Simulations of the Flow of the Ross Ice Shelf, Antarctica
Parameter Sensitivity Tests and Temperatur-Dependent Rate Factor
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Beschreibung
The simulation of the flow of the Ross lee Shelf is the focus of this work. This includes a detailed understanding of the Ross lee Shelf and, in particular, of its boundary conditions. These are later on the input quantities for the simulation that have been performed. The mathematical description of the flow was formulated by M.Weis (2001) in a shallow shelf approximation. which provides us with a set of elliptic partial integro-differential equations. These equations are solved by use of the finite element method in the C++ program FESSACODE. The physical understanding of the mechanism of the flow of polycrystalline ice is the basis for the simulation. Therefore, this results in an advanced implementation of the flow parameter rate factor, which parameterises the temperature dependence of the flow law. Consequently, beginning with a discussion of the rate factor, the thesis continues with a study of measured temperature profiles of ice shelves. This leads to a parameterisation of temperature profiles, which finally are used for simulations. Since we focus on the temperature dependence of the rate factor, the boundary condition needs to be derived first. This means in this work that satellite based ice surface temperatures have to be processed in order to obtain an observationally based surface temperature distribution of the Ross lee Shelf. Simulations are then performed for two different kinds of temperature profiles, one which represents melting underneath the ice shelf and one that represents freezing. This is not done for spatially unique temperature profiles only, but for distributions of melting and freezing, too. Based on the inferences derived from the simulations a reference simulation is defined, which is optimised for consistency with the measurements. To obtain best consistency an enhancement factor is introduced into the flow law, although its physical description is lacking, and the influence of the enhancement factor to the flow is investigated.
In a further step the sensitivity to other boundary conditions like inflow velocities, ice thickness and ice rises are studied. Finally, a change in the ice surface temperature due to global warming is simulated.
Autor*in
Angelika Humbert