Wave groups and spectral shape in ice

The reduction of arctic summer ice coverage has prompted a renewed interest in the physics of wave-ice interactions. Progress has been made on the observational, theoretical and modeling aspects of waves in the presence of ice.

This presentation will address our recent observational studies of spectral wave properties in the marginal ice zone, and in ice covered seas. Waves propagating through ice are attenuated and scattered, resulting in a pronounced change of the shape of the wave spectrum. In particular, the strong attenuation of the high frequency components affects wave steepness and the spectral bandwidth, and thus wave groupiness and the crest height distribution.

We present data for various ice conditions, obtained from drifting SWIFT buoys, a moored ADCP and moored inverted echosounders. All observations show well developed group structures of the waves. However, for different datasets we obtain opposite dependencies between wave groupiness and wave spectral characteristics. This suggests that depending on ice condition, both, the linear mechanism of wave superposition, or wave nonlinarites can be responsible for the wave group enhancement in ice. These mechanisms will be discussed.