11:30 〜 11:45
[ACG52-10] Degradation, Stabilization, and Recovery Signs of Post-Wildfire Permafrost in North Yukon Detected by ALOS/Sentinel-1 InSAR
キーワード：permafrost, wildfire, InSAR, surface deformation
In circum-arctic permafrost regions, wildfires were natural and frequent disturbances that significantly affect the permafrost dynamics, while permafrost could demonstrate resilience to such disturbances under stable climatic conditions. Numerous studies have utilized Interferometric Synthetic Aperture Radar (InSAR) to investigate post-wildfire permafrost ground surface deformation, addressing gaps in understanding post-wildfire permafrost dynamics on regional scales. However, most research has focused on subsidence signals occurring several years after fires, primarily due to permafrost degradation, while the long-term deformation patterns and the resilience or recovery of permafrost after wildfires remain poorly characterized, especially under the current warming climate.
To narrow such gaps, we employed the Advanced Land Observing Satellite (ALOS-1) InSAR from 2007 to 2010 and Sentinel-1 InSAR time-series analysis from 2017 to 2024 to investigate the permafrost ground deformation across wildfire scars in North Yukon, Canada. These regions, underlain by continuous permafrost, often experience large (>100 km2) wildfires, with burned areas documented over the past five decades. Therefore, although InSAR observations cannot directly capture decades of deformation information, the presence of adjacent burned areas from different decades offers a unique space-for-time substitution opportunity to investigate the evolution of permafrost deformation at varying stages after fires.
Our findings reveal that wildfires universally induce ground subsidence as a result of post-fire permafrost degradation. Subsidence rates range from 20 to 60 mm/year along the line of sight (LOS) within 5 years after the fires. These rates typically slow down to less than 20 mm/year 2~6 years later, but the recent warming and extreme heat anomalies have caused significantly greater subsidence in recently burned areas (0~10 years post-fire) due to the reduced buffer layers by fires. In the thawing seasons one or two decades after the fires, some burned areas exhibit greater subsidence (10~15 mm) compared to unburned areas (less than 10 mm). However, freezing-season uplift signals might compensate for such subsidence, resulting in near-stabilization of deformation on an annual timescale.
In burned areas over 15 years post-fire, the freezing-season uplift magnitude exceeded the thawing-season subsidence, especially in areas where the terrains are beneficial for water concentration, indicating the recovery phase with permafrost aggregation following the degradation period. The annual uplift rate could be 10~20 mm/year, lasting for about 20 years, and might taper off around 40 years after the fires occurred. The stabilization and recovery of permafrost could be attributed to the recovered vegetation, which might surpass per-fire conditions, at least in terms of remote sensing vegetation index. Notably, some burned areas from the 1990s have shown smaller subsidence during recent warming summers than unburned areas, potentially owing to the better vegetation conditions after fires.
Our study highlights the dynamic response and resilience of permafrost to wildfires, revealing a progression from initial subsidence to long-term stabilization and potential recovery. These findings provide critical insights into the long-term dynamics of post-wildfire permafrost in Arctic regions.
To narrow such gaps, we employed the Advanced Land Observing Satellite (ALOS-1) InSAR from 2007 to 2010 and Sentinel-1 InSAR time-series analysis from 2017 to 2024 to investigate the permafrost ground deformation across wildfire scars in North Yukon, Canada. These regions, underlain by continuous permafrost, often experience large (>100 km2) wildfires, with burned areas documented over the past five decades. Therefore, although InSAR observations cannot directly capture decades of deformation information, the presence of adjacent burned areas from different decades offers a unique space-for-time substitution opportunity to investigate the evolution of permafrost deformation at varying stages after fires.
Our findings reveal that wildfires universally induce ground subsidence as a result of post-fire permafrost degradation. Subsidence rates range from 20 to 60 mm/year along the line of sight (LOS) within 5 years after the fires. These rates typically slow down to less than 20 mm/year 2~6 years later, but the recent warming and extreme heat anomalies have caused significantly greater subsidence in recently burned areas (0~10 years post-fire) due to the reduced buffer layers by fires. In the thawing seasons one or two decades after the fires, some burned areas exhibit greater subsidence (10~15 mm) compared to unburned areas (less than 10 mm). However, freezing-season uplift signals might compensate for such subsidence, resulting in near-stabilization of deformation on an annual timescale.
In burned areas over 15 years post-fire, the freezing-season uplift magnitude exceeded the thawing-season subsidence, especially in areas where the terrains are beneficial for water concentration, indicating the recovery phase with permafrost aggregation following the degradation period. The annual uplift rate could be 10~20 mm/year, lasting for about 20 years, and might taper off around 40 years after the fires occurred. The stabilization and recovery of permafrost could be attributed to the recovered vegetation, which might surpass per-fire conditions, at least in terms of remote sensing vegetation index. Notably, some burned areas from the 1990s have shown smaller subsidence during recent warming summers than unburned areas, potentially owing to the better vegetation conditions after fires.
Our study highlights the dynamic response and resilience of permafrost to wildfires, revealing a progression from initial subsidence to long-term stabilization and potential recovery. These findings provide critical insights into the long-term dynamics of post-wildfire permafrost in Arctic regions.