Modeling of friction at the base of glaciers

The presence of water at the base of glaciers can modulate the friction between the ice and the rock. At the meso-scale (1-10 m), water-filled cavities can open on the lee side of the bedrock bumps. These cavities, by smoothing the apparent bedrock roughness, induce an increase of the sliding velocity of the glacier. Such increase in the glacier speed is observed in spring on alpine glaciers but also on outlet glaciers of the Greenland Ice Sheet.
A Coulomb-type friction law, linking basal shear stress, sliding velocity and the effective pressure, i.e. the difference between ice overburden pressure and water pressure, has been derived from analytical developments (Schoof, 2005) and further extended using finite element modeling (Gagliardini et al., 2007). The main limitations of this Coulomb-type friction law are that it assumes (i) a steady-state cavity geometry, (ii) a uniform water pressure at the base of the glacier, (iii) pure sliding at the interface between the ice and the bed and (iv) a two-dimensional geometry.
In the proposed internship, new simulations, following the modeling framework developed in Gagliardini et al. (2007), will be performed to extend this Coulomb-type friction law and overcome the previously listed limitations. In particular, the effect of a transient water pressure on the sliding response will be studied as well as how the Coulomb-type friction law is modified when assuming a more realistic three-dimensional geometry.
The modeling will be performed using the open-source finite-element software Elmer/Ice, mainly developed at IGE in collaboration with CSC in Finland. This internship is part of the newly funded ANR project SAUSSURE which aims at a better understanding of friction at the base of glaciers by coupling experimental, theoretical and modeling approaches on the Argentière glacier in the French Alps. In the framework of the SAUSSURE project, a PhD will start in October 2019.

Pour candidater : Adresser un CV et une lettre de motivation par email à l’adresse ci-dessous :
olivier.gagliardini univ-grenoble-alpes.fr