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Volume 12, issue 11 | Copyright
The Cryosphere, 12, 3439-3457, 2018
https://doi.org/10.5194/tc-12-3439-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Nov 2018

Research article | 01 Nov 2018

Ice cliff contribution to the tongue-wide ablation of Changri Nup Glacier, Nepal, central Himalaya

Fanny Brun1,2,*, Patrick Wagnon1,3, Etienne Berthier2, Joseph M. Shea3,4,5, Walter W. Immerzeel6, Philip D. A. Kraaijenbrink6, Christian Vincent1, Camille Reverchon1, Dibas Shrestha7, and Yves Arnaud1 Fanny Brun et al.
  • 1Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 2LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, 31400 Toulouse, France
  • 3International Center for Integrated Mountain Development, Kathmandu, Nepal
  • 4Center for Hydrology, University of Saskatchewan, Saskatoon, Canada
  • 5Geography Program, University of Northern British Columbia, Prince George, Canada
  • 6Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands
  • 7Central Department of Hydrology and Meteorology, Tribhuvan University, Kathmandu, Nepal
  • *Invited contribution by Fanny Brun, recipient of the EGU Cryospheric Sciences Outstanding Student Poster and PICO Award 2018.

Abstract. Ice cliff backwasting on debris-covered glaciers is recognized as an important mass-loss process that is potentially responsible for the debris-cover anomaly, i.e. the fact that debris-covered and debris-free glacier tongues appear to have similar thinning rates in the Himalaya. In this study, we quantify the total contribution of ice cliff backwasting to the net ablation of the tongue of Changri Nup Glacier, Nepal, between 2015 and 2017. Detailed backwasting and surface thinning rates were obtained from terrestrial photogrammetry collected in November 2015 and 2016, unmanned air vehicle (UAV) surveys conducted in November 2015, 2016 and 2017, and Pléiades tri-stereo imagery obtained in November 2015, 2016 and 2017. UAV- and Pléiades-derived ice cliff volume loss estimates were 3% and 7% less than the value calculated from the reference terrestrial photogrammetry. Ice cliffs cover between 7% and 8% of the total map view area of the Changri Nup tongue. Yet from November 2015 to November 2016 (November 2016 to November 2017), ice cliffs contributed to 23±5% (24±5%) of the total ablation observed on the tongue. Ice cliffs therefore have a net ablation rate 3.1±0.6 (3.0±0.6) times higher than the average glacier tongue surface. However, on Changri Nup Glacier, ice cliffs still cannot compensate for the reduction in ablation due to debris-cover. In addition to cliff enhancement, a combination of reduced ablation and lower emergence velocities could be responsible for the debris-cover anomaly on debris-covered tongues.

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On debris-covered glaciers, steep ice cliffs experience dramatically enhanced melt compared with the surrounding debris-covered ice. Using field measurements, UAV data and submetre satellite imagery, we estimate the cliff contribution to 2 years of ablation on a debris-covered tongue in Nepal, carefully taking into account ice dynamics. While they occupy only 7 to 8 % of the tongue surface, ice cliffs contributed to 23 to 24 % of the total tongue ablation.
On debris-covered glaciers, steep ice cliffs experience dramatically enhanced melt compared with...
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