Retroactions Between Basal Hydrology and Basal Sliding from Numerical Experiments

Wednesday, 17 December 2014
Olivier Gagliardini1, Olivier Passalacqua1 and Mauro A Werder2, (1)LGGE Laboratoire de Glaciologie et Géophysique de l’Environnement, Saint Martin d'Hères, France, (2)University of Bristol, Bristol, BS8, United Kingdom
The basal sliding of glaciers is modulated by the presence of basal water and more precisely its pressure. On one hand, where the basal water pressure increases, the ice friction on the bedrock is reduced and the basal sliding velocity increases. On an other hand, an increase of basal sliding will influence the development of the basal hydrology systems. These processes leads to non-steady ice velocities and have a seasonal or even diurnal signature. In this study, a basal hydrology model is coupled with an ice flow model through a water pressure dependent friction law. The basal hydrology model includes an inefficient cavity-type water sheet and a network of efficient discrete channels. Both systems are connected and evolve in time in response to the water inputs. Ice flow is modelled either solving the full-Stokes equations or the shallow shelf approximation. Basal hydrology and ice flow are connected through a Coulomb type friction law which depends on the basal water pressure. The equations of both ice flow and hydrology are implemented in the open source, finite element, ice sheet / ice flow model Elmer/Ice. The coupling of basal hydrology and ice flow is studied for different glacier geometries and external forcing having different amplitude and temporal signatures. The classically used one way coupling, where only the hydrology influence the ice flow, is compared to a two way coupling where both hydrology and ice flow interact in a fully coupled way.