Applications of Global Navigation Satellite System Reflectometry (GNSS-R) in sea ice science have been among the efforts and prospects of the GNSS-R community for a long time. This dataset provides the observations of the quad-polarization shipborne GNSS-R prototype (identified by FpolGNSSR) in the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. FpolGNSSR, with four polarization channels, explicitly inhibits direct signal contamination through high antenna gain (11.3 dB). The data are in NetCDF format, with in-file metadata and variable description.