Freshwater ice cover on inland water bodies is a sensitive indicator of climate change, and its monitoring is hampered by the decline of in situ observation networks since the 1980s. Previous applications of GNSS-Reflectometry (GNSS-R) have focused mainly on sea ice detection, while its capability for seasonal freshwater ice monitoring has remained insufficiently explored. The aim of this study is to assess the sensitivity of spaceborne L-band bistatic measurements to the processes of freshwater ice cover formation, growth, and break-up on large inland lakes, and to compare the scattering behavior with that of sea ice. A full annual cycle (September 2023 – August 2024) was analyzed using data from the GNOS-II instrument onboard the Feng-Yun 3E (FY-3E) satellite at two test sites: Great Slave Lake (Canada) for freshwater ice and the Sea of Okhotsk for sea ice. Statistical moments of the Doppler spectrum – width and kurtosis coefficient – were computed from delay-Doppler maps. The results were validated against meteorological records from the Yellowknife station, MODIS imagery, and ERA5 ice thickness reanalysis. A monotonic decrease in Doppler spectrum width with decreasing air temperature was established for freshwater ice, consistent with a reduction of effective surface roughness. For freshwater ice, peak power and kurtosis coefficient show a distinct dependence on ice thickness, reflecting signal attenuation within the ice volume and dominant reflection at the ice-water interface; for sea ice these parameters remain stable, since reflection occurs at the air-ice boundary owing to high brine salinity. The findings demonstrate that L-band bistatic reflectometry provides an effective all-weather tool for operational monitoring of freshwater and sea ice, including detection of freeze-up and break-up phases, ice thickness estimation, and support for Arctic navigation.
Kovaldov et al. (Mon,) studied this question.