Modeling Arctic Sea Ice
The pack ice is effected by both thermodynamic and mechanical processes. Thermodynamic processes result in mass changes at the atmosphere and ocean boundaries. These processes are coupled with mechanical properties that determine ice motion and deformation. The ice pack is able to move and deform in the winter in response to wind and ocean forces because of concentrated deformations at leads (cracks).  An elastic-decohesive constitutive model for pack ice has been developed that explictly accounts for leads. The constitutive model is based on elasticity combined with a cohesive crack law that predicts the initiation, orientation and opening of leads, and also has a simple closing model. A numerical technique called the material-point method (MPM) is used to solve the momentum balance equation with internal forces determined by the elastic-decohesive law. MPM is based on particle-in-cell technology and thus uses a Lagrangian set of material points with associated mass, position, velocity, stress, and other material parameters, and a background mesh where the momentum equation is solved. This method avoids the convection errors associated with fully Eulerian methods as well as the mesh entanglement that can occur with fully Lagrangian methods under large deformations. The model and numerical method will be illustrated on example calculations performed for regions of Arctic ice.Â