Abstract
Rock debris covers about a third of the total glacier ablation area in
High Mountain Asia. Sustained mass loss from these glaciers is causing
supraglacial debris layers to expand and thicken. Predicting the
evolution of debris-covered glaciers therefore requires including the
feedbacks between debris transport, mass balance and ice flow into
numerical glacier models. Our simulations of Khumbu Glacier in the
Everest region of Nepal demonstrate that the extensive supraglacial
debris layer has developed since the Little Ice Age (LIA) approximately
500 years before present. Since the glacier last advanced during the
LIA, 34% of the total ice volume has been lost, mainly by surface
lowering rather than terminus recession. As the glacier continues to
shrink in response to warming air temperatures, at least 8-10% of the
glacier volume will be lost by 2100 CE and the debris-covered tongue
will detach from the active upper section within the next 150 years.
However, although our model captures the important large-scale processes
and feedbacks that determine the behaviour of a debris-covered glacier,
these simulations underestimated by a factor of three the magnitude of
surface change on Khumbu Glacier identified from satellite imagery
spanning the last 40 years. This unaccounted-for mass
loss—sometimes referred to as the "debris-cover
anomaly"—could be due to surface processes that locally enhance
ablation including the formation and decay of ice cliffs and
supraglacial ponds. Here we explore the role of supraglacial and
englacial processes in contributing to the recent acceleration of mass
loss from Khumbu Glacier, using our glacier model alongside results from
a field monitoring campaign designed to constrain ablation and ice flow
processes on high-elevation debris-covered Himalayan glaciers.
Original language | English |
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Publication status | Published - 01 Dec 2019 |
Keywords
- 0710 Periglacial processes
- CRYOSPHERE
- 0776 Glaciology
- 1815 Erosion
- HYDROLOGY
- 1824 Geomorphology: general