Alaska Glaciers Show Dramatic Melting
Each December, the flock of scientists in Alaska gets a bit smaller as many fly to San Francisco to join thousands of other scientists at the American Geophysical Union meeting. Keith Echelmeyer is one of those Alaska scientists, and he's carrying to San Francisco compelling evidence of Alaska's disappearing glaciers.
Echelmeyer is a glaciologist at the Geophysical Institute at the University of Alaska Fairbanks. He and his colleagues, including Will Harrison, Anthony Arendt, By Valentine, Sandy Zirnheld, Craig Lingle and Reggie Muskett, have found that most Alaska glaciers 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.
The group of glacier scientists at the Geophysical Institute has calculated that Alaska glaciers are responsible for at least seven 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. That's possibly more than 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.
How do you measure volume loss on glaciers all over Alaska? First, the researchers checked the elevation and volume of glaciers on USGS maps from the 1950s to the present. In the early 1990s, Echelmeyer, who is also a pilot, teamed with other institute scientists, electronic technicians and machinists to create a laser device to measure the elevation of glaciers. By flying over glaciers with the device 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 maps and found that about 85 percent of the Alaska glaciers they measured had lost vast portions of themselves from the 1950s to the 1990s. By flying identical flight paths over the glaciers from the early 1990s to 2001, the researchers discovered that most Alaska glaciers are thinning at double the rates they did in the 40 years prior.
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 21 feet per year along the length of the glacier; Bering has lost more than 9 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 also pointed out that tidewater glaciers, such as Columbia, are indifferent to climate change because of the ocean's affect 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.
While the debate about a warmer world and its effects on glacial melt and sea level continues, Echelmeyer will continue to fly over Alaska. He and the group of glaciologists at the Geophysical Institute have 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.
