Experts get shrinking feel about Alaska glaciers

By Matt Volz

updated 3:50 p.m. ET Sept. 22, 2006

JUNEAU, Alaska - Less than 10 minutes after lifting off from the airport, the helicopter entered the frozen world suspended above Alaska’s capital.

Snowcapped mountains rose on either side as the small team of scientists and students peered down at a jagged blue carpet of ice below. The pilot turned up one arm of Mendenhall Glacier only to find the way blocked by a wall of fog. The storm was moving in; the work would have to be done quickly.

Hydrologist Eran Hood used a handheld global positioning system to guide the pilot higher up the ice field on a clearer path. Circling low, the scientists spotted what they were after: A tiny pyramid of wire nearly invisible in the field of white.

In this lonely corner of an ice field larger than Rhode Island, the packed snow crunching under their boots, the group set up shop. They were about to find out just how much this part of the glacier had melted over the summer and how fast it was moving.

Hood and physicist Matt Heavner, his colleague at the University of Alaska Southeast, measured at least 10 feet of ice loss since May there and at two other spots on the glacier.

Rain was beating down on the tourists at the glacier’s terminus below. The year’s consistently bad weather has been dreary for the visitors, but something of a reprieve for the melting Mendenhall Glacier.

“It’s a good summer to be a glacier,” Hood said.

There haven’t been too many, judging by the rate at which Southeast Alaska’s rivers of ice are melting.

Earlier estimates way off
Most of the glaciers stretching from Yakutat Bay to the Stikine Icefield, which goes into northwestern British Columbia, are thinning at twice the rate that was previously estimated, according to a new study co-authored by Hood’s mentor, glaciologist Roman Motyka of the University of Alaska Fairbanks’ Geophysical Institute.

Comparing radar mapping data from a space shuttle mission six years ago with air photos taken between 1948 and 1979, Motyka, UAF colleague Chris Larsen and three other scientists pinpointed the extent of the glaciers’ volume change.

They found that 95 percent of Southeast Alaska’s glaciers are thinning. Some glacier surface elevations had dropped as much as 2,100 feet since 1948, such as the Muir Glacier in the popular Glacier Bay National Park and Preserve.

David J. Sheakley / AP Hydrologists Eran Hood, right, and Mike Hekkers adjust instruments on the upper north branch of the Mendenhall Glacier in Alaska last Aug. 30 as part of their glacier monitoring work.

With the more precise data, they figured the rate of thinning was greatly underestimated from the last study done in 2002.

The scientists calculated that an average of 3.5 cubic miles of glacier ice melts each year in the region due to a combination of climate change and glacier dynamics. They say even that may be an understatement of the actual rate of melting.

Mendenhall Glacier is a relatively small river of ice compared to the rest of Southeast Alaska’s extensive network, but it stands out. It is Alaska’s most visited glacier, drawing 367,000 people to the U.S. Forest Service’s visitor center last year.

The glacier is rapidly shrinking up the mountainside — as rapidly as glaciers can, anyway. Visitors who have observed the glacier see the change themselves. Motyka estimated that the glacier’s terminus will pull out of Mendenhall Lake entirely within 10 years.

Hikers can trek up the side of the glacier along craggy rock that was under a deep layer of ice just two years ago. They can poke around in ice caves that weren’t there at the beginning of the summer — and which will be gone by the season’s end.

“We don’t want to spend too much time underneath,” Hood said in one such cave, as water from the blue roof dripped all around. “These are all pretty ephemeral.”

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