Multidecadal Evolution in Velocity and Ice Thickness of Illaulittuuq (Coronation) and Maattatujana (Maktak) Glaciers, Baffin Island Nunavut

Abstract

Marine-terminating glaciers often respond dynamically to ocean forcing, but Illaulittuuq Glacier, a primary calving outlet of Penny Ice Cap, is shifting towards behaviour more like its neighbouring land-terminating counterpart, Maattatujana Glacier. From 1958 to 2024, both glaciers retreated, thinned, and decelerated in similar fashion despite their contrasting terminus types. Illaulittuuq's retreat accelerated after the mid-1990s, while Maattatujana's response occurred later, yet both now lose mass at comparable rates and show similar velocity profiles with highest speeds in the upper ablation zone, decreasing rapidly toward their termini. Most revealing is Illaulittuuq's shifting mass budget: dynamic discharge accounted for nearly half of total mass losses in 2000-04 but <3% by 2020-24, even as total mass loss intensified. Sustained thinning was the dominant driver of velocity change at both glaciers, reducing basal sliding, particularly during spring and summer, and shifting flow toward internal deformation as ice thins and driving stress declines.