17 May 2012:
Retreat of Columbia Glacier
Vividly Captured in NASA Satellite Images
Two false-color thermal images taken by NASA satellites depict the rapid retreat of the Columbia Glacier in Alaska
over the past 25 years. Since 1986, the glacier’s end-point, or terminus, has retreated 12 miles up an inlet in Prince William Sound, and the glacier also has lost about half its total thickness and volume. The top image, taken by a Landsat 5 satellite in 1986, shows two branches of the glacier joining together just north of Heather Island. By 2011, the terminus had retreated far up the inlet, and is identifiable in the bottom image. The blue in the water below the 2011 terminus is floating ice that has calved off the leading edge of the Columbia Glacier, which descends from a 10,000-foot ice field in the Chugach Mountains. By 2011, the two branches of the glacier had become separated. The turquoise color in the images is snow, and it is more prevalent in 2011 because that image was taken in May, whereas the top image was shot in July.