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

• Published in: The Cryosphere
• Main Authors: Brun, Fanny, Wagnon, Patrick, Berthier, Etienne, Shea, Joseph, M, Immerzeel, Walter, W, Kraaijenbrink, Philip, Vincent, Christian, Reverchon, Camille, Shrestha, Dibas, Arnaud, Yves
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), International Centre for Integrated Mountain Development (ICIMOD), Universiteit Utrecht / Utrecht University Utrecht, Tribhuvan University
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; The Cryosphere
• Online Access: https://hal.science/hal-01952649; https://hal.science/hal-01952649/document; https://hal.science/hal-01952649/file/tc-12-3439-2018.pdf; https://doi.org/10.5194/tc-12-3439-2018

International audience 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 Pleiades tri-stereo imagery obtained in November 2015, 2016 and 2017. UAV- and Pleiades-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.