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"Investigating the Impacts of Impurities and Stress State on the Flow and Microstructural Evolution of Polycrystalline Ice"

Abstract

Understanding the behavior of glaciers and ice sheets is crucial for interpreting ice core records to comprehend past climates and predicting their future contributions to sea level rise. Ice deformation, influenced by numerous factors, including temperature, stress and impurities, is a critical aspect of glacier and ice sheet behavior. Natural polycrystalline ice contains an array of soluble and insoluble impurities as evidenced by ice core records, and variations in impurity concentrations have been associated with variations in deformation rates in ice sheets. While there has been an extensive body of research conducted on the physical and mechanical properties of pure polycrystalline ice, our understanding of the microstructural processes involved and effects of impurities on ice deformation remains limited. Previous research has shown that sulfuric acid decreases the strength and increases the creep rate of single crystals and polycrystals of ice but the effects of grain boundaries on the increased creep rate are unclear.

In addition, ice in ice sheets is subjected to various stresses, including compressive stresses caused by the weight of overlying ice, tensile stresses near the edges of ice sheets, and shear stresses at the base and along the margins of ice sheets. However, it is unclear what direct impacts different stress states, particularly simple shear have on the microstructural processes involved during ice deformation.

This proposal aims to answer three key questions related to polycrystalline ice:

1. How does sulfuric acid at concentrations applicable to polar ice sheets impact mechanical behavior?
2. How does sulfuric acid affect recrystallization, grain growth and fabric development?
3. How do different stress states, particularly simple shear in comparison to uniaxial compression affect viscosity and fabric evolution?

To address these questions, uniaxial compression creep tests and simple shear tests will be conducted on laboratory-prepared specimens of polycrystalline ice. Post-mortem microstructural analyses will be performed using polarized light thin-section imaging, electron backscatter diffraction, X-ray computed microtomography, Raman spectroscopy and energy dispersive spectroscopy.

This research aims to fill the knowledge gaps regarding ice core thinning and contribute to our understanding of past and future changes in polar regions.

Thesis Committee

• Ian Baker, PhD (Chair)
• Colin Meyer, PhD
• Mary Albert, PhD
• TJ Fudge, PhD

Contact

For more information, contact Theresa Fuller at theresa.d.fuller@dartmouth.edu.