Summer on ice

Tracking the movement of the fifth biggest icefield in the world

Posted: Sunday, August 27, 2000

JUNEAU ICEFIELD From the bottom of a 35-foot deep pit I looked up at the past winter, preserved in the Taku Glacier.

Bands of snow, some 4 feet thick, and thin ribbons of blue ice layered the walls of the pit that students with the Juneau Icefield Research Project had dug into the glacier, 30 miles northeast of Juneau. Like growth rings on a tree, each layer represented a storm that dumped snow on the icefield above Juneau last year.

Glaciers provide a precise record of Earth's continuous climatic change. For 50 summers, the University of Idaho's Maynard Miller has led a group of researchers and students to the Juneau Icefield to read the record on North America's fifth largest icefield.

This year's group included 34 high school and college students from around the country, Europe and Japan. Over the summer, they learned mountaineering and field research skills while studying geology, meteorology and glaciology. During the eight-week program they made a 120-mile traverse of the icefield from Juneau to Atlin, British Columbia.

 

The cold, wet weather that forms glaciers is not the best for people. Temperatures this summer often hovered in the mid-30s with winds blowing 5 to 15 miles per hour.

For protection from this inhospitable environment, researchers and students stayed in a series of five permanent camps across the icefield. Most were about 5,000 feet in elevation, so fog and clouds often limited visibility to just a few feet. But on this summer's few clear days, the crew had glorious views of the vast, flat glaciers and the steep rock pinnacles that rise some 2,000 feet over the broad expanse of glaciers.

On a typical July day, the survey crew set out at 10:30 a.m. to plot a line across the Taku Glacier. By returning to the line a couple of weeks later, they determined how fast the glacier was moving.

With its 5-mile width and 25-mile length, the Taku is a huge glacier. Determining its exact depth presents some real difficulties because rivers, crevasses and sometimes even underground lakes break up the layers. You can't just drill a hole in this glacier to find its depth the continually moving ice would bend the bit.

 

But evidence gained through seismic testing shows this massive glacier has cut a very steep, deep canyon into the Southeast Alaska coast. The cut may well go down to sea level, about 5,000 feet.

As we skied across the upper reaches of the glacier, we didn't worry much about crevasses. The past winter was a wet, warm one that dropped more than 30 feet of snow on the icefield. In fact, it was one of the warmest on record, with temperatures just nudging 20 below zero. In past years, temperatures of 30 below or colder were common, which meant less snow.

Even so, as the snow melted and evaporated, the deep blue cracks of crevasses emerged across the otherwise flat, white glacier.

We carried a very accurate, $45,000 global positioning survey system GPS. The instrument, provided by a geodetic research team from Munich, Germany, measures points on the Earth's surface to within a half-inch. It does this by receiving radio signals from satellites orbiting the Earth and by relating those signals to a set reference point established earlier on the bare rock near camp.

 

Every 100 yards or so, we plotted a point on the glacier, entered it in the system's computer and skied on to the next point. With broken clouds, no rain and no wind, the temperature climbed to a balmy 45 degrees on the ice. We had to watch for sunburn, especially since the ice and snow reflect nearly all of the sun's radiation.

By the end of the afternoon, we completed our survey line across the glacier. Fog enveloped us. The wind was dead still. When we stopped, there was not a sound. We stood in a completely white and gray, silent world. As we skied the five miles back to camp across the flat glacier and through the featureless fog, we heard only our skis swooshing over the snow.

On nunataks, bare rock islands sticking out of the icefield's glaciers, we often heard or saw ptarmigan and gray-headed finches. Once in a while, a hummingbird buzzed by looking for the heather or other flowers that eke out a living on the rocks above this world of snow and ice.

One blustery afternoon, while we were setting a survey reference point, a gyrfalcon swooped overhead. On the glacier below we chanced upon some scattered bones and a few feathers remains of a ptarmigan, which left no doubt about how that white falcon makes a living up here.

Miller reports that over the past 50 years of working on the icefield each summer, he's seen two brown bears crossing the glaciers. Marmots and mountain goats inhabit the lower nunataks, and the wind blows stray bugs across the snow and ice.

But generally the icefield is a lifeless place. Except for our Gortex and other bright equipment, it is colorless. That, along with a near lack of smells and sounds, causes sensory deprivation. So when we climbed down to places where flowers grow, their colors and smells seemed exhilaratingly bright and strong.

A couple weeks after we set the line in the snow, student researchers returned to find the center of the glacier had marched forward two feet per day. The glacier flows like a U-shaped river of ice, with points near the edge grinding along more slowly.

In other places, the center of the glacier was creeping a mere four inches a day, and when the glacier reaches an icefall, where it makes a sharp drop or goes over a cliff, it can move much faster, sometimes 15 feet in one day. These differences in speed cause stress that cracks the glacier and splits it apart, forming crevasses.

Measuring the glacier's speed is like taking a patient's pulse. A moving glacier is healthy, but a glacier that has stopped is dead. The Taku Glacier is moving at a healthy rate. Over the last 100 years, the glacier has grown nearly four miles in length.

It's one of the few glaciers in the world that has. Other glaciers, like the Mendenhall, are melting back so quickly they are receding as much as 150 feet per year.

The Taku Glacier begins at a higher elevation than other glaciers do, so its area of accumulation receives huge quantities of snow. As Miller likes to point out, areas where temperatures hang just below freezing, in the mid to high 20s, receive maximum snowfall. Those are the temperatures much of the Taku sees during the winter. So the bulk of the Taku Glacier receives huge snowfalls while other glaciers merely are getting rain.

It's hard to say how much the Taku will grow.

According to Roman Motyka, a researcher at the University of Alaska Southeast, the glacier's terminus has pretty much remained in the same location since 1987 because its growth has approximated the amount it has melted back.

In the late 1700s, however, it apparently grew to block Taku Inlet. The surge that this year's heavy accumulation of snow will cause will take at least 20 years to reach Taku Inlet.

The glaciers tell us that the world's climate is continuously changing, moving through cold and warm periods. The fast rate at which most glaciers are receding shows that the world's climate is warming, and quickly.

On average, the earth is warming at 0.5 degrees Celsius a century, said Geophysicist Josefino Comiso, who studies the polar ice cap from NASA's Goddard Space Flight Center at Greenbelt, Md. In the Arctic, the rise has been more dramatic at 0.7 degrees.

How much the current warming trend is caused by human activity is still an open question. Part of the answer may be found in the layers of ice above Juneau.

Phil Druker is a mountaineer and a University of Idaho faculty member who works with the icefield research program. He also teaches technical writing at the university. Students and faculty from the University of Alaska Southeast are also part of the program.



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