The Trans-Alaska Pipeline, one of the world’s largest oil pipelines, could be in danger.

Thawing permafrost threatens to undermine the supports holding up an elevated section of the pipeline, jeopardizing its structural integrity and raising the potential of an oil spill in a delicate and remote landscape.

The slope of permafrost where an 810-foot section of the pipeline is secured has started to shift as it thaws, causing several of the braces holding up the pipeline to twist and bend.

This appears to be the first instance that pipeline supports have been damaged by “slope creep” caused by thawing permafrost, records and interviews with officials involved with managing the pipeline show.

In response, the Alaska Department of Natural Resources has approved the use of about 100 thermosyphons — tubes that suck heat out of 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.