SOME PHYSICAL PROPERTIES OF SEA ICE. I

Abstract

This preliminary study is based mostly on work done at a shore station in Shippegan, N.B., during the winter of 1956–57, with some data from an icebreaker expedition in the summer of 1956. The Shippegan site had unrafted ice, tides of 5 feet or less, and negligible fresh-water runoff. The thickness of the ice was about proportional to the square root of the freezing exposure. Tritium dating of sea ice is an unsatisfactory method because of variable tritium concentration in Arctic waters. The jaggedness of ice crystals is suggested as a measure combining effects of age and thermal regime. Measurements of specific gravity, salinity, electrical resistivity, and permeability profiles all show progressive changes in annual sea ice throughout the winter. The tensile strength of sea ice at −20 °C was around 200 to 500 p.s.i., at various angles to the grain. For fresh-water ice, with stress parallel to the grain, it was in the range 500 to 1000 p.s.i. Shear strengths, with the shear plane parallel to the grain, were 80 to 160 p.s.i. for sea ice at −20 °C and 160 to 280 p.s.i. for pond ice, also at −20 °C.