Dangerous ice the focus of
By NED ROZELL
March 31, 2010
SAM CHARLEY SLOUGH - Winter travelers on the Tanana River can
save a mile by taking the shortcut through this serpentine channel
rather than following a lazy bend of the big river, but experienced
dog mushers and snowmachiners avoid Sam Charley Slough. After
driving here with a fleet of six snowmachines, we can see why.
Black, open leads yawn throughout the slough, and the gurgle
of water holes sounds eerie in late winter. This bad ice has
today drawn a team of ice-savvy travelers, scientists, and videographers.
They are trying to find out why some river ice breaks beneath
people and machines while other ice stays firm.
UAF ecologist Knut
Kielland checks out a mysterious hole in the ice of the Tanana
Photo by Ned Rozell
Video: A video of UAF ecologist Knut Kielland exposing thin ice
Tanana River: http://www.youtube.com/watch?v=PUZ5ZtXLses
Video by Ned Rozell.
Sam Charley Slough is like other puzzling sections of the Tanana
River that have patches of open water despite the kiss of sub-zero
air all winter long.
From his experiences out here
dog mushing and snowmachining, Knut Kielland knows the slough
well enough to point out the spot where wolves make a portage
trail over a lobe of forest pinched by the slough. He mentions
something strange he's observed after the slough freezes hard
"It's fine until around New Year's, and then it becomes
unsafe," Kielland says to Matthew Sturm and Chas Jones,
two scientists who have joined him on the trip about 20 miles
downriver from Fairbanks. "The ice goes to pot even as the
temperature drops from minus 20 to minus 50 (degrees Fahrenheit).
It continues to deteriorate despite colder air temperatures."
Kielland is an ecologist at the University of Alaska Fairbanks'
Institute of Arctic Biology. He is teaming with Bill Schneider,
curator of oral history for the Elmer E. Rasmuson Library, to
map and document dangerous ice conditions throughout Interior
Alaska with scientists and people who have traveled the river
for years. Schneider and his colleague Karen Brewster are capturing
on video the observations of experienced river travelers. With
funding from the National Science Foundation, they plan to examine
how local river travelers respond to changing ice conditions
and how these conditions affect subsistence activities ranging
from woodcutting to trapping. They also hope to bring together
locals and scientists to learn more about the frozen platform
used by so many winter travelers in Alaska.
From left, in foreground,
Matthew Sturm, Bill Schneider, Knut
Kielland, and Sam Demientieff look at possible paths through
a slough with
Photo by Ned Rozell
This column is provided
as a public service by the Geophysical
Institute, University of Alaska Fairbanks, in cooperation
with the UAF research community.
An impressive lineup of bush experience was standing there on
a snow-covered gravel bar on Sam Charley Slough that March day
- among them were Sam Demientieff, who was born in Holy Cross
on the Yukon and has traveled Alaska rivers for more than 60
years; Sturm, a snow scientist with the Cold Regions Research
and Engineering Laboratory at Fort Wainwright who has traveled
thousands of miles on ice; and Schneider, who has also run dogs
on Interior rivers and lakes for many years.
As they stopped their machines and looked over the ice of Sam
Charley Slough, the men agreed on one thing - ice, or the lack
of it in spots, is tough to figure out. One idea is that the
seepage of warm water springs weakens and erodes ice from below.
This would seem to favor ice melting over shallow parts of the
waterway, but the travelers on that March day found pools of
open water several feet deep. On a recent trip to the village
of Tanana, Kielland documented an area downriver with a skim
of half-inch ice covering a 10-foot hole right next to the winter
"That's what scares me," Kielland said. "Lots
of deep holes right next to the trail. The ice gradient is very
unpredictable. We want to identify what sort of mechanism can
account for this. How is this heat delivered (to the ice)?"
Standing next to one another, Sturm, Schneider, Kielland and
Demientieff looked out over Sam Charley Slough's pocked surface.
Each pointed to possible routes that a snowmachiner might weave
through the dangerous ice, but it's such a fickle substance that
they all came to the same conclusion.
"I vote we go back the way we came," Sturm said. Others
nodded in agreement.
Six snowmachines turned around, buzzed single-file on a path
back to the Tanana River, and left the mysteries of Sam Charley
Slough for another day.
Ned Rozell [firstname.lastname@example.org]
is a science writer at the institute.
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