Impact of basal friction law on the dynamics of Greenland outlet glaciers

Abstract:

Basal friction is one of the major processes controlling the flow of glaciers. An appropriate representation of basal friction in ice sheet models is needed to correctly capture ice dynamics and its temporal evolution more accurately. However, as few direct observations are available, the choice of the basal friction law in numerical models accounts for a large part of the uncertainty in future sea-level contribution from the ice sheets. Here we evaluate a variety of basal friction laws and friction law parameters to model marine-terminating glaciers that have experienced variations in ice flux of more than 1 Gt/yr over the past decade. We investigate the response of those glaciers when applied various friction laws to determine which friction law best reproduces the observed pattern of acceleration and thinning. Calving has been shown to drive the dynamic evolution of marine-terminating glaciers to a large extent, so we force the ice front position with observations in order to remove uncertainties coming from potentially inaccurate ice front positions and focus on the impact of sliding laws. This study shows that much uncertainty remains in the future sea-level contribution from Greenland glaciers due to the choice of basal friction law, and the choice of appropriate parameters could significantly improve the reliability of model simulations. Comparing friction laws makes it possible to assess the role of each parameter in friction laws and improve the representation of basal conditions of the Greenland ice sheet. More direct observations (e.g. basal water pressure) are needed to further constrain parameters in friction laws.

Acknowledgements This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Funding was provided by the JPL Strategic Research and Technology Development Program.