Post-wildfire surface deformation at Batagay, Eastern Siberia, detected
by L-band and C-band InSAR
Abstract
Thawing of ice-rich permafrost can form a characteristic landform called
a thermokarst. The impact of wildfire on thermokarst development remains
uncertain. Here we report on the post-wildfire ground deformation
associated with the 2014 wildfire near Batagay, Sakha Republic, Eastern
Siberia. We used Interferometric Synthetic Aperture Radar (InSAR) to
generate both long-term and short-term deformation maps, and examine the
temporal evolution of the post-wildfire ground deformation over the
permafrost area. Based on two independent satellite-based microwave
sensors, we could validate the measurement uncertainties without relying
on in-situ data. The inferred time-series based on L-band ALOS2 InSAR
data indicated that cumulative subsidence has been greater than 30 cm
since October 2015 at the area of greatest deformation, and that the
rate of subsidence is slowed in 2018. Meanwhile, C-band Sentinel-1 InSAR
data showed that the temporal evolution was not simply linear but rather
include episodic changes. Moreover, we could unambiguously detect frost
heave signals that were clearly enhanced inside the burned area during
the early freezing season but were absent in the mid-winter. We could
reasonably interpret the InSAR-based frost heave signals within a
framework of premelting dynamics.