Thawing permafrost threatens to undermine the supports holding up an elevated section of the Trans-Alaska Pipeline, jeopardizing the structural integrity of one of the world’s largest oil pipelines.
In a worst-case scenario, a potential rupture of the pipeline would result in an oil spill in a delicate and remote landscape where it would be extremely difficult to clean up.
A slope where an 810-foot long section of the pipeline is secured has started to slip due to the melting permafrost, in turn, causing the braces holding this section of the pipeline to twist and bend.
According to NBC News, this appears to be the first time that pipeline supports have been damaged by “slope creep” caused by thawing permafrost, records, and interviews with officials involved with managing the pipeline show.
To combat the problem, the Alaska Department of Natural Resources has approved the use of about 100 thermosyphons — tubes that suck heat out of the permafrost – to keep the frozen slope in place and prevent further damage to the pipeline’s support structure.
“The proposed project is integral to the protection of the pipeline,” according to the department’s November 2020 analysis.
There is some concern in using these cooling tubes – They have never been used as a defensive safeguard once a slope has begun to slide, and the permafrost is already thawing.
The irony behind using thermosyphons on thawing permafrost
According to the Journal of Commerce, the concept behind thermosyphons is simple. An aluminized metal tube up to eight inches in diameter is filled with liquid carbon dioxide under pressure.
The tube is buried vertically with much of the device sunk below ground. Pressurized CO2 below-grade boils at -30 C and begins to evaporate, rising as vapor and drawing heat from the soil.
The cooler CO2 condenses into liquid, descends, and continues the cycle — no external power or moving parts required. And that seems to be the irony write Inside Climate News.
The Arctic and Alaska are heating twice as fast as the rest of the globe because of global warming. And global warming is driving the thawing of permafrost that the oil industry must keep frozen to maintain the infrastructure that allows it to extract more of the fossil fuels that cause the warming.
On June 27, Digital Journal reported on a study presented in a May 31 paper in The Cryosphere, a publication of the European Geosciences Union. The study specifically focused on infrastructure in Alaska, including the Trans-Alaska pipeline.
The researchers found that roads, bridges, pipelines, and other types of infrastructure in Alaska and elsewhere in the Arctic will deteriorate faster than expected due to a failure by planners to account for the structures’ impact on adjacent permafrost.
The researchers focused on a portion of the Dalton Highway on Alaska’s North Slope about 10 miles south of the Prudhoe Bay oil fields. The highway runs parallel to the Trans-Alaska Pipeline System,
When seeking permission in February 2020 to install the thermosyphons on the slope northwest of Fairbanks near the Dalton Highway in the central part of the state, the Alyeska Pipeline Service Co., which operates the pipeline, confirmed that thawing permafrost posed a threat.
It should also be noted that there are about 124,000 thermosyphons arrayed along the path of the pipeline — a nod from its engineers to the importance of keeping the ground below it frozen.
The tubes are bored from 15 to 70 feet into the permafrost in areas where warming might cause it to thaw. But those chillers only cool the permafrost directly below the pipeline, which holds the supports.
This latest project, which started last month, will attempt to try and refreeze the thawing permafrost to keep a broader slope from collapsing or sliding and damaging the supports.
