3a.1 Observations and Modeling of Structural-optical Properties in First-year Sea Ice

An understanding of radiative transfer in sea ice is critical to understanding the heat and mass balance of the Arctic. Radiative transfer affects such processes as surface melting, ice-albedo feedback, solar heating of the upper ocean, and internal heat storage within the ice. Large temporal changes in the physical state of the ice cover cause large changes in its radiative properties, particularly during the summer. As the surface warms, melts, and forms ponds, there is a substantial decrease in its albedo. To better model changes in the physical state of the ice and its ability to backscatter light, we need a more complete understanding of its fundamental optical properties. Sea ice is a lattice of nearly pure ice with embedded inclusions of brine, vapor, precipitated salts, and occasional particulate material. The optical properties are determined not only by the bulk volumes of these constituents and their dielectric properties, but also by the inclusion distributions. While numerous studies have been done on the structural properties of sea ice (e.g. Weeks and Ackley, 1981; Perovich and Gow, 1991, 1996), and its optical properties (see Perovich, 1996), relationships between the two have not yet been firmly established. Because changes in temperature cause the relative amounts of ice, brine, vapor, and precipitated salt to adjust according to freezing equilibrium relationships (Cox and Weeks, 1983), we expect the optical properties of ice to also depend on temperature. The focus of this work is to improve our understanding of how temperature-dependent changes in microstructure govern the inherent optical properties of first-year sea ice.