Western Antarctica

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Western Antarctica Antarctic Ice Shelves

• Eric Leibensperger
• EPS 131

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Antarctica

• 98 covered by ice
• Remaining 2 barren rock
• Covered with about 70 of the Earths fresh water
• Averages only 1-3 inches of snow fall each year
• Much of land below sea level (ice is heavy!)

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Western Antarctica

• Contained in Western Hemisphere
• Transantarctic mountains create barrier between
  Western and Eastern Antarctica
• Warmer than larger Eastern Antarctica
• Includes Antarctic Peninsula and 100s of islands
• Land beneath West Antarctic Ice Sheet mostly
  under sea level

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Antarctic Ice Sheets

• Thought to be 35 million years old
• Ice sheet on average 2.5 km thick

• Ice sheets cover land, ocean and lakes
• West Antarctic Ice Sheet (WAIS)

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Ice Shelves

• Ice slides off the coast and begins to float
• The buoyancy of the ice holds glaciers and ice
  sheets in place
• Generally 100-1000 m thick

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Problem!

• Ice shelves have been thinning and breaking into
  the ocean
• Without the ice shelves, ice sheets and glaciers
  can retreat into the ocean with greater ease.
• 250 billion tons of ice fall into the ocean
  causing a sea level rise of .2 mm each year (10
  of yearly increase of sea level)

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Possible Mechanism of Ice Shelf Breaking

• Increased sea temperatures and air temperatures
  cause melting and cracking
• Melt ponds form
• Water seeps into cracks in the ice
• When water freezes again, it creates larger
  cracks
• Destruction of shelves takes many thawing and
  freezing seasons

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Larsen A and B Shelf Collapses

• In Jan. 1995, Larsen A Ice Shelf collapsed
• In 2002, numerous collapses occurred at the
  Larsen B Ice Shelf

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Results of Ice Shelf Collapses

• Glacier ice lost into the ocean is greater than
  newly deposited snow by 60
• It is estimated that the total loss of glacier
  ice from all ice shelf removal could be up to 5m!
• Remember ice produced from ice shelf collapses
  DO NOT increase sea level since they are already
  floating in the ocean. The addition of ice from
  the mainland increases the sea level.

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Whose fault is it?

• Global temperature increase (2.5ºC over last
  century)
• Most likely from global climate change induced by
  anthropogenic effects
• Additional global increases in temperature will
  cause further shelf collapses and more ice sheet
  and glacial ice introduction into the ocean
• Something to keep an eye on!

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References

• Hogan, J. (2005), Antarctic Ice Sheet is an
  Awakened Giant, NewScientist,
  http//www.newscientist.com/article.ns?iddn6962
• Lincoln, T. (2004), Global Change Glacial Pace
  Picks Up, Nature, 431, 519.
• National Snow and Ice Data Center, http//
  nsidc.org
• Scientists Report Increased Thinning of West
  Antarctic Glaciers, NASA Top Story,
  http//www.nasa.gov/centers/goddard/news/topstory/
  2004/0923westglaciers.html
• Shepard A., et al. (2004), Warm Ocean is Eroding
  West Antarctic Ice Sheet, Geophysical. Research
  Letters., 31, 255-258.