Sea Ice Melting State and Surface Albedo from C-Band Radar: Analysis of Dual-Polarization and Polarimetric Techniques
Scharien, Randall; Landy, J.; Barber, D.G.
University of Manitoba, CANADA

Upcoming satellite synthetic aperture radar (SAR) constellations missions, such as the European Space Agency's Sentinel-1 and the Canadian Space Agency's RCM, will significantly increase the revisit frequency of C-band SAR in the polar regions. These missions will not only ensure continuity with heritage C-band SAR systems ERS, Envisat, and Radarsat, they will introduce a new range of applications in sea ice monitoring and enhance region-specific process studies. A time series of polarimetric RADARSAT-2 images was acquired over a field study site of first-year sea ice in the central Canadian Archipelago during the spring-summer transitional period in 2012. Physical parameters (surface roughness, permittivity, temperature, density, etc.) were collected coincident to C-band polarimetric scattering data acquired using a surface-based scatterometer. In this study, a sea ice phenology encompassing key events associated with ice melting state and surface albedo is defined, and dual-polarization and polarimetric observables are evaluated. Firstly, optimized approaches for detecting phenological stages are provided within the context of future Sentinel and RCM missions which will not have fully polarimetric capabilities. Secondly, we place focus on the detection of sea ice melt ponds, a dynamic feature of late summer sea ice which strongly reduces the ice surface albedo, enhances the transmission of solar energy to the underlying ocean, and affects biogeophysical processes occurring in the upper ocean layer. An approach for detecting the sea ice melt pond fraction from dual-polarization C-band SAR is outlined, using imagery spatially co-located to aerial photographs taken over the study site. Together these results contribute to the application of satellite C-band SAR to the detection of essential climate variables (ECVs) sea ice melting state and surface albedo [1].

[1] Malenovsky, Z, H. Rott, J. Cihlar, M.E. Schaepman, G. Garcia-Santos, R. Fernandes, and M. Berger (2012), Sentinels for science: Potential of Sentinel-1, -2, and -3 missions for scientific observations of ocean, cryosphere, and land, Remote Sens. Environ., 120(15), doi:10.1016/j.rse.2011.09.026.