Oh, darn. Study: Most meltwater in Greenland fjords likely comes from icebergs, not glaciers

From the AMERICAN GEOPHYSICAL UNION

Most meltwater in Greenland fjords likely comes from icebergs, not glaciers

Image of Greenland glaciers and icebergs from lifeonthinice.com

Image of Greenland glaciers and icebergs from lifeonthinice.com

WASHINGTON, DC — Icebergs contribute more meltwater to Greenland’s fjords than previously thought, losing up to half of their volume as they move through the narrow inlets, according to new research.

Greenland, the world’s largest island, is almost entirely covered by a permanent ice sheet that has been shrinking and melting as global warming increases temperatures. In fjords, narrow inlets where glaciers meet the sea, ice breaks off from glaciers to form dense packs of icebergs.

The new study finds 10 to 50 percent of iceberg melting happens in the fjords, not in the open ocean as assumed by previous research. As a result, more than half of all meltwater entering Greenland’s glacial fjords can come from these dense packs of icebergs, outweighing the amount of freshwater coming from the island’s glaciers, according to the new study.

“We should now be able to better measure the freshwater fluxes that are coming off of Greenland,” said Ellyn Enderlin, a glaciologist at the University of Maine in Orono, and lead author of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union. “That could be really important when we’re thinking about how Greenland melts, how that influences ocean circulation and climate.”

The new study could help scientists better understand what happens at the ice-ocean interface where glaciers meet the water, according to Jason Amundson, a geophysicist at the University of Alaska Southeast in Juneau, who was not involved in the new study.

“The reason that’s interesting is that there’s been quite a few studies in the past 20 years that have shown that the stability of … glaciers depends on what happens at the ice-ocean interface,” he said.

Melting point

The Greenland Ice Sheet releases more than 1,000 cubic kilometers (240 cubic miles) of meltwater per year, according to the authors. Previous research found half of this meltwater comes from icebergs and half comes from glaciers, but the amount icebergs melted in fjords before they reached the ocean remained a mystery.

In the new study, Enderlin and her colleagues used satellite images of two Greenland fjords to calculate the total volume of icebergs within them. Tracking the icebergs over the course of days, weeks and months allowed the researchers to calculate how much volume the icebergs lost through melting before they reached the ocean.

The researchers determined that from October to April, melting icebergs dominate the freshwater flux into the fjords losing up to half of their volume — glaciers barely melt during the cold winter months. At their peak, these dense packs of icebergs melted at a rate of around 1,000 cubic meters per second (260,000 gallons per second), the equivalent of filling an Olympic-sized swimming pool every two and a half seconds. Even during the warm summer months, underwater glacier melting only occurs at a maximum rate of 400 cubic meters per second (about 100,000 gallons per second).

Icebergs are tiny in size compared to glaciers, but they contribute such a large fraction of meltwater to fjords because their large surface area allows them to melt more quickly, according to Enderlin.

“If you took an ice cube and put it in your drink, one solid ice cube would melt pretty slowly, but if you took it out, hit it with a hammer and put it back in, it would melt a lot faster,” she said.

Enderlin and her team also used satellite images to estimate the iceberg distribution in the two fjords, which they used to calculate the icebergs’ total underwater surface area. Multiplying the melting rate by the total underwater surface area, Enderlin and her colleagues found more meltwater in the fjords was coming from icebergs than from glaciers throughout most of the year.

“What I see now is that iceberg melting is huge, and so if you don’t take that into account you’re going to come up with some crazy high estimates for glacier melting that might not be representative,” Enderlin said.

Melting icebergs in the fjords create a layer of cold freshwater near glaciers. This freshwater can affect water circulation in the fjords, which can affect how glaciers melt and recede, Enderlin said.

Ocean circulation patterns could also be disrupted depending on where the icebergs melt and release their freshwater, according to Enderlin. Ocean circulation is a major driver of heat movement from the tropics to the poles, and disruptions to it could cause chaotic and unpredictable changes to weather and climate, she said.

Enderlin hopes to expand her studies on iceberg meltwater flux to other areas, like Antarctica. She said she will continue the work she started with Gordon Hamilton, who was a glaciologist at the University of Maine in Orono, and a co-author of new study. Hamilton died in October while doing research in Antarctica.

“I would say that really this was sort of our joint brainchild,” Enderlin said. “I bounced lots of ideas off of him … He was really instrumental to [the research] and it was sad that he couldn’t see it come to be finally.”

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This research article is open access for 30 days. A PDF copy of the article can be downloaded at the following link: http://onlinelibrary.wiley.com/doi/10.1002/2016GL070718/pdf.

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66 thoughts on “Oh, darn. Study: Most meltwater in Greenland fjords likely comes from icebergs, not glaciers

  1. “as global warming increases temperatures”

    And I always thought global warming was defined by an increase in temperature rather than the cause of the increase. Silly me.

    • In a world of ‘..see what I’m sayings . . . know what I means . . . I means’, it’s nice to ask for accuracy in the use of language, particularly the language describing scientific study findings.

      • No, that’s entirely accurate. ‘Global warming’ is a movement, a movement that is responsible for the skewing of data and bias in research, ergo, it “increases” temperature.

    • “The researchers determined that from October to April, melting icebergs dominate the freshwater flux into the fjords losing up to half of their volume”
      Is that not backwards? I thought the place froze over then.

    • Yes Bob, I picked up on that one too.

      global warming IS rising temperatures. This stupid phrase just says increasing temperatures cause temperatures to rise. Whooda thought?

    • At least they are starting to state how much of previous work is based on assumptions.

      As Trump starts to assert the need to for sane science they will soon be falling over each other to appear as rational, objective scientists, ie the one who deserve to retain funding.

    • In laboratories, models, and stable environments, yes. In the real world, science is corrupted through liberal use of inference, estimates, and departures from a limited frame of reference in time and space.

    • We should see a greater volume of studies that challenge the settled science orthodoxy now that Trump is President.

  2. Glaciers calve and become icebergs. Glaciers = icebergs, kind of like grated cheese is still cheese. (Cheese = grated cheese)
    I don’t see how the purpose, or the results of this study changes anything we didn’t already know. Interesting though, who payed for this study?

    • So melt water coming from the icebergs that break off from the glacier isn’t actually from the glacier?
      I believe I what the study is attempting to explain is that the heat transfer from the oceans into the face of the glacier is far more complex than merely measuring the face of the glacier and calculating melt rate based upon a woefully inadequate geusstimate of surface area and mixing conditions.

      • Bare in mind that while Some of the Bergs were previously calved from the glacirers and might therefore still be considered Glacial Ice as they melt, far more than that was from Fjord freezing in the winter months then berging as they thaw and break apart.

    • “…who payed for this study?”

      You did.

      Yeah I’m trying to figure exactly what’s being said. Glaciers slide downhill to the sea and maybe melt a little before they calve bergs into the water. In two words, so what?

      • Total Greenland ice loss is calving plus pre-calving melt water. If some of what is actually post-calving melt water is counted as pre- then it is double counted and the mass loss over estimated.

    • So a few things… a glacier is ice and an iceberg is ice, but the distributive property doesn’t work to say glacier = iceberg. If you need a picture to see the difference, scroll up. The long white river looking thing is a glacier, and the tiny specks of white in the water are icebergs. Also, the important thing here is the mechanisms at work. Cheese and grated cheese make look the same at the molecular level, but what makes the grated cheese grated is the important part of the study. For example, hot queso is also cheese, but the difference between hot queso and grated cheese is that one is worked over by heat and the other by mechanical action. Sort of like the difference between a glacier melting and a glacier calving. Calving occurs when the lack of support of the fjord water and the lack tensile strength of the glacier combine to cause a catastrophic (oh my!) failure in the glacier, and an iceberg is formed. If global warming is the catastrophic event, the long white glacier would be called a flowing river, and an iceberg would be called a water droplet.

    • If you assume that the icebergs melt in the open ocean you will attribute the fresh water in the fjords to glacier melt. You will add up the icebergs plus the supposed glacier melt and get a figure for total glacier loss. The glacier loss will be quite overstated.

    • This was my first thought too. It’s like saying that most meltwater on my kitchen floor comes from the ice cubes that fall out of the ice-maker, not the ice maker in the freezer.

    • I think the comparison attempted in this article is how much melting is due to warmer air (i.e., global warming) vs. how much is due to ice being in water (i.e., has something above freezing leaching out its heat and bringing about meltation). Most calving of icebergs, as I understand it, is due to weight; as more and more of the glacier grows outward and is suspended in chilly but not freezing water, sooner or later that suspended weight exceeds the holding power of the ice and calves off (also, don’t forget: the fact that the glaciers are growing enough to calve off icebergs demonstrates that there is enough snow falling, and therefore cold enough temperatures, to make the glaciers grow enough to send parts of themselves off into the fjords so they can break off). Glacial formation is part of a continuous cycle: snow falls, glaciers form, glaciers push parts of themselves off the deep end, icebergs from the glaciers melt in the above-freezing water, the melt-water both merges with other sea water and evaporates, forming clouds from which snow falls, etc. The writers have been surprised, and perhaps a bit dismayed, to learn that glacier melt does not come primarily from warm air on the island’s surface, but from calved icebergs in sea water. That’s how I read the article. Right or wrong, there it is . . .

  3. “Greenland, the world’s largest island”

    Hey????? .. Australia is more than 3 times the area.

    Greenland 2.166M km²
    Australia 7.696M km²

  4. This makes no sense to me. All the icebergs in the Greenland fjords originate from the glaciers and so does the resultant fresh water. Any pack ice formed in the fjords does not shange the fresh to salt water balance although as a result of a leaching process the pack ice gradually loses its salt content. But that does not change the salt/fresh water balance.

    • All the water that the ice is floating on above 80N is slightly above freezing, as the ice above it insulates it from the cold air.

    • and that is at sea level. The greenland ice sheet is 2-3 KM thick, so while it may be above freezing at sea level, the glacier itself will be 10-20 C cooler.

    • When Greenland was settled, it actually was green. People moved there and raised sheep and goats, ran fisheries, planted limited crops, and had several ice-free months of the year in the fjords. Only with the coming of the Little Ice Age did it get too cold for sheep; almost all the inhabitants left by the 14th and 15th centuries, and by then the island no longer looked green. The name, however, stuck. Since the settlers left, Greenland has never again approached the warmth of the Medieval Warm Period.

  5. “In a 2013 study published in Nature, 133 researchers analyzed a Greenland ice core from the Eemian interglacial. They concluded that GIS had been 8 degrees C warmer than today.”

    “Eemian interglacial reconstructed from a Greenland folded ice core”. Nature. 493: 489–494. January 24, 2013. doi:10.1038/nature11789.
    ============================

    so how could it have been 8C warmer without fossil fuel or extra CO2?

    • Because of Milankovitch cycles… in the Eemian the angle of the earth to the sun in northern summer was different, increasing insolation, warming the area.

      (This is basic climate change mechanics)

      Now we see it warming without the same orbital influence, so we look for other factors causing arctic sea ice melt – i.e. human CO2.

      • And, once again, Griff misses the point (or chooses to ignore it). Since, in a previous epoch, temperatures were much greater and the world didn’t boil away into paroxysms of slithey toves, we’re pondering why we need to be so alarmed now. You’re missing the “Catastrophic” part of Catastrophic Anthropogenic Glowball Warming.

      • Yes Griff,
        Although the potential causes are different the potential outcome needn’t be dissimilar except in the mind fearing calamity. The world was 8dC warmer 120,000 years ago and the world is just fine today. The polar bears survived it then, People survived it then, Animals survived it then, Plants survived it then…Or the world would be barren today and we couldn’t be having this particular conversation.

  6. Recent months have been so tense on all of us that everyone’s nerves seem to still be on edge – I know mine still are. In light of that, I think it’s appropriate for both sides in this climate change fight to sit back and take some time to contemplate this world and our place in it. These wise words are a good place to start:

    Desiderata

    You are a child of the universe,
    no less than the trees and the stars;
    you have a right to be here.
    And whether or not it is clear to you,
    Hillary Clinton will never be president.

  7. This news is both new and obvious. We have all fooled around with ice cubes. The idea that flux is a function of surface area is simple and almost intuitive. I don’t understand how the people studying glacier/fjord dynamics would not have adopted, long ago, a model that took account of the fragmentation of the glacier front as it calved into bergs, and as the bergs eddied around in the fjord, and dwindled. You could have put an observer at the mouth of the fjord estimating the size of departing bergs relative to their size when they first broke off. You might even have put somebody in a Zodiac with instruments to guesstimate volume and, measuring the isotherms in the water around the berg, figure out what the “melt field” looks like.

    I am making this up because I have no degree. But I have seen glaciers and bergs, and they are both mysterious and IMHO open to our best inquiry.

    Just puzzled at how sloppy the science seems to have been here.

  8. “Total Greenland ice loss is calving plus pre-calving melt water. If some of what is actually post-calving melt water is counted as pre- then it is double counted and the mass loss over estimated.”

    Very interesting. Has this methodological slop been implicitly favored because it produces results that are desirable?

    • Fundamental unwritten law of all commercial human enterprise: You do what the boss wants done and say what the boss wants said or one way or another you will no longer get a paycheck there.

  9. Too bad the hysterical writer of the recent New Yorker essay had not the benefit of this insight on how glaciers and bergs actually work. It would have messed up the Doom narrative a bit.

  10. So they are saying yet how much overestimated all the previous numbers on Greenland melting have been? (But it sounds like about 40% overestimated?)

  11. Speaking of oh darn, in Tim ‘the dams are never gunna fill’ Flannery country, the Murray Darling River folks have a wee problem with ignorant city slickers and their understanding of climate change-
    http://www.msn.com/en-au/video/watch/though-people-in-south-australias-riverland-are-delighted-by-the-high-flows-coming-down-the-river-murray-tourism-operators-are-concerned-those-outside-the-region-may-be-driven-away/vi-AAkyBM5?ocid=spartandhp
    Don’t be afraid of the bogeyman and it’s a lovely time to visit the Riverland folks.

  12. From Wikipedia: Gordon Hamilton, glaciologist – Died when his snow machine fell into a 30M crevasse. Age 50. Oct 25, 2016.

  13. do check out the current state of the arctic sea ice off Greenland – which has stalled then reduced in extent on the Atlantic side this week…

    a lot of the oldest thickest ice has been exported past Greenland and a lot of the ‘fast’ ice broke away from the Greenland coast this summer…
    http://www.telegraph.co.uk/news/2016/11/02/nasa-reveals-shocking-rate-of-decline-in-arctic-sea-ice/

    (is this website trying to avoid mentioning the recent state of arctic sea ice? It surely deserves discussion)

    • @Griff

      November 22, 2016 at 1:57 am: AGW is dead and far larger areas are now between -20 and -50C from Arctic air blown south. Almost the entirety of Russia and China for a start under snow, much of Canada, now Western Europe and the USA. And surprisingly many other places. Warm air reaching the Arctic and Antarctic is being chilled off to space, it is only Autumn, and we intend to keep a bit warmer from the bonfire of your vanities, Griffy.
      It is not lack of ice, nor snow, remember that, but the opposite you should fear, and you will soon. Bye bye.

      • A good portion of descrepancy is also inherent in individual data sources.
        For example:

        This image from the NSIDC paints a bleak image of conditions in the arctic area
        While this image

        From Cryosphere today paints a dramatically different picture of current arctic conditions

    • You can’t just label everything CO2. It damages your cause, if anything, as the more things you link to it, the more mistakes you will make, the more people will realise and they will end up distrusting on important matters.

      Who cares if the Arctic sea ice is low for the time of year. You know full well, or you should, that sea ice will keep on climbing in the arctic and by February there will be barely any difference between other years.

      If you want to panic over sea ice, worry about it in Spring, as that’s when the sharpest declines have been occurring.

      Now, in regards to the weather event taking place, which plunged large parts of the northern hemisphere into massively below average temperature, you know, where people live, that should be the headline, as people are dying from cold.

  14. The AMO cold bottom current is moving back to the Barents sea, possibly aided by negative AO winds (southerlies removing warmer Atlantic waters). This happens cyclicly over each c.63yrs but warmists have been claiming it is caused by AGW Greenland meltwaters, to save their bacon. This may have started in connection to that, wait for the claims. But the volumes have already been found to be totally inadequate….

    • Steve R,
      I agree that the olympic size pool is a poor metric. First, how many people have actually seen an olympic pool and can relate to the scale of it? Second, the meltwater, although impressive in volume, still takes 2.5 seconds to fill said pool and this is the age of twitter, nobody concentrates on anything for more than a second or two at most, by the time 2.5 seconds have passed you have lost your audience.

      I propose we adopt a new metric that is recognizable to the modern public, that can be measured in a second, and that generates numbers that are impressively large.

      I present the ‘grande latte’ scale. Applying this scale to the meltwater, we get the instantly recognizable and suitably impressive metric of being equivalent to over 2 miilion grande lattes per second. Whoa!

      Finally, we cannot adopt a new metric without establishing a standard of conversion from previous metrics. Studies that are currently underway suggest with up to 97% certainty that 2 million grande lattes per second of melting is roughly equivalent to one hiroshima bomb per hour. Other recognizable conversions would be the equivalent units for cow flatulence or toilet flushing.

  15. Still puzzling over this whole article. This seems useful: “The Greenland Ice Sheet releases more than 1,000 cubic kilometers (240 cubic miles) of meltwater per year,…” If we adopt Olympic Swimming Pools (OSPs) as the unit of measure that will appeal to us little folk, that’s 2.5 x 10exp3 cubic meters divided into 10 exp6 cubic meters or 4000 OSP’s a year. Impressive until you look at Wiki which informs us that the Greenland Ice Sheet is about 2.7 Million cubic kilometers or 11 million OSP’s. So if the annual meltwater loss were not replenished from fresh snowfall on the ice sheet (which it is), we would be facing an ice sheet extinction event in about 2500 years.

    Clearly we need to worry right now.

    Notice also how units of measure are used to impress us in other contexts. We don’t hear about atmospheric CO2 concentrations in parts per thousand or parts per ten thousand or per hundred-thousand. It’s parts per million, because that way we are zoomed all the way in and can see each little squiggle, much to our alarm.

    • Owen yours maths is way out. 2.7 million cubic km’s is at least an order of magnitude more than 11,000 olympic swimming pools. Each OSP is a mere 0.05 x 0.02 x 0.002 kilometres

  16. Since ca 1900 Greenland lost the equivalent of about 8,165 gigatonne ice cubes. 8,165 km3 equates to a 20 km x 20 km x 20 km cube of ice (3√ 8,165 = 20.136565). That would be quite a few Olympic-sized swimming pools. However, it’s not even a tiny nick when spread out over roughly 1.7 million square kilometers of ice surface. That works out a sheet of ice about 5 meters thick.

    The average thickness of the Greenland ice sheet is approximately 1.5 km (1,500 meters). 5 meters is 0.3% of 1,500 meters.

    Isopach map of Greenland ice sheet (Wikipedia). The “Lost Ice Cube” represents 8,165 cubic kilometers of ice.

    Radar Cross Section of Greenland Ice Sheet (Source: Columbia University). Note that even with a vertical exaggeration of 75 x, 5 meters is insignificant.

    The red line along the top of the cross section is approximately 5 meters thick. Here is an enlarged view…

    https://wattsupwiththat.com/2015/12/30/greenland-retained-99-7-of-its-ice-mass-in-20th-century/

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