Measuring melt and velocity of Alaskan mountain glaciers using phase-sensitive radar and differential GPS

Abstract:

Alaskan glaciers show some of the highest rates of retreat worldwide, contributing to sea level rise. This retreat is due to both increased velocity and increased melt. We seek to understand the role of glacial meltwater on velocity. Matanuska glacier, a land terminating glacier in Alaska, has been well-studied using traditional glaciological techniques, but new technology has emerged that allows us to measure melt and velocity more accurately. We employed high-resolution differential GPS to create surface velocity profiles across flow in the ablation zone during the summer of 2015. We also measured surface ablation using stakes and measured basal melt using phase-sensitive radar designed by the British Antarctic Survey. The positions acquired by differential GPS are obtained to a resolution of less than 0.5m, while feature tracking using time-lapse photography for the same time period yields positions with greater and more variable uncertainty. The phase-sensitive radar provides ice thinning rates. Phase-sensitive radar together with ground penetrating radar provides us with an understanding of the internal structure of the glacier. This suite of data allows us to determine the relative importance of surface melt, basal melt, and internal deformation on ice velocity in warm mountain glaciers.