Surface displacement revealed by L-band InSAR analysis in the Mayya area, Central Yakutia, underlain by continuous permafrost

Takahiro Abe,Alexander Fedorov,Kazuki Yanagiya,Petr V Efremov,Takeo Tadono,Takumi Kawamura,Alexey R Desyatkin,Go Iwahana,Yuri Zhegusov

doi:10.1186/s40623-020-01266-3

Abstract

Recent increases in global temperature have stimulated permafrost degradation associated with landform deformation caused by the melting of excess ground ice (thermokarst). Central Yakutia is underlain by ice-rich continuous permafrost, and there are complicated permafrost-related features in forested and deforested areas. This situation makes thermokarst monitoring necessary over a wide area to achieve a better understanding of its dynamics. As a case study, we applied L-band InSAR analysis to map surface subsidence due to thermokarst in this area and to demonstrate the suitability of L-band SAR for such monitoring. Our results show that InSAR detected subsidence/uplift signals in deforested areas and alasses; whereas, there were few ground deformation signals in forested areas with middle coherence. The InSAR stacking process, including both seasonal and inter-annual displacements, showed subsidence in deforested areas during 2007–2010 and 2015–2018, in the range of 0.5–3 cm yr−1. We also estimated the inter-annual subsidence to be up to 2 cm yr−1 during 2015–2018, using InSAR pairs that spanned the same seasonal interval but in different years. The magnitude of subsidence and the spatial patterns are qualitatively reasonable as thermokarst subsidence compared to observations using field surveys and high-resolution optical images. L-band InSAR was effective in maintaining coherence over a long period for a partially forested thermokarst-affected area, which resulted in deriving the inter-annual subsidence by the stacking using four interferograms. The advantage of the persistent coherence in L-band InSAR is crucial to better understand thermokarst processes in permafrost regions.

Highlights

Thermokarst is a characteristic landform that results from the thawing of ice-rich permafrost and melting of massive underground ice
The temporal ranges of the fine beam double polarization (FBD), stripmap mode 3 (SM3), and stripmap mode 1 (SM1) interferograms are in July–September 2009, September 2017–September 2018, and August– September 2018, respectively
Coherent interferograms spanning 1 year, using images obtained at the end of summer could be generated using Sentinel-1 C-band data in some cases (Strozzi et al 2018), our study indicates that L-band Synthetic Aperture Radar Interferometry (InSAR) maintains coherence over a few years (Additional file 1: Fig. S2), which could derive inter-annual subsidence (Fig. 4b), even when using a small number of interferograms, because of the low latency of Advanced Land Observing Satellite (ALOS)-2

Summary

Introduction

Thermokarst is a characteristic landform that results from the thawing of ice-rich permafrost and melting of massive underground ice (van Everdingen 2005; French 2017). Thermokarst processes can form large depressions in the ground, leading to ground inundation This irreversible subsidence leads to the formation of thermokarst lakes and changes the entire landscape. Many alasses developed thousands of years ago, and other open areas experienced surface disturbances by deforestation for land use in the 1970s Under these circumstances, thermokarst development has been ongoing in both forested and deforested areas for several decades. Satellite and airborne optical images have enabled better understanding of the development of thermokarst lakes, but they cannot derive the rate of surface displacement due to thermokarst settlement. Both techniques are limited in their application to monitoring thermokarst in the entire Central Yakutia

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Conclusion