Melt ponds on sea ice in the Canadian Archipelago: 2. On the use of RADARSAT‐1 synthetic aperture radar for geophysical inversion

Abstract

Microwave scattering from a first‐year sea ice (FYI) melt ponded surface is examined using RADARSAT‐1 synthetic aperture radar (SAR) data collected during the 1997 Collaborative‐Interdisciplinary Cryospheric Experiment (C‐ICE'97) near Resolute Bay, Nunavut. This paper (1) investigates the utility of time series of microwave scattering to detect melt pond formation and (2) investigates approaches toward geophysically inverting information on the physical and radiative properties of this surface. We found melt pond formation to coincide with a sharp rise in the temporal evolution of the microwave scattering coefficient (σ°) over FYI. RADARSAT‐1 incidence angle and surface wind speed explained >90% of the variation in σ°. RADARSAT‐1 σ° was sensitive ( R 2 = 0.80) to the fractional coverage of melt ponds during windy conditions (∼ 5.3 m s −1 ). Spatial and temporal coincident measurements of RADARSAT‐1 σ° and the integrated shortwave albedo revealed a strong negative statistical correlation ( R 2 = 0.91) during windy conditions (∼ 5.3 m s −1 ). A weaker, but strong, negative relationship ( R 2 = 0.78) was observed for less windy conditions (∼ 3.2 m s −1 ), and a very weak positive relationship ( R 2 = 0.19) was found for low wind speed conditions (∼ 1.5 m s −1 ). All relationships were observed for melt pond fractions between 13 and 34%.