Report on retrieval of sea ice thickness from the SAR wave-spectrum and validation

The procedure for the retrieval of sea-ice thickness will be applied to areas of frazil-pancake (FP) ice during periods of new ice formation and ice growth in regions of turbulence. Both ESA Sentinel-1 (S1) C-band and Cosmo-SkyMed (CSK) X-band SAR images, in areas of the Arctic (Greenland Sea) and of Antarctica (Ross Sea), will be used. A first phase of the study will focus on the development of a processing scheme for the automatic detection of FP ice fields and on the comparison of the results obtained with S1 and CSK images. By extracting a subset of the image across the ice edge, the SAR-wave spectra, both in ice and open sea, will be computed; these spectra will be used as input to a wave-ice interaction model to generate ice thicknesses. The results of this procedure will be validated with direct ice measurements performed during field campaigns carried out by other WPs of the project. The final deliverable will be seasonal pancake-frazil ice thicknesses (i.e. ice volume per unit sea surface area) and thus ice mass fluxes, for specific regions in which frazil-pancake ice is the dominant ice type. These will include: in the Antarctic the outer growing ice edge in early winter, and the Ross Sea and similar coastal polynyas throughout the year; in the Arctic the Odden ice tongue region and selected coastal polynyas in areas such as the Bering Sea coastline. In collaboration with UB, areas of thin ice will be selected where both SMOS and SAR imagery are available. UB will carry out SMOS retrievals yielding thickness values based on the SMOS algorithm, while UNIVPM and CNR will retrieve thicknesses using the pancake wave method. Results will be compared in an attempt to find a cross-correlation between SMOS and SAR in frazil-pancake ice regions.