Master's Thesis Defence | Michael Willette, Modelling the Subglacial Hydrology of Trinity-Wykeham Glaciers of the Northern Canadian Arctic

QNC 2101

Candidate

Michael Willette | Applied Mathematics, University of Waterloo

Title

Modelling the Subglacial Hydrology of Trinity-Wykeham Glaciers of the Northern Canadian Arctic

 Abstract

In Canada’s High Arctic region, the melting of glacial ice contributes substantially to the world’s increasing sea levels (Harig and Simons, 2016). Of the icebergs in the region, approximately 62\% are discharged by Trinity-Wykeham Glaciers. In the last twenty years, these glaciers have retreated approximately 5 km, also doubling in speed and tripling in iceberg production during that period (Van Wychen et al., 2016). It is argued that warming air temperatures are the primary cause of glacial retreat and consequently sea level rise in the Canadian High Arctic region (Cook et al., 2019). This is because the warmer air causes ice on the surface of glaciers to melt at a higher rate. This meltwater is routed to the base of the ice, where it can directly impact the glacier’s velocity. If the water spreads into high-pressure cavities over a large enough area, the ice can often accelerate. However, if the water input is great enough to form large, low-pressure channels at the base of the glacier, water will be drawn from the higher-pressure regions and the ice will often decelerate (Iken and Bindschadler, 1986).

The Glacier Drainage System (GlaDS) subglacial hydrology model (Werder et al., 2013) is used to examine the development of hydrological networks at the base of Trinity-Wykeham Glaciers in response to variable surface melt rates between 2016 and 2019. GlaDS couples distributed and channelized subglacial drainage, allowing the mathematical model to capture the spatiotemporal evolution of the subglacial drainage system. The interplay between these two modes of drainage is highly influential on glacier dynamics. Satellite-derived datasets are used as inputs to the model, including basal and surface topography, surface velocities, and daily ice surface runoff products. Model outputs including subglacial water sheet thickness, water pressure, and channel discharge are compared to satellite-derived glacier surface velocities to determine how subglacial hydrology affects Trinity-Wykeham Glaciers. Nine model runs are completed to gauge the sensitivity of the GlaDS model to variations in two poorly constrained parameters that control the ease of subglacial water flow and determine a practical range of values for these parameters in future studies.

The results of this project suggest that Trinity-Wykeham Glaciers' velocities are directly influenced by surface melting rates and the configuration of the subglacial hydrology networks. Model outputs indicate that high subglacial water pressures cause acceleration at Trinity-Wykeham Glaciers and that with a sufficiently high influx of water to the bed, an efficient channelized drainage network develops that reduces local water pressures and causes a drop in flow velocity. The year 2018 is identified as a year in which channelized drainage is minimal, resulting in comparatively high water pressures and velocities after the melt season.