Contrasting surface velocities between lake- and land-terminating glaciers in the Himalayan region
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Published:2021-12-10
Issue:12
Volume:15
Page:5577-5599
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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:
Pronk Jan BoukeORCID, Bolch TobiasORCID, King Owen, Wouters Bert, Benn Douglas I.
Abstract
Abstract. Meltwater from Himalayan glaciers sustains the flow of rivers such
as the Ganges and Brahmaputra on which over half a billion people depend for
day-to-day needs. Upstream areas are likely to be affected substantially by
climate change, and changes in the magnitude and timing of meltwater supply
are expected to occur in coming decades. About 10 % of the Himalayan
glacier population terminates into proglacial lakes, and such
lake-terminating glaciers are known to exhibit higher-than-average total
mass losses. However, relatively little is known about the mechanisms
driving exacerbated ice loss from lake-terminating glaciers in the Himalaya.
Here we examine a composite (2017–2019) glacier surface velocity dataset,
derived from Sentinel 2 imagery, covering central and eastern Himalayan
glaciers larger than 3 km2. We find that centre flow line velocities of
lake-terminating glaciers (N = 70; umedian: 18.83 m yr−1; IQR – interquartile range – uncertainty estimate: 18.55–19.06 m yr−1) are on average more than double those of land-terminating
glaciers (N = 249; umedian: 8.24 m yr−1; IQR uncertainty estimate: 8.17–8.35 m yr−1) and
show substantially more heterogeneity than land-terminating glaciers around
glacier termini. We attribute this large heterogeneity to the varying
influence of lakes on glacier dynamics, resulting in differential rates of
dynamic thinning, which causes about half of the lake-terminating glacier
population to accelerate towards the glacier termini. Numerical ice-flow
model experiments show that changes in the force balance at the glacier
termini are likely to play a key role in accelerating the glacier flow at
the front, with variations in basal friction only being of modest
importance. The expansion of current glacial lakes and the formation of new
meltwater bodies will influence the dynamics of an increasing number of
Himalayan glaciers in the future, and these factors should be carefully
considered in regional projections.
Funder
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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