West Antarctica's ice sheet loss "appears unstoppable"

  1. Greg Bernhardt

    Staff: Admin

    Sea level appears destined to rise at least 4ft. Anyone have data on how this will affect the world's coastlines?

    West Antarctic Glacier Loss Appears Unstoppable
    http://www.jpl.nasa.gov/news/news.php?release=2014-148

    The 'Unstable' West Antarctic Ice Sheet: A Primer
    http://www.jpl.nasa.gov/news/news.php?release=2014-147
     
  2. jcsd
  3. mheslep

    mheslep 3,531
    Gold Member

    Rate? Apparently melting the *entire* Western sheet is a 4000 year process. The lead author of the paper leading to the recent news, Rignot, said previously:

    https://www.youtube.com/watch?v=L7PRKTtuhZI

    Dotearth
     
    1 person likes this.
  4. Al Gore should go down there and stop it from moving...
     
  5. Bobbywhy

    Bobbywhy 1,908
    Gold Member

    Here is a map that shows how North American coastlines will be affected by sea level rise:

    http://sealevel.climatecentral.org/surgingseas/

    Bobbywhy
     
  6. This NOAA web site gives histograms of how much of the Earth's land area is at different elevations. According to Figure 2, the slope of the curve near the current sea level is 3.69E5 km^2/m. Since the current land area of the Earth is 1.49E8 km^2, this means that the impact is a loss of 0.25% of the Earth's land area per meter of sea level rise. While this is not a good thing if you live near the sea, it is hardly a catastrophe, especially since it will take hundreds to thousands of years to occur, giving people a chance to adapt. If you consider a city like New York(where I live), virtually none of the current infrastructure (buildings, subways, streets, ...) will last more than a few hundred years. So it will all need to be rebuilt in the next few hundred years anyway. Likely our descendants will decide to build their cities a little further from the sea.
     
  7. mheslep

    mheslep 3,531
    Gold Member

    Why? The Dutch have not gone anywhere.
     
  8. Good point. New York is actually fairly easy to protect from rising sea levels. Dikes at the current locations of the Verazzano Narrows and Hutchison bridges, as shown in the attached map, would protect much of the city from rising sea levels for at least the next thousand years. These have actually been discussed in response to the Hurricane Sandy flooding. I suspect they will be built at some point in the future, but no one will want to spend the money until they are really needed.
     

    Attached Files:

  9. Over the last 2.5 million years, the Earth has experienced more than a hundred Ice Ages and an equivalent number of interglacial periods. These are the result of orbital-forcing, not carbon-dioxide forcing (see Milankovitch Cycles). There have been ten full cycles in the last million years.

    During the many interglacials, both the Antarctic and the Greenland ice sheets have experienced significant melting, but in no case have they ever disappeared. They grow back again during the succeeding Ice Ages. We are currently some 20,000 years into an expected 50,000 year warming cycle. If the coming interglacial is anything like the last one, we can expect the world ocean to rise some 13 to 20 feet higher than it is at present.

    Al Gore used some of the proceeds from his movie, An Inconvenient Truth, to buy a condo on Fisherman's Wharf in San Francisco. The building sits about four feet above current sea level. If Al isn't worried, I'm not.
     
    Last edited: May 20, 2014
  10. jim hardy

    jim hardy 5,139
    Science Advisor
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    2014 Award

    We'll do what humans do best - adapt.

    First, though, Congress should repeal the "National Flood Insurance Program" .
     
  11. mheslep

    mheslep 3,531
    Gold Member

    Now there is a common sense proposal, sure to be opposed fanatically by owners of multimillion dollar beach front properties.
     
  12. jim hardy

    jim hardy 5,139
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    2014 Award

    I grew up in South Florida. There is a fascinating little book , "Land from the Sea" by a U of Miami geology professor.

    http://www.amazon.com/Land-Sea-Geologic-Story-Florida/dp/0870242687

    Author says about 20,000 years ago sea level dropped about twenty feet and South Florida, then a shallow sandbar like much of today's Bahamas Bank , appeared.

    So - it's not like sea level change should be a surprise..

    This fellow says measured level at Key West Harbor rose 0.73 feet(~9 inches) from 1913 to 2006. One would have to be really observant to notice that in his lifetime.

    http://www.keyshistory.org/Global_Warming.html
     
  13. Borek

    Staff: Mentor

  14. jim hardy

    jim hardy 5,139
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    2014 Award

    I'm looking for that old book by Hoffmeister. I quoted from memory...... i read it 40 years ago

    He's cited in a lot of works, but i've not yet found the right paragraph...

    if i'm off by 100 millenia, well so be it ; and i [STRIKE]will[/STRIKE] do apologize.


    will continue looking.

    old jim

    http://www2.fiu.edu/~whitmand/Courses/Fl_geo_notes.html
     
    Last edited: May 21, 2014
  15. mheslep

    mheslep 3,531
    Gold Member

    Last edited: May 21, 2014
    1 person likes this.
  16. D H

    Staff: Mentor

    What slowdown in sea level rise?

    [​IMG]

    Source: http://sealevel.colorado.edu/conten...a-level-time-series-seasonal-signals-retained


    You posted a link to a graph of the Antarctic sea ice anomaly, which is quite different from the topic of this thread. This thread is about the West Antarctica ice sheet. It's the melting of ice sheets and glaciers and the warming of the ocean that causes sea level rise. Sea ice? Not really. It's floating.

    The melting of the West Antarctica and Antarctic Peninsula ice sheets contributes to the seemingly paradoxical increase in Antarctic sea ice extent. That newly arriving fresh water floats atop the more dense sea water. Fresh water freezes more easily than does sea water. The summertime loss of ice from those ice sheets becomes a wintertime increase in sea ice.

    Other causes include a strengthening of the winds that encircle Antarctica and increased precipitation in the Antarctic. The strengthened winds open up polynyas in the sea ice, stretches of open water surrounded by ice. Those open stretches of water are much easier to freeze than is water shielded by a blanket of ice. The increased precipitation has the same effect as ice sheet melting. It adds easy-to-freeze fresh water to the surface.

    References:

    Abram, N. et al., "Evolution of the Southern Annular Mode during the past millennium," Nature Clim. Change, (2014)

    Shepherd, A. et al., "A Reconciled Estimate of Ice-Sheet Mass Balance," Science 338.6111 (2012): 1183-1189.

    Rignot, E. et al., "Ice-Shelf Melting Around Antarctica," Science 341.6143 (2013): 266-270.

    Zhang, J., "Increasing Antarctic sea ice under warming atmospheric and oceanic conditions," J. Climate 20 (2007), 2515-2529.

    Zhang, J., "Modeling the Impact of Wind Intensification on Antarctic Sea Ice Volume," J. Climate[/i[ 27 (2014), 202–214.
     
  17. mheslep

    mheslep 3,531
    Gold Member

    Long term ~3mm/yr, but 2005-2012 was 1.1 ± 0.8 mm/yr

    NOAA, The Budget of Recent Global Sea Level Rise 2005–2012

    Jason I-II based altimetry comes in a bit higher at 1.6 mm/yr ± 0.8

    also:

    Ablain et al, "A new assessment of global mean sea level from altimeters highlights a reduction of global trend from 2005 to 2008", Ocean Sci. Discuss., 6, 31-56, 2009

     
    Last edited: May 21, 2014
  18. jim hardy

    jim hardy 5,139
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    2014 Award

    Thanks mhslep, looks like i'm off by that 100k years.
    Apologies are hereby tendered.

    old jim
     
  19. mheslep

    mheslep 3,531
    Gold Member

    I've not seen a firm conclusion on the reason for the warming/retreat starting in the 1850's? Yes this was the end of the Little Ice Age, but why the end? Solar something?
     
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