Constraining Wave Dissipation and Non-Linear Interactions in The Marginal Ice Zone

Wave-ice interactions affect sea ice dynamics and must be adequately represented in numerical models in order to improve predictability, especially in a context of ice receding and thinning. How wave energy attenuates and redistributes when propagating in ice-covered seas have been studied for many decades. However, our current understanding relies on observational datasets that measure the apparent attenuation resulting from many processes that are not well-constrained. Here we investigate with observations and models how non-linear wave-wave interactions affect the estimation of wave dissipative processes. Observations of waves in a marginal ice zone of the St. Lawrence Estuary were obtained using bottom-moored pressure gauges and wave buoys deployed on sea ice over relatively short transects where ice thickness and floe size can be characterized. The apparent spectral attenuation rates follow a power law that is comparable to other datasets, but magnitudes are one to two orders of magnitude larger. They also display a roll-over at high frequencies that is indicative that other processes are occurring. To quantitatively assess the portion of the apparent attenuation that is due to dissipative processes in this coastal environment, we use a high-resolution configuration of the WAVEWATCH^® III spectral wave model applied to the bay. The bathymetry is obtained from a recent multibeam echosounder survey, sea ice coverage from georectified images taken by a camera overlooking the bay, and incident wave conditions from a moored acoustic wave and current profiler. Contributions of non-linear wave energy transfer and dissipative mechanisms in various ice conditions (thickness and floe size) will be investigated and discussed.