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

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sub glacial topography and ice discharge of the greenland ice sheet
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

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

Outline
introduction
Introduction
  • Ice thickness data collected periodically since the 1970’s.
  • 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)
bamber map
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)
flight lines
Flight Lines
  • The routes taken to obtain ice thickness data (radar images) by the University of Kansas (CReSIS) from 1993 until 2003.
definitions
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
research focus
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.
method of study
Method of Study
  • Determined the location of Greenland’s 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.
radar image
Radar Image
  • Example of original radar image
  • Ice sheet surface
  • Bed topography
  • Snow layers
refined radar image
Area in the orange rectangle

Bed topography only

Easier to read

Refined Radar Image
choosing valleys
Choosing Valleys
  • Wanted
    • Deeper valleys
  • Unwanted
    • Relatively flat
google earth image
Google Earth Image
  • Shows the location of the narrow sub-glacial valleys
  • Color coded for each year data was collected
location of valleys vs map of balance velocities
Location of Valleys vs. Map of Balance Velocities
  • Balance Velocities map
  • Map of the narrow valleys
summary
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
future work
Future Work
  • Obtain local bed topography 2-D image
    • Smaller Area
  • Compare the new 2-D image with Bamber’s 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
discussion
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
references
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/outline_maps.html
acknowledgements
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