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Earth Science Technology

Cracks in the Greenland Ice Sheet Are Producing Massive Waterfalls, Raising Scientists' Concerns For Sea Level Rise (washingtonpost.com) 176

At its peak, one meltwater lake drained the equivalent of an Olympic-size swimming pool every three seconds. From a report: A cerulean lake consisting of glacial meltwater on the surface of the Greenland ice sheet, located about 18 miles from where the Store Glacier meets the sea in west Greenland, briefly became one of the world's tallest waterfalls during the course of five hours in July 2018. The waterfall, like many others on the ice sheet's surface, was triggered by cracks in the ice sheet. In the case of this one meltwater lake that scientists closely observed in July 2018, the water cascaded more than 3,200 feet to the underbelly of the glacier, where the ice meets bedrock. There, the water can help lubricate the base of the ice sheet, helping the ice move faster toward the sea.

The observations of scientists, armed with aerial drones and other high-tech equipment, of the partial lake drainage that resulted could help researchers better understand how surface melting of the ice sheet could affect its melt rate, and improve global sea level rise projections. Scientists are keenly interested in how meltwater on the surface of the Greenland ice sheet -- the largest contributor to global sea level rise -- acts to speed up the movement of ice toward the sea by lubricating the underside of the ice surface. The new study, published Monday in Proceedings of the National Academy of Sciences, suggests that scientists are underestimating the number of melt ponds that partially, and rapidly, drain into the ice sheet each year. This means tweaks may be needed to the computer models used to predict sea level rise from Greenland.

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Cracks in the Greenland Ice Sheet Are Producing Massive Waterfalls, Raising Scientists' Concerns For Sea Level Rise

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  • by FeelGood314 ( 2516288 ) on Tuesday December 03, 2019 @12:32PM (#59480882)
    The Greenland ice sheet is so massive that its gravity nudges water into the North Atlantic. Everywhere within 2000km will see the sea level fall. Of coarse if you happen to be a small island in the South Pacific the opposite is true.
    • Re: (Score:3, Insightful)

      The Greenland ice sheet is so massive that its gravity nudges water into the North Atlantic.

      I'd like to see a citation for this.

      • Is googling greenland+ice+sheet+gravity really so much of an effort?

      • Post Glacial Rebound (Score:4, Informative)

        by spun ( 1352 ) <loverevolutionary&yahoo,com> on Tuesday December 03, 2019 @01:18PM (#59481122) Journal

        Here you go! The phenomenon is called "post-glacial rebound" and is well understood by geologists. See the section about half way down the page labelled "gravity field." https://en.wikipedia.org/wiki/... [wikipedia.org]

        • Re: (Score:3, Informative)

          by Aighearach ( 97333 )

          If you had spent your time reading that link, instead of spamming it, you'd have discovered that there is no citation for the above claims, and in fact it is already labelled there that a citation for the claim is needed. It is right to question it.

          The only citations are that changes in the gravity field have been detected. There is nothing cited that says anything about it being a big enough effect to make any specific difference in conditions. Just because something was measured, doesn't mean there is evi

        • by Anonymous Coward

          The GGP poster's idea of how post-glacial rebound works is so hopelessly flawed that his conclusions are right out of fantasy.

          The processes of sea level rise from melting land ice and of post-glacial rebound operate on utterly different timescales. The effect of meltwater draining off weight-depressed land and raising the sea level worldwide is virtually instantaneous on a geological timescale, whereas it takes many thousands of years for the crust in the affected land area to rebound.

          For all intents and p

        • by barakn ( 641218 )

          Nope. Your "gravity field" section is mostly about how the missing ice will allow mantle rock to flow back into the depression, altering the gravitational field of the earth substantially. The original poster was talking about a much smaller, short term effect: the gravitational field of the ice mass itself draws the surrounding sea level up a few millimeters. Were the ice to disappear, it would release that surrounding water, even before the mantle had a chance to react.

      • by barakn ( 641218 )

        Here's your citation. Mitrovica et al, Nature, 2001, are generally credited with recognizing that previously unexplained non-uniform changes in sea level were due to changes in gravitational forces from land-based ice appearing or disappearing.

        https://www.nature.com/article... [nature.com]).
        https://geodynamicsprogram.who... [whoi.edu]

        I would think that if you were the real Geoffrey Landis that worked for NASA you'd already know about this or would have been capable of looking it up yourself. What gives?

      • I'd like to see scientific notation in the summary.

        "miles"?

        "feet"

        Uh...

        We use METRIC these days, USA, please catch up!

  • Is that a metric or an imperial Olympic size swimming pool?
    • Is that a metric or an imperial Olympic size swimming pool?

      Metric of course. The only scholars who busy themselves with archaic units of measurement are archeologists and historians and even then only to figure out the conversion ratio to the metric system.

      • So how come there's 60 minutes in an hour and 24 hours in a day and seven days in a week but more or less 30 days in a month except when it's 28 but then only in certain years?

        • by ghoul ( 157158 )

          60 has the largest number of prime factors for any number till 100. It can be divided into half hours, 1/3rd hours, 1/4th hours, 1/5th hours and 1/6th hours as well as 1/10th hours.

          24 follows naturally once the hour is defined as 60 minutes times 60 seconds as the length of the day is fixed and around 24.25 hrs

          Once you have a 24 hr day you get a 365 day year.

          As the cycles of the moon are roughly 28-30 days it makes perfect sense to divide the year into 12 months of roughly 28-30 days.

          The Cycles of the moon

          • Once you have a 24 hr day you get a 365 day year.

            Well, you always get 365.25 days days/year, no matter how you divide your day.

            • by jbengt ( 874751 )
              If you're going to go for that many decimal places, 365.24 days per year is more exact. Of course, it depends on the types of year and day you're talking about.
          • Why do we divide seconds into milliseconds?

          • A typical american post about why "their measuring system is superior." With claims like "dividability", which is basically the stupids thing I ever heard since I learned dividing, which was I guess in second grade.

            You basically have everything reversed backward.

            The year has 360days, and that is why a circle has 360 degrees. Yes, we all know it is 365.25 days. Ah, and no a day has not 24.25 hours ... it is more 24.0000025 hours or something like that.

            It is convenient to divide the 360 degrees into 12 parts,

          • by jbengt ( 874751 )

            the length of the day is fixed and around 24.25 hrs

            Not true. In fact a sidereal day is about 4 mnutes shorter than an average solar day, and an average solar day is very close to 24 hours.

      • Unfortunately we have to assume that Olympic swimming pools have the same size ... regardless of unit of measurement :P

    • How many VW Beetles fit in one of those?
    • How many Libraries of Congress is one Olympic size swimming pool?
  • Greenland lies in Europe. Like any other country they use metres there.

  • by penandpaper ( 2463226 ) on Tuesday December 03, 2019 @01:04PM (#59481056) Journal

    This is why Denmark should sell Greenland to the US. Greenland is clearly broken and leaking all over Canada.

  • At its peak, one meltwater lake drained the equivalent of an Olympic-size swimming pool every three seconds.

    Hmmm...Olympic Swimming pool dimensions are 50m by 25m by 2m. So 2500 m^3. Call it 833m^3 per second. Which means in ONLYa thousand years, from that one meltwater lake, sea levels will rise by OVER SEVEN CENTIMETERS!!!

    Well, got to admit that's a bigger number than I expected. But I still can't find it in myself to get all that worried. When we get an increase rate over 1cm/year, I'll start carin

  • There is not a problem of global warming, we solved it. We know how to build safe, affordable, reliable, low CO2 energy. We've known how to do this for decades. We do this with onshore windmills, hydroelectric dams, geothermal power, and nuclear fission. From that energy we can produce carbon neutral hydrocarbon based fuels as a one-to-one replacement for the petroleum fuels we use now. If for some reason that is not enough then we can start using carbon negative building materials and agricultural pra

    • " The problem is solved."

      Tens of thousands of scientists from all over the planet would disagree with you.

      http://ipcc.ch/ [ipcc.ch]
      • " The problem is solved."

        Tens of thousands of scientists from all over the planet would disagree with you.

        Then they are saying that solar cells with batteries are not cheaper than coal. Either solar cells with batteries is cheaper than coal, and therefore we solved the problem of global warming from human activity, or coal is still cheaper than solar power and we need to panic. If there is a third option then please explain that to me.

        Since I'm being told repeatedly from many different sources that solar power with batteries is cheaper than coal then we must have solved the problem.

        Here's one third option to

        • by DogDude ( 805747 )
          The scientists aren't saying the problem still exists, it's politicians pretending to be scientists.

          That's 100% false. Every reputable scientist says that a very large problem exists. Economics is irrelevant.
          • That's 100% false. Every reputable scientist says that a very large problem exists.

            So, then what is preventing us from solving the problem? Once we agree on the science then the solution is just engineering. We know how to build affordable and low CO2 emitting energy sources. I've listed those sources many times, and I'll list them again. This list is onshore windmills, hydroelectric dams, geothermal, and nuclear fission. People disagree with this list, they will claim other energy sources like solar is cheaper and lower in CO2 emissions. That still just means we know what the solut

  • We need to stop Atlantic conveyor . Most current theories on little ice age is that large amount of freshwater was able to stop Atlantic conveyor. This basically caused ice age, and allowed Arctic to form some thick ice. While we are in global warming, perhaps, this would refreeze Arctic and counteract co2 while nations continued to move off fossil fuel.
    • by caseih ( 160668 )

      Interesting idea. Of course that would sacrifice insignificant places like the United Kingdom for the greater good.

      • I doubt that would sacrifice any nation. Stopping the conveyor, would allow the Arctic to hold it's coldness there, but with the sun still shining, combined with the co2 in the air, I doubt that Iceland would change much, let alone the UK.

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