mean temperature to provide an estimate of annual mean temperatures: . This example assumes the ice shelf 's surface is as cold as at 1000m altitude. Precipitation is directly tied to air temperature, and also depends on moisture above and around the ice sheet. Precipitation plays an important part in ice-sheet melting and accumulation. Calving Calving is still an active area of investigation in ice-sheet modelling. A total picture of calving will include many different aspects, including but not limited to tides, basal crevasses, collisions with ice bergs, thickness and temperature. The recent development of the concepts of Marine Ice Sheet Instability and Marine Ice Cliff Instability have contributed to more accurate results of ice-sheet calving processes. Examples CISM The Community Ice Sheet Model is part of the Community Earth Systems Model funded by the National Science Foundation and models ice dynamics. It is written in Fortran 90 and is open-source. The US Department of Energy has begun to contribute to CISM. The CISM project works on other adjacent projects in developing a cirriculum to expand knowledge on ice sheets, and engaging a broader community in ice-sheet modelling. Many ice-sheet modelling softwares have influenced CISM, including the Parallel Ice Sheet Model (PSIM) and Glimmer. seaRISE Sea-level Response to Ice Sheet Evolution (SeaRISE) is a subcommunity of CISM that sets out to estimate the upper limit of sea level rise from ice sheets. The project sets out to develop a set of experiments and assessments for ice sheet and sea level rise modelling, as well as make a unified input dataset for ice sheet models. Glimmer Glimmer (GENIE Land Ice Model with Multiply-Enabled Regions) is an ice-sheet model initially made to contribute to a more comprehensive earth system model, GENIE. PISM The Parallel Ice Sheet Model is an open-sourced 3D ice sheet model capable of high resolution. PISM is written in C++ and Python, and takes NetCDF files as input for the model. PISM uses a "SIA+SSA hybrid" model, using both the shallow shelf approximation and shallow ice approximation models as stress balance models and does not solve full Stokes equations. The model gets climatic information from an external General Circulation Model, and needs information like boundary temperature, mass flux into the ice, precipitation and air temperature. A horizontal grid of equal distance is used, with a variable vertical axis, and runs on a year timescale. See also Biosphere model Ice-sheet