The evolution of wind-driven surface waves in partial sea ice cover in the southern Beaufort Sea
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Date
2019
Authors
Campbell, Yanique
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Abstract
Surface waves play an important role in how energy is transported and distributed to both sea ice and atmosphere in Arctic seas. The region of marginal sea ice, termed the Marginal Ice Zone (MIZ), has been increasing alongside temperature, introducing even more open water spaces within the sea ice field. Little research has focused on the development of waves within these open water spaces, and how the wave field evolves under such restricted fetch environments. This study considers a set of observations collected using moorings from ASL Environmental Sciences in the southern Beaufort Sea. These observations suggest local wave development as the dominant source of wave energy tens of kilometers in the MIZ throughout the month of August. The significant wave heights (H_s) and peak periods (T_p) were kept low throughout the month, mainly remaining below a H_s of 0.6 m and a T_p of 6 s in sea ice. At the end of the month, open water waves were able to influence the wave characteristics and there were notable increases in both heights and periods. This study examines how the attenuation of such waves by sea ice differs from the attenuation of open water waves moving into the MIZ. The coherence and positive correlation between H_s and T_p were found to be predominant in the sea ice field. This differs from the classic attenuation of open water waves in sea ice where peak periods increase while wave heights decrease, producing a distinct negative relationship with distance in sea ice. There was no preferential increase or lengthening of the dominant waves under easterly and southerly winds where the wave fetches were long, and the wind speed was found to have limited influence on wave growth after development. Estimations of fetch using empirical relationships, supplemented by satellite imagery, indicate that the short fetches were the dominant factor in terms of wave growth, which indicates an evolution similar to open water waves until they reach an sea ice floe interface and are scattered, a process which depends greatly on the sea ice type, size, rheology and the length of the waves. The interplay among the sea ice (size, structure and concentration) and the wind during a storm event provides an interesting look at the behavior of locally developed waves and the transition to more open water characteristics and development as the sea ice becomes eroded close to the end of the month. While waves developed locally in sea ice are expected to be fairly low compared to open water waves, they play an important role in the fluxes of energy and momentum in the MIZ and the expansion of this region has implications for the overall energy balance in Arctic marine systems.
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Keywords
Waves, Arctic Ocean, Sea ice