Date of Award

12-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Statement

Doctor of Philosophy in Geophysics

Department

Department of Geosciences

Committee Chair

Truffer, Martin

Committee Member

Fahnestock, Mark

Committee Member

Larsen, Christopher

Committee Member

Tape, Carl

Table of Contents

Chapter 1: General introduction 

Chapter 2: A century of flow and surge history of Sít’ Tlein (Malaspina Glacier), southeast Alaska

Chapter 3: 20 years of elevation change for Sít’ Tlein (Malaspina Glacier, southeast Alaska): phases of a retreat in the making.

Chapter 4: Resolving the mass continuity equation of Sít’ Tlein  (Malaspina Glacier), southeast Alaska: spatial resolution versus accuracy.

Chapter 5: General conclusions.

Abstract

Sít’ Tlein, located in southeast Alaska, is the largest piedmont glacier in the world. Periglacial lake expansion, low-lying bed, and proximity to the Pacific Ocean put its glacier lobe at risk of rapid retreat. Its disappearance would equate to removing an area of land about half the size of Rhode Island. Sít’ Tlein exhibits complex ice flow responsible for its iconic folded moraines, and for its heterogeneous ice resupply in its lobe, which occasionally surges. This lobe is gradually mantled by debris and vegetation as the ice flow fades towards its margins, protecting it from melting. This the­ sis is dedicated to cataloging and understanding this glacier’s recent history and dynamics. Chapter 1 introduces glacier flow mechanics, remote sensing, and a global perspective on current knowledge of glacier surges and Alaskan glaciers. In Chapter 2, we use historical and modern datasets, cou­ pled with novel data interpolation and decomposition techniques, to shed light on the events that shaped the glacier’s lobe in the past century. Results indicate that our data treatment techniques can streamline the analysis of a glacier by highlighting spatio-temporal patterns in the ice surface velocities. The study identifies quasi-periodic surge cycles and quantifies the oscillation of ice flow direction, enabling the focus of surge ice resupply to targeted areas of the glacier’s lobe and termi­ nus. Chapter 3 provides an analysis of the glacier lobe’s surface changes between 2000 and 2022. It reveals how ice flow, surface cover, melt features, and calving collectively impact glacier thinning and participate in its retreat. Our analysis shows that the glacier lobe is dynamically decoupled from its accumulation area, quantifies the amount of ice displaced during multiple surges, and delineates their spatial extent. Chapter 4 presents a new method to calculate the ice flux divergence from remote sensing data. This method guides the choice of resolution that balances spatial detail with acceptable uncertainty, to provide spatially resolved climatic mass balance and flux divergence. We find that computing the flux divergence for areas less than 10 km2 bears uncertainties with the same magnitude as the results. We observe that the flux divergence effects on elevation change weaken away from the glacier’s throats, leaving climatic mass balance as the dominant driver of elevation change. Overall, the lobe was found to thin at a rate of 2.72 ± 0.02 ma-1, 54.4 m in total, between 2002 and 2022. Finally, Chapter 5 summarizes discoveries and methods that helped us understand how Sít’ Tlein behaved in the past decades, while making it relevant in a global context.

Download

Share

COinS