Reduced basal motion responsible for 50 years of declining ice velocities on Athabasca Glacier

• Published in: Journal of Glaciology
• Main Authors: David Polashenski, Martin Truffer, William Henry Armstrong
• Format: Article
• Language: English
• Published: Cambridge University Press 2024-01-01
• Subjects: glacier flow; glacier modeling; mountain glaciers
• Online Access: https://www.cambridge.org/core/product/identifier/S0022143024000510/type/journal_article

The time-evolution of glacier basal motion remains poorly constrained, despite its importance in understanding the response of glaciers to climate warming. Athabasca Glacier provides an ideal site for observing changes in basal motion over long timescales. Studies from the 1960s provide an in situ baseline dataset constraining ice deformation and basal motion. We use two complementary numerical flow models to investigate changes along a well-studied transverse profile and throughout a larger study area. A cross-sectional flow model allows us to calculate transverse englacial velocity fields to simulate modern and historical conditions. We subsequently use a 3-D numerical ice flow model, Icepack, to estimate changes in basal friction by inverting known surface velocities. Our results reproduce observed velocities well using standard values for flow parameters. They show that basal motion declined significantly (30–40%) and this constitutes the majority (50–80%) of the observed decrease in surface velocities. At the same time, basal resistive stress has remained nearly constant and now balances a much larger fraction of the driving stress. The decline in basal motion over multiple decades of climate warming could serve as a stabilizing feedback mechanism, slowing ice transport to lower elevations, and therefore moderating future mass loss rates.