Polythermal ice is found near the bed of the Greenland and Antarctic ice sheets. Presently, only a few computational models for ice sheet dynamics can accurately model polythermal ice. Most of these models are explicit, neglect the horizontal temperature diffusion and require temperature spin up of thousands of years for obtaining a steady state temperature field.

We present an implicit, fully three-dimensional computational model for the simulation of polythermal ice. The model is based on the enthalpy formulation proposed by Aschwanden et. al. (2012), with the addition of the gravity-driven moisture drainage model proposed by Schoof and Hewitt (2016). The enthalpy model is implicitly coupled with the Blatter-Pattyn ice sheet flow model. The resulting thermo-mechanical model is fully implicit and allows for the solution of the steady state for temperature and velocity without the need of performing a temperature spin up. We will present results on simplified geometries as well as for large-scale ice sheet problems, and compare them with results from the literature or obtained with other formulations.