Glacier retreat to slow as terminus creeps onto land

Scientists: Fewer calving events might help slow disappearance of Juneau's favorite chunk of ice

Posted: Monday, March 29, 2010

Residents who noticed dramatic changes in Juneau's backyard glacier might be pleased to know its retreat will slow a bit over the next few years.

Klas Stolpe / Juneau Empire
Klas Stolpe / Juneau Empire

Student-scientists from the University of Alaska shared the prediction with a roomful of the glacier's neighbors during a talk Friday at the Mendenhall Glacier Visitor Center.

The students measured and mapped changes to the glacier through hours of fieldwork as part of their courses of study.

Ivy Smith, a third-year University of Alaska Southeast student majoring in environmental science, explained that the terminus, or "face" of the glacier, is receding beyond an underwater basin and will soon sit on land.

The glacier will not calve as much while it is resting on rock instead of water, and therefore its retreat will slow, Smith explained.

Smith and other students confirmed the terminus was reaching the edge of an underwater basin - a theory posed about three years ago when students first saw the basin edge emerging - by taking a series of measurements from a motorized boat on the lake.

Less frequent calving doesn't mean the glacier is melting more slowly, however. The glacier loses enough water to fill 56,000 Olympic-sized swimming pools every year. It used to be 32,000 pools about a decade ago.

The students did not discuss the politics of global warming but said the facts they collect will add to the international discussion on climate change.

The audience Friday gasped at a series of time-lapsed photographs students recorded to show the changing face of the glacier over a period of less than one year.

Watching your neighborhood glacier melt is like watching a snowman slowly dissolve in the front yard - inevitable but still sad to some.

"It's dramatic changes," said adjunct faculty member Mike Hekkers. "It's sad because there won't be icebergs on the lake but I think that will be at least five years away."

The audience asked the students a lot of time-related questions, such as how long they would be able to see the glacier.

The students and faculty have a bet about when the glacier will no longer touch the lake. Many bets are on this year but others, such as Hekkers, give it more time.

Today, only a small portion of the glacier still terminates in the lake and much of the east side is already sitting on rock.

The glacier last year lost about 200 feet of ice, an average annual amount for the past decade. In 2004, the glacier lost nearly 1,000 feet.

As for the larger question: Students said the glacier wouldn't retreat out of sight until at least 2060.

The talk was the last in a series of lectures called "fireside chats" that take place during the off-season at the visitor center, which is run by the U.S. Forest Service.

The talks are free and attended by hundreds of locals every season. Participants have a chance to hear about the wide-ranging scientific studies going on in the region. Topics this year ranged from bears to potatoes.

• Contact reporter Kim Marquis at 523-2279 or kim.marquis@juneauempire.com.



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