Margin migration of ice streams

The Siple Coast ice streams are long, narrow bands of ice which are moving significantly faster than surrounding areas. At the stream margins, fast-flowing ice slows down rapidly over a short distance, causing intense shear heating. Observational evidence suggests that these margins can migrate over time. Previous research indicates that this migration results from an interplay of heating through lateral shearing, which warms the bed outside the ice stream and drives ice stream widening, and cooling through advection of cold ice from the sides of the stream, which suppresses widening. However, previous models have not provided a quantitative relationship between shear heating rate, advective heat flux and margin migration. Here we present a new boundary layer model that accounts for the mechanical and thermodynamic processes driving ice stream margin migration. Our results provide the first parametrization of ice stream migration for large scale ice sheet models.