Improved Arctic sea-ice motion in summer from the brightness temperature of the AMSR2 36GHz channel

Information on Arctic sea-ice motion in summer is critical for operational sea-ice monitoring and prediction and commercial navigation. Affected by the melting of the sea-ice surface, the accuracy and spatial coverage of the sea-ice velocity (SIV) retrieved by brightness temperature (TB) during the melting period are always lower than in winter. Our research indicates that the lack of ice-water discrimination in summer for the Advanced Microwave Scanning Radiometer 2 (AMSR2) 36 GHz TB is the main reason for the poor quality of its SIV results. We propose a new SIV retrieval scheme based on the polarization difference (P) of the 36 GHz TB. The 36-P SIV has a higher spatial coverage than that derived from 18-H, 36-H and 36-V SIVs and a higher maximum cross-correlation coefficient than 36 GH TB-derived SIVs. Compared with buoy and Synthetic Aperture Radar SIVs, the 36-P SIV's error is close to that of 18-H SIV and significantly lower than that of 36 TB SIV. Therefore, our results indicate that 36-P is more competitive than the 36 GHz TB in SIV retrieval in summer. Further analysis shows that our proposed scheme is compatible with the two current mainstream SIV tracking algorithms, demonstrating its great potential for future summer SIV retrieval.