Wind‐wave attenuation in Arctic sea ice: a discussion of remote sensing capabilities
|Author(s)||Collard Fabrice1, Marié Louis2, Nouguier Frederic2, Kleinherenbrink Marcel3, Ehlers Frithjof3, Ardhuin Fabrice4|
|Affiliation(s)||1 : OceanDataLab ,Locmaria‐Plousané ,France
2 : Univ. Brest, CNRS Ifremer IRD Laboratoire d’Océanographie Physique et Spatiale Brest ,France
3 : TU Delft ,Delft ,The Netherlands
4 : Univ. Brest, CNRS Ifremer IRD Laboratoire d’Océanographie Physique et Spatiale Brest ,France
|Source||Journal Of Geophysical Research-oceans (2169-9275) (American Geophysical Union (AGU)), 2022-07 , Vol. 127 , N. 7 , P. e2022JC018654 (16p.)|
|WOS© Times Cited||4|
|Note||This article also appears in: The Arctic: An AGU Joint Special Collection|
|Keyword(s)||wind waves, sea ice, remote sensing|
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.
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 be strongly attenuated and can contribute to breaking up the ice and pushing the ice around. Wavy patterns are clearly visible in remote sensing data collected by different instruments including the ICESat-2 laser altimeter, Sentinel-1 imaging radar, the Sentinel-2 optical imager, Sentinel-3 radar altimeter, and CFOSAT wave-measuring instrument SWIM. Here we show examples of such patterns and propose an quantitative interpretation of ICESat-2 and Sentinel-2 that is consistent with waves generated by storms in the Barents sea that are observed to travel under the ice over hundreds of kilometers. For Sentinel-3 and SWIM, a quantification of wave heights will have to be validated, possibly based on data from the other two instruments. This may strongly expand the quantity of available information for scientific investigations and operational applications.