Sea Ice Dynamics

Abstract

Sea ice dynamics examines the drift of sea ice forced by the winds and ocean currents. The existing mesoscale to large-scale models are based on continuum mechanics, where the continuum particles must be much larger than the floe size. The sea ice medium is described by ice state, a set of relevant material properties of ice, and rheology, which is a plastic law and specifies how the internal stress depends on the compactness, thickness, strain, and strain rate. Given ice state and rheology, the dynamics is determined by the equation of motion and ice conservation law. Three drift regimes are distinguished: stationary ice (the external load does not reach the yield level), free drift (no internal friction), and drift in the presence of internal friction. Free drift is a good approximation when compactness is less than 0.8, and then the ice velocity equals ocean current plus wind drift (wind vector contracted to 2–3% length and rotated 30° to the right/left in the Northern/Southern Hemisphere). Drift under internal friction is the normal case, and the ice flows in general large-length scales but with narrow deformation zones. The key problems are seen in the mechanical ice redistribution problem due to limited validation data sets, scaling laws, and ice–ocean dynamic interaction.