Wave Propagation in Frazil/Pancake Ice: The Beaufort Sea MIZ during Fall 2015

The wave frequency and the physical properties of the ice cover determine the way in which waves propagate in ice. Large floes interact with waves via a scattering process which results in an exponential decay of incoming wave energy with distance. Very small floes, like pancake ice where the individual cakes may be less than 3 m in diameter, interact in a different manner; they behave like a continuum and can be considered as a very viscous fluid which not only causes decay of the waves but also causes them to propagate with a different dispersion relation. A careful analysis of in situ measurements, collected in the Beaufort Sea during fall 2015 through the use of directional wave buoys, has allowed us to examine attenuation rates, spectral spread rates and anomalous dispersion for different ice conditions met in the MIZ during several in situ experiments. The buoys deployments lasted 1-3 days temporally and spanned up to 100 km spatially. After inter-calibrating the buoys, the vertical displacement (heave) time series for the buoys was hence analyzed for calculation of the scalar wave energy spectra and bulk wave parameters (i.e., significant wave height, dominant wave period). As expected, our measurements show that waves play an important role in inhibiting the fall freeze-up of the Beaufort Sea, especially near the ice edge facing the prevailing easterly winds. Results on the attenuation of waves in different MIZ conditions are presented and discussed.