Tertiary creep rates of temperate ice containing greater than 0.7% liquid water

Accurately modeling the deformation of temperate glacier ice, which is at its pressure-melting temperature and contains liquid water at grain boundaries, is essential for predicting ice sheet discharge to the ocean and associated sea-level rise. Central to such modeling is Glen’s flow law, in which strain rate depends on stress raised to a power of n=3-4. In sharp contrast to this nonlinearity, we find by conducting large-scale, shear-deformation experiments to tertiary creep that temperate ice is linear-viscous (n≈1.0) over common ranges of liquid water content and stress expected near glacier beds and in ice stream margins. This linearity is likely caused by diffusive pressure-melting and refreezing at grain boundaries and could help stabilize modeled responses of ice sheets to shrinkage-induced stress increases.