Multi‑Frequency (X‑, C‑, and L‑Band) F‑SAR Analysis of Scattering Behavior of Freshwater Ice on Noell Lake, Northwest Territories

Abstract

Lake ice plays a critical role in Arctic and sub-Arctic environments, influencing physical processes within lake systems while also supporting a range of socio-economic activities in northern communities. However, despite its importance, the interaction between lake ice and microwave signals remains inadequately understood, particularly in terms of backscatter behavior during the simultaneous acquisition of active microwave wavelengths. This study utilizes the fully polarimetric FSAR (Flexible Synthetic Aperture Radar) system developed by the Deutsches Zentrum für Luft- und Raumfahrt (DLR), which simultaneously acquired repeat-pass imagery at C-, X-, and L-bands over Noell Lake in the Northwest Territories to investigate the dominant scattering mechanisms associated with lake ice. The results of this study indicate that single-bounce scattering is the dominant scattering mechanism over Noell Lake at all frequencies, but with variable intensities proportional to the wavelength.

Furthermore, the influence of tubular bubbles is observed in X- and C-bands but is not detectable in the L-band, aligning with recent research suggesting that tubular bubbles do not significantly increase backscatter, but influence the roughness at the ice-water interface, and is therefore wavelength dependent. These coincident observations at X-, C-, and L-bands improve the understanding of microwave interactions with freshwater ice and the role of ice structural variability in influencing wavelength-dependent scattering responses. Additionally, the investigation of ice property retrieval provides a theoretical foundation for future SAR missions, including support for the NASA–ISRO (NISAR) and TanDEM-L L-band sensors.