Basal resistance for three of the largest Greenland outlet glaciers

• Published in: Journal of Geophysical Research: Earth Surface
• Main Authors: Shapero, D, Joughin, I., Poinar, K, Morlighem, M, Gillet-Chaulet, F.
• Other Authors: Polar Science Center Seattle, Applied Physics Laboratory Seattle (APL-UW), University of Washington Seattle -University of Washington Seattle, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: [SDE]Environmental Sciences; Greenland
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-01351975; https://hal-insu.archives-ouvertes.fr/insu-01351975/document; https://hal-insu.archives-ouvertes.fr/insu-01351975/file/2015JF003643.pdf; https://doi.org/10.1002/2015JF003643

International audience Resistance at the ice-bed interface provides a strong control on the response of ice streams and outlet glaciers to external forcing, yet it is not observable by remote sensing. We used inverse methods constrained by satellite observations to infer the basal resistance to flow underneath three of the Greenland Ice Sheet's largest outlet glaciers. In regions of fast ice flow and high (>250 kPa) driving stresses, ice is often assumed to flow over a strong bed. We found, however, that the beds of these three glaciers provide almost no resistance under the fast-flowing trunk. Instead, resistance to flow is provided by the lateral margins and stronger beds underlying slower-moving ice upstream. Additionally, we found isolated patches of high basal resistivity within the predominantly weak beds. Because these small-scale (<1 ice thickness) features may be artifacts of overfitting our solution to measurement errors, we tested their robustness to different degrees of regularization.