Patterns of Permafrost Thaw in Central Alaska: Tussock and Spruce Ecosystems May Be Protective

The Cryosphere, August 3

Permafrost with high levels of frozen organic carbon has been warming and degrading in many mixed-forest and wetland environments across central Alaska and westwards into the Seward Peninsula. These permanently frozen soils underlie approximately 40 % of the region. Thaw has penetrated deeper each year in the region around Fairbanks since 2013; with this area alone emitting amounts of CO2 equivalent, over these seven years, to one year of emissions from Australia . Heavily trafficked regions of central Alaska – specifically areas with trail crossings, infrastructure development, or wildfires – are associated with 25% deeper thaw from mid-August to early October than surrounding areas. Among less-trafficked ecosystems, mixed forest regions produce the warmest surface soils and highest degree of recent thaw degradation, potentially due to the fact that mixed forests grow in the aftermath of wildfires, a known cause of greater permafrost thaw. Tussock grass tundra and spruce forests exhibit the shallowest thawing, lowest permafrost soil temperatures, and presumably the least carbon emissions; indicating that preservation of these ecosystems provides some level of protection against permafrost thaw and related emissions. Authors warn that the loss of tall grasses, mosses, and spruce trees may considerably increase the risk of serious permafrost thaw.