Underwater sound propagation in the Arctic is characterized by a refractive surface duct with a rough boundary. As the result of scattering, attenuation is some two orders of magnitude greater than medium absorption. Scattering models usually assume statistical homogeneity. We propose a more realistic composite model consisting of spatially random patches having one of two different degrees of roughness. The resulting attenuation coefficient exhibits a relaxation-like transition from rougher to smoother area control as frequency increases. Standard deviations, correlation lengths, and relative areas for the two components are estimated from PDF's and wavenumber spectra of ice-draft profiles. Results are compared with reported attenuation measurements. [Work supported by ONR and NUSC.]