1:45 PM - 2:15 PM
[ACC28-01] Thermokarst subsidence in the Lena-Aldan interfluve, eastern Siberia, revealed by SAR interferometry
★Invited Papers
Keywords:Permafrost, Thermokarst, Eastern Siberia, Synthetic Aperture Radar interferometry, ALOS-2
Thermokarst is an irreversible process which changes local landform underlain by ice-rich permafrost, and has been observed in eastern Siberia and Alaska. In the area of Lena and Aldan rivers in eastern Siberia, topographic changes due to thermokarst has been remarkably identified (e.g., Fedorov et al., 2014; Crate et al., 2017), which has significant impacts on destroying infrastructure, change of water cycle and ecosystems, and lives of neighbors. Continuous observation of thermokarst in the Lena-Aldan interfluve has been performed in Yukechi by a research group of Melnikov Permafrost Institute during the last three decades. However, there had been no comprehensive observations of thermokarst subsidence, which led to uncertainty of assessment of permafrost degradation in the entire area. The spatial distribution of thermokarst subsidence could be an important index to assess permafrost degradation in the area, which is essential for visualization of the degradation.
Synthetic Aperture Radar (SAR) is a technique which obtains information about surface properties and distance between ground and satellite without any instruments on the ground surface. Interferometric SAR (InSAR) is a method to measure surface displacement by calculating the phase difference between two different SAR data. InSAR has been utilized to reveal geophysical phenomena related to surface displacements such as crustal deformation and glacier flow. Number of application studies of InSAR to permafrost monitoring has been increasing, and InSAR has become one of essential tools for understanding permafrost dynamics. This study used ALOS-2 SAR data obtained from 2014 to 2021 to examine inter-annual displacement associated with thermokarst development in the Lena-Aldan interfluve. We applied Small Baseline Subset (SBAS) InSAR time-series analysis (Berardino et al., 2002; Schmidt and Burgmann, 2003; Biggs et al., 2007; Yanagiya and Furuya, 2020) to as many interferograms as possible in order to calculate cumulative ground subsidence from 2014 to 2021.
Our study sites are Mayya, Churapcha, Amga, and Tyungyulyu, representatives of major towns in the Lena-Aldan interfluve where thermokarst-induced high-centered polygonal texture were identified. Abe et al. (2020) and Iijima et al. (2021) recently examined inter-annual thermokarst subsidence by ALOS-2 InSAR stacking, detecting clear subsidence at farming and abandoned arable land. Our analysis result shows that ground subsidence of 10-15 cm was detected in farming and abandoned arable land in Mayya, Churapcha, and Amga from 2014 to 2021. Similar subsidence was detected in Tyungyulyu, but the magnitude of the subsidence was smaller than that in the other areas. Polygonal relief was identified in all the area where the subsidence was detected. The size of the polygon and its spatial concentration corresponds to the distribution of the underlying ice wedge (Saito et al., 2018), and we are going to investigate the relationship between ground subsidence rate and the concentration.
Number of wildfires in eastern Siberia has been increasing in recent years, and there are concerns about the abrupt thawing of permafrost in the fire scars (e.g., Talucci et al., 2022). Some forest-fires occurred in our study area and period, and we are going to present some examples of significant ground subsidence at the fire scars detected by ALOS-2.
Synthetic Aperture Radar (SAR) is a technique which obtains information about surface properties and distance between ground and satellite without any instruments on the ground surface. Interferometric SAR (InSAR) is a method to measure surface displacement by calculating the phase difference between two different SAR data. InSAR has been utilized to reveal geophysical phenomena related to surface displacements such as crustal deformation and glacier flow. Number of application studies of InSAR to permafrost monitoring has been increasing, and InSAR has become one of essential tools for understanding permafrost dynamics. This study used ALOS-2 SAR data obtained from 2014 to 2021 to examine inter-annual displacement associated with thermokarst development in the Lena-Aldan interfluve. We applied Small Baseline Subset (SBAS) InSAR time-series analysis (Berardino et al., 2002; Schmidt and Burgmann, 2003; Biggs et al., 2007; Yanagiya and Furuya, 2020) to as many interferograms as possible in order to calculate cumulative ground subsidence from 2014 to 2021.
Our study sites are Mayya, Churapcha, Amga, and Tyungyulyu, representatives of major towns in the Lena-Aldan interfluve where thermokarst-induced high-centered polygonal texture were identified. Abe et al. (2020) and Iijima et al. (2021) recently examined inter-annual thermokarst subsidence by ALOS-2 InSAR stacking, detecting clear subsidence at farming and abandoned arable land. Our analysis result shows that ground subsidence of 10-15 cm was detected in farming and abandoned arable land in Mayya, Churapcha, and Amga from 2014 to 2021. Similar subsidence was detected in Tyungyulyu, but the magnitude of the subsidence was smaller than that in the other areas. Polygonal relief was identified in all the area where the subsidence was detected. The size of the polygon and its spatial concentration corresponds to the distribution of the underlying ice wedge (Saito et al., 2018), and we are going to investigate the relationship between ground subsidence rate and the concentration.
Number of wildfires in eastern Siberia has been increasing in recent years, and there are concerns about the abrupt thawing of permafrost in the fire scars (e.g., Talucci et al., 2022). Some forest-fires occurred in our study area and period, and we are going to present some examples of significant ground subsidence at the fire scars detected by ALOS-2.