Seasonal sea ice melt pond fraction and pond freezing estimation using dual-polarisation C-band synthetic aperture radar
Monday, 15 December 2014
Sea ice melt ponds play an important role in spring-summer radiation absorption and upper ocean warming, light transmittance and under-ice primary production, and biogeochemical exchanges. With a larger portion of Arctic first-year sea ice (FYI) compared to multiyear ice observed in recent years comes the expectation of greater melt pond fraction due to the absence of topographical controls on FYI. Despite progress in our understanding and modelling of pond fraction evolution and coupled processes at the local scale, a reliable means for monitoring variations at regional or greater scales, uninhibited by cloud cover, is lacking. In this study we demonstrate the ability of dual-polarisation C-band synthetic aperture radar (SAR) for estimating pond fraction and freezing conditions on level FYI in the Canadian Arctic Archipelago. We use a combination of in situ C-band scatterometer and radar-scale surface roughness observations to study the dual-polarisation channel (VV+HH and HV+HH) and channel ratio characteristics of individual melt ponds and ice patches. Aerial surveys of pond fraction are used to evaluate retrieval approaches from Radarsat-2 SAR fine quad-polarisation mode imagery. Accurate retrievals of pond fraction are found using the VV/HH polarisation ratio during melting conditions. Results demonstrate the potential of dual-polarisation SAR for regional scale observations with temporal frequency suitable for contributing to process-scale studies and improvements to model parameterizations.