Characterizing Evolving Dynamics of Belcher Glacier, Nunavut, Canada

Abstract

The Canadian Arctic is currently a major contributor to sea level rise and under a warming climate, is projected to continue losing significant mass to the oceans. Within this region lies Belcher Glacier, the largest tidewater terminating glacier of Devon Ice Cap (DIC) and its greatest source of mass loss via dynamic discharge. In 2015, Belcher Glacier began to experience a significant acceleration of its flow velocities, particularly in the near terminus region, and reminiscent of the recent speed-up observed at Trinity and Wykeham Glaciers, the fastest flowing glaciers in the Canadian Arctic. Previous studies have identified this acceleration, however, no investigation into the drivers of this recent speed-up or its impact on intra-annual dynamics had been conducted. Therefore, this study undertook an in-depth exploration of the acceleration of Belcher Glacier, accomplishing two major goals: (1) determine why Belcher Glacier began to accelerate in 2015 and characterize this dynamic change; and (2) investigate how the seasonality of Belcher Glacier’s flow velocities have evolved over more than a decade given its recent acceleration. A combination of remote sensing imagery, in situ observations, and ERA5 2 m surface temperature climate reanalysis data were used in this study to achieve these goals. Two distinct dynamic periods are identified on Belcher Glacier: a period of general stability prior to 2015, and a period of accelerated velocities from 2015 onwards, which in this study is described as a brief tidewater glacier cycle. Investigation into the geometry of Belcher Glacier identifies a period of dynamic thinning in the near terminus between 2011-2014. Thinning of the terminus driving extensive flotation allowed Belcher Glacier to detach from a basal pinning point, initiating a period of instability that manifested as an acceleration of flow velocities. Further acceleration and thinning of Belcher Glacier’s terminus promoted a major calving event between 2015-2016, resulting in retreat of the northern edge of the glacier front to a probable new pinning point. This has since resulted in a slight deceleration of velocities and a slowed rate of retreat. This multi-annual period of acceleration has also influenced intra-annual speed-up and a change in the glacier’s seasonality behaviour. Since 2022, the intra-annual velocities of Belcher Glacier have increased along the length of the glacier trunk, with acceleration identified as far as ~20 km from the terminus when compared to the seasonality in 2009. Despite a greater variability in surface temperature between the Day of Year (DOY) 170-243 in 2022 and 2023 compared to 2009, Belcher Glacier has evolved to experience larger seasonal acceleration events that now extend to higher elevations and occur later into the melt season. It is likely that these changes are driven by an expansion of the surface hydrology network to higher elevations, alongside a reduced firn storage capacity, allowing meltwater to penetrate to the bed later into the season and further up-glacier than has previously been observed. Collectively, these findings provide valuable insight into how a large tidewater glacier is evolving under a warming climate, which in turn can improve the understanding of glacier dynamics in the Canadian High Arctic.