Date of Award

Spring 1-1-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Harihar Rajaram

Second Advisor

Robert S. Anderson

Third Advisor

William T. Pfeffer

Abstract

Numerous field observations document enhanced ice flow of terrestrial glaciers during brief periods of increased delivery of water to the bed. Contemporary understanding of the effect of basal water fails to consistently predict these speedup events. We carried out laboratory experiments using a transparent silicone (PDMS) as an analog for glacier ice, to investigate how basal water enhances ice velocities. The PDMS was allowed to flow over a rough checkerboard bed topography inside a tilted rectangular channel. Water was injected into a basal water system beneath the PDMS. We tested various configurations of the basal water system, including linked cavity and conduit systems, and measured basal water pressure, storage, and discharge. Velocity fields at the PDMS surface and bed were calculated by tracking bead markers. Transient and steady-state experiments were conducted to define the water pressure conditions associated with enhanced sliding. We evaluate the implications of the experimental results on mechanisms controlling enhanced ice flow. Our results suggest that: (i) bed separation enhances ice flow by reducing basal drag; (ii) changes in water pressures affect ice flow rates by changing cavity geometry, and (iii) the development of an efficient conduit system reduces the extent of water at the bed, thus slowing enhanced ice flow.

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