Laboratory observations of the high temperature creep of polycrystalline ice

The largest source of uncertainty in predictions of future sea level is the contribution arising from the discharge of ice from the polar ice sheets. A key factor in reducing this uncertainty is to improve the numerical models used to predict ice sheet evolution. One important aspect of model development is to improve the constitutive relationship that describes the rheological properties of ice.

Factors influencing creep deformation rates include: the magnitudes of the stresses causing ice to deform; strain-induced anisotropy of polycrystalline ice, and temperature. Creep rates at high temperatures, within 2 degrees (K) of the melting point, are constrained by a relatively small number of laboratory observations due to the inherent difficulties in conducting experiments at such temperatures.

We present results from a series of laboratory ice deformation experiments conducted in simple shear at temperatures between -2°C and -0.3°C at 0.1 MPa (octahedral shear stress). Unlike previous experimental studies conducted at temperatures close to the melting point, these experiments were continued through to high shear strains (>10% strain) to ensure that anisotropic flow, compatible with the stress configuration, had developed.

These data contribute to the continued development of a constitutive relationship for polycrystalline ice that will improve the accuracy of ice sheet models and are relevant to model studies utilizing inverse methods to infer the spatial extent of basal sliding.