Quoted from: https://www.cesm.ucar.edu/models/cesm1.2/cism/docs/CESM_ice_sheets_documentation.pdf 

        Glimmer-CISM is a thermomechanical ice sheet model that solves the equations of ice flow, given suitable approximations and boundary conditions. The source code is written primarily in Fortran 90 and 95. The model resides on the BerliOS repository (http://glimmer-cism.berlios.de/), where it is under active development. The version targeted for CESM is developed on an NCAR Subversion repository (https://svn-cism-model.cgd.ucar.edu/). The ice-sheet model in CESM consists primarily of source code from Glimmer-CISM version 1.9.

        The dynamical core of the model, known as GLIDE, solves equations (1)–(3) for the conservation of mass, momentum, and internal energy. The version of GLIDE currently in CESM uses the shallow-ice approximation. However, a higher-order model is under development and will be included in future releases.

        The surface boundary conditions (e.g., the surface temperature and surface mass balance) are supplied by a climate driver. When Glimmer-CISM is run in CESM, the climate driver is GLINT, which receives the temperature and SMB from the coupler and downscales them to the ice-sheet grid. The lower boundary conditions are given by an isostasy model, which computes the elevation of the lower surface, and by a geothermal model, which supplies heat fluxes at the lower boundary.

        The model currently has simple treatments of basal hydrology and sliding. More complex schemes for subglacial water hydrology and evolution of basal till strength are being developed. Glimmer-CISM also provides several simple schemes for calving at the margins; these will be replaced by more realistic lateral boundary conditions in the future.

        For a detailed description of Glimmer-CISM’s dynamical core and software design, see Rutt et al. (2009) and the latest model documentation.