Brillouin spectroscopy has been used to measure the adiabatic elastic constants of laboratory-grown pure monocrystalline ice Ih at – 3°C. The values obtained were (in units of 108 N/m2): c11 = 136.96 ±0.60, c12 = 69.66± 0.45, c13 = 56.28±0.31, c33 = 147.02±0.68, c44 = 29.59±0.15. Comparison of these values with ultrasonic measurements quoted in the literature reveals no significant acoustic dispersion in ice over frequencies ranging to 1010 Hz. However, the results suggest that the elastic constants of ice may depend on the precise crystal quality and age of a given sample. The low experimental error in the values obtained, along with the inherent versatility of the method, indicate that Brillouin spectroscopy is an effective technique for systematically investigating the elastic properties of ice samples formed under natural conditions.

A core drill capable of drilling to more than 100 m depth in cold ice is described. It is designed with a view to fast operation and easy transport, core handling, and maintenance.

Increasing interest is being directed toward studies involving measurement of strain and strain-rates in sea and glacier ice. A number of techniques for obtaining these data over gauge lengths ranging from 1 m to several kilometers have been reported, but there has been little experience with shorter lengths. Use of commercially available electrical resistance strain-gauges (length 5–20 cm) intended for embedment in concrete offers a new approach in which multiple gauge, two- and three-dimensional arrays can be installed in ice with minimum effort and monitored with portable equipment. This report describes a pilot study designed to demonstrate the use of three types of electrical resistance strain gauges in sea ice under exposed field conditions. Results include detection of variations in strain fields related to tidal currents.

We discuss the possibility of the occurrence of thermal instability in ice sheets and glaciers. This may arise from the non-linear viscous heating term, which could provide for the existence of multiple steady states in the flow and temperature fields: a word of warning is given about the applicability of these ideas.

An approximate calculation is made of the rate at which a bottom crevasse in a cold ice shelf or tabular iceberg can close shut by freezing of water and can creep open through the creep deformation of ice. In all but the thickest ice shelves and icebergs, those with a thickness greater than about 400 m, the freezing process is the more important mechanism if the ice is cold (< – 10°C). Consequently in a cold iceberg or ice shelf a bottom crevasse, once formed, will freeze shut.