A new technique for ice-fabric analysis

Abstract

ABSTRACT. A new method for ice-fabric analysis which is easily automated is described. The technique relies on a set of digital images of an ice thin section viewed through crossed polarizers and rotated to various angles. From the acquired set of images, the c-axis orientation of all the grains in the image can be determined. The theoretical basis for the technique is described in detail, including corrections for refraction, as well as other corrections for off-axis grains and polarization/reflection effects. An experiment was performed comparing results of the new technique with those of the standard technique. Excellent agreement was obtained. It is expected that an automated system using this technique (currently almost complete) will have a large impact on the amount of information and physical knowledge which can be extracted from ice fabrics in the future.

Development, principles, and applications of automated ice fabric analyzers

“…There are some other subtleties that occur when a grain is initially already aligned close to the polar or equatorial positions, but we will not go into these here. Once the angles defining the c-axis direction for all the grains have been tabulated, corrections for refraction must be applied (Kamb, 1962;Wilen, 2000).…”

A direct optical method for the study of grain boundary melting

“…The principle of the technique [21], informed by earlier treatments of universal stage measurements [22], utilizes the uniaxial nature of the crystal. As a plane polarized wave traverses an ice crystal its polarization is rotated.…”

“…peated for multiple crystal positions enabling us to solve for c-axis position using the minimization scheme outlined in [21].…”

“…The magnitude of the crystallographic mismatch across a grain boundary is subsequently determined by independently measuring each crystal's orientation. The measurements are made using a technique modeled upon one developed for analyzing the ice fabrics of large ice core sections [21] and adapted to the geometry and constraints of our experimental ice growth cell in order to allow all orientation measurements to be made in situ.…”

“…Optional wedges can be used to add a rotation about the z-axis. Extinction angles (θxt) are recorded for each crystal and cell position, and a minimization scheme [21] is used to solve for c-axis orientation.…”