Ice viscosity is more sensitive to stress than commonly assumed

Accurate representation of the viscous flow of ice is fundamental to understanding glacier dynamics and projecting sea-level rise. Ice viscosity is often described by a simple but largely untested and uncalibrated constitutive relation, Glen's Flow Law, wherein the rate of deformation is proportional to stress raised to the power n. The value n = 3 is commonly prescribed in ice-flow models, though observations and experiments support a range of values across stresses and temperatures found on Earth. Here, we leverage recent remotely-sensed observations of Antarctic ice shelves to show that Glen's Flow Law approximates the viscous flow of ice with n = 4.1 +/- 0.4 in fast-flowing areas. The viscosity and flow rate of ice are therefore more sensitive to changes in stress than most ice-flow models allow. By calibrating the governing equation of ice deformation, our result is a pathway towards improving projections of future glacier change. The rate of deformation in Antarctic ice shelves is proportional to stress to the power of 4, not 3 as often used in models, according to a calibration of Glen's Flow Law with satellite remote sensing data from Antarctic ice shelves.

Automated summary

Accurately representing the viscous flow of ice is crucial for understanding glacier dynamics and predicting sea-level rise. Glen's Flow Law, a constitutive relation often used to describe ice viscosity, is typically represented by a constant value of n=3, but observations and experiments support a range of values across different stresses and temperatures. This study utilizes remote sensing data of Antarctic ice shelves to show that the viscous flow of ice in fast-flowing areas can be approximated by Glen's Flow Law with n=4.1±0.4, indicating that the viscosity and flow rate of ice are more sensitive to changes in stress than commonly assumed in ice-flow models.