Separability of sea ice types from wide swath C- and L-band synthetic aperture radar imagery acquired during the melt season

Abstract

Differentiating between first-year ice (FYI) and multi-year ice (MYI) in C-band synthetic aperture radar (SAR) imagery during spring–summer melt, when wet snow and melt ponds mask the underlying ice, is difficult. It has been suggested that the use of L-band SAR may alleviate this concern given increased penetration depths at longer wavelengths; however, this has not been thoroughly assessed. Here the separability of FYI and MYI is compared using horizontally polarized (HH) C-band (RADARSAT-2) and L-band (ALOS/PALSAR) ScanSAR images acquired over landfast sea ice in the Canadian Arctic Archipelago in the spring and summer of 2009. L-band provided enhanced contrast between FYI and MYI during early melt onset and during the drainage phase of advanced melt, while C-band was found to provide enhanced contrast when the wet snowpack was transitioning from the pendular regime to the funicular regime. At the time of the pendular–funicular transition, the backscatter signatures of FYI and MYI reversed at both C- and L-band. This behavior is well established at C-band, but has not been reported previously at L-band. The L-band imagery also provided improved definition of floe boundaries and ridges throughout the melt season. Finally, the L-band data had reduced speckle (equivalent number of looks ~ 12), relative to the C-band data (~ 9 equivalent looks). These results indicate that L-band SAR data acquired during the melt season could be used to enhance operational and scientific sea ice information products that have traditionally been derived from single-frequency C-band SAR data.