Jakobshavn Isbrae Glacial Retreat

1. Jakobshavn Isbrae Glacial Retreat Casey Horgan and Erin Cowles

2. Project Goals • Analyze the retreat of the Jakobshavn Isbrae glacier over at least the last 20 years • Estimate the additional freshwater input to oceans due to retreat • Analyze land cover change in areas where glacier has retreated • Climate change impact on retreat?

3. The Glacier Greenland • Location • Western Greenland near town of Ilulissat • Approximate latitude of 70 degrees N • Characteristics • Greenland’s largest outlet glacier • Drains 6.5% of total ice sheet area • Fastest flowing glacier in the world • Flow rate doubled between 1997 and 2003 • Distinct calving mouth that forms 40 km ice fjord/tongue • Widely studied • Glacier dynamics • Effects of Climate Change climatechange.umaine.edu Google Earth

4. Data and Images • Landsat 5 and 7 Images • From 1985, 2001, 2007, 2009, 2011 • All images from month of July, with exception of 1985 (Sept) • No images available from October 1992 to October 1997 • Google Earth • Used for reference dataa • Ilulisat Climate Record • Only goes back to 1988 • Preprocessing • Subsets with area coverage of 94.8 km E-W by 40.1 km N - S

5. Classifications • Classes • Glacier, Fjord Ice, Icebergs, Glacial Pools, Open Water, Barren/Uncovered Land, Vegetative Land • Similarities between glacier, ice sheet, fjord ice, and icebergs • Spectral signatures • Boundaries • Locations • Unsupervised and two supervised classifications • Highly inaccurate

8. Simple Random Accuracy Assessment of the Seven Class Supervised Image

10. Digitizing • More appropriate and accurate than classifying • Land covers digitized • Glacier • Recently uncovered/barren land • Fjord ice/tongue of glacier • Extent of connected ice only • Digitizing provided ability to… • Calculate change in coverage areas of the glacier and ice sheet • Measurement of glacier retreat • Visual representation of glacier and tongue retreat • Amount of land recently uncovered by the retreat • Estimate amount of fresh water added to oceans from Jakobshavn retreat

12. Area Analysis Calculations • Did area calculations in ArcMap, using the vector files created when digitizing • Had to do unions between image pairs for 1985 and 2001, 1985 and 2007, 1985 and 2009, 1985 and 2011, 2001 and 2007, 2007 and 2009, and finally 2009 and 2011 • Then clipped to the area of the glacier and used attribute table to find amount of change

13. Table of Area Calculations

14. Table of Ice Sheet Area Calculations

15. Jakobshavn Isbrae Changes • Retreated by 162.7 square kilometers, which is just over 64 square miles • If estimate that the glacier is 1.1 meter thick, this inputs 167.2 million cubic meters of water. • 47.8 square kilometers of subglacial land, the rest is lakes, or part of the ice fjord • The subglacial land appears to be rocky with sparse or no vegetation • Vegetation coverage seems to increase as exposure time increases

17. Conclusions • Since we have not done a thorough accuracy assessment, we would not use our information for more detailed projects • However, we can conclude that the glacier has retreated significantly from 1985 to the present.  • In addition, our analysis can be applied to other glaciers around the world to see how climate change may be impacting their growth or retreat.

18. Questions?