Greenland ice melt

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Greenland ice melt

• Ben Lee
• EPS 131
• Friday 10/28/2005

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Overview

• Ice melt mechanism
• Past trends
• Recent developments
• Implications
• Natural or anthropogenic?

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What happens as ice melts

• Ice melt flows down to bedrock through crevasses
  and moulins (large tunnels)
• Water between bedrock and ice sheet acts as
  lubricant
• Allows ice sheet to move faster toward the
  coastline

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• Ice movement-rate increases from 31.3 cm (12.3
  inches) per day in winter to 40 cm (15.7 inches)
  per day in the summer.
• It was initially thought to occur only under
  small mountain glaciers, not large ice sheets.

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NASA P-3B Laser altimeter GPS

• Knowing the position and altitude of aircraft
  and speed of laser allows for the precise
  calculation of ice sheet elevation.
• Spans an area of about 650 feet wide below
  aircraft.
• Accuracy within 10 cm.

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• Thinning along the coast leading to a rise of
  sea level of 0.25 mm per year.
• Thickening in Southeast Greenland by about a
  meter between 2002 and 2003.
• Recent paper in Science Johannessen et al.,
  2005 found an increase in ice sheet height of
  6.4 /- 0.2 cm per year above 1500 m elevation.

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Implications

• A 25 cm decrease in average height of central
  Greenland ice sheet would result in a 1 mm
  increase in the sea level of the worlds oceans.
• A complete melt would result in an increase in
  the worlds sea level by 7 m.
• Loss of lives, destruction to property and
  ecosystems, as well as extinction of many
  species.
• Positive feedbacks
• Weaken or disrupt the thermohaline circulation??
• Benefits???

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Natural or Anthropogenic???

• Is the melting part of a natural cycle?
• Are we entering a natural warming period?
• Could it be due to large-scale atmospheric
  circulation (i.e. Arctic Oscillation)?
• Is the melting anthropogenically induced?
• Global warming from greenhouse gases?

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References
Abdalati, W. and K. Steffen (2001), Greenland ice
sheet melt extent 1979-1999, J. Geophys. Res.,
106(D24), 33,983-33,989 Johannessen, O. M., K.
Khvorostovsky, M. W. Miles and L. P. Bobylev,
Recent Ice-Sheet Growth in the Interior of
Greenland, Published online October 20 2005
10.1126/science.1115356 (Science Express
Reports) National Aeronautics and Space
Administration, http//www.nasa.gov Krabill, W.,
E. Hanna, P. Huybrechts, W. Abdalati, J.
Cappelen, B. Csatho, E. Frederick, S. Manizade,
C. Martin, J. Sonntag, R. Swift, R. Thomas and J.
Yungel (2004), Greenland Ice Sheet Increased
coastal thinning, Geophys. Res. Lett., 31,
L24402, doi10.1029/2004GL021533 Krabill, W., R.
Thomas, K. Jezek, K. Kuivinen and S. Manizade
(1995), Greenland ice sheet thickness changes
measured by laser altimetry, Geophys. Res. Lett.,
22(17), 2341-2344 National Snow and Ice Data
Center, http//nsidc.org