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UMaine Today Magazine


Denali Ice
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 Denali Ice
Photographs by Ron Lisnet
 

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Every spring, mountain climbing parties from across the globe gather at a base camp on the Kahiltna Glacier in preparation for scaling North America's highest peak. More than 1,000 climbers registered with the National Park Service this year to climb the 20,320-foot Mt. McKinley. Among them were seven scientists from the University of Maine and University of New Hampshire.

While the other alpine adventurers had their sights set on the summit, the university researchers searched for the best location to drill and extract an ice core from Kahiltna and nearby Upper Yetna Glacier. Their goal: to learn about climate past to better predict its future.

"These glaciers have certainly been here for thousands of years, if not longer," says Karl Kreutz, associate professor of Earth sciences affiliated with the University of Maine Climate Change Institute and a co-principal investigator on the expedition in May with Cameron Wake, a research associate professor at the University of New Hampshire Climate Change Research Center.

"Here in the upper part of the glacier, the snow that falls from year to year doesn't melt; it just keeps on piling up," Kreutz says. "When you (drill an ice core) straight down, you get something that essentially looks like tree rings. You have layer upon layer of snow that's fallen, allowing you to reconstruct how the climate has been changing over time. You're going back in time the deeper you go into the glacier."

Like the pages of a history book, the layers of snow and ice that accumulate each year on the glacier tell a story. Chemicals contained in the layers have the potential to yield information on such climate controls as pollution transport, temperature and atmospheric circulation.

"Ice cores are really the best way to look at long records of atmospheric pollution," says Erich Osterberg, a postdoctoral researcher at Dartmouth who did his Ph.D. work at UMaine's Climate Change Institute. "Every year, new snowfalls and it takes the pollution down with it. It's an ideal record for us."

For instance, previous work in Alaska by the Climate Change Institute has proven to be an accurate gauge of the economic growth of the Pacific-Asian region. The manmade pollutants Osterberg found in his Alaskan ice core work in 200102 correlate with the growth of Asian industry.

"Starting in the '70s or even the late '60s when economic growth really started picking up, particularly in China, you could see this really good correlation," he says. "It doesn't really matter what you look at. You can look at their GDP, you can look at their energy output, you can look at their CO2 output and they all match pretty well. It's been going up quite quickly the last 30 years."

While the science of analyzing the chemistry of ice cores can be quite complex, the actual process of removing a 3-inch column of snow and ice from a glacier is fairly simple. The ice core drill looks much like the auger used by ice fishermen. A fiberglass pipe running through the middle of the drill holds the core as it is pulled to the surface. Deep cores are hoisted using a winch and cable. 

The Denali cores the UMaine-UNH team retrieved this past May were 20 meters long. The deepest cores ever extracted measured more than 3,200 meters (nearly 2 miles) long, drilled in East Antarctica by a European team of researchers.

Perhaps the trickiest part of a coring expedition comes once the ice is pulled to the surface. Any melting of the core results in loss of climate information contained in its distinct layers. Cores are packed in insulated boxes and buried in the snow until time for transport. 

Within five days of retrieval, the Denali ice cores were flown to Anchorage for freezer storage. From there, they were sent in insulated containers via Federal Express to Boston. There, a freezer truck transported the cores to UNH and UMaine.

UMaine maintains two ice core freezers containing more than 1,500 meters of ice drilled from around the world.

"From a place like Alaska, cargo services are in place to make it happen," says Kreutz. "But working Asia, for example, it becomes much more of a challenge to get a piece of ice back to the laboratory. You might be dealing with carrying pieces of ice on the backs of Yaks or other animals or trekking through the mountains."

Despite all the planning that goes into an expedition like the Denali trip, the hauling of 3,000 pounds of gear to do the drilling and the shipping of a 60-foot-longcolumn of ice across the continent, it is still the fieldwork that draws Kreutz and many of his colleagues to this research.

"The winter landscape has always fascinated me," he says. "In addition to the exciting science that goes on, to be able to come to a place like this and live in this environment for a time is really great. Working in the lab and doing the science back home at the university can be quite exciting, but for many of us, being out here in the field, collecting samples, living in this environment is really a big part of why we do it."

by Ron Lisnet
September-October, 2008

 

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