Sea ice melt pond fraction estimation from dual-polarisation C-band SAR – Part 1: In situ observations

Abstract

Abstract. An understanding of the evolution of melt ponds on Arctic sea ice is important for climate model parameterizations, weather forecast models, and process studies involving mass, energy and biogeochemical exchanges across the ocean-sea ice–atmosphere interface. A field campaign was conducted on landfast first-year sea ice in the Canadian Arctic Archipelago during the summer of 2012, to examine the potential for estimating melt pond fraction from C-band synthetic aperture radar (SAR). In this study, in situ dual-polarisation radar scatterometer observations of pond covered ice are combined with surface physical measurements to analyse the effects of radar and surface parameters on backscatter. LiDAR measurements of ice surface roughness and ultrasonic wind-wave height profiles of melt ponds are used to quantify the sea ice surface rms-height. Variables contributing to the roughness of wind-generated melt pond surface waves within the fetch-limited pond environment are evaluated, and we show that pond roughness and backscatter cannot be explained by wind speed alone. The utility of the VV / HH polarisation ratio (PR) for retrieving melt pond properties including pond fraction, due to the dielectric contrast between free surface water and sea ice, is demonstrated and explained using Bragg scattering theory. Finally, the PR approach is discussed in the context of retrievals from satellite C-, L-, and P-band dual-polarisation SAR.