Presentation Information
[ACC42-01]InSAR-Detected Permafrost Aggradation in a Wildfire-Affected Drained Lake in the Northwest Territories, Canada
*Zetao Cao1, Masato Furuya2,3 (1.Graduate School of Science, Hokkaido University, 2.Faculty of Science, Hokkaido University, 3.Arctic Research Center, Hokkaido University)
Keywords:
permafrost,drained lake,wildfire,InSAR,ground deformation,Northwest Territories
Recent studies have demonstrated that wildfires can induce long-lasting permafrost degradation and ground subsidence in Arctic and subarctic regions, while the post-fire ground subsidence and active layer thickening would induce significant hydrological changes, which could, in turn, affect permafrost dynamics. Such interlocking post-fire permafrost processes remain less constrained by observations. In this study, we report InSAR-detected permafrost aggradation associated with a newly drained thermokarst lake identified in the summer of 2024 within a previously investigated wildfire-affected subsidence region in the Northwest Territories, Canada.
Both optical satellite imagery and SAR backscatter images confirm that a lake drained rapidly during the 2024 summer (Figure 1), exposing a lake basin of approximately 0.6 km². Using Sentinel-1 data, we applied time-series InSAR analysis to quantify ground deformation across the drained lake basin and the surrounding fire-affected areas.
Our results reveal a pronounced surface uplift within the drained lake basin during the winters of 2024–2025 and 2025–2026, with cumulative uplift reaching 30 mm (Figure 2). This uplift is spatially coherent with the former lake extent and contrasts sharply with the surrounding lake bank area. The burned area surrounding the lake continues to exhibit subsidence during summer thaw seasons of approximately 20 mm (Figure 2). The observed uplift could be interpreted as evidence of permafrost aggradation driven by enhanced winter heat release, refreezing of saturated sediments, and excess ice formation following lake drainage. Therefore, our findings provide insights into a strong spatial heterogeneity in post-fire permafrost changes. Wildfire disturbance promotes sustained subsidence due to active layer deepening and ground ice loss, which would greatly alter the surface and underground hydrological processes. Lake drainage is one of the subsequent changes of permafrost degradation, while drained lake basins may undergo rapid permafrost re-aggradation on interannual timescales once surface water is removed. This contrast underscores the critical role of hydrological regime shifts in modulating permafrost thermal and mechanical responses to disturbance.
This study provides new observational evidence of the complex wildfire-affected permafrost dynamics, depending on local geomorphic and hydrological conditions. The results emphasize the need to explicitly consider rapid lake changes after wildfires in future assessments of Arctic permafrost under intensifying wildfires and ongoing climate change.
Both optical satellite imagery and SAR backscatter images confirm that a lake drained rapidly during the 2024 summer (Figure 1), exposing a lake basin of approximately 0.6 km². Using Sentinel-1 data, we applied time-series InSAR analysis to quantify ground deformation across the drained lake basin and the surrounding fire-affected areas.
Our results reveal a pronounced surface uplift within the drained lake basin during the winters of 2024–2025 and 2025–2026, with cumulative uplift reaching 30 mm (Figure 2). This uplift is spatially coherent with the former lake extent and contrasts sharply with the surrounding lake bank area. The burned area surrounding the lake continues to exhibit subsidence during summer thaw seasons of approximately 20 mm (Figure 2). The observed uplift could be interpreted as evidence of permafrost aggradation driven by enhanced winter heat release, refreezing of saturated sediments, and excess ice formation following lake drainage. Therefore, our findings provide insights into a strong spatial heterogeneity in post-fire permafrost changes. Wildfire disturbance promotes sustained subsidence due to active layer deepening and ground ice loss, which would greatly alter the surface and underground hydrological processes. Lake drainage is one of the subsequent changes of permafrost degradation, while drained lake basins may undergo rapid permafrost re-aggradation on interannual timescales once surface water is removed. This contrast underscores the critical role of hydrological regime shifts in modulating permafrost thermal and mechanical responses to disturbance.
This study provides new observational evidence of the complex wildfire-affected permafrost dynamics, depending on local geomorphic and hydrological conditions. The results emphasize the need to explicitly consider rapid lake changes after wildfires in future assessments of Arctic permafrost under intensifying wildfires and ongoing climate change.