A large frozen debris avalanche entraining warming permafrost ground—the June 2021 Assapaat landslide, West Greenland

Abstract

A large landslide (frozen debris avalanche) occurred at Assapaat on the south coast of the Nuussuaq Peninsula in Central West Greenland on June 13, 2021, at 04:04 local time. We present a compilation of available data from field observations, photos, remote sensing, and seismic monitoring to describe the event. Analysis of these data in combination with an analysis of pre- and post-failure digital elevation models results in the first description of this type of landslide. The frozen debris avalanche initiated as a 6.9 * 106 m3 failure of permafrozen talus slope and underlying colluvium and till at 600–880 m elevation. It entrained a large volume of permafrozen colluvium along its 2.4 km path in two subsequent entrainment phases accumulating a total volume between 18.3 * 106 and 25.9 * 106 m3. About 3.9 * 106 m3 is estimated to have entered the Vaigat strait; however, no tsunami was reported, or is evident in the field. This is probably because the second stage of entrainment along with a flattening of slope angle reduced the mobility of the frozen debris avalanche. We hypothesise that the initial talus slope failure is dynamically conditioned by warming of the ice matrix that binds the permafrozen talus slope. When the slope ice temperature rises to a critical level, its shear resistance is reduced, resulting in an unstable talus slope prone to failure. Likewise, we attribute the large-scale entrainment to increasing slope temperature and take the frozen debris avalanche as a strong sign that the permafrost in this region is increasingly at a critical state. Global warming is enhanced in the Arctic and frequent landslide events in the past decade in Western Greenland let us hypothesise that continued warming will lead to an increase in the frequency and magnitude of these types of landslides. Essential data for critical arctic slopes such as precipitation, snowmelt, and ground and surface temperature are still missing to further test this hypothesis. It is thus strongly required that research funds are made available to better predict the change of landslide threat in the Arctic.

Widespread rock wall permafrost degradation in Greenland by the end of the 21st century under CMIP6 projections

“…Therefore, rock wall permafrost in the future is very likely to degrade in this region, increasing the predisposition to slope failure as MARST approaches the critical value of 0 °C (Mamot et al 2020). Considering the high density of recorded landslide in the area (Svennevig, 2019), and the recent studies exploring the connection between permafrost degradation and these catastrophic events (Svennevig et al, 2020(Svennevig et al, , 2022(Svennevig et al, , 2023, as well as the societal stakes, we recommend increasing the monitoring efforts relating to rock walls and rock slopes in Greenland.…”

“…This subject is rapidly gaining interest also in Greenland, since the mountain ranges occupy most of the coastline and local communities are in direct proximity to rock walls and steep terrain. Several landslides have been described in the Disko Bay and the Nussuaq Peninsula (Pedersen et al 2002;Dahl-Jensen et al 2004;Svennevig et al, 2019Svennevig et al, , 2020Svennevig et al, , 2022Svennevig et al, , 2023Svennevig et al, , 2024, with one catastrophic event causing casualties and community relocation (Strzelecki and Jaskólski, 2020).…”

Prevention/mitigation of natural disasters in urban areas

“…Cluster 4: soil erosion and landslide-type debris flow (e.g. [12,[80][81][82][83]). Number of publications and top 10 journals publishing the papers…”

Kinematic Evolution of a Large Paraglacial Landslide in the Barry Arm Fjord of Alaska

“…Alaska (USA) has a history of tsunamis caused by both subaerial and submarine landslides along the Gulf shoreline (e.g., Haeussler et al., 2014; Higman et al., 2018; Miller, 1961), and abundance of narrow and deep fjords that can exacerbate their impact (e.g., Fritz et al., 2009; Yavari‐Ramshe & Ataie‐Ashtiani, 2016). Warming temperatures due to climate change have enhanced glacier retreat and permafrost degradation, increasing the abundance of potentially unstable slopes in southcentral and southeast Alaska (e.g., Bessette‐Kirton & Coe, 2020; Coe et al., 2018; Dai et al., 2020; Higman et al., 2018; Kim et al., 2022), as well as in many other parts of the world (e.g., Allen et al., 2009; Fan et al., 2022; Haeberli et al., 1997; Holm et al., 2004; Klimeš et al., 2021; Penna et al., 2023; Svennevig et al., 2022).…”