Daily to multi-decadal velocity variations at Athabasca Glacier, Alberta, Canada

Variations in glacier velocity affect subglacial erosion rates and mass transfer from accumulation areas to ablation zones and/or calving fronts. Changes in these processes impact downstream water resources, aquatic habitat, and sea level rise. Significant strides have been made to describe the physics of glacier basal motion that drive rapid shifts in glacier velocity, but little is known about how these processes change over long timescales. Athabasca Glacier (Jasper National Park, Alberta, Canada) is an ideal site to study long-term changes in glacier basal motion due to a baseline dataset obtained from several borehole inclinometry campaigns in the 1960s. Here, we present records from eight GPS stations along a 3 km longitudinal profile on Athabasca Glacier maintained from March to September 2020. These position data allow investigation of changes in the glacier's surface speed over two timescales: 1) the course of the 2020 melt season, and; 2) the past 50+ years since the baseline fieldwork. We analyze the short timescale data in combination with an ice-marginal weather station to assess the glacier's seasonal cycle of meltwater generation, lubrication of the ice-bed interface, and associated changes in basal motion. For the long timescale, we use GPS positions and digitized historical glaciological data in combination with digital elevation models to probe changes in glacier velocity caused by decades of mass loss and associated geometric change. This work is part of a larger effort including borehole drilling and numerical modeling to examine how the distribution and magnitude of basal motion on Athabasca Glacier has evolved as its geometry and hydrology have adjusted in response to modern climate change.