A comparison of viscous-plastic sea ice solvers with and without replacement pressure. (July 2017)

• Record Type: Journal Article
• Authors: Kimmritz, Madlen; Losch, Martin; Danilov, Sergey
• Is Part Of: Ocean modelling. Volume 115(2017:Jul.)
• Page Start: 59
• Page End: 69
• Publication Date: 2017-07
• Subjects: Sea ice -- VP rheology -- EVP rheology -- MITgcm -- Adaptive relaxation parameter -- JFNK -- Replacement pressure; 00-01 -- 99-00; Oceanography -- Periodicals; Océanographie -- Périodiques; Oceanography; Periodicals; 551.46
• DOI: 10.1016/j.ocemod.2017.05.006
• Languages: English
• ISSNs: 1463-5003

Abstract

Highlights: Comparison of mEVP and aEVP in realistic setting, JFNK solutions as reference. Convergence rates of aEVP generally similar or even better than those of mEVP. In practice, aEVP and mEVP can be used efficiently with very few subcycling steps. Convergence of aEVP, mEVP, JFNK depend dramatically on use of replacement pressure RP. Resultant effects of RP reducable at cost of stiffer equations and thus higher costs. Abstract: Recent developments of the explicit elastic-viscous-plastic (EVP) solvers call for a new comparison with implicit solvers for the equations of viscous-plastic sea ice dynamics. In Arctic sea ice simulations, the modified and the adaptive EVP solvers, and the implicit Jacobian–free Newton–Krylov (JFNK) solver are compared against each other. The adaptive EVP method shows convergence rates that are generally similar or even better than those of the modified EVP method, but the convergence of the EVP methods is found to depend dramatically on the use of the replacement pressure (RP). Apparently, using the RP can affect the pseudo-elastic waves in the EVP methods by introducing extra non-physical oscillations so that, in the extreme case, convergence to the VP solution can be lost altogether. The JFNK solver also suffers from higher failure rates with RP implying that with RP the momentum equations are stiffer and more difficult to solve. For practical purposes, both EVP methods can be used efficiently with an unexpectedly low number of sub-cycling steps without compromising the solutions. The differences between the RP solutions and the NoRP solutions (when the RP is not being used) can be reduced with lower thresholds of viscous regularization at the cost of increasing stiffness of the equations, and hence the computational costs of solving them.