Increased mean annual temperatures in 2014–2019 indicate permafrost thaw in Alaskan national parks

Abstract

Rising temperatures in the Arctic can result in thaw of permafrost, with widespread implications for ecosystems and infrastructure. We analyzed mean annual air and ground temperatures in the eight northernmost national parks in Alaska using data from thirty-three National Park Service climate monitoring stations and eight National Weather Service stations. Mean annual air temperatures (MAATs) from 2014 to 2019 increased in a stepwise fashion relative to the preceding thirty-year period by at least 1°C at all locations in the study area; the increase was near 2°C in Denali National Park and most of the Arctic Alaska parks and 3°C in the far western coastal areas of the Arctic parks. The increase in mean annual ground temperatures (MAGT) was approximately equal to the increase in MAAT in windswept tundra areas with minimal snow, whereas under deeper taiga and alpine snowpacks the increase in MAGT was about half as large as the increase in MAAT. If the warm temperatures observed during 2014 to 2019 persist, there will be widespread degradation of permafrost in portions of these national parks and in similar environments across Alaska.

Permafrost thaw‐related slope failures in Alaska’s Arctic National Parks, c. 1980–2019

“…FDL are widespread in the valleys in the southern half of Gates of the Arctic National Park, 13,29 within the area where modeling 30 predicts formation of persistent taliks during the current century (shaded gray in Figure 2). As mentioned previously, mean annual ground and air temperatures for the period 2014–2019 were about 2°C above the 30‐year pre‐2014 averages, 31 approximately the predicted amount of change in ground temperatures for the 2050s, based on moderate emission scenarios from a composite of five global climate models 30 . Whether the recent 2°C positive temperature shift will persist in the near future is unknown, but even the warming that has occurred to date may have put other FDL in this region at risk of destabilization like the one shown in Figure 9.…”

“…The appearance of new RTS is more closely linked to weather 1 and new RTS declined precipitously from episode 2 to 3, as did the area of new ALD, which as discussed above are closely tied to summer weather. The decline in ALD and RTS activity from episodes 2 to 3 occurred in spite of the record high mean annual air temperatures during 2014–2019 31,38 (Figure 3). It is possible that the sites that were most vulnerable to failure did so in the late 2000s (episode 2), and summers were not warm and wet enough to trigger failure at new locations prior to episode 3.…”

“…Prior to 2014, most of my four study areas had mean annual air temperatures below −6°C and modeled mean annual ground temperatures at the base of the active layer below −3°C (Table 2) 30 . This implies that, even with the recent (post‐2013) increase of +2°C in air and ground temperatures, 31 permafrost below the active layer generally remained stable. Thus, deep thaw events triggered slope failures (episode 2) that were followed by a period of stability (episode 3).…”

“…Modeled mean annual ground temperatures for the 2000–2009 decade in the study areas were mostly −3 to −8°C, with the warmest locations in study area 4 above −3°C 30 (Table 2). Observations at ARCN climate monitoring stations and nearby National Weather Service stations showed that mean annual ground and air temperatures for the period 2014–2019 were about 2°C above the 30‐year pre‐2014 averages 31 . Taliks (unfrozen areas in permafrost) are expected to develop as the climate continues to warm in the current century 30 (Figure 2).…”

Caribou and reindeer migrations in the changing Arctic

“…It has been suggested that colder temperatures in fall may trigger migratory movements [88,89] and, therefore, warmer temperatures associated with climate change might dampen migratory cues for Rangifer in fall. Warmer temperatures are also associated with permafrost degradation [90]. Loss of permafrost can lead to catastrophic lake draining and the development of thermokarst features.…”