Seasonal evolution of L-band SAR backscatter over landfast Arctic sea ice

• Published in: Remote sensing of environment 2020-12, Vol.251, p.112049, Article 112049
• Main Authors: Mahmud, Mallik S., Nandan, Vishnu, Howell, Stephen E.L., Geldsetzer, Torsten, Yackel, John
• Format: Article
• Language: English
• Subjects: Arctic; Arctic sea ice; Backscatter; Backscattering; C band; Data acquisition; Evolution; Ice; Ice breakup; Ice cover; Imagery; L-band; Microwaves; Monitoring; Polar environments; Radarsat; Robustness; SAR; Scatterometers; Sea ice; Snow cover; Superhigh frequencies; Synthetic aperture radar; Thermodynamics; Winter
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2020.112049

We construct and present the first baseline, time series evolution of L-band SAR microwave backscatter (σ0HH) for landfast Arctic first-year (FYI) and multi-year (MYI) sea ice from ALOS PALSAR. We compare the winter to freeze-up seasonal L-band σ0HH signatures with C-band RADARSAT-2 SAR imagery and Ku-band QuikSCAT scatterometer data. We also explored the utility of L-band σ0HH to detect FYI and MYI melt onset dates. For both ice types, L-band exhibited a similar σ0HH evolution to C- and Ku-bands. A rise in L-band σ0HH was observed from winter to melt onset, however, with a lower magnitude attributed to the larger penetration of L-band microwaves through the snow-covered sea ice medium. Over FYI, L-band σ0HH exhibited the most robust response and greater diversity in melt onset signature, compared to C- and Ku-bands. Over MYI, L-band σ0HH declined during the winter to melt onset transition contrasting the C- and Ku-band evolution of σ0HH during melt onset. Although, a distinct L-band σ0HH response was not found during pond onset, a very strong σ0HH response was found during sea ice break-up, which could operationally be utilized to identify sea ice break-up timing. During freeze-up, L-band σ0HH showed greater diversity compared to C- and Ku-bands. Our study also found that, L-band detected melt onset dates were up to 6 days later than C- and Ku-band detected dates, for both ice types. The melt response was the strongest at L-band for FYI, where C-band detected a robust melt onset date for MYI. Therefore, for operational sea ice monitoring, L-band suits better for FYI, whereas C-band is still a better choice for MYI. In the warming Arctic, where FYI has become the dominant ice type, L-band demonstrates promise to be the optimal choice for sea ice operational monitoring with high spatiotemporal data acquisition from existing, upcoming and proposed L-band SAR missions. •Time series evolution of L-band σ0HH for Arctic sea ice was presented.•L-band exhibited similar σ0HH evolution to C- and Ku-band over first-year ice.•L-band σ0HH evolution over multi-year ice was opposite to C- and Ku-band.•Over first-year ice, L-band σ0HH exhibited greater diversity in melt signature.•L-band detected melt onset dates were up to 6 days later than C- and Ku-band.