| The stability of marine-based ice sheets depends upon sea-level changes, the relief and character of the subglacial bed, climatic temperature and precipitation forcing, and the thermomechanical properties of the ice sheet itself. Defining the precise mechanisms affecting ice-sheet stability is particularly important for understanding changes in the West Antarctic Ice Sheet. If predicted sea-level rise were to occur, increasing portions of the ice may float. Such flotation may in turn enhance seaward flow of the remaining grounded ice.; A transient finite-element model of flow-plane thermomechanics is adapted to investigate how these processes may affect the stability of an ice sheet at the ice-sheet/ice-shelf interface. The formulation uses fully piecewise-biquadratic basis functions for velocity and temperature in the model domain, and fully piecewise-quadratic functions along the domain boundary. Specific attention has been paid to boundary condition specifications. In particular, basal sliding is implemented with the use of zero-thickness interface elements, eliminating the need for sliding laws that prescribe basal velocities.; Model results indicate that the ice stream is extremely sensitive to boundary conditions, particularly lateral drag, and that ice retreat is favored over ice advance. Through simulations of sea-level and climatic mass balance changes, this research indicates that the grounding zone is a particularly sensitive section of the flow plane, facilitating a rapid start to any response to climatic change. |
