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Volume 11, issue 5 | Copyright
The Cryosphere, 11, 2247-2264, 2017
https://doi.org/10.5194/tc-11-2247-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 Sep 2017

Research article | 22 Sep 2017

Structure and evolution of the drainage system of a Himalayan debris-covered glacier, and its relationship with patterns of mass loss

Douglas I. Benn1, Sarah Thompson2, Jason Gulley3, Jordan Mertes4, Adrian Luckman2, and Lindsey Nicholson5 Douglas I. Benn et al.
  • 1School of Geography and Sustainable Development, University of St Andrews, St Andrews, UK
  • 2Department of Geography, Swansea University, Swansea, UK
  • 3School of Geosciences, University of South Florida, Tampa, FL, USA
  • 4Department of Geological and Mining Engineering and Sciences, Michigan Tech, Houghton, MI, USA
  • 5Institute for Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria

Abstract. We provide the first synoptic view of the drainage system of a Himalayan debris-covered glacier and its evolution through time, based on speleological exploration and satellite image analysis of Ngozumpa Glacier, Nepal. The drainage system has several linked components: (1) a seasonal subglacial drainage system below the upper ablation zone; (2) supraglacial channels, allowing efficient meltwater transport across parts of the upper ablation zone; (3) sub-marginal channels, allowing long-distance transport of meltwater; (4) perched ponds, which intermittently store meltwater prior to evacuation via the englacial drainage system; (5) englacial cut-and-closure conduits, which may undergo repeated cycles of abandonment and reactivation; and (6) a "base-level" lake system (Spillway Lake) dammed behind the terminal moraine. The distribution and relative importance of these elements has evolved through time, in response to sustained negative mass balance. The area occupied by perched ponds has expanded upglacier at the expense of supraglacial channels, and Spillway Lake has grown as more of the glacier surface ablates to base level. Subsurface processes play a governing role in creating, maintaining, and shutting down exposures of ice at the glacier surface, with a major impact on spatial patterns and rates of surface mass loss. Comparison of our results with observations on other glaciers indicate that englacial drainage systems play a key role in the response of debris-covered glaciers to sustained periods of negative mass balance.

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This paper provides the first complete view of the drainage system of a large Himalayan glacier, based on ice-cave exploration and satellite image analysis. Drainage tunnels inside glaciers have a major impact on melting rates, by providing lines of weakness inside the ice and potential pathways for melt-water, and play a key role in the response of debris-covered glaciers to sustained periods of negative mass balance.
This paper provides the first complete view of the drainage system of a large Himalayan glacier,...
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