Periglacial Process in Alaska
Application:
Alaska
Pipeline
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Permafrost
regimes
Tectonics
Alaska Pipeline
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~ 800 miles long (409 mi. buried; 382 mi. above ground)
Trans Alaska Pipeline System (TAPS), formed by seven oil
companies, announced plans in February 1969 to build a 4-foot
diameter pipeline to carry crude oil from Prudhoe Bay to Valdez
The temperature of the oil coming out of the ground was 80 deg C
1970 USGS Circular 632, "Some Estimates of the Thermal Effects of
a Heated Pipeline in Permafrost” predicted that buried pipe would
float, twist, and break
Pipeline and storage tank construction at Valdez began in 1975
The initial estimated cost of installing 800 miles of buried pipeline
was $900 million, and the actual cost was more than $8 billion
Oil flows at 4 mph in the pipeline taking a week to reach Valdez
http://menlocampus.wr.usgs.gov/50years/accomplishments/pipeline.html
145°F
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"There are 78,000 VSMs [vertical support
members] and every single one of those had a 24inch hole drilled for it and every single one of them
had a qualified person analyzing what came out of
the hole to determine what kind of VSM it should
be. There was actually a field design manual that
was based on the soil."
-- Bill Howitt, Alyeska engineer
http://www.alyeska-pipe.com/pipelinefacts/PipelineEngineering.html
http://geoimages.berkeley.edu/GeoImages/Johnson/Biomes/BiomesSub/AlaskaPipeline
Thaw Lakes
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Thawing of the uppermost portion
of the permafrost
Melting of permafrost leads to
subsidence
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Excess pore water is expelled
Surrounding permafrost forms an
impermeable bowl
If depth> ~2m., lake will not
freeze solid, developing unfrozen
underlying material called a thaw
bulb or talik
Water absorbs more solar energy
than soil
Continued thawing leads to more
subsidence and deepening of lake
http://www.sciencefriday.com/vide
os/watch/10008
Arctic environment change
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Thermokarst:
 Landscape features caused by structural failure
following the melting of ground ice
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Results from deepening of the active layer and
thawing of top of permafrost
Thickening of the active layer has two immediate
effects:
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Collapse, erosion, and slope instability assoc. with
thawing permafrost
Decomposed plant material frozen in the upper
permafrost thaws, exposing the carbon to microbial
decomposition, releasing carbon dioxide and
methane to the atmosphere
Ice in the upper permafrost is converted to water
When ice-rich permafrost thaws, the ground
surface subsides
Arctic environment change
This downward displacement of the ground
surface is termed thaw settlement (Fig. 6).
Settlement is nonuniform creating a chaotic surface
with small hills and wet depressions known as
thermokarst terrain
Also common in areas underlain by ice
wedges (Fig. 7).
When thermokarst occurs beneath a road,
house, pipeline, or airfield, the structural
integrity is threatened.
If thermokarst occurs in response to
regional warming, large areas can subside
and, if near the coast, can be inundated by
encroaching seas.
http://thermokarst.psu.edu/
A 40-mile stretch of Alaskan coastline along the
Beaufort Sea is eroding at a rate of 45 feet per
year.
That's double the erosion rate of just a few
years ago.
A study describing the work was recently
published in Geophysical Research Letters.
Changing conditions such as declining sea ice
extent, increasing summertime sea-surface
temperature, rising sea level, and increases in
storm power may have all contributed to the
coastal decline
A cabin along the Arctic Alaska coastline
was recently washed into the ocean
because the bluff it was sitting on top of
was eroded away.
Courtesy of Benjamin Jones, USGS
http://www.sciencefriday.com/program/archives/200903273
USGS researcher Benjamin Jones measures erosion
along a part of Alaska’s Arctic coast.
Courtesy of Christopher Arp, USGS
Rising temperatures are causing a reduction in sea ice and thawing of permafrost
along the coast.
Reduced sea ice allows higher storm surges to reach the shore and the thawing
permafrost makes the shoreline more vulnerable to erosion.
excerpt from Arctic Climate Assessment, Internat’l Arctic Science Committee, 2008,
http://www.acia.uaf.edu/