Wind‐wave attenuation in Arctic sea ice: a discussion of remote sensing capabilities

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Collard, Fabrice, Marié, Louis, Nouguier, Frederic, Kleinherenbrink, Marcel, Ehlers, Frithjof, Ardhuin, Fabrice
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2022
• Subjects: wind waves; sea ice; remote sensing; Arctic; Sea ice
• Online Access: https://archimer.ifremer.fr/doc/00776/88814/94456.pdf; https://doi.org/10.1029/2022JC018654; https://archimer.ifremer.fr/doc/00776/88814/

Wind-generated waves strongly interact with sea ice and impact air-sea exchanges, operations at sea, and marine life. Unfortunately, the dissipation of wave energy is not well quantified and its possible effect on upper ocean mixing and ice drift are still mysterious. As the Arctic is opening up and wave energy increases, the limited amount of in situ observations is a clear limitation to our scientific understanding. Both radar and optical remote sensing has revealed the frequent presence of waves in ice, and could be used more systematically to investigate wave-ice interactions. Here we show that, in cloud-free conditions, Sentinel-2 images exhibit brightness modulations in ice-covered water, consistent with the presence of waves measured a few hours later by the ICESat-2 laser altimeter. We show that a full-focus SAR processing of Sentinel-3 radar altimeter data also reveals the presence and wavelengths of waves in sea ice, within minutes of Sentinel-2 imagery. The SWIM instrument on CFOSAT is another source of quantitative evidence for the direction and wavelengths of waves in ice, when ice conditions are spatially homogeneous. In the presence of sea ice, a quantitative wave height measurement method is not yet available for all-weather near-nadir radar instruments such as altimeters and SWIM. However, their systematic co-location with optical instruments on Sentinel-2 and ICESat-2, which are less frequently able to observe waves in sea ice, may provide the empirical transfer functions needed to interpret and calibrate the radar data, greatly expanding the available data on wave-ice interactions. Key Points Wave patterns in sea ice can be found in radar and optical remote sensing data We provide a quantitative estimation of wave height, wavelength and direction from ICESat-2 and Sentinel-2 data Wavelengths and directions in full-focus SAR altimetry and CFOSAT SWIM are consistent with other sensors Plain Language Summary Waves generated by winds over the ocean propagate in ice-covered regions where they can ...