The distribution of basal motion beneath a High Arctic polythermal glacier

L Copland, MJ Sharp, P Nienow, RG Bingham

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)


The longitudinal pattern of surface velocity of a large, predominantly colds polythermal glacier (John Evans Glacier, Ellesmere Island, Canada) was measured over summer and winter periods. In the accumulation and upper ablation areas, where ice is predominantly cold-based, summer velocities were slightly higher than overwinter velocities. Predicted velocities due to ice deformation alone in these areas closely matched these observations in the winter, with limited basal motion likely in the summer. In the lower ablation area, where ice is likely warm-based, measured summer velocities were up to double overwinter velocities. Predicted ice deformation could not account for all of these measured velocities in either summer or winter. This suggests that basal motion occurs throughout the year over at least part of the lower ablation area. This finding is supported by radio-echo sounding, subglacial drainage reconstructions and analyses of early-summer meltwater chemistry, which suggest that subglacial water is present throughout the year in this region. In Summer, basal motion may account for up to 75% of the total surface velocity throughout the lower ablation area. The inferred rate of basal motion increases sharply directly below a set of moulins by which most surface meltwater reaches the glacier bed.
Translated title of the contributionThe distribution of basal motion beneath a High Arctic polythermal glacier
Original languageEnglish
Pages (from-to)407 - 414
Number of pages8
JournalJournal of Glaciology
Publication statusPublished - 2003

Bibliographical note

Publisher: International Glaciological Society, Cambridge


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