Relationships between the History and Structure of Sea Ice and its Physical and Mechanical Properties

This project involves two aspects of sea ice mechanics that are important building blocks leading to an improved understanding of the natural behavior of this common, naturally occurring Arctic material. The first is the influence that structure, properties and growth history have on the strength and mechanical properties of sea ice at different scales. Currently, we are investigating the interrelations between (1) the degree of c-axis alignment in the horizontal plane, the degree of substructure development, the vertical variation in grain size, and also the development of brine drainage features and (2) the local small scale flexural and compressive strengths as determined on plates and beams. In particular, we are emphasizing the development of experimental and theoretical bases for estimating the properties of first-year sea ice during the spring and early summer when brine drainage channels are well-developed within the ice. These features, which can be centimeters in diameter and may extend vertically throughout most of the ice sheet, must strongly influence the bulk properties of sea ice at these times of year. Yet, to date, the presence of these ubiquitous features have been completely ignored in treatments of ice properties.

The second objective of the project is to study the refreezing rate of first year pressure ridges. Recent ridges are ubiquitous feature of pack ice and must be considered in analyses of sea ice on any scale larger than that of individual floes. Yet data is lacking concerning the speed with which these features reheal and thus reestablish continuity between the floe fragments. We are currently carrying out both observational and modeling studies of this process.

In conjunction with the above studies, we are also collecting data on interrelations between ice temperatures, ice growth rates and ice salinity profiles. We plan to utilize this information in improving current numerical models that predict changes in the profile properties of sea ice during the complete ice growth season.

ONR Grant N00014-92-J-1429: Scientific Personnel; W. D. Harrison, L. H. Shapiro and W. F. Weeks