Spatial Patterns of Summer Speedup on South Central Alaska Glaciers

Seasonal changes in glacier basal motion are attributable to variations in subglacial hydrology and cause variations in both ice discharge and glacier erosion. We develop a novel workflow based upon Landsat 8 feature tracking to document differences between spatial patterns of summer and winter glacier surface speed, which reflect changes in the distribution of basal motion. We identify and characterize summer speedups on 13 of 19 land-terminating glaciers in Alaska's Wrangell-St Elias Ranges. The speedups are relatively uniform over much of the ablation zones, and the speedup magnitudes vary by only a factor of similar to 2 between glaciers whose velocities span an order of magnitude. Summer speedups extend up to similar to 30km up glacier from termini and often end at the bases of icefalls. These data provide systematic observation of the spatial pattern of enhanced summer glacier basal motion and suggest the possibility of its parameterization in glacier models.