Transcript Jakobshavn Isbrae Glacial Retreat

Jakobshavn Isbrae
Glacial Retreat
Casey Horgan and Erin Cowles
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?
Greenland
The Glacier
 Location
 Western Greenland near town of Ilulissat
 Approximate latitude of 70 degrees N
 Characteristics
 Greenland’s largest outlet glacier

climatechange.umaine.edu
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
Google Earth
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
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
Simple Random Accuracy Assessment of
the Seven Class Supervised Image
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
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
Table of Area Calculations
Table of Ice Sheet Area Calculations
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
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.
Questions?