Ocean eddy signature on SAR‐derived sea ice drift and vorticity

• Published in: Geophysical Research Letters
• Main Authors: Cassianides, Angelina, Lique, Camille, Korosov, Anton
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2021
• Subjects: mesoscale eddies; SAR images; sea ice eddies interaction; Arctic; Arctic Ocean; Arctic Basin; Sea ice
• Online Access: https://archimer.ifremer.fr/doc/00679/79137/81640.pdf; https://doi.org/10.1029/2020GL092066; https://archimer.ifremer.fr/doc/00679/79137/

In the Arctic Ocean, the observation of mesoscale eddies is impeded by the presence of sea ice. To address this problem, we develop a new method of ocean eddy detection based on their signature in sea ice vorticity retrieved from Synthetic Aperture Radar (SAR) images. We examine the case of one eddy in October 2017 in the marginal ice zone of the Canadian Basin, which was sampled by mooring observations. Although the eddy could not be identified by visual inspection of the SAR images, its signature is revealed as a dipole anomaly in sea ice vorticity, which suggests that the eddy is a dipole composed of a cyclone and an anticyclone, with a horizontal scale of 80‐100 km and persisted over a week. The robustness of our method will allow us to detect more eddies as more SAR observations become available in the future. Plain Language Summary Mesoscale eddies are routinely observed by satellites in the ocean. Yet, in the ice‐covered Arctic Basin, the presence of sea ice makes it challenging to characterise the eddy field. Here, we present a detection method of surface ocean eddies based on their signature in the displacement of sea ice, using high spatial resolution satellite images. A dipole composed of a cyclonic and an anticyclonic eddy is identified over a week in mid‐October 2017 with a horizontal scale of 80‐100 km. Its presence is confirmed by high values of ocean speed in the surface layer during the same period. This work demonstrates that processing are required for identifying the signature of eddies in sea ice, which is not always obvious at first sight.