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Discussion papers
https://doi.org/10.5194/tc-2019-177
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2019-177
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 18 Sep 2019

Submitted as: research article | 18 Sep 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).

Debris cover and the thinning of Kennicott Glacier, Alaska, Part B: ice cliff delineation and distributed melt estimates

Leif S. Anderson1,2, William H. Armstrong1,3, Robert S. Anderson1, and Pascal Buri4 Leif S. Anderson et al.
  • 1Department of Geological Sciences and Institute of Arctic and Alpine Research, University of Colorado Campus Box 450, Boulder, CO 80309, USA
  • 2GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany
  • 3Department of Geological and Environmental Sciences, Appalachian State University, 033 Rankin Science West, ASU Box 32067, Boone, NC 28608-2067, USA
  • 4Geophysical Institute, University of Alaska-Fairbanks, 2156 Koyukuk Drive, Fairbanks, AK 99775, USA

Abstract. The mass balance of many valley glaciers is enhanced by the presence of ice cliffs within otherwise continuous debris cover. We assess the effect of debris and ice cliffs on the thinning of Kennicott Glacier in three companion papers. In Part A we report in situ measurements from the debris-covered tongue. Here, in Part B, we develop a method to delineate ice cliffs using high-resolution imagery and use empirical relationships from Part A to produce distributed mass balance estimates. In Part C we describe feedbacks that contribute to rapid thinning under thick debris.

Ice cliffs cover 11.7 % of the debris-covered tongue, the most of any glacier studied to date, and they contribute 19 % of total melt. Ice cliffs contribute an increasing percentage of melt the thicker the debris cover. In the lowest 4 km of the glacier, where debris thicknesses are greater than 20 cm, ice cliffs contribute 40 % of total melt.

Surface lake coverage doubled between 1957 and 2009, but lakes do not occur across the full extent of the zone of maximum glacier thinning. Despite abundant ice cliffs and expanding surface lakes, average melt rates are suppressed by debris, the pattern of which appears to reflect the debris thickness-melt relationship (or Østrem’s curve). This suggests that, in addition to melt hotspots, the decline in ice discharge from upglacier is an important contributor to the thinning of Kennicott glacier under thick debris.

Leif S. Anderson et al.
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Short summary
Thick rock cover (or debris) disturbs the melt of many Alaskan glaciers. Yet the effect of debris on glacier thinning in Alaska has been overlooked. In three companion papers we assess the role of debris and ice flow on the thinning of Kennicott Glacier. In Part B, we develop a new method to delineate ice cliffs and quantify the effect of debris and ice cliffs across the glacier tongue. Ice cliffs contribute a significant amount of melt but cannot explain the pattern of glacier thinning.
Thick rock cover (or debris) disturbs the melt of many Alaskan glaciers. Yet the effect of...
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