Observations of the water-vein system in polycrystalline ice

Abstract

The geometry of the vein system in ice has been investigated using photographs of enlarged veins in ice samples that were grown in the laboratory. The veins, which are non-uniform, act as tiny triangular-shaped, water-filled prisms that refract the light passing through them.The three vein widths in the cross-section of a vein can be deduced from two photographs taken from different directions. The dihedral angle along a given vein edge can be observed directly by viewing it at a node, where four veins meet, from a particular direction. The dihedral angles range from 25° ± 1° to 105° ± 1°. It is shown that the vein cross-section can be constructed, given the three widths of a vein and one of the dihedral angles, providing that the radius of curvature around the vein wallsrv is a constant. This assumption can be checked if the values of at least two of the dihedral angles associated with the vein cross-section are known. Ifrv is a constant, then the solid-liquid interfacial energy ϒsl must be isotropic for the veins in question and any deviations from uniform equilibrium geometry must derive primarily from anisotropy in the grain-boundary energy ϒss. The cross-sections of three veins that meet in a particular node are constructed. The assumption of isotropic ϒsl is found to hold for this node.

Ice structures, patterns, and processes: A view across the icefields

“…Their experimental observations seem to support the idea that FIG. 8 The vein-node network in polycrystalline ice: (a) Micrograph published originally in Mader (1992); (b) schematic from Nye (1992), modified from Smith (1948). Together they appear as Fig.…”

Light scattering from an isotropic layer between uniaxial crystals

“…optical microscopy techniques (Mader 1992, Walford et al 1987. Additional water structures, such as water lenses, are observed in the presence of non-hydrostatic stresses (Nye 1991).…”

Anomalous diffusion of multiple impurity species: Predicted implications for the ice core climate records

“…The sizes of the ice grains are anticorrelated with the bulk impurity concentrations through most of the depth of the polar cores [Thorsteinsson et al, 1997;de la Chapelle et al, 1998]. Curvature effects should cause the vein radii to be roughly uniform [Mader, 1992a[Mader, , 1992bNye, 1992], so variations in grain size imply variations in the liquid fraction, with larger grains corresponding to smaller f. The observed spatial variations in grain sizes and bulk impurity concentrations occur over much shorter length scales than do changes in the intergranular concentrations inferred from the gradual variations in temperature along the core. Hence, the variation in liquid fraction implied by the observed grain-size distribution is consistent with equation (6) only if f ) k, a point to which we return later; however, this sets the stage for our model of impurity transport with…”