Advance and Retreat of Exit Glacier, Alaska
Ü
5
Glacial Extent
1973
1974
Feet
0
30
60
1978
1984
120
1985
Above: Contour lines of the foot of Exit Glacier for some years between 1973 and 1985 are displayed over a
1985 satellite image of the glacier. Each year the glacier retreats farther to the West. However, this frame
shows only a short span of years and does not accurately depict the long-term dynamics of a retreating glacier.
Below: The contour line and satellite image for the year 2008 are displayed along with lines predicting the
glacier’s extent in 20 years. Prediction 1 was made using the average rate of retreat from 1973 to 2008 while
prediction 2 was made using the average from 1950 to 2008. The large difference is illustrative of how
conflicting claims of glacial retreat arise.
Glacial Extent
1950
Ü
1973
1985
1993
Feet
A S K A
A L
Glacial Extent
Feet
0
150 300
600
2008
2030 prediction 1
2030 prediction 2
Exit Glacier
Kenai Fjords National Park
0 125 250
500
750
1,000
1998
2008
Exit Glacier is located in Kenai Fjords National Park in Alaska. As the only glacier readily
accessible by foot in the park, it has been well documented since it was first explored in
1911. Contour lines of the farthest extent of Exit Glacier in various years were traced from
dated photographs and satellite images. Here the lines are layered on top of a 2008
satellite image of the glacier. Notice that while the Exit Glacier has retreated dramatically
since 1950 it has undergone various stages of advance and retreat over the last 35 years.
This is a much more typical long-term trend than the consistent retreat shown for a short
time span in the upper left display. Due to these variations, glacial retreat rates cited in
literature on global climate change often conflict as shown to the lower left display.
Author: Katie Baumann
Sources: United States National Parks Service and LiveSearch Maps (http://maps.live.com)