Validation of effective subglacial hydrology models

The presence of subglacial lubrication networks at the ice-bed interface is a key component for ice sheet dynamics. A subglacial network has the potential to facilitate rapid ice flow through reduction in basal friction, possibly resulting in the formation of surges and ice streams. A wide range of numerical models are designed to simulate the impact such networks on ice flow. Validating these models is crucial to ensure that the important subglacial physical processes are accurately resolved.

One class of subglacial network models is based on an effective porous medium (EPM) approach. A major component of such models involves a nonlinear diffusion equation for the subglacial water pressure, which include variable transmissivity that represent a range of subglacial and groundwater processes.

We present solutions to a generalized nonlinear diffusion equation that can model a wide range of flows of this kind. We use scaling analysis to find general similarity solutions and other solutions with explicit time-dependent transmissivity. We use this method to validate the parallel implementation of the Confined–Unconfined Aquifer System model (CUAS-MPI) for subglacial hydrology. The model is based on an effective porous media (EPM) approach. Our results show, that CUAS-MPI is able to accurately solve highly non linear flows, equivalent to cavity opening and creep closure terms in subglacial hydrology. Because of their generality, our solutions are readily applicable to other subglacial hydrology models that are based on the EPM approach. We anticipate that a validated hydrology model with our solutions can achieve more credible results in subglacial network simulations, and consequently in predicting ice sheet evolution.