Determining the Influence of Lateral Margin Mechanical Properties on Glacial Flow

• Main Author: Hruby, Kate
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2019
• Subjects: flow modeling; glacier modeling; ice; margin; fabric; temperature; Dynamic Systems; Glaciology; Mineral Physics; Numerical Analysis and Computation; Jarvis Glacier; glacier; glaciers; Alaska
• Online Access: https://digitalcommons.library.umaine.edu/etd/2955; https://digitalcommons.library.umaine.edu/context/etd/article/4030/viewcontent/Hruby__Kate_Final_4.16.2019.pdf

The lateral margins of glaciers and ice streams play a significant role in glacial flow. Depending on their properties, like temperature and ice crystal orientation, they can cause a resistance to flow or enhance it. In combination with our current changing climate, flow patterns can dictate the mass balance of an ice body. It is therefore more important than ever to understand the impact that variations at the margins can have on flow. However, the lateral margins of glaciers and ice streams are an often-neglected part of ice dynamics; they are harder to sample than the center of a glacier’s flow path because of debris and crevassing, so we have little data about them. We are attempting to change that. To assess the sensitivity of flow to material properties of the ice, I join computer modeling with measurements taken on the lateral margin of a mountain glacier. My sensitivity analysis is two-fold: 1) I combine synthetic geometries and parameters to provide conclusions regarding the effect lateral margins have on glacier flow, and 2) I use properties of Jarvis Glacier, Alaska as a case study for the input of in situ fabrics and temperatures into my model. In complementary work, we have measured the geometry and velocity of Jarvis Glacier, Alaska, as well as the thermal profile and crystal orientation at two locations 25 m and 100 m from the lateral margin. This access to a realistic scenario provides a reference for the sensitivity tests, allowing us to understand what parameters have the greatest impact on 3D glacial velocity. In the following chapters, the questions I address in depth are: 1) to what extent do ice crystal fabric and temperature in the lateral margins matter in determining glacial flow, and 2) have we accurately captured the essential mechanics of these parameters and their relationship to flow? Results show that while Jarvis’s warm lateral margin temperatures do alter flow, the glacier’s weakly-oriented fabric does not. However, if the ice crystals in a glacier were more oriented than they ...