Steady State Convergence Limited By Ethalpy Diffusivity Discontinuity #3
Description
Per communication with Adrien Gilbert, the enthalpy solver in Elmer can only achieve steady-state convergence with a tolerance of 1e-3 or 1e-4. Adrien has suggested the lack of convergence is due to the discontinuity in the enthalpy diffusivity between cold and temperate ice.
The discontinuous enthalpy diffusivity has caused problems in other ice-sheet model, ISSM dealt with the problem by implementing a solver specific stabilization method (Ruckamp et al, 2020). This is out of the scope of what we can do in Elmer on our timescale.
A simpler approach might be fitting a smooth function between the cold and temperate diffusivity as a form of regularization (see Wilson and Flowers, 2013).