Thermal Expansion Coefficients For Sea Ice

Abstract

Coefficients of thermal linear expansion were determined for sea ice using a Michelson interferometer. Over a temperature range of −4 °to −15 °C, the coefficients varied from 45 ×10⁻⁶ to 54×10⁻⁶ °C⁻¹ for ice with a salinity of 2 ppt, and from 33 ×10⁻⁶ to 53 ×10⁻⁶ °C⁻¹ for ice with a salinity of 4 ppt. Initially, warming the sea ice resulted in coefficients that were the same as those for fresh-water ice, within the limits of experimental error. Subsequent sea-ice cooling resulted in coefficients that were initially lower than those for fresh-water ice, but that asymptotically approached the coefficient values for fresh-water ice at colder temperatures. On the second warming and cooling cycle, the coefficients of thermal linear expansion exhibited hysteresis and a decrease in magnitudes. We have also shown that Pettersson’s (1883) and Malmgren’s (1927) measurements of the thermal volume expansion of sea ice were the result of phase transitions that caused brine expulsion, when air-free sea ice was cooled, and internal porosity increases, when sea ice was warmed.Our results indicate that Petterson’s (1883) and Malmgren’s (1927) measurements of the thermal volume expansion of sea ice are in error. Consequently, theoretical descriptions based on their results are incorrect (Anderson, 1960; Zubov and Savelyev (given in Doronin and Kheisin (1977)); Doronin and Kheisin, 1977). Our results for the initial sea-ice warming cycle do agree with Cox’s (1983) analysis.