X-, C-, and L-band SAR signatures of newly formed sea ice in Arctic leads during winter and spring

摘要

We examine an extensive synthetic aperture radar (SAR) data set from the Arctic Ocean spanning a time periodfrom January to June 2015, with the aim of identifying multi-polarization parameters that can be used toaccurately separate newly formed sea ice from the surroundings. Newly formed sea ice areas both providefavourable routing for ship traffic, and are key to Arctic climate science because they enable heat exchangebetween the ocean and the atmosphere. Our data set encompasses three different frequencies, X-, C- and L-band,at a range of incidence angles, and were acquired under different environmental conditions. Our results suggestthat by combining the scattering entropy and the co-polarization ratio we can successfully separate the newlyformed sea ice from open water and thicker sea ice within all three frequencies throughout the winter and springseason. We observe a high correlation between scattering entropy values calculated using quad-polarization CandL-band data and scattering entropy values calculated using the same scenes reduced to the co-polarizationchannels (HH and VV). We therefore conclude that dual-polarization (HH and VV) X-band scenes can be directlyused to complement quad-polarimetric C- and L-band scenes for studies of newly formed sea ice. To confine thequad-polarimetric data sets to their co-polarization channels one can ensure a higher signal-to-noise ratio.Incidence angles below 35° are needed to keep the signal-to-noise ratios sufficiently high for the scatteringentropy and co-polarization ratio. Due to its lack of incidence angle dependency, the polarization difference canprovide additional support in newly formed sea ice studies. The regular coverage of the Arctic Ocean with CbandSAR means that such scenes should to be included in any automatic monitoring, however, X- and L-bandSAR can, based on their difference in penetration depth, provide additional information about newly formed seaice types and surface structure.