GRANTISM: An ExcelTM model for Greenland and Antarctic ice-sheet response to climate changes

Over the last decades, the response of large ice sheets on Earth, such as the Greenland and Antarctic ice sheets, to changes in climate has been successfully simulated with large-scale numerical ice-sheet models. Since these models are highly sophisticated, they are only applicable on the scientific level as they demand a large amount of CPU time. Based on similar physics, a computationally fast flowline model of the Greenland and Antarctic ice sheet is presented here, primarily designed for educational purposes. Using an over-implicit numerical scheme, the model runs fast and behaves in a similar way to changes in background temperature forcing as major ice-sheet models do. A user-friendly interface and the implementation within a common spreadsheet program (ExcelTM) make the model suitable for the classroom.