Keith Echelmeyer and his co-authors, Anthony Arendt, Will Harrison, Craig Lingle and Virginia Valentine have monitored about one-fifth of all Alaska glaciers. Many have melted at an incredible rate since the 1950s, and the rate of volume loss has doubled since the early 1990s. Former mountains of ice have become relative molehills in the last four decades.
"Most glaciers have thinned several hundred feet at low elevations in the last 40 years and about 60 feet at higher elevations," Echelmeyer said.
Geophysical Institute co-authors Echelmeyer, Arendt, Harrison, Lingle, Valentine and glaciologists Sandy Zirnheld and Reggie Muskett have calculated that Alaska glaciers are responsible for at least 9 percent of the global sea-level rise during the past century, and Alaska's glaciers raise the level of Earth's oceans by more than one-tenth of a millimeter each year. This is roughly equivalent to the melting that occurs on the massive Greenland ice sheet. These new observations show that the contribution of Alaska's glaciers to global sea-level rise is far more dramatic than scientists thought.
Researchers measured the volume loss on Alaska' glaciers by checking glacier elevation and volume data on U.S. Geological Survey maps from the 1950s.
In the early 1990s, Echelmeyer, who is also a pilot, teamed with other institute scientists, electronic technicians and machinists to create a laser altimetry system to measure the elevation of glaciers. By flying over glaciers with the system mounted in the belly of his plane, Echelmeyer is able to determine glacier elevations along his flight path. Echelmeyer has flown over glaciers from the Brooks Range to Washington state with his laser measuring device.
He and the other glaciologists compared his measurements of glacier elevation with those on maps and found that about 85 percent of the Alaska glaciers they measured had lost vast portions of their mass between the 1950s and the 1990s. By flying identical flight paths over some of these glaciers from the early 1990s to 2001, the researchers discovered that most were thinning at double the rates they did in the 40 years before.
A few Alaska glaciers are bucking the trend by getting larger, but most are melting rapidly.
Columbia Glacier in Prince William Sound and Bering Glacier in the St. Elias Mountains are two glaciers losing ice at an alarming rate: during the past decade, Columbia has shrunk by an average of about 24 feet per year along the length of the glacier; Bering has lost more than 10 feet per year.
Echelmeyer is hesitant to say these recent changes are the result of a warmer climate because he feels one decade is not long enough to tell the complete story.
He points out that tidewater glaciers, such as Columbia, are less affected by climate change because of the ocean's effect on the face of the glacier and its foundation.
Smaller mountain glaciers, such as McCall Glacier in the Brooks Range or glaciers near Seward and Juneau, are better indicators of climate change because they are not connected to a large body of water.
Echelmeyer has mapped more than 100 glaciers, sizing up Alaska's ice from McCall Glacier in the Brooks Range to Salmon Glacier near Hyder, in Southeast Alaska. While the debate about a warmer world and its effects on glacial melt and sea level continues, glaciologists at the Geophysical Institute will continue their measurements and calculations to obtain an even more complete picture of how Alaska glaciers are changing.
NOTE TO EDITORS: Photographs and video clips are available electronically through the AAAS Office of Public Programs at (202) 326-6440 or firstname.lastname@example.org.
CONTACT: Keith Echelmeyer, Geophysical Institute Glaciologist and co-author of article at (907) 474-0362 on July 15 only, or Anthony Arendt, Geophysical Institute Glaciologists and co-author at (907) 474-7146 or Vicki Daniels Geophysical Institute Public Relations Public Specialist at (907) 474-5823.
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