7th Annual ARCUS Award for Arctic Research Excellence

Honorable Mention Physical Science

Submitted by		Hans-Peter Marshall
Authors		Hans-Peter Marshall, J. T. Harper, W. T. Pfeffer, and N. F. Humphrey
Category		Physical Science
Title		Depth-Varying Constitutive Properties Observed in an Isothermal Glacier
Affiliation		Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder, Boulder, CO, USA

Abstract

Detailed three-dimensional in-situ measurements of deformation at depth are used to examine the rheology of a 6 x 10⁶ m³ block of temperate glacier ice. Assuming that the viscosity of this ice is primarily dependent on stress, the relationship between inferred stress and measurements of strain-rate above ~115 m depth suggest a constitutive relationship with a stress exponent n ~ 1. Deformation below 115 m is described by a non-linear flow law with a power exponent of approximately 3–4. A sharp transition between the two flow regimes is likely caused by a change in the dominant mechanism from superplastic flow, basal slip, and/or diffusional flow near the surface to dislocation and intragranular deformation at depth.