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.
| Original language | English |
|---|---|
| Pages (from-to) | 3439-3457 |
| Number of pages | 19 |
| Journal | Cryosphere |
| Volume | 12 |
| Issue number | 11 |
| DOIs | |
| Publication status | Published - 1 Nov 2018 |
Funding
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. Acknowledgements. We thank Sonam Futi Sherpa, Arbindra Khadka and Aurélie Gourdon for their assistance in the field. This work has been supported by the French Service d’Observation GLACIOCLIM, the French National Research Agency (ANR) through ANR-13-SENV-0005-04-PRESHINE, and by a grant from Labex OSUG@2020 (Investissements d’avenir – ANR10 LABX56). This study was carried out within the framework of the Ev-K2-CNR Project in collaboration with the Nepal Academy of Science and Technology as foreseen by the Memorandum of Understanding between Nepal and Italy. Thanks to contributions from the Italian National Research Council, the Italian Ministry of Education, University and Research and the Italian Ministry of Foreign Affairs. Funding for the UAV survey was generously provided by the United Kingdom Department for International Development (DFID) and by the Ministry of Foreign Affairs, Government of Norway. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 676819). Etienne Berthier acknowledges support from the French Space Agency (CNES) and the Programme National de Télédétection Spatiale grant PNTS-2016-01. The International Centre for Integrated Mountain Development is funded in part by the governments of Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan. The views expressed are those of the authors and do not necessarily reflect their organizations or funding institutions. Fanny Brun, Patrick Wagnon, Christian Vincent and Yves Arnaud are parts of Labex OSUG@2020 (ANR10 LABX56). We thank the editor and four anonymous reviewers for their constructive comments, which greatly improved this article.