Inference of the impact of wildfire on permafrost and active layer thickness in a discontinuous permafrost region using the remotely sensed active layer thickness (ReSALT) algorithm

• Published in: Environmental Research Letters
• Main Authors: Roger J Michaelides, Kevin Schaefer, Howard A Zebker, Andrew Parsekian, Lin Liu, Jingyi Chen, Susan Natali, Sarah Ludwig, Sean R Schaefer
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2019
• Subjects: permafrost; wildfire; InSAR; radar remote sensing; geophysics; active layer; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Yukon; Active layer thickness; Kuskokwim; Subarctic; Tundra; Alaska
• Online Access: https://doi.org/10.1088/1748-9326/aaf932; https://doaj.org/article/11d82423fb7a4e4e86668f7f11510f99

The Yukon–Kuskokwim (YK) Delta is a region of discontinuous permafrost in the subarctic of southwestern Alaska. Many wildfires have occurred in the YK Delta between 1971–2015, impacting vegetation cover, surface soil moisture, and the active layer. Herein, we demonstrate that the remotely sensed active layer thickness (ReSALT) algorithm can resolve the post-fire active layer dynamics of tundra permafrost. We generated a stack of Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar interferograms over a study region in the YK Delta spanning 2007–2010. We applied ReSALT to this stack of interferograms to measure seasonal subsidence associated with the freezing and thawing of the active layer and subsidence trends associated with wildfire. We isolated two wildfire-induced subsidence signatures, associated with the active layer and the permafrost layer. We demonstrate that InSAR is sensitive to increases in active layer thickness following wildfire, which recovers to pre-fire values after approximately 25 years. Simultaneously, we show that fire gradually thins the permafrost layer by 4 m, which recovers to pre-fire thickness after 70 years.