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Velocity variability of Devon Ice Cap tidewater glaciers Open Access


Other title
Devon Ice Cap
tidewater glacier
glacier velocity
Belcher Glacier
Canadian Arctic
Type of item
Degree grantor
University of Alberta
Author or creator
Danielson, Bradley D
Supervisor and department
Sharp, Martin (Department of Earth and Atmospheric Sciences)
Examining committee member and department
Hamilton, Gordon (Climate Change Institute & School of Earth & Climate Sciences)
St. Louis, Vincent (Biological Sciences)
Kavanaugh, Jeffrey (Department of Earth and Atmospheric Sciences)
Sanchez-Azofeifa, Arturo (Department of Earth and Atmospheric Sciences)
Department of Earth and Atmospheric Sciences

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Tidewater outlet glaciers drain approximately 47% of the ~105,000 km^2 covered by ice caps in the Queen Elizabeth Islands of Nunavut, Canada, suggesting that iceberg discharge may be an important process in the mass balance of these ice caps. Seasonal and inter-annual velocity changes of tidewater glaciers may result in the misestimation of annual or multi-year iceberg calving fluxes, if these are estimated on the basis of short-term ice velocity measurements derived from repeat satellite imagery. The aim of this study is to observe and quantify the variability of tidewater glacier velocity at a range of time scales, and to examine the processes driving these variations, with a focus on the impact of temporal and spatial variations in the delivery of surface meltwater to the glacier bed. High-frequency ice surface velocity measurements were made at four tidewater outlet glaciers of the Devon Ice Cap. Observations over three summers on Belcher Glacier revealed an annually consistent pattern of ice velocities higher than the annual mean during the 50-60 day long melt season. During this fast-flow period, surface meltwater entered the glacier via moulins and the rapid drainage of supra-glacial melt ponds and water filled crevasses. Rapid drainage events coincided with short-duration ice velocity fluctuations. Inter-annual variations in the magnitude of the enhanced velocity in summer and the velocity variability during the fast-flow period were linked to factors which affect the rate and timing of meltwater delivery to the subglacial drainage system, such as variations in spring snowpack thickness and the degree of variability in late summer meltwater production. The effective contribution to the annual displacement resulting from enhanced velocities during the summer melt season was only ~5-8% at the glacier terminus, due to the relatively short duration of the fast-flow period. On the lower 5-8 km of the Belcher Glacier and North Croker Glacier, multi-year changes in annual mean velocity were observed that were not clearly linked to inter-annual variations in the amplitude and/or timing of the seasonal velocity cycle. Because of their flow mechanics, these glaciers may be poised to respond extremely sensitively to even minor long-term changes in driving stress. For such glaciers, it may be extremely difficult to identify any obvious external forcing for relatively large, long-term changes in velocity and rates of iceberg discharge. Overall, the results provide a demonstration of the seasonal bias that may be expected in different zones of the Devon Ice Cap if annual mean glacier velocities are estimated from velocity measurements made over periods less than a full annual cycle.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Danielson, B. D. and M. J. Sharp 2013. Development and application of a time-lapse photograph analysis method to investigate the link between tidewater glacier flow variations and supraglacial lake drainage events. Journal of Glaciology 59(214), 287-301.

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