EGU2020-6941, updated on 02 Sep 2020
https://doi.org/10.5194/egusphere-egu2020-6941
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Evidence of uplift at Argentière glacier (Mont Blanc area, France)

Christian Vincent1, Andrea Walpersdorf2, Adrien Gilbert1, Olivier Gagliardini1, Florent Gimbert1, Fabien Gillet-Chaulet1, Luc Piard1, Bruno Jourdain1, Diego Cusicanqui1, Luc Moreau3, Olivier Laarman1, and Delphine Six1
Christian Vincent et al.
  • 1Institut Geosciences et Environnement-Department Glaciology Grenoble- CNRS/UGA, Saint Martin d Hères, France (christian.vincent@univ-grenoble-alpes.fr)
  • 2Institut des Sciences de la Terre Grenoble CNRS/UGA Saint Martin d Hères, France
  • 3Laboratoire Environnement et Dynamique des Territoires de Montagne Chambery France

Understanding basal processes is a prerequisite for predicting the overall motion of glaciers and its response to climate change. Although a number of studies have shown that subglacial hydrology affects glacier’s basal sliding motion, the involved mechanisms remain poorly known. Several studies suggested that glacier velocity increases with englacial and subglacial water storage, but observational quantification of subglacial water storage and associated velocity changes are challenging to make due to uncertainties on velocity measurements and on vertical straining.

Here we tackle this observational challenge through analyzing numerous field measurements from the surface and from the subglacial observatory on the Argentière Glacier (French Alps). We analyze specifically the relationships between daily sliding velocities (measured continuously at the glacier base), surface horizontal and vertical velocities from DGPS observations and ice thickness changes over years 2018 and 2019. We find strong upward surface movements of about 0.5 m during the winter until the beginning of May that cannot be explained by longitudinal strain rate changes. We support that it is caused by water volume increase in subglacial cavities.

Further analyzing the relationships between cavity growth, sliding and surface velocities, we find that unlike in previous studies bed separation variations are not synchronous with sliding speed variations. Surface uplift starts in winter, which is long before the spring sliding acceleration, and surface drop occurs mid-summer, which is long before the end of summer sliding deceleration. These findings support that the link between subglacial water storage and sliding speed may not be as direct as previously thought.

How to cite: Vincent, C., Walpersdorf, A., Gilbert, A., Gagliardini, O., Gimbert, F., Gillet-Chaulet, F., Piard, L., Jourdain, B., Cusicanqui, D., Moreau, L., Laarman, O., and Six, D.: Evidence of uplift at Argentière glacier (Mont Blanc area, France), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6941, https://doi.org/10.5194/egusphere-egu2020-6941, 2020

How to cite: Vincent, C., Walpersdorf, A., Gilbert, A., Gagliardini, O., Gimbert, F., Gillet-Chaulet, F., Piard, L., Jourdain, B., Cusicanqui, D., Moreau, L., Laarman, O., and Six, D.: Evidence of uplift at Argentière glacier (Mont Blanc area, France), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6941, https://doi.org/10.5194/egusphere-egu2020-6941, 2020