Journal Article

Decades‐Long Evolution of Post‐Fire Permafrost Deformation Detected by InSAR: Insights From Chronosequence in North Yukon

Cao, Zetao, Furuya, Masato

2025

Overview

Permafrost, a critical global cryospheric component, supports subarctic boreal forests but is frequently disturbed by wildfires, an important driver of permafrost degradation. Wildfires reduce vegetation, organic layers, and surface albedo, leading to active layer thickening and ground subsidence. Recent studies using interferometric synthetic aperture radar (InSAR) have confirmed the rapid and extensive post‐fire permafrost degradation, and have largely focused on short‐term impacts. However, the longer‐term post‐fire permafrost deformation, potentially persisting for decades, remains poorly understood due to limited data. Here, we applied InSAR in North Yukon to detect deformation signals across multiple fire scars in the past five decades. Using a chronosequence (space‐for‐time substitution) approach, we summarize a continuous trajectory of post‐fire permafrost evolution: (a) an initial degradation stage, characterized by abrupt subsidence up to 50 mm/year and gradually slowing over the first decade, with cumulative subsidence exceeding 100 mm locally; (b) an aggradation stage from approximately 15 to 30 years after fire, marked by ground uplift reaching 25 mm/year before gradually declining, compensating for the earlier subsidence; and (c) a stabilization stage beyond three to four decades, where permafrost nearly recovers to pre‐fire conditions with indistinguishable deformation between burned and unburned areas. Notably, the rarely‐reported uplift phase appears closely related to vegetation regeneration and fire‐greening feedback that provide thermal protection, suggesting a critical mechanism of permafrost recovery. These findings provide new insights into the resilience of boreal‐permafrost systems to wildfires and also underscore the importance of long‐term InSAR monitoring in understanding permafrost responses to wildfires under climate change. Plain Language Summary Permafrost plays an important role in global climate systems and is closely associated with the circum‐Arctic boreal forest environments. While wildfires are common disturbances of sub‐arctic boreal forests. Wildfires remove insulating vegetation and organic layers, allowing more heat to reach the ground, leading to permafrost thaw and ground subsidence. Currently, many studies have shown how permafrost degrades soon after wildfires, but little is known about what happens over the following decades. In this study, we used satellite radar technology to monitor ground deformation in North Yukon, Canada, across areas that burned recently to nearly five decades ago. We found that permafrost typically follows three stages after wildfire: initial subsidence over the first decade, uplift over the next 15–30 years as permafrost recovers, and finally a recovered phase when burned areas behave similarly to undisturbed ground. A key discovery is that the ground can recover to pre‐fire condition two to three decades after a fire, owing to vegetation regrowth that helps the ground stay frozen again. These findings suggest that, in cold sub‐arctic boreal forest regions like North Yukon, permafrost can recover after wildfires, showing resilience, but long‐term monitoring is essential as climate change and wildfires continue to intensify. Key Points Interferometric synthetic aperture radar is applied to study long‐term post‐fire permafrost deformation in North Yukon by chronosequence Wildfires cause permafrost degradation and ground subsidence, but recovery with ground uplift can occur over decades Permafrost may recover to pre‐fire conditions in three decades due to the vegetation regeneration that helps ground ice aggradation

• Publisher: Wiley
• Subject: ground deformation / interferometric synthetic aperture radar / permafrost / post‐fire degradation‐aggradation cycle / post‐fire evolution / wildfire