Periglacial Process in AlaskaPeriglacial Process in Alaska

Application: Application: Alaska Alaska

PipelinePipeline

Permafrost Permafrost regimesregimes

TectonicsTectonics

Alaska PipelineAlaska Pipeline ~ 800 miles long (409 mi. buried; 382 mi. above ground)~ 800 miles long (409 mi. buried; 382 mi. above ground) Trans Alaska Pipeline System (TAPS), formed by seven oil Trans Alaska Pipeline System (TAPS), formed by seven oil

companies, announced plans in February 1969 to build a 4-companies, announced plans in February 1969 to build a 4-foot diameter pipeline to carry crude oil from Prudhoe Bay foot diameter pipeline to carry crude oil from Prudhoe Bay to Valdezto Valdez

The temperature of the oil coming out of the ground was 80 The temperature of the oil coming out of the ground was 80 deg Cdeg C

1970 USGS Circular 632, "Some Estimates of the Thermal 1970 USGS Circular 632, "Some Estimates of the Thermal Effects of a Heated Pipeline in Permafrost” predicted that Effects of a Heated Pipeline in Permafrost” predicted that buried pipe would float, twist, and breakburied pipe would float, twist, and break

Pipeline and storage tank construction at Valdez began in Pipeline and storage tank construction at Valdez began in 1975 1975

The initial estimated cost of installing 800 miles of buried The initial estimated cost of installing 800 miles of buried pipeline was $900 million, and the actual cost was more pipeline was $900 million, and the actual cost was more than $8 billion than $8 billion

Oil flows at 4 mph in the pipeline taking a week to reach Oil flows at 4 mph in the pipeline taking a week to reach Valdez Valdez

http://menlocampus.wr.usgs.gov/50years/accomplishments/pipeline.html

145°F

"There are 78,000 VSMs [vertical support "There are 78,000 VSMs [vertical support members] and every single one of those had a members] and every single one of those had a 24-inch hole drilled for it and every single one 24-inch hole drilled for it and every single one of them had a qualified person analyzing what of them had a qualified person analyzing what came out of the hole to determine what kind of came out of the hole to determine what kind of VSM it should be. There was actually a field VSM it should be. There was actually a field design manual that was based on the soil."design manual that was based on the soil."

-- Bill Howitt, Alyeska engineer-- Bill Howitt, Alyeska engineer

http://geoimages.berkeley.edu/GeoImages/Johnson/Biomes/BiomesSub/AlaskaPipeline.html

http://www.alyeska-pipe.com/pipelinefacts/PipelineEngineering.html

Thaw LakesThaw Lakes Thawing of the uppermost Thawing of the uppermost

portion of the permafrostportion of the permafrost Melting of permafrost leads to Melting of permafrost leads to

subsidencesubsidence Excess pore water is expelledExcess pore water is expelled

Surrounding permafrost forms Surrounding permafrost forms an impermeable bowlan impermeable bowl

If depth> ~2m., lake will not If depth> ~2m., lake will not freeze solid, developing freeze solid, developing unfrozen underlying material unfrozen underlying material called a thaw bulb or talikcalled a thaw bulb or talik

Water absorbs more solar Water absorbs more solar energy than soilenergy than soil

Continued thawing leads to Continued thawing leads to more subsidence and more subsidence and deepening of lakedeepening of lake

http://www.sciencefriday.com/http://www.sciencefriday.com/videos/watch/10008videos/watch/10008

Arctic environment changeArctic environment change

Thermokarst: Landscape features caused by structural

failure following the melting of ground ice Collapse, erosion, and slope instability assoc.

with thawing permafrost Results from deepening of the active layer

and thawing of top of permafrost Thickening of the active layer has two

immediate effects: 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 changeArctic environment change

This downward displacement of the groundsurface 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 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

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

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/