A study of microfabric and structures in glacial ice: insights from Storglaciären, northern Sweden
type: CreativeWork
description: Better understanding of the flow of ice is essential for helping to predict and adapt to the global mean sea level rise in the coming decades and centuries. Flow produces internal structures and fabrics in glaciers that in turn influence the flow. Documenting and understanding the internal structure of glaciers is thus important for understanding how glaciers behave and respond to changing conditions. This thesis focuses on establishing the significance of commonly described but enigmatic crystallographic ice fabrics and associated structures, with specific examples taken from Storglaciären, a small, polythermal valley glacier in northern Sweden. Characteristic microstructures in deformed ice in valley glaciers and at the base of ice sheets include large, irregularly shaped interlocking grains with no clear shape-preferred orientation, little internal distortion, and c-axis crystallographic preferred orientations (CPOs) defined by several maxima. Such fabrics develop in warm ice (T> -10 o C). They are difficult to quantify and interpret in part because the large grain size and interlocking texture creates issues with quantifying the true size and shape of individual crystals, and thus with determining a representative CPO. All but one previous study have analyzed these fabrics using techniques that can only measure c-axis orientations and thus partial CPOs. A newly developed sample preparation method allows for the first use of electron backscatter diffraction (EBSD) on such coarse-grained ice, which then provides high accuracy measurements of full crystallographic orientations (c- and a-axis measurements). Both EBSD and the older Rigsby stage optical technique (c-axis only) are used in this study and this allows for comparison of the two methods and the results of this study with the results of previous work. In all samples analyzed from Storglaciären, the ice has been entirely recrystallized by dynamic recrystallization accommodated by grain boundary migration. Th…
abstract: Better understanding of the flow of ice is essential for helping to predict and adapt to the global mean sea level rise in the coming decades and centuries. Flow produces internal structures and fabrics in glaciers that in turn influence the flow. Documenting and understanding the internal structure of glaciers is thus important for understanding how glaciers behave and respond to changing conditions. This thesis focuses on establishing the significance of commonly described but enigmatic crystallographic ice fabrics and associated structures, with specific examples taken from Storglaciären, a small, polythermal valley glacier in northern Sweden. Characteristic microstructures in deformed ice in valley glaciers and at the base of ice sheets include large, irregularly shaped interlocking grains with no clear shape-preferred orientation, little internal distortion, and c-axis crystallographic preferred orientations (CPOs) defined by several maxima. Such fabrics develop in warm ice (T> -10 o C). They are difficult to quantify and interpret in part because the large grain size and interlocking texture creates issues with quantifying the true size and shape of individual crystals, and thus with determining a representative CPO. All but one previous study have analyzed these fabrics using techniques that can only measure c-axis orientations and thus partial CPOs. A newly developed sample preparation method allows for the first use of electron backscatter diffraction (EBSD) on such coarse-grained ice, which then provides high accuracy measurements of full crystallographic orientations (c- and a-axis measurements). Both EBSD and the older Rigsby stage optical technique (c-axis only) are used in this study and this allows for comparison of the two methods and the results of this study with the results of previous work. In all samples analyzed from Storglaciären, the ice has been entirely recrystallized by dynamic recrystallization accommodated by grain boundary migration. Th…
author: Monz, Morgan
language: en
keywords: Crystallographic preferred orientation (CPO), electron backscatter diffraction, faulting, glacier, microstructure, Storglaciären
date published: 2021-06
date modified: 2026-07-24T05:19:54Z
provider: University of Minnesota
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Minnesota

PropertyValue
property ID: Handle
value: https://hdl.handle.net/11299/224664