Signatures of Breaking Waves in a Coastal Polynya Covered with Frazil Ice: A High-Resolution Satellite Image Case Study of Terra Nova Bay Polynya.
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| Title: | Signatures of Breaking Waves in a Coastal Polynya Covered with Frazil Ice: A High-Resolution Satellite Image Case Study of Terra Nova Bay Polynya. |
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| Authors: | Bradtke, Katarzyna1 (AUTHOR) katarzyna.bradtke@ug.edu.pl, Brodziński, Wojciech1,2 (AUTHOR), Herman, Agnieszka1,2 (AUTHOR) |
| Source: | Remote Sensing. Sep2025, Vol. 17 Issue 18, p3198. 22p. |
| Subjects: | Water waves, Polynyas, Remote-sensing images, Oceanography, Ice crystals, High resolution imaging |
| Geographic Terms: | Antarctica, Ross Sea (Antarctica) |
| Abstract: | Highlights: What are the main findings? Wave crest shadows in high-resolution imagery reveal breaking waves in frazil ice–covered polynyas. A dedicated filter improves detection of whitecaps, reducing false positives along ice streaks. What is the implication of the main finding? Spatial distribution of breakers reveals the complexity of wave–ice interactions in coastal polynyas. Whitecaps' spatial patterns can locally increase reflectance, mimicking ice in lower-resolution imagery. 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 assessment of whitecap coverage is crucial for improving our understanding of the interactions between wave generation, air–sea heat exchange, and sea ice formation in these complex environments. 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 indicator of wave crests, particularly in frazil streak zones. The algorithm is optimized to exploit these conditions and minimize false positives along frazil streak boundaries. We applied the algorithm to a WorldView-2 image covering different parts of Terra Nova Bay Polynya (Ross Sea), a dynamic polar coastal zone. This case study demonstrates that the spatial distribution 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 was not possible due to the lack of in situ data, the method performs reliably under a range of conditions. Limitations of the proposed approach are pointed out and discussed. Finally, the study highlights the risk of misinterpretation of lower-resolution reflectance data in areas where whitecaps and sea ice coexist at subpixel scales. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Highlights: What are the main findings? Wave crest shadows in high-resolution imagery reveal breaking waves in frazil ice–covered polynyas. A dedicated filter improves detection of whitecaps, reducing false positives along ice streaks. What is the implication of the main finding? Spatial distribution of breakers reveals the complexity of wave–ice interactions in coastal polynyas. Whitecaps' spatial patterns can locally increase reflectance, mimicking ice in lower-resolution imagery. 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 assessment of whitecap coverage is crucial for improving our understanding of the interactions between wave generation, air–sea heat exchange, and sea ice formation in these complex environments. 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 indicator of wave crests, particularly in frazil streak zones. The algorithm is optimized to exploit these conditions and minimize false positives along frazil streak boundaries. We applied the algorithm to a WorldView-2 image covering different parts of Terra Nova Bay Polynya (Ross Sea), a dynamic polar coastal zone. This case study demonstrates that the spatial distribution 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 was not possible due to the lack of in situ data, the method performs reliably under a range of conditions. Limitations of the proposed approach are pointed out and discussed. Finally, the study highlights the risk of misinterpretation of lower-resolution reflectance data in areas where whitecaps and sea ice coexist at subpixel scales. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 20724292 |
| DOI: | 10.3390/rs17183198 |
