Twenty feet of snow on Valdez Glacier
After a winter of outstanding snow conditions, three scientists drove snowmachines up Valdez Glacier this spring, curious to see how far they could get.
They made it across the frozen lake at the toe of the glacier, up the First Bench and then the Second Bench (both named by prospectors long ago who labored up the glacier, trying the low-percentage “All-American Route” to the Klondike).
The researchers followed the curve of the Third Bench, cruising through a bend in the glacier normally riddled by crevasses. They kept on, and on, until the snow finally bogged down their slow-moving machines. When they turned off the engines and absorbed the silence, they had reached a magnificent white pass near the top of the 21-mile long glacier.
There, at about 5,500 feet above the salt water of Port Valdez, their machines rested on about 20 feet of snow that had fallen there during the winter. Using measurements they took along the way, the researchers will figure how much water the glacier will pump out this summer, and whether the glacier’s flow might threaten the bridge that is the city of Valdez’s Richardson Highway only road connection to the outside world.
“We were able to get a near-complete longitudinal profile of snowpack up to the ice divide,” said Gabriel Wolken of the Alaska Division of Geological and Geophysical Surveys. “This was the only year in the last decade we could have done it — the icefalls and crevasses were pretty much filled with snow.
Valdez’s snowfall in 2011 and 2012 was more than 400 inches by mid-April 2012, which is not a record but is extreme, even for Valdez.
“It motivated us to try and find out how much snow was on the glacier,” Wolken said.
The scientists knew with that much snowfall that the usual method of measuring snow depth on a glacier — stopping every so often to stick probes in the snow and then dig snow pits — would be too labor intensive. But Wolken knew of Alessio Gusmeroli’s portable radar system, small enough to fit on a sled, and decided to try that method.
“It went surprisingly well,” Wolken said.
Wolken and his two partners on the out-and back traverse — glaciologists Anthony Arendt of the Geophysical Institute and Gusmeroli of the International Arctic Research Center and Alaska Climate Science Center — towed the radar system in a sled. While Wolken motored along at 5 miles per hour, the radar sent a signal through the snow, where it bounced off the base of this year’s snowpack and came back. This gave the scientists an idea of snow depth along the glacier that varied from about 20 feet up high to three wind-blown feet down low.
“What this shows is that there’s considerable variability of snowpack on the glacier,” Wolken said. “It allows us to think about the mass balance much better and the potential for glacier-related hazards in Valdez.”
Wolken and his colleagues will travel to Valdez Glacier a few more times in spring and summer, installing weather stations and driving stakes into the glacier they will check later to look for movement and snow lost or gained. They are studying the glacier because the glacier’s runoff has the potential to damage property and infrastructure, including the bridge over Valdez Glacier Stream. The bridge, about 180 feet long, sits in the flood plain of a glacial river prevented from wandering by a levee.
“Right now the Valdez Glacier Stream goes through a very small synthetic aperture (the bridge), where normally it’d be much more distributed,” Wolken said.
This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell is a science writer at the institute.
