Fetch-limited wind-wave generation in partial sea ice cover

Wave-ice interactions are critical for correctly modelling air-sea exchanges and ocean surface processes in polar regions. While the role of sea ice in damping open-water swell waves has received considerable research interest, the impact of sea ice on locally generated wind-wave growth in partial ice cover remains uncertain. The current approach in spectral wave models is to scale the wind input term by the open-water fraction, \(1-φ\), for \(φ\) the sea ice concentration (SIC), but this neglects the impact of subgrid-scale patterns of sea ice coverage in limiting fetch for wind-wave growth. Here, we use the spectral wave model SWAN to simulate wave growth in realistic, synthetic fields of explicitly resolved sea ice floes over a range of SICs and floe size distributions (FSDs). Through geometric arguments, we show that the fetch available for wind-wave growth, and thus the resulting wave statistics, depends on a combination of the SIC and the FSD. The combination of geometric scaling and empirical wave laws allows the prediction of bulk wave statistics as a function of SIC, a characteristic floe size, and wind speed. We show that due to the difference in spectral character from attenuated propagating open-ocean swell, these waves may have an outsized impact on ocean mixing regimes.