A FINITE-ELEMENT TREATMENT OF SEA-ICE DYNAMICS FOR DIFFERENT ICE RHEOLOGIES

In this paper the effects of four different rheologies on the evolutio n of a large-scale sea ice pack are determined and compared. Two rheol ogies are of viscous-plastic form, and two are viscous fluid relations . The initial pack domain is rectangular, and the motion is driven by wind stress and resisted by ocean drag. Two adjacent edges are rigid s hore boundaries, and the other two are free boundaries at open water w hich move during the pack motion, so that the pack domain changes in t ime. Two different forms of boundary conditions at the rigid shore edg es are considered, which also influence the evolution. The governing e quations are solved numerically using a finite-element method, and, un like previous numerical treatments, no artificial viscosity is incorpo rated to stabilise the algorithm near interfaces between converging an d diverging flow. Instability arises when any tensile stress is abrupt ly cut-off when diverging flow is initiated, and an alternative view i s offered. (C) 1998 John Wiley & Sons, Ltd.