  Discretization of the equations of Viscous Plastic and Elastic Viscous
Plastic (EVP) sea ice dynamics on triangular meshes can be done by placing
discrete velocities at vertices, cells or edges. Since there are more cells and
edges than vertices, the cell- and edge-based discretizations simulate more
linear kinematic features at the same mesh than the vertex discretization.
However, the discretization based on cell and edge velocities suffer from
kernels in the strain rate or stress divergence operators and need either
special strain rate computations as proposed here for cell velocities, or
stabilization as proposed earlier for edge velocities. An elementary Fourier
analysis clarifies how kernels are removed, and also shows that cell and edge
velocity placement leads to spurious branches of stress divergence operator
with large negative eigenvalues. Although spurious branches correspond to fast
decay and are not expected to distort sea ice dynamics, they demand either
smaller internal time steps or higher stability parameters in explicit EVP-like
methods.
