Near-Surface Permafrost Vanishing Rapidly From Denali NP; Slumps And Landslides Accelerating

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Like much of Alaska, many parts of Denali National Park are underlain with permafrost, meaning ground that remains at or below freezing for two or more years in a row. As climate change warms the planet, much of the shallow permafrost is thawing. In the 1950s, 75 percent of Denali had near-surface permafrost, which is located just below the active layer that freezes and thaws seasonally. The figure dropped to around 50 percent in the 2000s and is projected to drop to 6 percent by the 2050s. In areas where the near-surface permafrost is thawing, deeper permafrost may still exist, since permafrost can be hundreds of feet thick, and even over 2,000 feet thick in some northern locations in Alaska.

Recently, three National Park Service researchers, including David Swanson, an ecologist, and Pam Sousanes and Ken Hill, both physical scientists, published a study in the journal Arctic, Antarctic, and Alpine Research analyzing air and ground temperatures in Alaska’s eight northernmost national parks. They found the mean annual air temperature increased by at least 1.8 degrees Fahrenheit (1 degree Celsius) from 2014 to 2019 in the study area when compared with the previous 30-year period, with a near 3.6°F (2°C) increase in Denali and most Arctic parks. The increase rose to around 5.4°F (3°C) in certain western coastal park areas. Mean annual ground temperatures were also on the rise. “If the warm temperatures observed during 2014 to 2019 persist, there will be widespread degradation of permafrost in portions of these national parks and similar environments across Alaska,” the authors wrote. Projections show Denali temperatures will likely continue to rise, according to a 2018 study by Patrick Gonzalez and colleagues published in Environmental Research Letters.

Alaska has eight national parks and 16 other sites overseen by the National Park Service, including national monuments, preserves, and historic areas. Thawing permafrost is affecting those lands in many ways, from infrastructure challenges to ecosystem impacts.

In Denali, slides occasionally force closure of the Denali Park Road. In 2013, blocks of permafrost the size of small houses slid down a steep hillside above Igloo Creek and blocked the road for four days, and in 2014 part of the road washed out so severely that private planes and park helicopters were enlisted to extract visitors from a private lodge. In July 2016, the Eagle’s Nest landslide caused a closure that lasted for four days, with several additional days of limited access. Then, in 2019, 17 buses with 300 visitors were trapped on the far side of the park, uninjured but delayed for hours.

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https://www.nationalgeographic.com/environment/article/thawing-permafrost-forces-denali-national-park-to-reimagine-its-future

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