Glacier and Ice-sheet models in the Geodynamics Group, Research School
of Earth Sciences, Australian National University.
The Geodynamics Group
engaged in several different methods of computer assisted ice-mass modeling.
Much work has been done with isostatic rebound models - current lithospheric
rebound rates have been used to infer the extent of ice caps through paleo
time - but on this page physics based forward modeling approaches will
be presented. These approaches are currently in the development stage (like
everything else on the web) but we think they are interesting enough to
present none the less.
This research is being performed by Jonathan
Tomkin , a PhD student, and Jean
Braun, a Fellow of the Research School
of Earth Sciences.
2-D Finite Element Modeling with a twist - Dynamic Lagrangian Remeshing.
A 2-D FEM has been developed for ice sheets by modifying a model (Braun,
J. & Sambridge, M., 1994. Dynamical Lagrangian Remeshing (DLR): A new
algorithm for solving large strain deformation problems and its application
to fault-propagation folding. Earth and Planetary Sciences Letters, 124,
211-220.) designed to examine lithospheric interaction. Like standard time
dependent FEMs temperature and stress are solved by iteration. Stress and
strain are linked through Glen's flow law and through this displacement
is calculated. By incorporating Dynamic remeshing, the node movement caused
by this displacement changes the structure of elements over time, but the
progress of individual points within the ice mass can be tracked. This
allows the creation of zones within the ice that may have different physical
properties; anisotropy caused by uniaxial strain for example, or the effects
entrained till have on erosion rates.
2-D Shallow Ice Approximation - Cascades on Ice.
Cascades (Braun, J. & Sambridge, M., 1997. Modelling landscape evolution
on geological time scales: a new method based on irregular spatial discretization.
Basin Research, 9, 27-52. ) is a 2-D erosion model that tracks the path
of cascading water to determine the erosion caused by run off. This is
performed on an irregular grid. Orographic rainfall, diffusion (rockslides)
and tectonic uplift are also in the model, which is run over time to determine
the evolution of river systems and landscapes. The time dependence is solved
using explicit finite differencing (see Hindmarsh & Payne, 1996, Time-step
limits for stable solutions of the ice-sheet equation. Annals of Glaciology,
23, 74-85.) . By including an ice evolution model based on the shallow
ice approximation the model can incorporate the erosive effects of glaciers.
Snow fall is determined by an altitude and latitude based temperature model.