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

2 of XX 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

3 of XX 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)

4 of XX 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)

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

6 of XX 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

7 of XX 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.

8 of XX Method of Study –Determined the location of Greenland’s sub- glacial valleys using radar data from 1993 until –Mapped the location of narrow sub-glacial valleys using Google Earth. –Compared location of valleys with the map of balance velocities.

9 of XX Radar Image Example of original radar image Ice sheet surface Bed topography Snow layers

10 of XX Refined Radar Image Area in the orange rectangle Bed topography only Easier to read

11 of XX Choosing Valleys Unwanted Relatively flat Wanted Deeper valleys

12 of XX Google Earth Image Shows the location of the narrow sub-glacial valleys Color coded for each year data was collected

13 of XX Location of Valleys vs. Map of Balance Velocities Balance Velocities map Map of the narrow valleys

14 of XX 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

15 of XX 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

16 of XX 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

17 of XX References Bamber, J.L., S.P. Gogineni, R.L. Layberry. December 27, A New Ice Thickness and Bed Data Set for the Greenland Ice Sheet. Journal of Geophysical Research Vol 106, No. D24, Pages 33, , 780. Glacier. Reference.com. Columbia Electronic Encyclopedia. Columbia University Press. (accessed: July 05, 2007). Greenland. Reference.com. Columbia Electronic Encyclopedia. Columbia University Press. (accessed: July 03, 2007). Greenland Data. The Center for Remote Sensing of Ice Sheets. Kansas University. Topography. Reference.com. Columbia Electronic Encyclopedia. Columbia University Press. (accessed: July 03, 2007). World Maps Online.

18 of XX 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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