Abstract
ABSTRACTPrevious studies reported that Good Friday Glacier had been actively surging in the 1950–60s, 1990s and again in 2000–15. Based on observations of terminus position change from air photos and satellite imagery, we fill the gaps between previous studies and conclude that the glacier has been advancing continuously since 1959. Ice surface velocities extracted from optical and synthetic aperture radar satellite images show higher flow rates than on most other marine-terminating glaciers in the region. This behaviour contrasts with the regional trend of glacier retreat over this period. Possible explanations involve a delayed response to positive mass-balance conditions of the Little Ice Age, or a dynamic instability. There is, however, insufficient evidence to attribute this behaviour to classical glacier surging as suggested in previous studies. Based on present-day ice velocity and glacier geometry patterns in the terminus region, we reconstruct the evolution of ice motion throughout the advance, and suggest that what has previously been interpreted as a surge, may instead have been a localised response to small-scale perturbations in bedrock topography.
Highlights
Surge-type glaciers experience irregular flow regimes and are typically described as cycling between long quiescent periods and short-lived active/surge periods where velocities increase by one or two orders of magnitude above quiescent levels (Meier and Post, 1969)
Out of 51 surge-type glaciers previously inventoried in the northern Canadian Arctic Archipelago (CAA: Ellesmere, Axel Heiberg, and Devon islands), the most dramatic terminus advances were documented on western Axel Heiberg Island, with three glaciers advancing between 4 and 7 km in the 1959–99 period (Copland and others, 2003)
We examine the spatial variability in dynamics in the terminus region of GF in relation to local variations in bedrock topography, and propose an alternate interpretation to surging for the temporal evolution of ice motion at the glacier front throughout the advance
Summary
Surge-type glaciers experience irregular flow regimes and are typically described as cycling between long (decades to centuries) quiescent periods and short-lived (months to years) active/surge periods where velocities increase by one or two orders of magnitude above quiescent levels (Meier and Post, 1969). The classic pattern of surging involves a rapid transfer of mass down-glacier, resulting in dramatic velocity increases over most of the glacier length, and significant changes in glacier geometry such as rapid terminus advance and fluctuations in ice thickness (Raymond, 1987). Out of 51 surge-type glaciers previously inventoried in the northern Canadian Arctic Archipelago (CAA: Ellesmere, Axel Heiberg, and Devon islands), the most dramatic terminus advances were documented on western Axel Heiberg Island, with three glaciers advancing between 4 and 7 km in the 1959–99 period (Copland and others, 2003). Recent observations indicate that the glacier terminus was still advancing in the 2000–15 period, with surface velocities reaching up to 350 m a−1 at the terminus (Van Wychen and others, 2014, 2016; Millan and others, 2017)
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