Classification of Arctic Sea Ice Using AMSR2 Data

Classification of sea ice by age is one of the most important tasks of Arctic satellite monitoring. The solution of this task is necessary to ensure the safety of navigation in ice. This paper presents a new method for classifying sea ice in the Arctic by age (type) with the data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) based on the significant variations in differences D of vertically polarized effective emission coefficients of sea ice of different age gradations. A database of polygons with three sea ice types with significantly different radiative properties—multiyear, first-year, and young ice—was created. Each polygon had a 100% partial sea ice concentration. The database was created using the facilities of the Arctic Portal based on analysis of Sentinel-1 synthetic aperture radar (SAR) images. AMSR2 measurements collocated with Sentinel-1 SAR images in space and time were used in the analysis of D. The effective emission coefficients for different sea ice types were calculated using the AMSR2 measurements and a previously developed method for atmospheric microwave radiation parameter estimation, not requiring additional data for its application. The probability density functions for the three differences between the coefficients of the vertically polarized sea ice emission at the frequencies of 36.5, 23.8, 18.7, 10.65, and 6.9 GHz turned out to be practically nonoverlapping, which made it possible to propose a method for sea ice classification based on the use of D threshold values. The method is applicable only to 100% sea ice concentration areas. The method was verified by a comparison with the Exploitation of Meteorological Satellites (EUMETSAT) Ocean and Sea Ice Satellite Application Facility (OSI SAF) data.