Landslide Risk on Alaska’s National Park Roads Is Rising With the Climate

The Denali Park Road in a slide area in 2021, displaced 14 feet. The road has since been closed while a solution is engineered. Image from the National Park Service's page.

Climate change affects not only the natural and cultural resources of parks but also their infrastructure — sometimes severely. Alaska's parks have little infrastructure, but their roads are hard to maintain in harsh conditions, especially over thawing permafrost, and more intense precipitation — heavier rains and bigger snowfalls — adds to the damage.

Mean annual air temperatures in Alaska's parks have all shifted sharply upward in recent years, with many places nearing or passing the freezing point — warming that is arriving several decades earlier than expected.

The study

Landslides along park roads threaten public safety, visitor access and subsistence activities, and damaged roads are costly to fix. In these areas of near-surface permafrost, landslide risk goes with mean annual air temperatures above freezing and with heavy precipitation.

The researchers compared historical (1981–2020) air temperatures and summer precipitation, from the European Centre for Medium-Range Weather Forecasts' ERA5 reanalysis, with downscaled climate projections for mid-century (2021–2060) and late century (2061–2100) in three parks:

Findings

• Historically, every location had average air temperatures below freezing — but all three parks were warming significantly, by 0.3–0.6 °C per decade.
• At weather stations, 11 of 18 showed statistically significant warming.
• Temperature risk: elevated by mid-century for the Denali Park and McCarthy roads, and for all three corridors by late century.
• Summer rain risk: elevated in every period for all the road corridors.

The best-known example is the Pretty Rocks Landslide on the Denali Park Road, where a bridge over the slide was planned.

Sources

Based on "Landslide Risks Along Park Roads Increase in a Warming Climate," National Park Service, summarizing Lader R, Sousanes P, Bhatt US, Walsh JE, Bieniek PA, "Climate indicators of landslide risks on Alaska national park road corridors," Atmosphere 14(1): 34 (2023); the NPS text is in the public domain, and the study's abstract is rewritten in hubnx's own words.