Analyses of C-band microwave backscatter to wind roughened first-year sea ice melt ponds

Variations in wind forcing over summer first-year sea ice (FYI) melt ponds occur at hourly to weekly scales and are a significant contributor to backscatter (σ°) variability observed from space borne synthetic aperture radar (SAR) platforms (e.g., ENVISAT-ASAR and RADARSAT-1). This variability impairs our ability to use SAR to derive information on summer sea ice thermodynamic state and energy balance parameters such as albedo and melt pond fraction. The surface roughness contribution to like-polarized, C-band σ° estimates from FYI melt ponds in the Canadian Arctic is addressed through a spectral and statistical analysis of surface wave height profiles for varying wind speeds, upwind fetch lengths, and melt pond depths. Our hypothesis is that the perturbation of wind-roughened melt pond surfaces to wavelengths that are resonant to C-band SARs is driven by upwind fetch and wind speed. Significant scale surface roughness was observed even at wind speeds of 3 m s^-1 resulting in σ° (HH) ranging from -6 dB at 20° incidence to -24 dB at 50° incidence. Results from a multivariate linear regression analysis show that 53.4% of observed variance in σ° (HH or VV) can be explained by wind speed (0.9 m height), upwind fetch from melt pond edges, and depth of melt ponds, with no appreciable difference in the relative contribution of those explanatory variables.