A wave-based model for the marginal ice zone including a floe breaking parameterization

Abstract

The marginal ice zone (MIZ) is the boundary between the open ocean and ice-covered seas, where sea ice is significantly affected by the onslaught of ocean waves. Waves are responsible for the breakup of ice floes and determine the extent of the MIZ and floe size distribution. When the ice cover is highly fragmented, its behavior is qualitatively different from that of pack ice with large floes. Therefore, it is important to incorporate wave-ice interactions into sea ice-ocean models. In order to achieve this goal, two effects are considered: the role of sea ice as a dampener of wave energy and the wave-induced breakup of ice floes. These two processes act in concert to modify the incident wave spectrum and determine the main properties of the MIZ. A simple but novel parameterization for floe breaking is derived by considering alternatively ice as a flexible and rigid material and by using current estimates of ice critical flexural strain and strength. This parameterization is combined with a wave scattering model in a one-dimensional numerical framework to evaluate the floe size distribution and the extent of the MIZ. The model predicts a sharp transition between fragmented sea ice and the central pack, thus providing a natural definition for the MIZ. Reasonable values are found for the extent of the MIZ given realistic initial and boundary conditions. The numerical setting is commensurate with typical ice-ocean models, with the future implementation into two-dimensional sea ice models in mind. Copyright 2011 by the American Geophysical Union.