Modeling ice flow over a `wet base' with a 3D thermo-mechanical higher-order ice-sheet model: examples from the Siple Coast ice streams and Lake Vostok, Antarctica
Abstract
Key areas in ice sheets are transition zones between ice frozen and ice not frozen at the bed. Such a transition zone is in a sense comparable to a grounding line between an ice sheet (high basal stress) and an ice shelf (stress-free base). Although ice flow over a lubricated area, such as a subglacial lake or an ice stream, is characterized by low driving stresses and hence governed by normal stretching and horizontal shearing, the transition zone (onset area in case of an ice stream) involves vertical shearing as well. Modeling such a system demands a higher-order model that incorporates all these relevant stresses. A new 3D thermo-mechanical higher-order model is developed and employed to study complex ice flow. The model solves the force-balance and flow-law equations in the form of a set of highly non-linear elliptic equations using the method presented by Pattyn (2002). Model results of the Siple Coast area, Antarctica, display all aspects of observed ice-stream features, such as the surface flattening downstream from the onset area, the associated velocity increase and the importance of lateral drag in the force balance. Simulation of the ice flow over Lake Vostok results in a local flattening of the surface, a velocity increase over the lake, and a deviation of the ice flow from the main direction. The presence of the lake only influences the ice flow in the vicinity of the lake. Such features are also observed from field measurements.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....6213P