Perturbation of ice sheet surface stress via basal lubrication

Surface meltwater on the Greenland Ice Sheet (GrIS) can lubricate the bottom of the ice sheet via surface-to-bed pathways, such as moulins and vertical hydrofracture. The basal lubrication reduces the friction between the ice and the bed, which leads to perturbations in the velocity, strain rate, and stress fields that are felt laterally away from the location of the basal water as well as through the entire thickness of the ice column up to the surface.  In some instances, the induced surface stress may be sufficient to break new cracks, leaving the GrIS more vulnerable to rapid lake drainage via hydrofracture.  It is therefore important to understand the dominant physical parameters which control the magnitude and spatial extent (i.e. the coupling lengthscale) of stress perturbations induced by the basal meltwater lubrication.  To constrain the importance of surface slope, bed slope, and ice thickness as controls on this stress response, we used a 2D simulation of Stokes flow over a slippery patch with various basal boundary conditions, simulating the presence of meltwater lubrication.  We found that the magnitude of the stress response scales with the surface slope while the coupling lengthscale scales with the ice thickness.  This indicates that inland ice may experience a weaker but longer-range stress perturbation in response to water lubrication at the bed.