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Retreat Begins At Taku

March 28, 2021

By Paul Homewood




For nearly four decades, Mauri Pelto has been studying the advance and retreat of glaciers around the globe. He has watched them succumb, one-by-one, to rising temperatures. Of 250 glaciers that he has watched, all had retreated (or shortened) except one: Taku Glacier.

Now a new analysis shows that Taku has lost mass and joined the rest of the retreating glaciers. “This is a big deal for me because I had this one glacier I could hold on to,” said Pelto, a glaciologist at Nichols College. “But not anymore. This makes the score climate change: 250 and alpine glaciers: 0.”

Taku stands north of Juneau, Alaska, and is one of 19 notable glaciers in the Juneau Icefield. (The area also includes the famous Mendenhall Glacier, which has experienced an unusually fast retreat—about one third of a mile in the past decade.) Taku is extremely thick: In fact, it is one of the thickest known alpine glaciers in the world, measuring 4,860 feet (1,480 meters) from surface to bed. It is also the largest glacier in the Juneau Icefield.

Using satellite imagery, aerial photography, and GPS field mapping, glaciologists with the Juneau Icefield Research Program (JIRP) have been tracking the thickness of Taku’s annual snow layer since 1946. Pelto has personally observed the glacier over a span of three decades, and even spent six months living on the glacier in huts and tents with JIRP in the 1980s.

In his latest research, he used Landsat imagery to look at changes in the transient snowline—the boundary where snow transitions to bare glacier ice. At the end of the summer, the height of the snowline represents the point where the glacier experienced an equal amount of melting and snow accumulation. If a glacier experiences more melting than snow accumulation in a season, the glacier’s snowline migrates to higher altitudes. Researchers can calculate net changes in glacier mass by tracking the shift of the snow line.

For half a century, the Taku Glacier was the only glacier in the Juneau Icefield that did not experience a net loss in mass. In fact, Pelto and colleagues found that the glacier was advancing and gaining mass at around 0.42 meters (1.4 feet) per year from 1946-1988. But by 1989, glacier thickening slowed down significantly; eventually, the researchers noticed some thinning. The terminus also slowed its advance and then stalled


As Mr Pelto should know, Taku is a tidewater glacier, and this is what tidewater glaciers do – advance and retreat. Here is a good explanation by another expert:


To understand the dynamics of Taku Glacier, we have to know the story of the tidewater glacier cycle. Here is a summary derived from a lecture delivered to JIRP students by Martin Truffer earlier this summer at Camp 17. As the end of a tidewater glacier, known as the terminus, rests in a fjord, the elevation of the glacier’s bed is below sea level. As a result, the melt water beneath the terminus of the glacier becomes pressurized so that it can still flow into the ocean despite the weight of the seawater column. The terminus is quickly eroded as big chunks of ice peel away during calving events and as warm sea water circulates against the terminus. Consequently, the glacier is driven into a rapid retreat, and it recoils up its valley until it reaches a resting point above sea level. There, the glacier is able to stabilize and to eventually begin an advance by pushing its dirty, icy terminus forward on a terminal moraine (a pile of sediment collected by the glacier at its terminus as it grinds forward). By advancing a homemade mound of sediment ahead of itself, the glacier can rest above the deep water of the fjord and the subglacial hydraulics are less pressurized, so the glacier is protected from the intense melting and erosion that previously drove it back. As it continues to bulge onward, the glacier eventually reaches a state where its surface balance nears zero, which means that its accumulation and ablation (melting) are equal. At this point, the glacier can reenter a rapid retreat as the tidewater glacier cycle continues.

And this is a good illustration of how it works:


<i>Illustration by Meghan Murphy</i><br /> This illustration shows a tidewater glacier slowly advancing on a sediment pile. The melting glacier terminus eventually begins to erode the sediment pile. That undercuts the ice's support and triggers a rapid collapse, in a process explained by a new model developed by a University of Alaska Fairbanks researcher.

llustration by Meghan Murphy
This illustration shows a tidewater glacier slowly advancing on a sediment pile. The melting glacier terminus eventually begins to erode the sediment pile. That undercuts the ice’s support and triggers a rapid collapse, in a process explained by a new model developed by a University of Alaska Fairbanks researcher.

Studies have established that there have been at least five major cycles of growth and recession in the last three thousand years on the Taku glacier. In the most recent era, the Taku reached its fullest extent around 1750. Although it has been growing since 1890, prior to then there had been a rapid retreat way back up the valley. Neither that retreat or the subsequent advance had anything to do with climate change:




There is one more chart to show you, which illustrates how the glacier has seesawed over the years:





The idea that mankind can have any influence on these mammoth natural forces is farcical.

  1. March 28, 2021 4:33 pm

    The Swiss glaciers at, say, Grindelwald have very noticably retreated.
    This from personal observation over the past 3 decades.
    Surely that is natural, perhaps on the basis of warming after the Little Ice Age?

    Of course, the Swiss are getting worried about instability of the Alpine permafrost.

  2. Broadlands permalink
    March 28, 2021 4:49 pm

    “The idea that mankind can have any influence on these mammoth natural forces is farcical.”

    Even more farcical is the current view that humanity can prevent it by rapidly lowering carbon emissions to zero and then to NET-zero. Mankind is not even able to capture and store one ppm of CO2, never mind the massive amounts needed to potentially affect the climate.

    The alpine glaciers have been advancing and retreating for hundreds of years…during which time atmospheric CO2 was pre-industrial.

    • Nancy & John Hultquist permalink
      March 29, 2021 12:36 am

      ” never mind the massive amounts needed to potentially affect the climate ”

      That is good. We don’t want all the plants dying.

  3. March 28, 2021 4:58 pm

    Glacier retreat as such is not the problem. Humans claiming humans are responsible for it is the problem.

  4. Gamecock permalink
    March 28, 2021 5:05 pm

    ‘Retreat begins at Taku Glacier’

    How many people will die?

  5. 1saveenergy permalink
    March 28, 2021 5:06 pm

    Are we doomed yet …
    or is there another exiting episode next week ???

  6. Tim Leeney permalink
    March 28, 2021 6:14 pm

    At the start of the little ice age, whole villages were obliterated by advancing glaciers in the Alps. This will of course happen again, but not I hope too soon.

  7. ThinkingScientist permalink
    March 28, 2021 6:38 pm

    Modern alpine glacial retreat globally clearly began around 1840 – 1860, with some even slightly earlier. Glacier bay has a longer, well documented history of retreat.

    I have loads of published papers plus the global glacier database that shows this to be true.

    Sea level also appears to have started rising about 1850, consistent with glacial retreat data.

    But CMIP5 & 6 model forcings are net negative and do not become net positive until the turn of the 20th Century. Global temperature data shows warming from about 1910, as do climate models driven by those forcings.

    That is a glaring inconsistency and a problem for the Global Warming theory. Seems highly unlikely its the glacial retreat data that’s wrong. There are even photographs of the glaciers at different times. In 1854 the Mer de Glace was photographed actually in the main Chamonix valley, it subsequently retreated at its fastest rate BEFORE the climate models and global temps say anything should have happened from around 1910.

    I am submitting an abstract on these points for a conference in May.

    • Graeme No.3 permalink
      March 28, 2021 10:03 pm

      “Glacier bay has a longer, well documented history of retreat.”

    • Phoenix44 permalink
      March 29, 2021 9:27 am

      Yes if you visit Chamonix there are both photos and physical evidence everywhere that showed the glacier was much lower in the 19th century and started to retreat well before any possible manmade warming. It is clear, indisputable evidence of natural warming – if current retreats are also evidence of warming – that the models ignore.

      • ThinkingScientist permalink
        March 29, 2021 11:26 am

        Hi Phoenix44, if you visit the glacier museum/education centre up at Montenvers above the Mer de Glace they have great models and discussion of the glacier. I was there about 6 or 7 years ago. What was remarkable (for me) was I could find no reference or discussion at all about “Climate Change” or “Global Warming”.

  8. David permalink
    March 28, 2021 9:54 pm

    Perhaps we could place a large container ship across the end to stabilise it.

  9. Nancy & John Hultquist permalink
    March 29, 2021 12:34 am

    I have wandered around mountain glacial territory so I am impressed when I see the hand drawn maps of glacial advance and retreat, such as you have found for Taku. At least some of this map is via vertical aerial photography. There is a lodge ( 58.490437, -133.941981 ), built in 1923. Fun stuff. Thanks for the post.

    I have always like the Nohokomeen Glacier on Jack Mountain in the Washington Cascades:
    48.7743396, -120.964910 (~2,350 m)

    Tide water it is not.
    The Wikipedia entry has a photo from the northwest.
    In the current (8/19/2016) Google Earth image the snow/ice extent looks much like the 1966 photo.

    An old earth-science/geography text book for a college class had a photo that attracted my attention. I have wanted to visit but it is a long hike and climb. I’ll not make it.

  10. Steve Brantner permalink
    March 29, 2021 1:13 am

    Excellent piece, although Taku Inlet is South (east) of Juneau

  11. Phoenix44 permalink
    March 29, 2021 9:23 am

    Hardly anybody doubts that’s it a bit warmer now than 50-70 years ago and a fair bit warmer than 120-150 years ago. So what? There’s plenty of evidence climate has changed on all sorts of timescales. Proving climate changes doesn’t prove Climate Change.

    • Gamecock permalink
      March 29, 2021 12:32 pm

      Average temperature going up or down a few degrees is not climate change.

  12. March 29, 2021 2:47 pm

    I wonder why the latest photo NASA show is from 2019. Even Google Earth has a photo from 2020 available. Could it be because the glacier advanced again in 2020?

    • Gamecock permalink
      March 29, 2021 3:33 pm

      I had looked at Google Earth from 1984 to 2020 . . . 36 years, and I didn’t see much difference, if any, in those 36 years.

      “This is a big deal for me because I am a strange person”

      Fixed it.

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