Signatures of Breaking Waves in a Coastal Polynya Covered with Frazil Ice: A High-Resolution Satellite Image Case Study of Terra Nova Bay Polynya

The study focuses on the detection of breaking wave crests in the highly dynamic waters of an Antarctic coastal polynya using high-resolution panchromatic satellite imagery. Accurate as-sessment of whitecap coverage is crucial for improving our understanding of the interactions be-tween wave generation, air–sea heat exchange, and sea ice formation in these complex environ-ments. As open-ocean whitecap detection methods are inadequate in coastal polynyas partially covered with frazil ice, we discuss an approach that exploits specific lighting conditions: the alignment of sunlight with the dominant wind direction and low solar elevation. Under such conditions, steep breaking waves cast pronounced shadows, which are used as the primary indi-cator of wave crests, particularly in frazil streak zones. The algorithm is optimized to exploit these conditions and minimize false positives along frazil streaks boundaries. We applied the algorithm to a WorldView-2 image covering different parts of the Terra Nova Bay Polynya (Ross Sea), a dynamic polar coastal zone. This case study demonstrates that the spatial distribu-tion of detected breaking waves is consistent with ice conditions, and wind forcing patterns, while also revealing deviations that point to complex wind-wave-ice interactions. Although quantitative validation of satellite-derived whitecaps coverage wasn’t possible due to the lack of in situ data, the method performs reliably across a range of conditions. Limitations of the pro-posed approach are pointed out and discussed. Finally, the study highlights the risk of misinter-pretation of lower-resolution reflectance data in areas where whitecaps and sea ice coexist at subpixel scales.