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Full-Text Articles in Physical Sciences and Mathematics
Depth-Varying Constitutive Properties Observed In An Isothermal Glacier, H. P. Marshall, Joel T. Harper, W. Tad Pfeffer, Neil Humphrey
Depth-Varying Constitutive Properties Observed In An Isothermal Glacier, H. P. Marshall, Joel T. Harper, W. Tad Pfeffer, Neil Humphrey
Geosciences Faculty Publications
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 about 115 m depth suggest a constitutive relationship with a stress exponent n about 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 …
Basal Conditions And Glacier Motion During The Winter/Spring Transition, Worthington Glacier, Alaska, U.S.A., Joel T. Harper, Neil Humphrey, Mark C. Greenwood
Basal Conditions And Glacier Motion During The Winter/Spring Transition, Worthington Glacier, Alaska, U.S.A., Joel T. Harper, Neil Humphrey, Mark C. Greenwood
Geosciences Faculty Publications
Observations of the motion and basal conditions of Worthington Glacier, Alaska, U.S.A., during late-winter and spring melt seasons revealed no evidence of a relationship between water pressure and sliding velocity. Measurements included borehole water levels (used as a proxy for basal water pressure), surface velocity, englacial deformation, sliding velocity, and time-lapse videography of subglacial water flow and bed characteristics. The boreholes were spaced 10-15 m apart; six were instrumented in 1997, and five in 1998. In late winter, the water-pressure field showed spatially synchronous fluctuations with a diurnal cycle. The glacier's motion was relatively slow and non-cyclic. In spring, the …