Transient Freeze‐Thaw Deformation Responses to the 2018 and 2019 Fires Near Batagaika Megaslump, Northeast Siberia

Abstract

Wildfires in Arctic regions impact landforms via permafrost degradation and subsequent deformation that can last for many years. However, it remains uncertain on if and how much deformations occur, and what controls their magnitude, particularly during the first couple of years. Here, we examine the transient post‐fire deformation responses near the Batagaika megaslump, which is the world's largest retrogressive thaw slump at Batagay, Sakha Republic. There were wildfires in the summers of 2018 and 2019 on the same slope, which could trigger the formation of another megaslump; many fires occurred nearby in 2019. We use interferometric synthetic aperture radar (InSAR) to measure surface displacements, including both post‐fire and span‐fire images. We also perform onsite measurements of temperature and thaw depth around the two scars near Batagaika megaslump in 2019, 2020, and 2021 and around the 2014 scar in 2019. At the three fire scars formed in 2018 and 2019, we demonstrate year‐to‐year and location‐specific changes in the amplitude of subsidence, heave, and duration. The 2018 scar shows cumulative subsidences of up to 10 cm by March 2021, more clearly than the nearby 2019 scar. On the other hand, another 2019 scar adjacent to the 2014 scar shows up to 13 cm net subsidence during the first span‐fire year, although the subsiding area is limited. These diverse transient post‐fire responses demonstrate that under the yedoma area the spatial heterogeneities of the active layer depth and the timing of fires will control subsequent thermokarst processes.

Multitemporal UAV LiDAR detects seasonal heave and subsidence on palsas

“…Anders et al, (2020) performed three TLS measurements over 14 months (June 2015, Aug 2015 and Aug 2016) to observe thaw subsidence of a permafrost area in Northwest Territories, Canada, finding a total change of 1.4 cm; they determined that the TLS measurements were more accurate than those from field-based surveying. Another approach to quantify the effect of seasonal freeze/thaw dynamics on topography is through the use of InSAR remote sensing (de la Barreda-Bautista et al, 2022;Kou et al, 2021;Yanagiya et al, 2023) which can be an effective method to detect the signal of subsidence. Due to its coarser spatial resolution, however, it is likely to underestimate actual heave and subsidence values of smaller isolated features such as palsas.…”

Fire in the Earth System: Introduction to the Special Collection

“…Yanagiya and Furuya (2020) demonstrated the deformation of permafrost surfaces after a 2014 fire in Siberia, where more than 3 million m 3 of permafrost thawed, leading to irreversible subsidence. Yanagiya et al (2023) built on those findings by studying additional geomorphic impacts of 2018 and 2019 fires in Siberia using field measurements and satellite Interferometric Synthetic Aperture Radar (InSAR), finding transient and spatially heterogenous ground deformation in the permafrost terrain that they attributed to fire effects on the active-layer depth. They concluded that the permafrost depth before the fire plays a crucial role in controlling postfire subsidence and thermokarst evolution.…”