A transient, two-dimensional, thermomechanical, ice-flow model is formulated in order to accurately model the flow field in regions of transitional flow, where all terms in the stress-equilibrium equations are important. The model solves the non-steady, advective-diffusive heat equation and the equations for ice flow in plane strain using the Finite Volume Method. A unique aspect of the model is the use of an orthogonal, curvilinear coordinate system, which simplifies discretization of the governing equations and the implementation of boundary conditions.; The model is applied to three different regions of transitional flow for which a full stress model is necessary to describe the flow field. In the first study, the flow and thickness history of Siple Dome, a local ice divide in West Antarctica, is constrained using forward modeling to match observations obtained near the dome summit. Results indicate that stable divide flow started 3 thousand years ago and that the dome thinned 350 meters from 15-14 thousand years ago. Thinning may have occurred in response to a period of rapid sea-level rise (meltwater pulse 1A) that occurred around the same time.; In the second study, the model is used to investigate how basal sliding, stresses in the ice, and frictional melting interact to allow a slow-to-fast sliding transition to migrate upstream over time. A positive feedback, which allows the transition to move tens of ice thicknesses upstream over short timescales (∼10 years), is ultimately limited by topographic diffusion. The feedback also increases the magnitude and upstream-propagation speed of perturbations to the ice thickness.; In the third study, the model is used to simulate the flow of Mount St. Helens crater glacier as it was squeezed between a newly expanding lava dome and the crater wall in early 2005. The glacier, which contains a large fraction of rock debris, was monitored extensively during the squeezing event. Those observations serve as targets for flow modeling in which the bulk-glacier density and the flow enhancement factor are treated as free parameters. Results indicate that ice containing 15-30% rock debris is between 5 and 10 times stiffer than clean glacier ice.
展开▼
