Download - Western Antarctica & Antarctic Ice Shelves
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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 Earth’s 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?id=dn6962
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.