| Most sea ice models for climate type simulations are based on the viscous-plastic
(VP) rheology. The resulting stiff system of partial differential equations on ice
velocity is either solved implicitly at great computational cost, or explicitly with
added pseudo-elasticity (elastic-viscous-plastic, EVP). A recent modification of
the EVP approach seeks to improve the convergence of the EVP method by
reformulating it as a pseudotime VP solver. It is shown that convergence
is reached provided the stability requirements are satisfied and the number of
pseudotime iterations is suffciently high. Only in this limit, the VP and the
modified EVP solvers tend to converge to the same solution. Related questions
of the impact of mesh resolution and incomplete convergence additionally are
addressed. |