| Summary: | Icefalls are steep ice flow features that form over steps in bedrock elevation. With their high driving stresses, icefalls have long been assumed to have a constant ice flowspeed. This assumption has not been thoroughly tested as methods using satellite feature tracking rapidly loose coherence and long-term GPS installations on the ground are unlikely to be retrievable. In this study, we test the hypothesis that the Vaughan Lewis Icefall in Southeast Alaska experiences daily velocity variations with daily variations in subglacial hydrology. Using high resolution tiltmeters, we observe change in ice surface tilt across eight days at two sites near the glacier centerline. We find daily variation in ice surface tilt, suggesting there are variations in daily ice flowspeed velocity. A weak and lagged correlation with air temperature suggests that velocity variations may be due to daily variations in subglacial hydrology. Future modeling efforts focused on describing ice flow over icefalls should consider adding daily or seasonal velocity variations. These results additionally have implications for theoretical models of ogive formation, which could result from seasonal flow speed variations across icefalls.
|
|---|