Propagation and Directional Scattering of Ocean Waves in the Marginal Ice Zone and Neighboring Seas

As Arctic sea ice continues to decline in coming decades, retreating farther from the coastlines, the Arctic Ocean is experiencing increasing expanses of open water, in summers, leading to more intense, larger, more frequent storms and higher waves. The expanding open ocean allows larger fetches, and therefore, more energetic wind-driven waves, which result in enhanced destruction of more sea ice, creating a positive feedback. Recent studies suggest that energetic ocean waves can propagate through sea ice for hundreds of kilometers from the ice edge and that the attenuation rate is almost linear for large waves and therefore sufficiently low that the waves can propagate much farther than is possible with the commonly assumed exponential decay rate. Thus, the marginal ice zone (MIZ), which is the boundary between open seas and ice-covered pack-ice, can be hundreds of kilometers wide, consisting of broken ice floes of various sizes, thicknesses, and concentrations. Although wave-ice interactions are thought to play an important role in the Arctic ice retreat, modern operational wave models, such as WAVEWATCHIII (hereafter WW3), usually parameterize sea ice as a solid boundary, like land, and only recently have subroutines for wave-ice interactions been constructed. In particular, wave-ice interactions, involving directional scattering have not generally been implemented in operational wave forecast models. However, besides breaking ice floes and changing floe distributions, wave-ice interactions can open leads, modifying air-sea fluxes of momentum and heat, as well as the albedo and the underlying ocean boundary layer. These effects can delay winter ice formation and speed up summer ice melt. Therefore, besides day-to-day Arctic marine forecasts, it is also important to implement accurate wave-ice parameterizations in climate model systems. There are three objectives to the proposed work. Firstly, we will contribute to the collection of field data, by capturing high resolution remotely sensed satellite synthetic aperture radar (SAR) data from RADARSAT-2 remote sensing images that collocate with in situ observations of waves, sea ice and winds in the MIZ. The SAR data will support development of models for wave attenuation and scattering, collocating with field programs that are underway in the Sea State DRI. Secondly, we will develop an efficient operational numerical model for wave attenuation and scattering in the MIZ, for implementation in WW3. This builds on our previous work that used a second generation wave model, and on recent analysis that allows us to optimize our model, include ice floe flexure, as well as multiple wave scattering. Thirdly, we will add value to the presently funded research within the Sea State DRI, by partnering and collaborating with other researchers.