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Optimising ice flow law parameters using borehole deformation measurements and numerical modelling
Author(s) -
Chandler David,
Hubbard Bryn,
Hubbard Alun,
Murray Tavi,
Rippin David
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl033801
Subject(s) - creep , borehole , geology , glacier , rheology , constitutive equation , deformation (meteorology) , flow (mathematics) , geotechnical engineering , mechanics , geomorphology , mineralogy , thermodynamics , materials science , composite material , finite element method , oceanography , physics
Internal ice strain rates have been measured along two boreholes drilled through Glacier de Tsanfleuron, Switzerland. Differences between these measurements and the output from a 3D numerical model of glacier motion have been minimized by a scheme that optimizes three rheological parameters in the constitutive equation for ice creep: the stress exponent n , the rate factor A , and a Lower Zone (basal ice) enhancement factor E LZ . Results suggest that a linear rheology dominated by diffusion creep ( n = 1) is more appropriate for modelling ice flow in this relatively thin (generally <80 m thick) glacier than the conventional n = 3, and that E LZ is ∼2. For n = 1, the predicted ice crystal size and value of E LZ are both consistent with measurements made on ice cores recovered from the glacier, providing independent support for the optimization technique and the linear creep model.