A basal water model for ice sheets

A previously existing ice sheet model is described. The model accounts for ice deformation, themo-mechanical coupling, isostasy, and simple climatology. After reviewing the current and past literature pertaining to the melt water systems that exist within glaciers and ice sheets, a basal water model for ice sheets is formulated. The model takes the form of a conservation equation for basal water coupled with a relationship for the velocity of basal water and an expression for the potential field experienced by the basal water system. The model also accounts for basal water flowing through a permeable under-layer based on some assumptions about the till that is under ice sheets. The differential equations that arise from formulation of the model are solved numerically with the finite element method. The model is tested for its sensitivity to various physical parameters. A sliding law is formulated in terms of the basal water distribution. The first set of tests is conducted on the Ross Ice Streams of Antarctica. The parameters considered are the interaction with the aquifer and the velocity of the water. The study demonstrates that with a proper sliding law, an accurate reproduction of the positions and the velocities of the Ross Ice Streams is possible. The second sensitivity test considers the glaciation and de-glaciation of the Northern Hemisphere. The second test demonstrates a clear advantage of ice sheet models that use a basal water distribution to estimate sliding over models that simply have sliding where ever the bed is thawed. With a basal water model for ice sheets, it is possible to identify sub-glacial lakes from geographic data sets. This is done in Antarctica. The position of the sub-glacial lakes identified from data sets compares favorably with the position of sub-glacial lakes identified in field studies. The set of sub-glacial lakes are analyzed for their stability and potential contribution to a basal water system. It is shown that sub-glacial lakes can play a significant role in maintaining or stagnating ice streams.