Elastic Constants of Artificial and Natural Ice Samples by Brillouin Spectroscopy

Abstract

The method of Brillouin spectroscopy has been used to measure the dynamic elastic moduli of local homogeneous regions in ice samples representing four different environments of formation. These included artificial ice frozen from distilled water, clear monocrystalline glacial ice, bubbly lake ice, and sea ice. The samples studied were found to have identical local elastic properties. Accordingly the elastic properties of homogeneous monocrystalline ice have been found not to vary with sample age, with impurities present at the time of freezing, or with crystal quality. The bulk elastic properties of ice remain, of course, subject to modification by different crystal grain textures and the presence of inclusions of various sorts. Because the elastic constants obtained in the present work are subject to smaller overall uncertainty than values measured previously, it is believed that they are the most reliable obtained to date. The values at −16 °C were determined to be c11 = 139.29 ± 0.41, c12 = 70.82 ± 0.39, c13 = 57.65 ± 0.23, c33 = 150.10 ± 0.46, c44 = 30.14 ± 0.11 (units of 108 N m− 2 or kbar). A full range of derived elastic parameters for monocrystalline ice and for homogeneous isotropic polycrystalline ice has been calculated.

Cohesion versus friction in controlling the long‐term strength of a self‐healing experimental fault

“…As the ice plate thickens, grains get smaller, varied in shape but still with an average characteristic length of about 2cm (widely dispersed), 1 order of magnitude smaller than the radial dimension of the ice plate and much larger than its thickness of typically a few millimeters. As Ice Ih exhibits elastic [Gammon et al, 1983] and viscoplastic [Duval et al, 1983] anisotropies relatively to the c axis orientation of the crystal, such microstructure would likely generate stress heterogeneities within the ice plate. To avoid this, we sprayed water droplets at 0°C and 3bars over the water tank to increase the nucleation sites and therefore to decrease the grain size.…”

Plastic faulting: Brittle‐like failure under high confinement

“…Taking t o = (s 1 À s 3 )/2 at terminal failure and conservatively assuming t i = 0.5t o , the predicted increase in temperature associated with the propagation of slip across the grain boundary barrier are several degrees for ice and several hundred degrees for rock. In this calculation we set G = 3.5 GPa for ice [Gammon et al, 1983] and assume d = 10 À3 m and d = 10 À2 m for rock and ice, respectively.…”

Elastic dynamics and tidal migration of grounding lines modify subglacial lubrication and melting

“…[3] Previous interpretations of tidal flexure using elastic models included only the floating shelves, clamped at a fixed GL over a stiff bed (stiff-fixed models, Figures 1a and 1b) [Holdsworth, 1977]. Such models predicted ice elasticity that varies significantly between different glaciers [Vaughan, 1995;Rignot, 1996;Sykes et al, 2009] that varies with tidal phases in the same glacier [Schmeltz et al, 2002] and is significantly smaller than measured experimentally [Gammon et al, 1983]. These discrepancies have led to the inclusion of viscous deformation in the modeling of tidal flexure [Reeh et al, 2003;Gudmundsson, 2011;Walker et al, 2013].…”