Flow law for ice in polar ice sheets

Theories of glacier flow are based commonly on the assumption that ice is not a newtonian fluid, but has a non-linear stress-dependent viscosity 1–5 . Here we re-examine the spreading of Antarctic ice shelves and suggest that the data cannot define a unique flow law. Tilt measurements in four boreholes in both the Arctic and Antarctic seem to show that a linear flow law ε̇ = A 1 τ (where A 1∼10 −15 s −1 Pa −1 at −28 °C), where ε̇ is the effective strain rate and τ the effective shear stress, may be just as appropriate for describing the flow of polar ice sheets.