Simulations of Ice Stream Size and Frequency Scaling with Ice Sheet Radius

Corridors of fast ice flow, ice streams, dominate the mass discharge of contemporary ice sheets. Ice streams are points of vulnerability for ice sheet instabilities, and so to understand past and future ice sheet change we need to understand ice stream behaviour. Computer simulations can replicate the position and magnitude of palaeo and contemporary ice streams with some skill, but for accurate future projections of ice mass change we need confidence that simulated ice streams will evolve and adjust to a retreating ice sheet in a realistic manner. This is much harder to constrain with empirical evidence, and there is still considerable uncertainty regarding ice stream response to changes in wider ice sheet geometry.

 

To explore the behaviour of simulated ice streams on a fundamental level, we run simulations of a circular ice sheet on a flat bed using the BISICLES numerical ice sheet model. We simulate a series of idealised circular ice sheets of various radii, finding that plausible ice stream spacing and magnitude is simulated even on a flat bed, and that ice stream size and frequency scales with ice volume. We apply the idealised model to the bed of the Last Glacial Maximum Icelandic Ice Sheet, resulting in a simulation with less frequent ice streams, each with a greater size than would be expected based on the idealised case. The realistic topography makes ice stream position broadly insensitive to changes in topographic roughness and geothermal heat flux. These simulations provide increased confidence in the ability of ice sheet models to simulate dynamic ice stream change and could act as a starting point for more realistic simulations of the advance and retreat of the last Icelandic Ice Sheet.