NASA-UCI Study Indicates Loss of West Antarctic Glaciers Appears Unstoppable

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A new study by researchers at NASA and the University of California, Irvine, finds a rapidly melting section of the West Antarctic Ice Sheet appears to be in an irreversible state of decline, with nothing to stop the glaciers in this area from melting into the sea.

The study presents multiple lines of evidence, incorporating 40 years of observations that indicate the glaciers in the Amundsen Sea sector of West Antarctica "have passed the point of no return," according to glaciologist and lead author Eric Rignot, of UC Irvine and NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. The new study has been accepted for publication in the journal Geophysical Research Letters.

These glaciers already contribute significantly to sea level rise, releasing almost as much ice into the ocean annually as the entire Greenland Ice Sheet. They contain enough ice to raise global sea level by 4 feet (1.2 meters) and are melting faster than most scientists had expected. Rignot said these findings will require an upward revision to current predictions of sea level rise.

"This sector will be a major contributor to sea level rise in the decades and centuries to come," Rignot said. "A conservative estimate is it could take several centuries for all of the ice to flow into the sea."

Three major lines of evidence point to the glaciers' eventual demise: the changes in their flow speeds, how much of each glacier floats on seawater, and the slope of the terrain they are flowing over and its depth below sea level. In a paper in April, Rignot’s research group discussed the steadily increasing flow speeds of these glaciers over the past 40 years. This new study examines the other two lines of evidence.

The glaciers flow out from land to the ocean, with their leading edges afloat on the seawater. The point on a glacier where it first loses contact with land is called the grounding line. Nearly all glacier melt occurs on the underside of the glacier beyond the grounding line, on the section floating on seawater.

Just as a grounded boat can float again on shallow water if it is made lighter, a glacier can float over an area where it used to be grounded if it becomes lighter, which it does by melting or by the thinning effects of the glacier stretching out. The Antarctic glaciers studied by Rignot's group have thinned so much they are now floating above places where they used to sit solidly on land, which means their grounding lines are retreating inland.

"The grounding line is buried under a thousand or more meters of ice, so it is incredibly challenging for a human observer on the ice sheet surface to figure out exactly where the transition is," Rignot said. “This analysis is best done using satellite techniques."

Written By: NASA
continue to source article at nasa.gov

13 COMMENTS

  1. In every question and answer site I inhabit ( and that is a lot! ) the deniers are in their full denial mode. One of the most common refrains.

    ” It is part of a cycle and it has happened in the past, is happening now and will happen in the future. “

    Perhaps it did happen in the past ( albeit more slowly ) but there were not seven billion humans on the planet then with a predilection for seaside living. And if it happens in the future, as deniers think, there may be no denier ancestors to see it.

  2. I read this on Huffington Post yesterday and the comments nearly gave me a concussion from the face-palm. A couple of them thought this was a ploy by NASA to generate more funding. In truth, if Nasa wanted money that badly they’d join the deniers and be drowning in cash.

    • In reply to #2 by rjohn19:

      I read this on Huffington Post yesterday and the comments nearly gave me a concussion from the face-palm. A couple of them thought this was a ploy by NASA to generate more funding. In truth, if Nasa wanted money that badly they’d join the deniers and be drowning in cash.

      Don’t the deniers love making up the sort of crap motives they themselves hold, and then attributing the attitudes to others!

      Guess what? ESA’s satellites support the NASA findings. Who would have thunk it?? Those scientists must be able to measure after all!! – (Despite what creationists, denialists and quackologists say!)

      Esa’s Cryosat mission sees Antarctic ice losses double – http://www.bbc.co.uk/news/science-environment-27465050

      Antarctica is now losing about 160 billion tonnes of ice a year to the ocean – twice as much as when the continent was last surveyed.

      The new assessment comes from Europe’s Cryosat spacecraft, which has a radar instrument specifically designed to measure the shape of the ice sheet.

      The melt loss from the White Continent is sufficient to push up global sea levels by around 0.43mm per year.

      Scientists report the data in the journal Geophysical Research Letters.

      The new study incorporates three years of measurements from 2010 to 2013, and updates a synthesis of observations made by other satellites over the period 2005 to 2010.

      Cryosat has been using its altimeter to trace changes in the height of the ice sheet – as it gains mass through snowfall, and loses mass through melting.

      http://www.esa.int/Our-Activities/Observing-the-Earth/CryoSat

    • In reply to #3 by veggiemanuk:

      Meanwhile, some states have resorted to banning even the mention of raising sea levels. As if that is any way to deal with the problem.

      it deals with the problem of compensating those affected

  3. Rignot said these findings will require an upward revision to current predictions of sea level rise.

    On this topic, it’s not the first time I read these most disquieting words “upward revision” and I’m afraid we’re going to be hearing those two terrible words again in the near future.

  4. West Antarctica, in a warmer world, is a large group of islands, with much of its present ice resting on the bedrock below sea-level.

    One implication of rising sea-levels is that ice floats, and if warm currents of sea water get under this ice cap, it will break up rapidly, float off into the ocean, and melt quickly!

    • In reply to #6 by Alan4discussion:

      West Antarctica, in a warmer world, is a large group of islands, with much of its present ice resting on the bedrock below sea-level.

      One implication of rising sea-levels is that ice floats, and if warm currents of sea water get under this ice cap, it will break up rapidly, float off into the ocean…

      This is a very real point, that the scientific community has not made as strongly as it should. The sheer mass of the ice has depressed the land mass below sea level. The coastal ice packs act as a plug that prevents oceanic water from infiltrating under the “out of water” continental land ice cap. With the “plugs” gone, hydrostatic pressure will lift the ice cap and increase the gradient. Glaciers will flow faster, and more ice gets into the ocean faster.

      As the mass on the land decreases, the underlying land rebounds, as is happening now at the Canadian Shield, and the gradient increases further.

      For a long time I questioned the ability of the Antarctic pack to melt quickly, as had been hypothesized. My argument was simple, “Where is the heat going to come from?” To melt that much ice things would have to get hotter, faster than any present predictions.

      The hydrostatic gradient model gets a lot of ice into the ocean in a relatively short time without the need for enough heat to grill us of the planet. Once in the ocean, sea levels go up immediately, and the heat available in the ocean will melt the ice as it drifts. Yes, to some extent this will provide a cooling effect, but that will have little effect on rising sea levels, other than to slow the natural increase in volume of water with temperature change.

  5. Here’s an idea of the costs involved in sea level rise and the assets it threatens. The numbers make the costs of an earlier investment in the new businesses and business practices we would inevitably have to make anyway, and that would incidentally help mitigate the risk and the rate of accumulation of costly damage, look very attractive in retrospect.

    The money used for pre-emptive mitigation is use-twice money. The money used to fix the mess after the fact is use-once and in value for money terms is much much less good if needed quickly. Slow enough environmental changes are accommodated by natural societal evolutions.

    • In reply to #9 by phil rimmer:

      Here’s an idea of the costs involved in sea level rise and the assets it threatens.

      The list on your link is staggering, but not unexpected!

      1 Sea-Level Rise Damage Context Note for: Mitigation of short-lived climate pollutants slows 21st century sea-level rise,
      Nature Climate Change

      Key Points on SLR Damage

      • • Average sea-levels could rise by as much as 6 feet by 2100, and regional differences will cause some areas to experience as much as 20% higher sea levels than the average.
      • • Sea- level rise is one of the most concerning and costly effects of climate change, with both direct and indirect costs.
      • •A rise of only 1.6 feet by 2070 puts at risk 150 million people and $35 trillion in assets in just 20 ofthe world’s most vulnerable and fastest growing port cities, more than half of which are in Asia.
      • •A rise of 1 foot could inundate ~500 square miles
        in the Caribbean islands, a third of the airports, and cause capital loss equal to as much as 12% of projected GDP in 2050.
      • •A 100-yr storm surge, which is expected to begin occurring every 3-20 years, could cost New York City $5 billion in direct damages after 1 foot of sea-level rise.
      • •The cost of protecting coastal assets and infrastructure can be staggering

      Sea-level rise will affect societies both directly and indirectly on many levels. “Direct costs from climate change impacts can be staggeringly high, especially related to natural disasters and sea level rise. For example, shoreline retreat in the United States is projected to cost between USD 270 billion to 475 billion for each metre of sea level rise; analogous costs in some developing nations can amount to one-third of annual GDP.”

      Unfortunately, sea shorelines often have beaches with enough sand to bury millions of denier heads.

  6. Sheepdog @7 -

    One implication of rising sea-levels is that ice floats, and if warm currents of sea water get under this ice cap, it will break up rapidly, float off into the ocean…

    This is a very real point, that the scientific community has not made as strongly as it should.

    Meanwhile – back in the Arctic!!

    Greenland’s long glacier fjords point to higher seas – http://www.bbc.co.uk/news/science-environment-27469488

    Greenland has more than 200 major outlet glaciers along its periphery

    Greenland’s ice sheet may be more vulnerable to melting than previously thought, say scientists.

    A new study has reassessed the shape of the great fjords down which glaciers drain to the ocean.

    It finds them to be far deeper and to stretch further back inland than was recognised in earlier research.

    Dr Mathieu Morlighem told the Nature Geoscience journal that this could expose the glaciers to more prolonged erosion by warm seawaters.

    “We know that many of these Greenland glaciers are accelerating and that their fronts are retreating because of the action of warmer ocean waters,” he said.

    “And because we now know these canyons are far longer than we thought, it means the ice forms can retire much further back, before rising on to land where they won’t be in contact with the ocean anymore.”

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