Description and Evaluation of the Community Ice Sheet Model(CISM) v2.1

Abstract. We describe and evaluate version 2.1 of the Community Ice Sheet Model (CISM).CISM is a parallel, 3-D thermomechanical model, written mainly in Fortran,that solves equations for the momentum balance and the thickness andtemperature evolution of ice sheets. CISMu0027s velocity solver incorporates ahierarchy of Stokes flow approximations, including shallow-shelf,depth-integrated higher order, and 3-D higher order. CISM also includes asuite of test cases, links to third-party solver libraries, andparameterizations of physical processes such as basal sliding, icebergcalving, and sub-ice-shelf melting. The model has been verified for standardtest problems, including the Ice Sheet Model Intercomparison Project forHigher-Order Models (ISMIP-HOM) experiments, and has participated in theinitMIP-Greenland initialization experiment. Inmultimillennial simulations with modern climate forcing on a 4 km grid, CISMreaches a steady state that is broadly consistent with observed flow patternsof the Greenland ice sheet. CISM has been integrated into version 2.0 of theCommunity Earth System Model, where it is being used for Greenlandsimulations under past, present, and future climates. The code is open-sourcewith extensive documentation and remains under active development.