Wave attenuation in landfast sea ice in Svalbard

Abstract:

The extent of wave energy propagation into the sea ice cover is largely determined by the properties of the ice layer. To improve weather and climate forecasting, modelers need additional observations and parameterizations of the dissipation rate of wave energy in the ice. Current studies have largely focused on wave energy attenuation in pancake and broken ice, but measurements in fast ice remain rare. In this study, we present observations of wave energy attenuation in landfast sea ice. The vertical motion of the ice was measured at three points along the main axis of Gronfjorden in Svalbard, with instruments being about 600-700 apart. The first instrument was deployed approximately 500 m from the solid ice edge and roughly 7 km from the entrance of the fjord. The fast ice edge remained relatively stable during the experiment, whereas ice conditions between the landfast ice and the fjord entrance were more dynamic. During the experiment the significant wave height varied between 2 and 10 cm, with peak periods between 8 and 16 s. The observed attenuation rate for swell (between 8 and 12 s) in landfast ice is about an order of magnitude larger than those typically seen in broken and pancake ice. Our measurements further substantiate the common perception that wave energy dissipation in sea ice covers are strongly determined by the properties of ice layer.