On the Damping Time Scale of EVP Sea Ice Dynamics

We propose to make the damping time scale, which governs the decay of pseudo‐elastic waves in the Elastic Viscous Plastic (EVP) sea‐ice solvers, independent of the external time step and large enough to warrant numerical stability for a moderate number of internal time steps. A necessary condition is that the forcing on sea ice varies slowly on the damping time scale, in which case an EVP solution may still approach a Viscous Plastic one, but on a time scale longer than a single external time step. In this case, the EVP method becomes very close to the recently proposed modified EVP (mEVP) method in terms of stability and simulated behavior. In a simple test case dealing with sea ice breaking under the forcing of a moving cyclone, the EVP method with an enlarged damping time scale can simulate linear kinematic features which are very similar to those from the traditional EVP implementation, although a much smaller number of internal time steps is used. There is more difference in sea‐ice thickness and linear kinematic features simulated in a realistic Arctic configuration between using the traditional and our suggested choices of EVP damping time scales, but it is minor considering model uncertainties associated with choices of many other parameters in sea‐ice models. Plain Language Summary Numerical simulations of sea ice in ocean or climate models most frequently rely on the Elastic Viscous Plastic (EVP) method. Computational expenses of this method depend on its internal time step which is limited by the requirements of numerical stability. It is shown that some adjustment of dissipation time scale in the EVP method allows the time scale to be increased, thereby reducing the numerical costs without sacrificing the results of simulations. Key Points Elastic Viscous Plastic (EVP) stability can be improved by proper selection of the time scale governing the decay of elastic waves A significant reduction of the required number of EVP sub‐cycles can be achieved on high‐resolution meshes EVP and the modified EVP simulate very similar sea‐ice thickness and concentration