Title: Triggers of Rapid Change in Glacier Dynamics
Abstract: Global ice mass loss and subsequent sea level rise is dominated by mass loss from the fast-flowing outlet glaciers and ice streams that drain the Greenland and Antarctic ice sheets. For the outlet glaciers, changes to their dynamics (flow speed, thickness, and length) dominate their present and future mass loss. One of the main limitations in predicting future glacier mass loss under future emissions scenarios is the lack of representation of glacier instabilities in global models. Global glacier models still do not adequately represent the processes that govern the development of instabilities from perturbations at the ice-rock and ice-ocean interfaces (glacier bed and terminus, respectively) due to knowledge gaps that arise, in part, from the difficulty of directly observing these interfaces. For this dissertation, I developed automated methods for processing large remote sensing datasets to observe changes in glacier dynamics at fine spatial and temporal scales. Analysis of the automated glacier change observations for southeast Greenland and Alaska revealed complexity in the interplay of external (environmental) and internal factors that influence glacier dynamics at sub-seasonal to multi-year timescales. The studies presented in this dissertation were the first to show that (1) the mountain glaciers in Greenland can undergo anomalous, synchronous retreat in response to an annual surface melt anomaly and that (2) surging glaciers can undergo annual order-of-magnitude speedups outside of their surges, challenging the traditional definition of the quiescent phase. The annual speedups were linked to seasonal evolution of the glacier hydrological system and were primarily driven by surface meltwater input modulated by summer air temperatures. The studies revealed that glaciers respond to environmental perturbations on shorter timescales than previously thought. My work demonstrates that analyzing glacier change with greater spatial and temporal resolution can lead to improved understanding of the physical processes that drive glacier dynamics.
Advisor: Ellyn Enderlin
Committee Members: Dylan Mikesell, HP Marshall, Christine Dow