Modelling sea ice as a granular medium
by
Joshua Downer
Otago University

The Antarctic sea ice can fluctuate in areal extent from 4-20 million square kilometres each year. This has a tremendous impact upon climate by reflecting solar radiation and insulating the ocean beneath it. Yet this geophysical structure is also very sensitive. The processes (thermodynamic and mechanical) that interconnect the ocean, ice, and atmosphere are intimately dependent upon one another; small changes in the behaviour of one area can have profound effects upon the others. It is a complex system.

To facilitate a better understanding of this inter-relationship between the sea ice and the processes that surround it we are studying the interaction between the ocean waves and sea ice. We focus on the marginal ice zone (MIZ) surrounding the Antarctic ice pack; a region of broken ice subject to (sometimes) intense agitation by ocean waves. Most investigations into the dynamical behaviour of sea ice have assumed that a continuum approximation is valid. The validity of this assumption in the MIZ varies and a definitive answer is, perhaps, inappropriate. However, as an alternative approach, we are looking at the problem from the paradigm of granular media and asking the question, ``How will an ensemble of ice floes behave subject to ocean wave forcing?'' This presentation is on the progress that has been made towards answering that question.

Date received: May 25, 1999