If you want to drive into or out of Alaska, at some point you will find yourself on the Alaska Highway. Sometimes colloquially referred to as the Alcan, it is a beautiful drive, from central Alaska into Canada, down through Yukon and into British Columbia, officially ending at Dawson Creek just shy of the Alberta border. The highway twists and turns pasts rivers, lakes and hot springs, through forests and around the base of mountains; bison can appear (I can attest from experience) around the corner at anytime, as can bears.

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Its construction, 70 years ago in 1942, was a fairly remarkable feat of engineering, as Cornelia Dean notes in the New York Times:

The road would traverse 1,500 miles of mountainous subarctic terrain, most of it unsettled, heavily forested and unmapped. Engineers would face fierce cold, fierce heat, vicious insects, and vast stretches of permafrost and boggy terrain called muskeg that swallowed bulldozers whole. Nevertheless, the Alaska Canada Military Highway was declared open the following October. Nicknamed the Alcan, this so-called pioneer road was little more than a gravel lane passable only by military trucks. Still, people called it the 20th century’s greatest engineering feat, after only the Panama Canal.

Today, the road is paved from start to finish, and connects to other, similarly-well-paved, roads at either end. Increasingly, however, as Dean also notes, its maintenance is problematic. The reason is found beneath its surface, in the form of permafrost, the permanently-frozen layer of ground that underlies much of the highway and is a defining presence of terrestrial Arctic and sub-Arctic environments. As Alaska warms, and as dark pavement absorbs more sunlight and thus warms the ground below, that permafrost is beginning to melt; in many places the road is cracking and sinking.

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It is not just the highway: melting permafrost is damaging roads and buildings throughout Alaska and northern Russia. Woodlands that have sunk into the ground as permafrost melts have earned the epithet 'drunken forests' because of the way the trees topple sideways, while melting permafrost is causing buildings to buckle and building costs to rise in many northern regions.

According to a 2005 study by the National Center on Atmospheric Research, the top 10 feet of the Northern Hemisphere's permafrost layer could be "decimated" over coming decades, leading to construction and infrastructure damage across the region.

There is potentially still greater concern about this permafrost melt: it has been estimated that permaforst contains twice as much carbon as the atmosphere, and as that carbon – in the form of carbon dioxide and methane – is released, it will serve only to further intensify warming.

Should that happen, the result would be something of a "ticking time bomb" that would have profound consequences – consequences far more severe than potholes in a 70-year-old road.

IMAGE: Alaska Highway and mountain landscape, Yukon. (Yves Marcoux, Corbis)