Pancake Ice Thickness Mapping in the Beaufort Sea From Wave Dispersion Observed in SAR Imagery Journal of Geophysical Research: Oceans

The early autumn voyage of RV Sikuliaq to the southern Beaufort Sea in 2015 offered very favorable opportunities for observing the properties and thicknesses of frazil‐pancake ice types. The operational region was overlaid by a dense network of retrieved satellite imagery, including synthetic aperture radar (SAR) imagery from Sentinel‐1 and COSMO‐SkyMed (CSK). This enabled us to fully test and apply the SAR‐waves technique, first developed by Wadhams and Holt (1991), for deriving the thickness of frazil‐pancake icefields from changed wave dispersion. A line of subimages from a main SAR image (usually CSK) is analyzed running into the ice along the main wave direction. Each subimage is spectrally analyzed to yield a wave number spectrum, and the change in the shape of the spectrum between open water and ice, or between two thicknesses of ice, is interpreted in terms of the viscous equations governing wave propagation in frazil‐pancake ice. For each of the case studies considered here, there was good or acceptable agreement on thickness between the extensive in situ observations and the SAR‐wave calculation. In addition, the SAR‐wave analysis gave, parametrically, effective viscosities for the ice covering a consistent and narrow range of 0.03–0.05 m2 s−1.