NASA finds dirty glaciers in Alaska – may melt faster

Over the years, scientists have captured spectacular photographs while mapping ice during NASA’s Operation IceBridge mission. Many of the photographs have featured the icy landscapes of Greenland and Antarctica, over which lengthy missions are flown each year over. But the views during shorter duration IceBridge missions over Alaska reveal some equally majestic icescapes.

Chris Larsen of the University of Alaska, Fairbanks, snapped these photos in late May 2018 during research flights to monitor Alaska’s mountain glaciers. He has led two sets of IceBridge-Alaska flights each year since 2009.

The first image shows part of the Wrangell Mountains of eastern Alaska. Clouds like these were persistent throughout the mission, but the researchers still managed to collect data during 10 of 11 possible flight days.

Larsen snapped this photograph while flying over the end of Nabesna Glacier. Nabesna stretches more than 75 miles, making it the longest interior valley glacier in the world.

The glaciers here are not necessarily pristine ice. As this photo shows, debris has accumulated on the ice—everything from silt to rocks—imparting a dark color. Ridge-shaped accumulations of the debris, or “medial moraines,” run down the middle of the glacier. “This is very common in the Wrangells and actually in many interior Alaska mountain ranges,” Larsen said.

Medial moraines are also visible in these photographs of upper (top) and lower (bottom) Klutlan Glacier. This glacier, about 40 miles long, flows from eastern Alaska into Canada’s Yukon Territory. Larsen noted the extensive crevassing in the lower part of the glacier, which makes it appear “almost like the surface is shattered.”


Source: NASA Earth Observatory

References and Related Reading

Operation IceBridge photos by Chris Larsen, University of Alaska, Fairbanks. Story by Kathryn Hansen.


See here’s the thing. A darker glacier means a lower albedo, and that means the dark and dirty glacier will absorb more sunlight than a pure white one with a higher albedo. More sunlight absorbed means a greater likelihood of melting.

Here’s some data: (Via Wikipedia)

Sample albedos

Surface Typical

albedo

Fresh asphalt 0.04[4]
Open ocean 0.06[5]
Worn asphalt 0.12[4]
Conifer forest

(Summer)

0.08,[6] 0.09 to 0.15[7]
Deciduous trees 0.15 to 0.18[7]
Bare soil 0.17[8]
Green grass 0.25[8]
Desert sand 0.40[9]
New concrete 0.55[8]
Ocean ice 0.5–0.7[8]
Fresh snow 0.80–0.90[8]

A dirty glacier surface might be closer to worn asphalt than ice or snow, and we all know how much warmer asphalt gets in the sun.

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56 thoughts on “NASA finds dirty glaciers in Alaska – may melt faster

  1. I wonder how much the ash deposition from Mt. St. Helens contributed to the measured decline. I might imagine the glaciers directly down wind in Glacier National Park might have seen some of this.

    • St. Helens could indeed have affected the northern Rockies, but AK not so much. There have however in the past ~40 years been some eruptions upwind of the Wrangell Range, such as Tobalchik 1975, Mt. Augustine 1976, Atlasov Island 1981, Chikurakchi 1986, Kliuchevsko 1987, Mt. Redoubt 1989-90, Mt. Spurr 1992, Shiveluch 2001, Mt. Okmok and Kasatochi 2008, Sarychev Peak 2009 and Mt. Ontake 2014.

      https://en.wikipedia.org/wiki/List_of_large_volcanic_eruptions_of_the_20th_century

      But IMO “black carbon” from Chinese coal plants could have polluted Alaskan glaciers and Arctic sea ice both.

    • At the time of the Mt. St. Helens eruption, I lived directly down wind. A sunny morning turned dark by midday with streetlights on. Supprisingly the ash was light grey (and very abrasive). As I recall, it was much lighter than the dark areas of the glaciers pictured above.

      • I remember the ash as well in west central Colorado. I reference to your last line, adding a bit of water would make the light ash much darker.

  2. I wonder what the make up is of the “debris”? Volcanoes probably attribute the greatest amount but unfiltered coal burning could add some as well.

      • While Anthony may have primarily shown images, Operation Ice Bridge is indeed a study:
        “…Operation IceBridge images Earth’s polar ice to better understand connections between polar regions and the global climate system. IceBridge studies annual changes in thickness of sea ice, glaciers and ice sheets. ICEBridge bridges the gap between the ICESat missions.”

        • Ice Bridge is one of the wayyy coolest science things government has ever spent our money on… 😎

      • Nick, in your rush to complain, you were inattentive. This is a NASA press release, about operation icebridge. Whine to them.

    • Bingo. And this is natural till sediment incorporated into all glaciers so I don’t see how anything has changed.

      • These are flyovers, so they don’t know for certain what the composition of the darkening agent is. Carbon soot may play a role.

      • Mainly broken up rock gouged from the glacier walls and floor. Median lines are from a tributary glacier joining the main valley glacier

        • “Median lines are from a tributary glacier joining the main valley glacier”

          Not quite. A medial morain is formed when two glacier streams merge and consists of debris from the tongue of rock separating the two glaciers. You can tell from the number of medial morains how many tributary glaciers have joined “upstream”

    • Commie, this looks like a resource for air conditioning in summer. Put snow into bunkers netted with brine tubes. When I was a boy, they used to saw ice blocks from the lake, store it in a log icehouse buried in sawdust. It was available for old fashioned home refrigeration and for ice chips for your gin and tonic.

      • Gary,
        The city of Phoenix (AZ) had tunnels in the downtown area. (I don’t know if they still exist.) They would harvest lake ice up north in the Winter and haul it down to Phoenix. They would pile the ice in the tunnels, and place large fans to blow the cold air through the tunnels and up into stores to cool them in the Summer.

      • Yup–the ranch had an ice house, and on summer visits ice cream was made in a hand-driven churn. Those visits were when Dad was away in the War. But the main reason for the ice house would have been to provide ice for the cooler in the kitchen. Two Chinese cooks.
        In southern B.C.
        Bob Hoye

    • commieBob,
      You are exactly right! An entrained, fine, dark debris (like soot) would absorb all the sunlight entering the ice and conduct the heat to the ice. On the other hand, it is common to find pebbles (and meteorites in Antarctica) on ice columns or pedastals; the dark, solid object has shaded and insulated the ice. Therefore, the ice immediately under the rock melts more slowly than the snow/ice exposed directly to the sun’s rays. Things like the thermal conductivity and thickness of the rock certainly come into play. So, I think it would be a mistake to assume that all situations will follow a general rule.

  3. Of course modern era glaciers have rock, gravel, and sand mixed into the ice. Glaciers are mountain grinding, gravel making, gravity powered, rivers of ice machines! Melting/thinning of the mile-thick glaciers over the last 20,000 years means only the their bottom most layers remain, with their attendent load of crushed rock debris.

    Would we expect the exposed ‘rock loaded’ bottom layer of a glacier to melt faster than the top layer of a mile thick glacier topped with fresh snow? Of course we would!

    • J Mac,
      Something that I had the privilege of observing first-hand, when I was in the Army, was what the glaciologist at the CRREL (Hanover, NH) dubbed “shear moraines” in the Greenland glaciers. The ice would be deflected upwards over rough bedrock. The ground moraine would then come out at the snout of the glacier some distance above the underlying bedrock. It had the appearance of armoring the snout and protecting it against rapid melting. Not all glaciers will have similar conditions, so not all glaciers will exhibit similar behavior. Nature is usually more complex than what it appears to be, especially to those unacquainted with the subtleties.

      http://www.erdc.usace.army.mil/Media/Fact-Sheets/Fact-Sheet-Article-View/Article/476744/cold-regions-research-and-engineering-laboratory/

  4. Why do we need to guess at the albedo of any glacier. I would think we’d be able to measure it. Isn’t that what satellites and pyrometers are for?

  5. “NASA finds dirty glaciers in Alaska – may melt faster”
    Faster? Well, if it got dirtier. But there is nothing here to say that it hasn’t always been covered with rocks and muck.

    • The thing is water, and even more so snow, is a lousy conductor of heat. When the only source of heat is from above radiant from sun and more importantly contact with warming particulates and detritus the only way it can melt is down slowly accumulating more and more debris on it surface. I suspect that there is a limit to how dirty a glacier can become before the overlying sediment acts as insulation.

  6. A good cover of rocky debris on a glacier surface can act as insulation, keeping the heat out (because the rock does not conduct heat very well) and shading the surface from sunlight. So don’t assume a dark surface or streak on a glacier surface implies unusual melting. The long rocky streaks in these photos represent the joining lines between glaciers from separate valleys. More rock at the edge of each glacier, the edges merging at the confluence of the valleys.

    If melting was occurring due to the colour of the streaks, then you would expect to see long deep depressions coinciding with the line of rock. This generally does not happen.

  7. In some Himalayan glaciers the opposite was found. The glaciers that got dirtier were the ones that were melting more slowly. That’s why they got dirtier I guess.

    Scherler, D., Bookhagen, B., & Strecker, M. R. (2011). Spatially variable response of Himalayan glaciers to climate change affected by debris cover. Nature geoscience, 4(3), 156.

    http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/debriscover.pdf

    “More than 65% of the monsoon-influenced glaciers that we observed are retreating, but heavily debris-covered glaciers with stagnant low-gradient terminus regions typically have stable fronts. Debris-covered glaciers are common in the rugged central Himalaya, but they are almost absent in subdued landscapes on the Tibetan Plateau, where retreat rates are higher. In contrast, more than 50% of observed glaciers in the westerlies-influenced Karakoram region in the northwestern Himalaya are advancing or stable. Our study shows that there is no uniform response of Himalayan glaciers to climate change and highlights the importance of debris cover for understanding glacier retreat”

    • “there is no uniform response of Himalayan Glaciers to climate change” — I wonder, what you mean climate change, is it global warming or something else???. Reports show that Indian annual temperature has raised by 0.5 oC but this is the contribution by night temperature in association with urban-heat-island effect. If add the unaccounted rural-cold-island effect, practically no global warming in India. The southwest monsoon rainfall showed a 60-year cycle and the frequency of occurrence of floods in northwestern India followed this.

      “got dirtier were melting slowly”, is it in Himalayan zone, albedo affect is insignificant?

      On important factor, we rarely account on glaciers melt is human activity. This is growing with the time.

      Any how government of India informed the parliament after returning from 2015 Paris agreement that more than 86.6% of glaciers no change.

      Dr. S. Jeevananda Reddy

      • Perhaps there is a reverse albedo effect in that dark debris on Himalayan glaciers (at 25-30 degrees latitude and very high altitude) radiate more heat every night while Alaskan glaciers (at 60-70 degrees and lower altitude) undergo long periods of sustained daylight.

    • Well that would appear to be Anthony’s contribution to the post. It would be useful for there to be a clear difference between what has been copied and pasted from NASA’s webpage and what has been added by Anthony. As far as I can tell – everything above the sentence “See here’s the thing” has been copied and the rest is pure speculation and has nothing to do with NASA.

  8. Hmmm, they didn’t mention the Hubbard Glacier in Southern AK. It is the largest tidewater glacier in North America. It is still advancing for over 100 years. Look it up. I hate to use wackapedia, but:
    https://en.wikipedia.org/wiki/Hubbard_Glacier

    Can’t believe I found this one on the weather channel:

    https://weather.com/science/environment/news/alaska-hubbard-glacier-growth

    There used to be a link showing the advance since about 1880s – can’t find now, I guess it’s been scrubbed…It was much further back than now…
    JPP

  9. I still feel that glaciers are wasted water. Nothing can swim in them, they don’t evaporate and contribute to rainfall, and Greentards want more of them.

    • However slowly, they do contribute to the water cycle eventually, through ablation, ie melting, sublimating and calving ice bergs.

  10. Yet more silly press-releasy ”me too science”.

    Glaciers always are ”dirty”, i e contain rock debris, “moraine”. Large thick icecaps with no protruding nunataks normally only have moraine in their lower parts, though it can “surface” in blueice areas. Montane valley glaciers, like in Alaska, has abundant moraine material at the surface. And, yes, this will promote melting in summer.

    Volcanic ash is different it collects in a thin layer all over the ice surface which is then usually covered by snow and encased as a thin horizontal layer in the ice. Of course if the eruption occurs in summer, or the snow is thin enough to melt next summer it will also enhance melting.

    Airborne dust (including soot and micrometeorites) is a third component. This accumulates more or less continuously which means that some of it will be exposed by melt every summer in the ablation zone. It is usually fine enough to move with meltwater and tends to accumulate in meltwater lakes and hollows.

    And then there are organisms (bacteria and algae) that lives in the snow using nutrients from the three abovementioned sources and these will also darken snow (usually being green or reddish) and enhance melting.

    All this was worked out and described, in detail, by Scandinavian glaciologists during the second half of the nineteenth century.

    “Larsen noted the extensive crevassing in the lower part of the glacier, which makes it appear “almost like the surface is shattered.”

    Also an utterly silly remark. Moving glaciers are always “shattered” near the surface. Ice is too stiff to deform plastically more than very slightly at low pressures. At higher pressures at depth it does deform plastically. Normally crevasses therefore don’t extend more than to about 100 meters depth, but can be deepened by meltwater in summer.

  11. Alta just outside of Salt Lake City has been famous for its deep powder snow. And slopes steep enough to make the deep snow outstanding. Skiied it many times. Back in the day==sigh.
    Extra precipitation was provided by the “lake effect” from the Great Salt Lake. Also, dry winds from the desert would distribute a fine dust.
    Then late in the season the snow would consolidate showing the accumulated dust. Did the darker surface radiate heat as a black body or did it absorb heat?
    Didn’t think about it–spring skiing was too good.

  12. It is my understanding that ice skates work by causing the ice to melt under the blade creating a film of water for the skate to glide on. This works because the pressure causes the ice to melt. Isn’t the same thing going on under glaciers? Depending on the temperature of the ground and the depth of the ice, height of the glacier, would there not be a great enough flow of water released due to this pressure to account for some of these pictures I see of “Melting Glaciers?”

    • “Isn’t the same thing going on under glaciers?”

      Sometimes yes, sometimes no. They are called “warm-based” and “cold-based” glaciers respectively. Cold-based glaciers are slow-moving and contain very little moraine material.

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