Abstract:

Corridors of fast ice flow, Ice Streams, dominate the 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 accuracy, but for accurate future projections we need confidence that simulated ice streams will evolve in a dynamic and realistic manner. This is much harder to constrain with empirical evidence, and there is still considerable uncertainty regarding ice stream response to changes in 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. 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 magnitude and frequency scales with ice volume. We apply the idealised model to the bed of the Last Glacial Maximum Icelandic Ice Sheet, and simulated less frequent ice streams with a greater magnitude than would be expected based on the idealised case. The realistic topography makes ice stream position broadly insensitive to changes in topography and geothermal heat flux. These simulations may act as a starting point for more realistic simulations of the demise of the Icelandic Ice Sheet, and for an integrate model-data comparison approach.

All are welcome.