| Accurate computation of ice-stream location and dynamics is a key aspiration for theoretical
glaciology. Ice-sheet models with thermo-viscous coupling have been shown to exhibit
stream-like instabilities using shallow-ice approximation mechanics, but the location and
width of these streams depends on the numerical implementation and are not unique. We
present results from thermo-viscously coupled ice-sheet models incorporating membrane
stresses. Spontaneous generation of fast-flowing linear features still occurs under certain
parameter regimes, with computed stream widths between 20km to 100km, comparable with
observations. These features are maintained as the grid-size is decreased. The basic
thermo-viscous feedback mechanism that generates ice-streams under the shallow ice
approximation still seems to operate, but now selects a unique stream size. Computations
of thermo-viscous ice flows should include membrane stresses when the bed is
approximately flat, e.g. parts of Antarctica and former ice-sheets of the Northern
hemisphere. Calculations using the shallow ice approximation should be reassessed. |