As Alaska thaws, engineers eye strange new world
Tempest
WARMING: Melting permafrost poses new challenges to designers.
By Doug O'Harra
Anchorage Daily News
http://www.adn.com/front/story/2434881p-2483179c.html
So how do you demonstrate the impact of global climate change on
Alaska's roads, bridges, buildings and pipelines?
With charts showing rising temperatures and melting permafrost across
the Arctic? With satellite peeks at the shrinking polar ice? With
gargantuan models by bit-busting supercomputers?
How about a 25-foot-deep muck hole at Mile 1263 of the Alaska Highway?
Last summer, a lens of frozen ground simply dissolved under a culvert at
that location, about 75 miles from the Canadian border near the Northway
Junction. State crews kept the sinkhole from consuming the highway, but
not before the culvert had snapped off and silty water had flushed away
a 100-foot stretch of earth along the shoulder.
"This is the kind of thing we're facing in the field on a regular
basis," said George Levasseur, Southcentral district manager for the
Alaska Department of Transportation.
As the changing climate warms the Earth, melts glaciers and dumps
increasing snow and rain over much of the region, state crews have been
grappling with damage to road surfaces, bridges and channels. That's
what Levasseur told about 35 engineers and scientists on Wednesday as he
showed slides of boiling rivers and silty channels.
He was among a half dozen speakers at a conference for scientists and
engineers at the University of Alaska Anchorage called "The Warming
World: Designing for Climate Change."
The presenters ranged from a leading atmospheric scientist to a road
maintenance chief to the retired captain from a U.S. Coast Guard
icebreaker. They described a world where it's getting warmer, wetter and
more unpredictable.
But the ultimate focus was on finding practical ways to use this
information to create roads, bridges, airstrips, buildings and pipelines
that will work in a world where the bottom threatens to wash out.
The conference continues today at the UAA business education building
with talks on rural Alaska's infrastructure and designing for climate
change. UAA engineering professor and conference organizer Orson Smith
told group members that they would also need to make explicit
recommendations for planners, engineers and policy-makers.
The Arctic has definitely warmed over the past few decades, with the
most dramatic warming concentrated in the spring and winter, said John
Walsh, a leading climate scientist and the president's professor at the
International Arctic Research Center at the University of Alaska
Fairbanks.
Sea ice has been shrinking -- with 2002 marking the smallest polar ice
cap on record. Alaska glaciers have lost mass, contributing to about
half of the measurable rise in world sea levels. Increased flows in
Arctic river systems suggested that precipitation has been rising as
well, Walsh said.
Even more dramatic, five different climate models project warming trends
through the end of the 21st century, with overall average temperatures
rising 7 degrees to 15 degrees Fahrenheit, he said.
"Which is substantial warming," he added.
The same models also suggest that Alaska's permafrost frontier will
slowly migrate north as much as 200 miles over the next century -- from
southern Alaska to central Alaska, Walsh said.
Such melting permafrost exposes coastal communities to erosion, buckles
roads, destabilizes foundations.
In Alaska, the potential impact is huge. Permafrost can be found in 166
Alaska communities with nearly 90,000 residents, and underlies 1,700
miles of Alaska roads, according to Lawson Brigham, deputy executive
director of the U.S. Arctic Research Commission and the coordinator of a
federal Permafrost Task Force. At least 700 miles of the 800-mile
trans-Alaska oil pipeline cross discontinuous or permanent permafrost.
While pipeline operators don't worry too much about the very cold
permafrost north of the Brooks Range, they do monitor pipeline supports
stuck in much warmer permafrost further to the south, said engineer J.
David Norton, who has worked with Alyeska Pipeline Service Co. for many
years. Some 182 of 78,000 the T-shaped pipeline supports are being
closely monitored -- and 24 have been replaced since 2000 when they
became too unstable, he said.
"The pace of climate change, if it continues, will be slow enough for
the (pipeline) owners to respond and take corrective action," he said.
All of this meltdown has dumped silt and gravel into rivers and creeks
in the Copper River basin -- filling culverts, causing floods,
undercutting bridges, shifting channels, Levasseur said.
The Copper River has been carrying 100,000 tons of gravel per day into
the delta during peak flows -- almost double what it carried 10 years
ago, Levasseur said. All that additional grit has been shifting the
river. What was once a main channel under a big, well-built bridge near
Mile 27 of the Copper River Highway is now a trickle, while the main
stem is rushing through overflow channels further east.
"We've had to extend those bridges twice," Levasseur said.
This year, Levasseur's crews had to rebuild about 45 miles of highway in
hundreds of locations throughout the region. It cost $4.5 million.
"The whole Alaska Highway from Northway to the border is coming apart,"
he said in an interview. "It's just exploding."
--
The modern conservative is engaged in one of man's oldest exercises in
moral philosophy; that is, the search for a superior moral justification
for selfishness.
--John Kenneth Galbraith