PISM consists of several sub-models corresponding to various physical processes and parameterizations. In short, these are
Ice dynamics and thermodynamics (stress balance, ice rheology, mass and energy conservation, ice age)
Subglacial processes (hydrology, basal strength, bed deformation)
Marine ice-sheet modeling (parameterization of calving processes, calving front advance and retreat, iceberg removal)
All these sub-models are controlled by command-line options and configuration parameters.1
In additions to this, one has to choose the computational grid, the modeling domain, and so on.
This section describes how to understand and make these modeling choices.