Origins of foliations and related phenomena in valley glaciers and ice sheets

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Student thesis: Doctoral ThesisDoctor of Philosophy

Original languageEnglish
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  • Natural Environment Research Council
Award date17 Feb 2017
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Abstract

This study examines how longitudinal foliation develops in glaciers and ice sheets in a wide range of topographic, climatic, and dynamic settings, at a variety of spatial scales. Study locations include four valley glaciers in Svalbard (Austre Brøggerbreen, Midtre Lovénbreen, Austre Lovénbreen, and Pedersenbreen), a valley glacier in Canada (Sermilik Glacier), and seven outlet glaciers in Antarctica (Hatherton Glacier, Taylor Glacier, Ferrar Glacier, Lambert Glacier, Recovery Glacier, Byrd Glacier, and Pine Island Glacier). Detailed structural mapping of the valley glaciers from satellite imagery and field-based measurements were used to document the formation of longitudinal foliation in small-scale ice masses. These findings were ‘up-scaled’ and applied to much larger glaciers and ice streams. Longitudinal foliation develops in concentrated bands at flow unit boundaries as a result of enhanced simple shear. However, longitudinal foliation is not directly observable from satellite imagery at the surface of larger-scale valley glaciers. The longitudinal structures visible at the surface of larger-scale glaciers form at flow unit boundaries and are composed of bands of steeply dipping longitudinal foliation; however, they appear as individual linear features on satellite imagery as a result of the comparatively low spatial resolution of the imagery. The persistence of flowlines in the Antarctic Ice Sheet through areas of crevassing and net ablation (blue-ice areas) suggests that they are the surface representation of a threedimensional structure. Flowlines are therefore inferred to be the surface expression of flow unit boundaries composed of bands of steeply dipping longitudinal foliation. The survival and deformation of flowlines in areas of ice flow stagnation indicates that flowlines form in their initiation zones and not along their entire length. Furthermore, these ice stagnation areas indicate that flowlines record past ice dynamics and switches in ice flow.