Post-fire stabilization of thaw-affected permafrost terrain in northern Alaska.

• Published in: Scientific Reports
• Main Authors: Jones, Benjamin M, Kanevskiy, Mikhail Z, Shur, Yuri, Gaglioti, Benjamin V, Jorgenson, M Torre, Ward Jones, Melissa K, Veremeeva, Alexandra, Miller, Eric A, Jandt, Randi
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2024
• Subjects: Arctic; Ice; permafrost; Tundra; wedge*; Alaska
• Online Access: https://doi.org/10.1038/s41598-024-58998-5; https://pubmed.ncbi.nlm.nih.gov/38605076; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11009396/

In 2007, the Anaktuvuk River fire burned more than 1000 km2 of arctic tundra in northern Alaska, ~ 50% of which occurred in an area with ice-rich syngenetic permafrost (Yedoma). By 2014, widespread degradation of ice wedges was apparent in the Yedoma region. In a 50 km2 area, thaw subsidence was detected across 15% of the land area in repeat airborne LiDAR data acquired in 2009 and 2014. Updating observations with a 2021 airborne LiDAR dataset show that additional thaw subsidence was detected in < 1% of the study area, indicating stabilization of the thaw-affected permafrost terrain. Ground temperature measurements between 2010 and 2015 indicated that the number of near-surface soil thawing-degree-days at the burn site were 3 × greater than at an unburned control site, but by 2022 the number was reduced to 1.3 × greater. Mean annual ground temperature of the near-surface permafrost increased by 0.33 °C/yr in the burn site up to 7-years post-fire, but then cooled by 0.15 °C/yr in the subsequent eight years, while temperatures at the control site remained relatively stable. Permafrost cores collected from ice-wedge troughs (n = 41) and polygon centers (n = 8) revealed the presence of a thaw unconformity, that in most cases was overlain by a recovered permafrost layer that averaged 14.2 cm and 18.3 cm, respectively. Taken together, our observations highlight that the initial degradation of ice-rich permafrost following the Anaktuvuk River tundra fire has been followed by a period of thaw cessation, permafrost aggradation, and terrain stabilization.