Attenuation of ocean surface waves in pancake and frazil sea ice along
the coast of the Chukchi Sea
Abstract
Alaskan Arctic coastlines are protected seasonally from ocean waves by
presence of coastal and shorefast sea ice. This study presents field
observations collected during the autumn freeze up of 2019 near Icy
Cape, a coastal headland in the Chukchi Sea of the Western Arctic. The
evolution of the coupled air-ice-ocean-wave system during a four-day
wave event was monitored using drifting wave buoys, a cross-shore
mooring array, and ship-based measurements. The incident wave field was
attenuated by coastal pancake and frazil sea ice, reducing significant
wave height by 1 m over less than 5 km of cross-shelf distance spanning
water depths from 13 to 30 m. Spectral attenuation coefficients are
evaluated with respect to wave and ice conditions and the proximity to
the ice edge. Attenuation rates are found to be three times higher
within 500 m of the ice edge, relative to values farther in the ice
cover. Attenuation rates follow a power-law dependence on frequency,
with an exponent in the range of (2.3,2.7) m^-1.