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

Ms. Amber E. Smith – REU StudentMr. 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 2003.

– 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, 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

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

19 of XX