The Utrecht Finite Volume Ice-Sheet Model: UFEMISM (version 1.0)

Abstract. Improving our confidence in future projections of sea-level rise requires models that can simulate ice-sheet evolution both in the future and in the geological past. A physically accurate treatment of large changes in ice-sheet geometry requires a proper treatment of processes near the margin, like grounding line dynamics, which in turn requires a high spatial resolution in that specific region. This leads to a demand for computationally efficient models, where such a high resolution can be feasibly applied in simulations of 10⁵–10⁷ yr in duration. Here, we present and evaluate a new ice-sheet model that solves the SIA and SSA approximations of the stress balance on a fully adaptive, unstructured triangular mesh. This strongly reduces the number of grid points where the equations need to be solved, increasing the computational efficiency. We show that the model reproduces the analytical solutions or model intercomparison benchmarks for a number of schematic ice-sheet configurations, indicating that the numerical approach is valid. Because of the unstructured triangular mesh, the number of vertices increases less rapidly with resolution than in a square-grid model, greatly reducing the required computation time for high resolutions. A simulation of all four continental ice sheets during an entire 120 kyr glacial cycle, with a 4 km resolution near the grounding line, is expected to take 100–200 wall clock hours on a 16-core system (1,600–3,200 core hours), implying that this model can be feasibly used for high-resolution paleo-ice-sheet simulations.