Speaker
Description
Arctic wildfires can trigger long-lasting changes in permafrost landscapes, but the magnitude and persistence of these responses depend strongly on local environmental conditions. Here, we investigate post-fire landscape dynamics across North American Arctic tundra using a space-for-time approach, comparing fire scars of different ages along a gradient of permafrost conditions and ground temperatures derived from the ESA CCI Permafrost dataset. We used L- and C-band SAR data to investigate InSAR-derived annual and thaw-season deformation rates. In addition, C-band backscatter was analysed to characterize post-fire changes in surface conditions over time. Deformation and backscatter responses were evaluated relative to adjacent undisturbed areas, reducing the influence of year-to-year fluctuations.
We observed enhanced thaw-season subsidence following fire, with the response varying across regions. While annual deformation generally approached those of the surrounding undisturbed areas within approximately 10 years, the thaw-season deformation signal remained elevated for approximately 50 years on average, with recovery taking slightly longer in colder environments. The direction of deformation trends was generally consistent across regions, with initially increased subsidence, radar backscatter showed a much stronger regional dependence, with contrasting trend directions across ground-temperature conditions. Warmer permafrost environments generally showed enhanced summer backscatter after fire events, by about 1 dB, whereas colder regions predominantly exhibited initial reductions of approximately 0.5 dB or less. These contrasting responses likely reflect differences in the relative contributions of soil moisture, vegetation recovery, and changes in surface structure and roughness.
Comparing regions across a range of permafrost conditions revealed distinct regional differences in fire-scar characteristics, highlighting the need to consider multiple environmental factors when assessing post-fire recovery.