In climate modelling, Ice-sheet models use numerical methods to simulate the evolution, dynamics and thermodynamics of ice sheets, such as the Greenland ice sheet, the Antarctic ice sheet or the large ice sheets on the northern hemisphere during the last glacial period. They are used for a variety of purposes, from studies of the glaciation of Earth over glacial–interglacial cycles in the past to projections of ice-sheet decay under future global warming conditions. History Beginning in the mid-18th Century, investigation into ice sheet behavior began. Since the Journal of Glaciology's founding, physicists have been publishing glacial mechanics. The first 3-D model was applied to the Barnes Ice Cap. In 1988, the first thermodynamically coupled model incorporating ice-shelves, sheet/shelf transition, membrane stress gradients, isotatic bed adjustment and basal sliding using more advanced numerical techniques was developed and applied to the Antarctic ice sheet. This model had a resolution of 40 km and 10 vertical layers. When the first IPCC assessment report came out in 1990, ice sheets were not an active part of the climate system model, their evolution was based on a correlation between global temperature and surface mass balance. When the second IPCC assessment report came out in 1996, the beginning of both 2D and 3D modelling was shown with ice sheets. The 1990s heralded several more computational models, bringing with it the European Ice Sheet Modelling Initiative (EISMINT). The EISMINT produced several workshops throughout the 1990s of an international collaboration, comparing most models of Greenland, Antarctic, ice-shelf, thermomechanical and grounding-line. The 2000s included integrating first-order approximation of full Stokes Dynamics into an ice-sheet model. The fourth IPCC assessment report showed ice-sheet models with projections of rapid dynamical responses in the ice, which led to evidence of significant ice loss. In 2016, part of the Coupled Model Intercomparison Project Phase 6 (CMIP Phase 6) was the Ice Sheet Model Intercomparison Project, which defined a protocol for all variables related to ice sheet modelling. The project allowed for both improvement in numerical and physical approaches to ice sheets. Modelling Ice-Flow Shallow Ice Approximation Shallow Ice Approximation (SIA) is a simple method to model ice flow without having to solve full-Stokes equations. The approximation is best applied to ice sheet with a small depth-to-width ratio, without many sliding dynamics and a simple bed topography. SIA does not include many forces on an ice sheet, and can be considered a 'zero-order' model.