Crack velocities in freshwater and saline ice

Abstract

This paper presents experimental results on both mode 1 and 2 crack velocities measured in a wide variety of ice types, columnar sea ice, columnar lake ice, laboratory‐grown columnar saline ice, and freshwater columnar and granular ice, in the temperature range from −5° to −35°C. Measurements of ice electrical conductance, electrical capacitance, and electromagnetic emissions from cracks as a function of time were used to determine crack velocities in samples with dimensions ranging from 0.05 to 30 m. In laboratory‐grown freshwater ice and in lake ice, average crack velocities varied from a few hundred to 1320 m/s. In contrast, in natural sea ice and laboratory‐grown saline ice, crack velocity was very low at about 10 m/s. This remarkable difference in the velocity of cracks growing in freshwater and saline ice is probably due to the dynamic resistance of unfrozen water in brine pockets and/or the large size of a crack tip process zone in saline ice. It was also found that cracks propagate discontinuously in saline ice owing to the strong interaction with microstructural elements such as drainage channels.