Sub-seasonal variability of supraglacial ice cliff melt rates and associated processes from time-lapse photogrammetry
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Published:2022-11-11
Issue:11
Volume:16
Page:4701-4725
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Kneib MarinORCID, Miles Evan S.ORCID, Buri PascalORCID, Fugger StefanORCID, McCarthy Michael, Shaw Thomas E.ORCID, Chuanxi Zhao, Truffer Martin, Westoby Matthew J.ORCID, Yang Wei, Pellicciotti FrancescaORCID
Abstract
Abstract. Melt from supraglacial ice cliffs is an important contributor to the mass
loss of debris-covered glaciers. However, ice cliff contribution is
difficult to quantify as they are highly dynamic features, and the paucity
of observations of melt rates and their variability leads to large modelling
uncertainties. We quantify monsoon season melt and 3D evolution of four ice
cliffs over two debris-covered glaciers in High Mountain Asia (Langtang
Glacier, Nepal, and 24K Glacier, China) at very high resolution using
terrestrial photogrammetry applied to imagery captured from time-lapse
cameras installed on lateral moraines. We derive weekly flow-corrected digital elevation models (DEMs)
of the glacier surface with a maximum vertical bias of ±0.2 m for Langtang Glacier and ±0.05 m for 24K Glacier and use change detection
to determine distributed melt rates at the surfaces of the ice cliffs
throughout the study period. We compare the measured melt patterns with
those derived from a 3D energy balance model to derive the contribution of
the main energy fluxes. We find that ice cliff melt varies considerably
throughout the melt season, with maximum melt rates of 5 to
8 cm d−1,
and their average melt rates are 11–14 (Langtang) and 4.5 (24K) times higher
than the surrounding debris-covered ice. Our results highlight the influence
of redistributed supraglacial debris on cliff melt. At both sites, ice cliff
albedo is influenced by the presence of thin debris at the ice cliff
surface, which is largely controlled on 24K Glacier by liquid precipitation
events that wash away this debris. Slightly thicker or patchy debris reduces
melt by 1–3 cm d−1 at all sites. Ultimately, our observations show a
strong spatio-temporal variability in cliff area at each site, which is
controlled by supraglacial streams and ponds and englacial cavities that
promote debris slope destabilisation and the lateral expansion of the
cliffs. These findings highlight the need to better represent processes of
debris redistribution in ice cliff models, to in turn improve estimates of
ice cliff contribution to glacier melt and the long-term geomorphological
evolution of debris-covered glacier surfaces.
Funder
H2020 European Research Council Royal Geographical Society
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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