Intensified paraglacial slope failures due to accelerating downwasting of a temperate glacier in Mt. Gongga, southeastern Tibetan Plateau
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Published:2022-01-11
Issue:1
Volume:10
Page:23-42
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ISSN:2196-632X
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Container-title:Earth Surface Dynamics
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language:en
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Short-container-title:Earth Surf. Dynam.
Author:
Zhong YanORCID, Liu QiaoORCID, Westoby MatthewORCID, Nie YongORCID, Pellicciotti FrancescaORCID, Zhang Bo, Cai JialunORCID, Liu Guoxiang, Liao Haijun, Lu XuyangORCID
Abstract
Abstract. Topographic development via paraglacial slope failure
(PSF) represents a complex interplay between geological structure, climate,
and glacial denudation. Southeastern Tibet has experienced amongst the
highest rates of ice mass loss in High Mountain Asia in recent decades, but
few studies have focused on the implications of this mass loss on the
stability of paraglacial slopes. We used repeat satellite- and unpiloted aerial
vehicle (UAV)-derived
imagery between 1990 and 2020 as the basis for mapping PSFs from slopes
adjacent to Hailuogou Glacier (HLG), a 5 km long monsoon temperate valley
glacier in the Mt. Gongga region. We observed recent lowering of the glacier
tongue surface at rates of up to 0.88 m a−1 in the period 2000 to 2016,
whilst overall paraglacial bare ground area (PBGA) on glacier-adjacent
slopes increased from 0.31 ± 0.27 km2 in 1990 to
1.38 ± 0.06 km2 in 2020. Decadal PBGA expansion rates were
∼ 0.01 km2 a−1, 0.02 km2 a−1, and 0.08 km2 in the
periods 1990–2000, 2000–2011, and 2011–2020 respectively, indicating an
increasing rate of expansion of PBGA. Three types of PSFs, including
rockfalls, sediment-mantled slope slides, and headward gully erosion, were
mapped, with a total area of 0.75 ± 0.03 km2 in 2020. South-facing
valley slopes (true left of the glacier) exhibited more destabilization
(56 % of the total PSF area) than north-facing (true right) valley slopes
(44 % of the total PSF area). Deformation of sediment-mantled moraine
slopes (mean 1.65–2.63 ± 0.04 cm d−1) and an increase in
erosion activity in ice-marginal tributary valleys caused by a drop in local
base level (gully headward erosion rates are 0.76–3.39 cm d−1) have
occurred in tandem with recent glacier downwasting. We also observe
deformation of glacier ice, possibly driven by destabilization of lateral
moraine, as has been reported in other deglaciating mountain glacier
catchments. The formation, evolution, and future trajectory of PSFs at HLG
(as well as other monsoon-dominated deglaciating mountain areas) are related
to glacial history, including recent rapid downwasting leading to the
exposure of steep, unstable bedrock and moraine slopes, and climatic
conditions that promote slope instability, such as very high seasonal
precipitation and seasonal temperature fluctuations that are conducive to
freeze–thaw and ice segregation processes.
Funder
National Natural Science Foundation of China
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Geophysics
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