Simulating deformation structure in viscous-plastic sea-ice models with CD-grid approaches

Linear Kinematic Features (LKFs) are found everywhere in the Arctic sea-ice cover. They are strongly localized deformations often associated with the formation of leads and pressure ridges. Viscous-plastic sea-ice models start to produce LKFs at high spatial grid resolution, typically with a grid spacing below 5km.  Besides grid spacing, other aspects of a numerical implementation, such as discretization details, may affect the number and definition of simulated LKFs. To explore these effects, simulations with different sea-ice models such as MPAS, CICE, ICON, FESOM and MITgcm are compared in an idealized configuration.

We found that the nonconforming finite-element  CD-grid discretization produces more LKFs than the CD-grid approximation based on a sub-grid discretization. Furthermore the nonconforming finite-element approach simulates the same number of LKFs as conventional Arakawa A-grid, B-grid, and C- grid methods, but on grids with less degrees of freedom ( a  coarser mesh). This is due to the fact that CD-grid approaches have a higher number of degrees of freedom to discretize the velocity field. Due to its enhanced resolving properties, CD-grid methods are an attractive alternative to conventional discretizations.