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Neal Iverson, Geological and Atmospheric Sciences, (515) 294-8048
Skip Derra, News Service, (515) 294-4917
ISU RESEARCH DEEP UNDER ICE
AMES, Iowa -- Neal Iverson, associate professor of geology and atmospheric sciences at Iowa State University, is leading a team of seven researchers to a spot 700 feet under ice to get a first-hand look at how glaciers move across rock and sediment and how they shape the landscape. They are the only team that lives and works beneath a thick glacier to do their research.
The team that will be heading to Norway's Svartisen Subglacial Laboratory includes Iverson; Denis Cohen, a research associate in geophysics at Yale University; Tom Hooyer, an assistant professor at the Wisconsin Geological Survey; Urs Fischer, a research professor at the Swiss Federal Institute of Technology (ETH); Miriam Jackson, a research scientist at the Norwegian Water Resources and Energy Administration; and graduate students Peter Moore (Iowa State) and Marie Rousselot (ETH).
For three weeks (April 3-24), Iverson and his colleagues will live and work beneath a 700-foot-thick river of ice. The laboratory is located in a tunnel excavated in rock beneath the Svartisen Ice Cap. It contains living quarters and equipment that allow sustained, direct study of glaciers as they slip over their substrates.
The tunnel was constructed in 1993 by the Norwegian state power company, which collects the water from the glacier for hydropower. Inside the tunnel, the temperature will be a constant 35 F, and humidity will be near 100 percent. The only opportunity to see the Sun will be a 30-minute walk down the tunnel, once every couple of days.
"It's not a pleasant place to work," Iverson says. "But it's a great natural lab to study glaciers and glacier motion in large-scale experiments."
Basic understanding the goal
"We want to learn about the mechanics of what is going on at the bottom of the glacier, where ice meets rock or sediment," Iverson said.
Specifically, they want to find out what controls the glacier's speed, how certain physical conditions at the ice/rock interface influence the glacier's speed and how sediment is moved via glaciation. Previous studies have shown that ice at the bottom of a glacier is softer and flows easier than ice higher in the glacier, and that sediment beneath the ice may shear and help glaciers move over their beds.
"Glaciers can move very rapidly," Iverson said. "Surging glaciers can slip over their beds as fast as 50 meters per day, more than half the length of a football field. We want to learn exactly how glaciers slip over rock and sediment.
"Understanding how glaciers move, and what causes them sometimes to greatly increase their speed, will ultimately lead to a better understanding of how they impact Earth's climate. Glaciers not only respond to climate change but also sometimes trigger it," he said.
Front row seats to glaciation
Once at Svartisen, the researchers (working from the tunnel in rock under the glacier) will melt a 10-foot-by-10-foot tunnel through the ice for about 100 feet to a spot on the glacier bed where they worked last year. At that spot is a bed-sized trough. They will fill the trough with sediment and instruments for measuring stresses on the sediment and its deformation beneath the ice.
They also will place instruments flush with the rock surface to measure the friction between the ice and rock. The instruments (load cells, extensometers and thermistors) will record the stresses on the rock, and the speed and temperature of the ice as it slips across the glacier's bed.
While doing this they will need to continually "blast" away at the ice, using hot water to cut and re-cut tunnels into the glacier. Iverson said because of the extreme forces put on ice at these depths, it acts like toothpaste and flows into any cavity it can find. As a result, the tunnels melted at the bottom of the glacier disappear in as few as two days.
With their instruments in place, the researchers will let the tunnels fill back up with ice and then measure the stresses on the bed and rates of glacier movement. Iverson said the research team will repeat the experiments they did last year in an effort to reproduce the results.
To vary the range of physical conditions at the ice/rock interface, the team will pump water into their heavily instrumented, sediment-filled trough. This simulates the full range of water pressure expected to occur in the pores of sediment beneath glaciers.
"We found that when water pressure is low, there is no shear deformation of sediment and the ice moves slowly," Iverson said. "When water pressure is medium high -- about 50 to 70 percent of the downward ice pressure -- sediment shears beneath the ice, which allows the ice to increase its speed. When water pressure is really high, when it's more than about 70 percent of the downward ice pressure, the ice decouples from the sediment. The ice floats on top, which can cause rapid movement of glaciers."
Iverson would like to see the results of the research applied to larger ice masses, which feed water to the oceans and affect global climate. He added that the team also would like their data to lead to better mathematical models of glacier movement.
"During the ice ages, glaciers profoundly affected much of Earth's climate and landscape," Iverson said. "A full understanding of how modern glaciers move is required to determine how they've triggered climate change and shaped landscapes. This includes the landscape of central and northern Iowa, which was shaped by a glacier 14,000 years ago."
Iverson's research is funded by the National Science Foundation.
A downloadable photograph of Iverson is available at
Ames, Iowa 50011, (515) 294-4111
Published by: University Relations,
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