In-Situ monitoring of sea ice dielectric properties and implications for the tracking of seasonal evolution of microstructure

Abstract

The microstructure of sea ice evolves throughout the seasonal cycle, from ice formation in the fall through melt in the summer. Observations of this seasonal evolution and its effect on the interaction between sea ice and the surrounding environment face fundamental challenges, however. Any removal of ice cores to obtain data on ice properties results in the loss of brine and alterations of microstructure. The remoteness of field sites also limits observations. Methods to monitor sea ice microstructure continuously and non-destructively are therefore being explored. This thesis examines the potential for the electric properties of sea ice, highly sensitive to the brine distribution within the ice, to serve as a proxy for microstructure and hence other ice transport properties. Throughout the Spring of 2013 and 2014, measurements of low frequency complex dielectric permittivity in the range of 10 Hz to 95 kHz were made in landfast ice off the coast of Barrow, Alaska. Temperature and salinity measurements and ice samples were collected for ice microstructure characterization. Results reveal a significant correlation between measurements of complex dielectric permittivity, brine volume fraction, and microstructural characteristics including pore volume and connectivity. The influence of temperature and salinity variations and further explanation of the relationships between ice properties, microstructural characteristics, and dielectric behavior are explored through multivariate analysis of the combined data set. The findings are discussed in terms of future research directions and promising approaches for in-situ ice property monitoring based on dielectric measurements.