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Grad student talk - Glacier sliding from space: multiscale remote sensing, geodesy, and numerical...

Thursday, April 20, 2017, 12:30PM - 1:30PM


Billy Armstrong


SEEC room S225

Full title

Glacier sliding from space: Multiscale remote sensing, geodesy, and numerical modeling to understand glacier mechanics


Glacier basal sliding is a poorly understood aspect of glacier mechanics, and its spatial and temporal distribution affects glacier change and the evolution of alpine landscapes. Sliding occurs at the glacier bed, but can be observed from temporal variations in ice surface velocity. In this study, we use on-glacier GPS, moderate- and high-resolution optical satellite imagery, and numerical ice flow modeling to study the mechanics of glacier sliding across a variety of scales.
We employ on-glacier GPS to investigate the intimate link between subglacial water pressure and the rate of glacier sliding in response to the onset of spring melting, as well as unseasonably large water inputs associated with an outburst flood and fall rain events. We find sensitive links between water pressure and glacier speed when subglacial water pressure is high and low sensitivity at lower water pressure. We then use high-resolution WorldView satellite imagery to document the spatial pattern of the seasonal evolution of ice surface velocity over the 45 km2 terminal reach of Kennicott Glacier, Alaska. We develop a numerical ice flow model to explore the distribution of basal sliding required to explain our surface observations. We find the ice surface speedup is insensitive to the exact distribution of basal sliding, which may allow for simpler sliding parameterizations in glacier models.

Finally, we investigate Landsat 8 satellite imagery to characterize spatial patterns of glacier sliding over a 45,000 km2 area covering 64 glacier longitudinal profiles from ice divide to terminus. We find the entire ablation area of glaciers speeds up in a uniform manner, with the speedup magnitude insensitive to presumably deformation-dominated winter surface speeds. These patterns of sliding may drive patterns of glacier erosion that leads to the formation of icefalls.