Curious Alaska: What is climate change doing to the haul road?

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Question: How is the Haul Road being impacted by climate change? What happened to that “tidal wave” of melted permafrost that was rolling towards the Dalton Hwy a few years ago?

The Dalton Highway is 414 miles of engineering marvel and trouble. And climate change is only making things more complicated.

The highway runs from Livengood, north of Fairbanks, to Deadhorse, on the edge of the Arctic Ocean, linking the North Slope with the rest of Alaska’s limited road system. It’s as long as the trip from Washington D.C. to Boston, but with hardly a human settlement along the way.

The main user constituency is the hundreds of trucks hauling materials to the oil fields that rumble up and down the pavement-and-gravel everyday, making the highway a vital economic link for Alaska.

The Dalton Highway slices through an Arctic region that’s experiencing some of the most dramatic effects of warming anywhere on the earth. That translates to new and pressing challenges for keeping the road open and viable, said Jeff Currey, the northern region materials engineer with the State of Alaska’s Department of Transportation and Public Facilities.

“Not all of it is problematic, but a lot of it is,” Currey said.

The highway faces three major categories of threats linked to a warming climate, Currey said: It’s “kind of the poster child” for difficulties related to the loss of permafrost. It is at risk of being hammered by floods of increasing frequency and intensity. And perhaps most cinematically, ominous frozen debris lobes – large, slow-moving underground landslides of rock, dirt and tree -- loom over it. At least one spot has already been rerouted to avoid being crushed.

The Department of Transportation spells out the problem on its website: “The warming Arctic climate has increased our maintenance challenges,” the Department of Transportation says.

The Dalton Highway region is clearly changing, as is the whole of Arctic Alaska, said Rick Thoman, a climate specialist with the International Arctic Research Center Alaska at the University of Alaska Fairbanks.

“The entire Dalton Highway is getting warmer and it’s getting wetter,” he said.

Permafrost

First, there’s the chronic problem of melting permafrost, according to Currey. When permafrost thaws, the road on top of it collapses, creating sinkholes and heaves.

“If it sank down uniformly, that would not be so bad,” he said.

But it sinks in divots, creating a surface that ranges between potholes to undriveable. That’s always been an issue for maintaining roads through permafrost. But the area’s underlying ground is changing fast, and permafrost in some areas is nearly guaranteed to decline or even disappear in areas along the highway in the future.

“The long term trend is pretty clear: Over the next half-century there’s no doubt that more and more of the area south of the (Brooks Range) will have continued degrading permafrost and in some areas, the loss of permafrost,” said Thoman.

In some places south of the Brooks Range “you look at it wrong and it starts thawing,” Currey said.

Part of the solution might be using more flexible road surfaces in the future, so that fixing sunken spots is less labor intensive. For now, it just means more maintenance workers and money are necessary to stay on top of the problem, Currey said.

Flooding

The second big problem is flooding, especially on the shallow, braided Sagavanirktok River, which parallels the final 100 miles of the highway.

In 2015, an unusual flooding event on the river caused the highway to shut down twice during the spring and early summer. The road was closed for 28 days total between the two incidents, grinding truck deliveries to the North Slope oil fields to a halt. The state spent $17 million on immediate emergency repairs, which included raising a section of the road by 8-10 feet to hedge against future flooding events.

The DOT has now spent $70 million in state and federal funds to raise the highway over the new flood levels, according to Inside Climate News.

The Sagavanirktok River will likely flood more in the future because of increased precipitation driven by warming, Thoman said.

Frozen debris lobes

The next big issue has its own acronym: frozen debris lobes, also known as FDL. Frozen debris lobes are like a landslide in slow motion, huge chunks of rock, soil, ice and trees that slowly slump down slopes.

Dozens of frozen debris lobes have been located at various points along the Dalton. One, known as Frozen Debris Lobe A, was on a course to overtake a section of the highway.

They were confronted with a movie-like choice: Stop the FDL. Or move the highway. In 2018, the state opted to reroute the highway, shifting the road 400 feet to the west at the cost of about $2 million.

That bought some time, maybe 13-15 years according to Currey.

“That number is fuzzy — some years it moves faster than others. It moves more in warmer years than cooler years.”

Frozen Debris Lobe A is still moving: As of today, a UAF monitoring site estimates it’s less than a meter away from the old highway site, and 109.7 meters from new, rerouted Dalton Highway.

“We recognize that if the old road doesn’t stop it, at some point it’s coming for the road,” Currey said.

The Dalton Highway is a useful tool to measure changes in climate, both because the road provides easier access to scientists monitoring efforts and because the structure itself is a barometer for the warming, Thoman said. It’ll become even more valuable in the coming decades.

“It provides a window we wouldn’t otherwise have had.”