Basal conditions of Denman Glacier from hydrology modeling and their application to various friction laws

The key process of basal sliding in Antarctic glaciers is often incorporated into ice dynamics models via the use of a friction law, which relates the basal shear stress to the effective pressure. With few ice dynamics models actively coupled to subglacial hydrology models, the effects of subglacial hydrology often manifest in the friction coefficient – an unknown parameter in the friction law. We investigate the impact of friction coefficients for Denman Glacier, East Antarctica, by comparing Ice-sheet and Sea-level System Model (ISSM) inversion simulations using the effective pressure produced from the Glacier Drainage System (GlaDS) model compared with  a typically prescribed effective pressure using a combination of ice overburden pressure and height above sea level (N_O). We apply these comparative model runs for the Budd and Schoof friction laws. In regions of fast ice flow, we find a positive correlation between the GlaDS output effective pressure and the friction coefficient for the Schoof law. In addition, using the GlaDS output effective pressure compared to  N_O leads to a smoother friction coefficient as well as smaller differences between the simulated and observed surface velocity. In general we find that spatial variations in the Schoof law match more closely with the known physics of subglacial hydrology than the Budd law and therefore suggest that using the GlaDS output effective pressure compared to N_O produces more realistic results. This demonstrates the need to couple ice sheet and subglacial hydrological systems to accurately represent ice flow.