A
Publication of
The University of Montana
Spring 2006
Going Global: UM's international efforts link Montana to the world
Speeding Glaciers: UM researchers study movement of ice rivers
Ranching Human Lice: This story will make you itch
An Angry Earth: Researcher delves into terrible Pakistan quake
Research View is published twice a year by the offices of the Vice President for Research and Development and University Relations at The University of Montana. Send questions, comments or suggestions to Rita Munzenrider, managing editor, 327 Brantly Hall, Missoula, MT 59812, or call (406) 243-4824. Production manager and designer is Cary Shimek. Contributing editors and writers are Brianne Burrowes, Patia Stephens, Shimek and Cory Walsh. The photographer is Todd Goodrich. For more information about UM research, call Judy Fredenberg in the Office of the Vice President for Research and Development at (406) 243-6670.
GEOLOGY
Speeding
Glaciers
UM researchers
study movement of ice rivers
At first glance, some academic field research projects seem like abstract exercises in extreme summer vacationing, resulting in reams of data and what-I-did-this-summer photography.
Take, for example, what UM geology Assistant Professor Joel Harper and his small cadre of geology students have been up to over the last couple summer field seasons: camping on a remote glacier in Alaska’s Chugach Mountains and using a large, homemade drill to bore holes in it.
When asked the name of a mountain towering over the glacier, Harper says, “You’d have to go 50 miles to find something with a name.”
In fact, he points to a beautiful picture of the glacier, blown up poster-size and hanging on his office wall, that he and his students spent months studying and says, “This glacier doesn’t really matter …”
Other glaciers, arguably more meaningful ones, such as Alaska’s huge Columbia Glacier or the massive ice cap covering Greenland, are undergoing what Harper calls “catastrophic” changes. As the climate changes, these and other glaciers are warming up.
Meltwater is finding its way to the bed of the glaciers, causing them to move at astonishing rates -- for glaciers, anyway.
Harper said
sea levels have risen some 120 meters since the end of the last ice
age about 18,000 years ago. The world’s glaciers
contain another 70 meters of sea level in the form of stored ice, and
about 10 percent of this potential future ocean water sits on
top of Greenland.
The gradual melting of the world’s remaining glaciers will make an obvious impression on islands and coastal communities around the globe. And, as they thaw, glaciers deliver massive amounts of freshwater to the salty ocean. This conveyance of freshwater has a major impact on the salinity levels in the oceans, in turn driving changes in currents and weather patterns. While few, if any, would notice if Harper’s glacier speeds up or even disappears, the changes happening to other glaciers -- such as the behemoths covering Greenland -- will have a significant global impact.
“To understand these changes,” Harper says, “we have to understand how glaciers move and how they deliver their water to the ocean.”
His desire to better understand glacier physics is what brought him and his field crew to the middle of nowhere.
For years, glacier scientists made the assumption that an increase in water pressure underneath the glacier caused an increase in the glacier’s speed. This hypothesis had never been proven, yet the only way the role of water enters prevailing models that scientists use to predict a glacier’s movement is through a representation of the water pressure. Harper had a hunch that the role of meltwater in glacier physics was misunderstood, and he designed a project that would rigorously test long-held beliefs.
“It was a big battle to convince people that this had to be done,” Harper says.
Finally,
Harper and collaborators from the universities of Colorado
and Wyoming secured a grant from the National Science Foundation
to test the role of water pressure in glacier movement.
Harper’s remote glacier perfectly suited his needs, and it was
one he’d flown over several other times while working on other
projects in Alaska. The glacier is long (about 8 kilometers), wide (about
1 kilometer) and thick (about 200 meters). Its relatively gentle surface
topography also appeared safe enough for him and his team to spend weeks
at a time living and working on.
His plan was to drill holes along the entire length of the glacier, from the head all the way down to the terminus. His team also would bore a grid of holes in the middle of the ice river. Once the holes were drilled, the researchers would lower devices to measure the pressure of the water at the intersection of the glacier ice and the bedrock -- along with the turbidity and velocity of the water moving beneath.
Scientists have drilled holes in glaciers to test water pressure before, but previous experiments were generally limited to a few locations on a given glacier. The 47 holes that he and his team completed with their homemade drill was an unprecedented and ambitious effort.
Harper’s group built a drilling system that could be hauled in a three-sled system. The team had all its gear, including tents, food, scientific instrumentation and a snow machine, slung in by helicopter. They spent two summer field seasons on the glacier -- weeks at a time doing little but boring holes in ice with their drill, taking measurements and hauling equipment from site to site.
They found that Harper’s hunch about the limited role of water pressure on glacier speed was correct.
In spring, glaciers speed up for about a week -- suddenly traveling about 10 times faster than usual. The glacier Harper and his team studies is no exception to this pattern. Harper’s data show that when the glacier goes through this somewhat dramatic increase in speed, the water pressure doesn’t change drastically. However, the drainage pattern -- how meltwater moves under the glacier -- undergoes a remarkable shift.
“The drainage system becomes really connected,” Harper says, “and starts ‘talking’ to the glacier.” In effect, the change in the way the water moves under the glacier drives the increase in speed -- not the pressure of the water itself.
The next step is to use what they’ve learned to help create a new model to predict glacier movement in places like Greenland.
The impacts of climate change will go largely unnoticed at Harper’s remote summer study sites. Like he said, that one glacier doesn’t really matter. But by using this relatively insignificant one as a proxy, he and his colleagues corrected a long-held -- and incorrect -- assumption about the physics of glacier movement.
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| University glaciologist Joel Harper at work. |
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| UM graduate student Jonathan Reeve uses red dye to study how water moves through the glacier. |
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| Researchers focused on this glacier, an 8-kilometer-long river of ice near the coast of southcentral Alaska. |
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