Strain-Induced Fabric Development in Ice Under Hydrostatic Pressure

Understanding the flow rate of ice is critically important for climate reconstruction and for predicting the fate of the earth's large ice sheets under climate change scenarios. Numerous studies have shown that fabric development plays a crucial role in determining flow rate, and the importance of understanding the processes that underlie fabric development is generally recognized. Thus, the aim of this project is to understand fabric formation in ice sheets. Our working hypothesis is that slipping grains can propagate without requiring their recrystallization, and that this process is closely associated with anisotropy in grain boundary mobility during deformation. To seek evidence of these mechanisms, we are performing the following series of laboratory observations on granular freshwater ice:

  1. Conducting confined compression experiments at low deviatoric stresses and a range of pressure and temperature to develop a preferred c-axis orientation and produce grain growth.
  2. Using standard techniques to document c-axis orientations, grain size and shape of the deformed microstructures for several temperatures and shear stress levels.
  3. Employing electron backscatter pattern (EBSP) analysis to document a- and c-axis orientations of slipping and abutting grains in the deformed material.
  4. Using surface etching to identify slip line arrays in the deforming grains, and couple these observations with the grain boundary structures observed in the EBSP results.

This series of observations will allow us to determine whether and to what extent the various proposed grain growth mechanisms operate, and support the development of physically-based models of the development of preferred lattice orientations in deforming ice masses.

Funded by the National Science Foundation, Arctic Natural Sciences