Sub-Glacial Topography and Ice Discharge of the Greenland Ice Sheet

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Sub-Glacial Topography and Ice Discharge of the
Greenland Ice Sheet

• Ms. Amber E. Smith REU Student
• Mr. Eunmok Lee GRA
• Dr. Kees van der Veen Advisor

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Outline

• Introduction
• Bamber Map
• Flight Lines
• Definitions
• Greenland
• Sub-Glacial
• Topography
• Research Focus
• Method of Study
• Radar Images

• Method of Study (cont.)
• Choosing Valleys
• Google Earth Image
• Balance Velocities Map
• Summary
• Future Work
• Discussion
• References
• Acknowledgements

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Introduction

• Ice thickness data collected periodically since
  the 1970s.
• Jonathan Bamber developed a map of the
  sub-glacial topography of Greenland. (Bamber,
  2001)
• Narrow sub-glacial valleys are believed to affect
  the movement of the ice sheet. (Van der Veen and
  others, 2007)

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Bamber Map

• Created by Jonathan Bamber in 2001
• Shows the elevation of the bed topography of
  Greenland
• Elevations calculated by subtracting the ice
  thickness grid from a DEM (Digital Elevation
  Model)

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Flight Lines

• The routes taken to obtain ice thickness data
  (radar images) by the University of Kansas
  (CReSIS) from 1993 until 2003.

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Definitions

• Greenland The largest island in the world,
  located between the North Atlantic and Arctic
  oceans
• Sub-Glacial Beneath a glacier
• Glacier An enormous mass of ice, formed by
  compacted snow, slowly flowing over land
• Topography Portrayal of the features and layout
  of land surfaces

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Research Focus

• Reanalyze the radar images and identify narrow
  sub-glacial trenches.
• Determine if narrow valleys affect the movement
  of the ice sheet by comparing their locations
  with the balance velocities of the ice sheet.

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Method of Study

• Determined the location of Greenlands
  sub-glacial valleys using radar data from 1993
  until 2003.
• Mapped the location of narrow sub-glacial valleys
  using Google Earth.
• Compared location of valleys with the map of
  balance velocities.

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Radar Image

• Example of original radar image
• Ice sheet surface
• Bed topography
• Snow layers

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Refined Radar Image

• Area in the orange rectangle
• Bed topography only
• Easier to read

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Choosing Valleys

• Wanted
• Deeper valleys

• Unwanted
• Relatively flat

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Google Earth Image

• Shows the location of the narrow sub-glacial
  valleys
• Color coded for each year data was collected

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Location of Valleys vs. Map of Balance Velocities

• Balance Velocities map
• Map of the narrow valleys

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Summary

• Reanalyzed radar profiles to identify narrow
  sub-glacial trenches
• Narrow valleys located along the edge of the ice
  sheet, mainly on the eastern side
• Jakobshavn area, on the western coast, an
  exception

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Future Work

• Obtain local bed topography 2-D image
• Smaller Area
• Compare the new 2-D image with Bambers bed DEM
  and the balance velocities map
• Narrow sub-glacial valleys seem to affect the
  movement of the ice sheet
• Depend more on the depth of the valleys than the
  number of valleys
• Determine the presence of water in the valleys

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Discussion

• MATLAB find a way to keep the image from
  overlapping when the data has similar coordinates
• Radar images represent data in the same format
• Give the scale for the horizontal axis
• Keep the longitude and latitude units consistent

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References

• Bamber, J.L., S.P. Gogineni, R.L. Layberry.
  December 27, 2001. A New Ice Thickness and Bed
  Data Set for the Greenland Ice Sheet. Journal of
  Geophysical Research Vol 106, No. D24, Pages 33,
  773-33, 780.
• Glacier. Reference.com. Columbia Electronic
  Encyclopedia. Columbia University Press.
  http//www.reference.com/browse/columbia/glacier
  (accessed July 05, 2007).
• Greenland. Reference.com. Columbia Electronic
  Encyclopedia. Columbia University Press.
  http//www.reference.com/browse/columbia/Greenlan
  (accessed July 03, 2007).
• Greenland Data. The Center for Remote Sensing of
  Ice Sheets. Kansas University.
• http//www.cresis.ku.edu/research/data/greenland_
  data.html
• Topography. Reference.com. Columbia Electronic
  Encyclopedia. Columbia University Press.
  http//www.reference.com/browse/columbia/topograp
  (accessed July 03, 2007).
• World Maps Online. http//worldmapsonline.com/out
  line_maps.html

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Acknowledgements

• Dr. Kees van der Veen
• Mr. Eunmok Lee
• Mr. Randy Justin
• Mr. Eduardo Cabret
• Mr. Jilu Li
• Mr. Edil Sepulvedo
• Mr. Michael Ziegler
• CReSIS
• National Science Foundation

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