A Two-Part Model for Wave-Sea Ice Interaction: Attenuation and Break-Up

Waves and sea ice form a closely coupled system: waves govern sea ice through stress, floe break-up, and wave-induced currents, while sea ice affects waves through attenuation and reflection. Wave-induced sea ice break-up is particularly important as it can regulate air-sea interaction and consequently also regulate the growth and melt of sea ice. This coupled nature is complex and generally, especially at the large scale, neglected in modeling of the polar climate system. Here, we explore a novel way of coupling through wave-induced ice break-up, and conduct a case study for the Antarctic summer of 2019/2020. Our modeling approach builds upon previous investigations as follows: (a) sea ice takes a binary form, either broken or unbroken, (b) waves may break sea ice, transitioning it from unbroken to broken, (c) a threshold separating breaking and nonbreaking wave fields is used to identify when this occurs, (c) two modes of attenuation for waves in ice (dependent upon the ice state), representing the observed on/off switch in wave attenuation. By characterizing wave attenuation and sea ice break-up as described above, we achieve two-way wave-sea ice coupling, thereby allowing wave-sea ice feedbacks. This model is limited to the ice-melt season as refreeze is not represented here. We demonstrate that our model can simulate both the wavefield in and the evolution of the Marginal Ice Zone. Our results show the validity of empirically derived wave-induced sea ice break-up threshold, and substantiate that waves have a critical influence on the morphology of the Marginal Ice Zone.

Automated summary

Waves and sea ice are closely coupled, with wave-induced ice break-up regulating air-sea interaction and sea ice growth/melt. This coupling is often neglected in modeling the polar climate system.