| Popis: |
Tidewater glaciers drain a significant proportion of the Greenland Ice Sheet and ice masses of the Canadian Arctic and provide the primary source of icebergs in Canadian waters. However, there remains uncertainty surrounding the processes controlling ice discharge from Canadian Arctic glaciers, the drift paths of icebergs in Canadian waters, and the proximity of icebergs to shipping in the region. This thesis quantifies the processes controlling glacier dynamics from four primary glacier basins on the Prince of Wales (POW) Icefield and using a multi-year dataset of iceberg drift tracks, identifies drift patterns and proximity to ships throughout the eastern Canadian Arctic. On the POW Icefield between 2009 and 2019, Cadogan and Ekblaw glaciers underwent multiyear acceleration and deceleration limited to their lower parts, consistent with characteristics of "pulse-type" glaciers. Trinity and Wykeham glaciers underwent repeating multiyear periods of velocity acceleration between 2009 and 2019 which coincided with significant thinning at their termini. As of 2017, Trinity and Wykeham were each within ~10 m of flotation over their lowermost 4 km. These findings suggest that Trinity and Wykeham glaciers have transitioned to a flow type dominated by dynamic thinning, which is strongly influenced by subglacial topography and may be susceptible to instability of the glacier front and large-scale collapse. Given that both glaciers are grounded below sea level for ~40 km up-glacier from their termini, this process could lead to significant increases in acceleration, retreat, and solid ice discharge. Using a multi-year dataset (2011-2019) of in-situ iceberg drift locations, it was found that icebergs consistently drifted southeast along the east coast of Baffin Island, controlled by a combination of local conditions including short-term wind events, ocean surface currents and semi-diurnal tidal oscillations. A test of the assumption that icebergs drift at 2% of the wind speed indicates that this rule does not apply for the majority of icebergs in this study, which typically exceeded 2% of the wind speed, particularly at low values. The highest median iceberg drift speeds occurred during the winter and spring, reaching up to 2.3 m s⁻¹ in Nares Strait. Icebergs in this study commonly became grounded near eastern Coburg Island and along the SE coast of Baffin Island, where mean residence time exceeded 180 days in all seasons. Through an analysis of a comprehensive database of ship tracks derived from AIS (automatic identification system) data in combination with a subset of iceberg drift locations derived from in-situ satellite trackers and the Canadian Ice Island Drift, Deterioration, and Detection Database (CI2D3), areas of iceberg-ship coexistence throughout Baffin Bay were identified between 2012 and 2019. The regions that saw the largest increases in iceberg-ship coexistence were along the east coast of Baffin Island and east of Bylot Island for dry bulk vessels, and northward into Smith Sound for passenger vessels. As passenger vessels commonly have little ice strengthening, this could pose an elevated hazard to vessels operating in these regions. The results of this study provide a comprehensive examination of the factors controlling glacier terminus dynamics and stability on SE Ellesmere Island, and the drift paths of icebergs once calved. This provides insights into the life cycle of icebergs in Canadian waters, how they may change in a warming climate, and the hazards that they may pose for shipping, particularly given the rapid recent increase in ship transits across the Canadian Arctic. |
