The Interaction of Microwaves with Antarctic Sea Ice

                               by

                       Kenneth M. Golden

           JWB 335, 3:20pm  Monday, October 30, 1995

                                Abstract

 The sea ice pack in the polar regions plays a fundamental role
 in global climate as the boundary layer separating the ocean
 and atmosphere in these regions. Due to its vast extent, the
 physical properties of the sea ice pack are often studied via
 electromagnetic remote sensing from satellites and airplanes,
 in the microwave regime.

 In this talk we give an overview of ongoing investigations of
 the interaction of microwaves with sea ice. This interaction is
 particularly interesting in the case of sea ice, which is a
 composite of pure ice with random brine and air inclusions,
 whose geometry can depend dramatically on temperature.

 Our mathematical investigations focus on applying modern
 techniques of homogenization to estimating the effective
 electromagnetic properties of the sea ice. These techniques
 include using the analytic continuation method to obtain bounds
 on the complex permittivity $\epsilon^*$ of the ice under
 constraints on the microgeometry, and using percolation theory
 to understand the transition in effective properties as the
 brine pockets coalesce when the temperature rises above the
 critical temperature $T_c \approx -5^\circ C$. We shall also
 discuss recent efforts to model dynamic thermal profiles of the
 ice, which are important in determining the electromagnetic
 properties, using nonlinear advection/diffusion equations.
 Finally, we will describe some experiments performed in
 conjunction with the mathematical work, including microwave
 backscatter experiments we have conducted at C band (5.3 GHz)
 on first year sea ice.

 These experiments were conducted on a cruise to the Weddell
 Sea, Antarctica during July and August 1994, and we will show a
 short video which recounts this adventure.