How sea ice affects edge waves in the Sea of Okhotsk

Abstract Long-term observations, which were collected in the Sea of Okhotsk coastal zone under open-water conditions and at times when the sea was ice-covered from mid-January to mid-March 2022, are interpreted. The project augments preceding work using three synchronously-recording, seafloor-mounted, pressure transducers sampling at 1 Hz to acquire time series of inshore wave oscillations. Units are deployed nearer to the shore and closer together than was done during the previous studies. Spectral analyses of open-water sea level oscillations perpendicular to the coast reveal a wide band of energy, suggestive of a propagating edge wave at about 5-min period with an offshore-to-inshore gain up to 1.5. Similar wave characteristics occur alongshore. Intriguingly, the peak edge wave period at 5 min migrates to 6–7 min when the sea becomes covered with ice, and narrower bands at periods from 0.5 to about 3 min emerge. Other period ranges also appear to be affected by the onset, presence and eventual disintegration of sea ice. Whilst a shift of the dominant edge wave period can be attributed to changes in spectral refraction arising from the incoming swells being low-pass filtered by sea ice, because of the observed tidal signal it is speculated in this case that the observed period adjustment and attendant expansion of bandwidth may also be associated with instability around the fundamental frequency. The potential for edge wave solitons to exist is explored.