On applying granular flow theory to a deforming broken ice field

Abstract

The prediction of arctic ocean ice dynamics relies on a correct modelling of the stresses acting on the ice field, including the Coriolis effect, wind and current stresses and the ice interaction. Observations made in the past decade show significant ice interaction and flow patterns which can be consistently modeled with a plastic rheology. The main local physical process considered in these rheologies is the pressure ridging phenomenon. However recent arctic field work carried out in the marginal ice zone (less than 100 km from the edge of the ice field) shows the ice very near the edge to consist of a large number of discrete floes. While a plastic rheology may well have application under compact conditions in this region, under dispersed conditions the rheology may be different. In order to address this issue, in this work the ice floe collisions induced by ice deformation are analyzed. The internal kinematics as represented by the ice floe fluctuations is derived. Comparisons between the results and field data show excellent correlation. However, the theoretically predicted floe fluctuations are about one order of magnitude lower than the field measurements. Possibilities for this discrepancy are proposed and discussed.