The joint driving effects of climate and weather changes caused the Chamoli glacier-rock avalanche in the high altitudes of the India Himalaya

Abstract

Ice avalanches are one of the most devastating mountain hazards, and can pose a great risk to the security of the surrounding area. Although ice avalanches have been widely observed in mountainous regions around the world, only a few ice avalanche events have been studied comprehensively, due to the lack of available data. In this study, in response to the recent catastrophic rock-ice avalanche (7 February 2021) at Chamoli in the India Himalaya, we used high-resolution satellite images and found that this event was actually a glacier-rock landslide, where the collapse of the rock-ice body was caused by the sliding of the bedrock beneath the glacier, for which the source area and volume loss were about 2.89×10 5 m 2 and 2.46×10 7 m 3 , respectively, corresponding to an average elevation change of about −85 m. Furthermore, visual analysis of the dense time-series satellite images shows that the overall downward sliding of the collapsed rock-ice body initiated around the summer of 2017, and thereafter exhibited clear seasonality (mainly in summer). Meteorological analysis reveals a strong rainfall anomaly in the initiation period of the sliding and a remarkable winter warming anomaly in the 40 days before the collapse. Comparisons of multi-temporal digital elevation models (DEMs) further suggest that the glacier geometry in the collapsed areas was likely changing (i.e., accelerated surface thinning in the lower part of the glaciers and insignificant change in the upper part), which is consistent with the region-wide climate warming. Finally, by combining the above findings and a geomorphic analysis, we conclude that the rock-ice avalanche event was mainly caused by the joint effects of climate and weather changes acting on a steeply sloping and fracture-prone geological condition. The findings of this study provide new and valuable evidence for the study of slope/glacier instability at high altitudes. This study also highlights that, for the Himalaya and other high mountain ranges, there is an urgent need to identify the glaciers that have a high risk of ice avalanches.

Pre-collapse motion of the February 2021 Chamoli rock–ice avalanche, Indian Himalaya

“…Syn-collapse seismic signals show that there was no seismic trigger for the collapse (Pandey et al, 2021;Shugar et al, 2021;Cook et al, 2021). Nearby meteorological stations and reanalysis data reveal heavy snowfall and a ∼ 5 K positive temperature anomaly in the week preceding collapse, as well as a temperature inversion in the valley (e.g., Pandey et al, 2021;Dandabathula et al, 2021;Zhou et al, 2021;Shugar et al, 2021). In the longer term, this region has warmed an estimated 0.014 (Zhou et al, 2021) to 0.033 K yr −1 (Shrestha et al, 2021) since 1980, for a total warming of 0.4 to 0.9 K over the past 3 decades.…”

7 February Chamoli (Uttarakhand, India) Rock-Ice Avalanche Disaster: Model-Simulated Prevailing Meteorological Conditions

“…They have also documented that the sudden increase in temperature was 'felt by people of nearby areas' on and a day before the event [53]. Zhou et al (2021) [47,76] argued that a winter warming was observed within 40 days before the event, which might have led to a winter melting. While it is not possible to validate the arguments of Zhou et al (2021) [47,76] from our model results, our analysis based on model-simulated variables qualitatively conform the findings of Mao et al (2022) [54] and Pandey et al (2021) [53].…”

Pre-collapse motion of the February 2021 Chamoli rock-ice avalanche, Indian Himalaya

“…Nearby meteorological stations and reanalysis data reveal heavy snowfall and a 5 K positive temperature anomaly in the week preceding collapse, as well as a temperature inversion in the valley (e.g. Pandey et al, 2021;Dandabathula et al, 2021;Zhou et al, 2021;Shugar et al, 2021). On the longer term, this region has warmed ∼0.14 K per decade (Qi et al, 2021;Shrestha et al, 2021).…”

“…On the longer term, this region has warmed ∼0.14 K per decade (Qi et al, 2021;Shrestha et al, 2021). Zhou et al (2021) and Dandabathula et al (2021) propose that this sudden temperature increase may have triggered the the day of collapse, and liquid water would not have been present at the surface (Shugar et al, 2021;Dandabathula et al, 2021). Positive summer temperatures (Shrestha et al, 2021) and a steep surface slope of the collapse block will have prevented strong cumulative surface loading of the collapse block through snow deposition.…”