinking about they thought that the more robust Lightnings might have survived better so went back for them.

      • What I meant by the melt and refreeze thing, was the 4-H club experiment, where you hang weights on a wire over a block of ice, and the ice melts under the wire due to the pressure, and the water flows around the wire and refreezes, so the wire cuts through the ice block but leaves it intact.
        So in principle the weight of the planes resting on snow could have melted the snow over the 60 years, so the planes slowly sank into the ice.
        Perhaps less likely if they filled up with snow, which supported the structure from inside.

  6. Another case of better living through modeling. Why get out in the weather when you can experience the world from your windowless basement?

  7. “The ice that formed from snow that fell in Greenland during the last ice age is about three times softer than the ice being formed today,”
    Increased CO2 gives ice a stiffy.

  8. I presume that if the temperature is slightly warmer, the snow will be wetter, more akin to the type of snow common in the UK than to dry alpine snow. As such, there is less air in the snowpack , and solid ice is more readily formed. It seems that the fear that the Greenland ice sheet would rapidly melt away and cause global flooding were premature at best. Maybe it’s just another negative feedback.

  9. “The ice that formed from snow that fell in Greenland during the last ice age is about three times softer than the ice being formed today,”
    How can ice (snow) be softer unless the snow crystals were more elaborate? How can this be measured?

    • Read the abstract. The assertion is that there was more dust in the snow earlier, and that dust made the ice softer so faster creeping. Dust from where? Canada was glaciated then boreal forested. Greenland is far north of Saharan dust today, and back then the Sahara was a savanna with a large lake.
      The abstract claims the ice became cleaner so harder so less flowing. Doesn’t make much sense based on my experience with ice.
      Greenland is pretty simple. The underlying rock is bowl shaped. Ice is accumulating inside the bowl. It is lost in summer outside the bowl rim through melt and iceberg calving. The balance determines net mass gain or loss. NOAA’s report card has the 2015net loss well below the average over the observational period although greater than the estimate for 2014, and the iceberg calving the least in the observational period.

    • The ice that formed at the start of the last ice age is now 3kms deep and has warmed up from -45C when it fell to -3.0C now at the bottom. It has slowly warmed from the ground up due to heat rising from the bedrock/mantle.
      If fact, this ice that formed 114,000 years ago is mostly melting now due to the combination of pressure from above and temperature of the bedrock below. There no layers in this ice anymore.

  10. Fourth possibility,Climatology 101 ™ ;
    The ice is crouching, getting ready to attack.
    The onslaught of the hostile Greenland Ice, combined with the newly awakened trees(Mobile due to CO2 enrichment) will sweep man from the planet.
    Sarc Off.
    I am beginning to sense that actual scientific study of this planet,weather and such will not be coming from government funded institutes

    • “Crouching Iceberg, Hidden Glacier” a new movie in the meteorological arts genre opening in your area in ? years. Unfortunately, am anticipating negative reviews!

  11. Glaciers flow due to the phenomenon of ‘cold flow’ (no pun intended) in which solid materials such as ice are malleable, and yield under pressure. The greater the pressure the faster the material yields. The material will also move downhill.
    The conclusion that lower pressure due to less overlying ice will result in slower flows should be trivial.

    • Agreed, gravity and mass are the engines that move glaciers. Less mass should mean slower glaciers. It is strange that they are presenting their findings so awkwardly.

  12. Earth scientists need to realise that the uniformitarianism line of thought applies better to the the long term. In the long term a fault such as the Anatolia or the San Andreas produce slow and continuous displacement, it the short term it is a series of jerky movements such as a relaxation oscillator would produce. Glaciers also behave as a relaxation oscillator. The terminus surges forward and retreats in a quasi periodic motion due to internal processes that have thresholds, are not linear, and external inputs that are a combination of periodic and random.
    They seem to have again discovered that the Earth is not flat and linear and are surprised by the results. They also seem to be apologising to their patrons for making public their observations. Quel surprise all over again!

  13. I have no doubt that if mountain glaciers were growing in tandem with expanding ice sheets as we descend into another glacial maximum, the alarmists would simply move the goal-posts yet again, and point to that as additional proof of our culpability. They already seem to have covered their rear-ends by citing every natural phenomena, including heat waves, polar vortexes, as well as natural disasters like hurricanes and blizzards as proof of man-made climate change in all its complexity. Scientific progress and all that…
    At what point will people stop listening to them?

  14. I would love to hear their explanation of ‘measure of softness’ and how one snow can be 3 times softer than another. ‘This snow is softness 12, and this is softness 36. making it 3 times softer.’ Such a scale would seem silly. I suspect that their statement on a property of snow varying by 200% increase in any physical property, in general seems absurd.

  15. Before criticizing, at least look at the data and methodology.
    Joe MacGregor – Research Associate, Lead Author
    This has links to the article (pay walled), data, and animations like the one below
    NASA | Greenland’s Ice Layers Mapped in 3D

    Explains how the data was collected and what the current interpretation is.
    It is also interesting that he apparently has a new job at/with GISS NASA.

    As of 8 February 2016, I will be part of the Cryospheric Sciences Laboratory (Code 615) at NASA’s Goddard Space Flight Center. Eventually something interesting will be at this new personal webpage, and my personal UTIG website will be removed.

    • Thanks for the links. The video is interesting, but it doesn’t say anything about telling how fast the ice was moving thousands of years ago. Nor do the other two animations I found on that page.

  16. I have concluded Homer Simpson is right, “it’s not that I’m not interested it’s just that I don’t care”.

  17. Obviously it’s moving abnormally slow because of climate change. How do I know this? Because everything out of the ordinary is caused by climate change, and it would be anti-science to suggest otherwise.

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