Consistent generation of ice‐streams via thermo‐viscous instabilities modulated by membrane stresses

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 20 km to 100 km, comparable with observations. These features are maintained as the grid‐size is decreased. The thermo‐viscous feedback mechanism that generates ice‐streams under the shallow ice approximation still operates, now selecting 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. Previous calculations of spontaneous ice‐stream generation using the shallow ice approximation should be reassessed.