1. Decadal Observations of Internal Wave Energy, Shear, and Mixing in the Western Arctic Ocean.
- Author
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Fine, Elizabeth C. and Cole, Sylvia T.
- Subjects
SEA ice ,WAVE energy ,INTERNAL waves ,TURBULENT mixing ,OCEANIC mixing ,ARCTIC climate ,OCEAN - Abstract
As Arctic sea ice declines, wind energy has increasing access to the upper ocean, with potential consequences for ocean mixing, stratification, and turbulent heat fluxes. Here, we investigate the relationships between internal wave energy, turbulent dissipation, and ice concentration and draft using mooring data collected in the Beaufort Sea during 2003–2018. We focus on the 50–300 m depth range, using velocity and CTD records to estimate near‐inertial shear and energy, a finescale parameterization to infer turbulent dissipation rates, and ice draft observations to characterize the ice cover. All quantities varied widely on monthly and interannual timescales. Seasonally, near‐inertial energy increased when ice concentration and ice draft were low, but shear and dissipation did not. We show that this apparent contradiction occurred due to the vertical scales of internal wave energy, with open water associated with larger vertical scales. These larger vertical scale motions are associated with less shear, and tend to result in less dissipation. This relationship led to a seasonality in the correlation between shear and energy. This correlation was largest in the spring beneath full ice cover and smallest in the summer and fall when the ice had deteriorated. When considering interannually averaged properties, the year‐to‐year variability and the short ice‐free season currently obscure any potential trend. Implications for the future seasonal and interannual evolution of the Arctic Ocean and sea ice cover are discussed. Plain Language Summary: Changes in the Arctic climate have resulted in less summertime Arctic sea ice. These changes in ice‐cover have the potential to influence internal waves, which carry energy deep into the ocean, providing the energy source for most ocean mixing. In this study, we use 15 years of observations to assess how changes in sea ice are related to changes in both the internal wavefield and the turbulent mixing caused by internal wave breaking. We find that while sea ice decline creates a more energetic internal wavefield, the mixing that internal waves causes doesn't increase in ice‐free conditions. We show that this apparent contradiction occurs because in ice‐free conditions the internal wavefield tends to consist of waves with larger vertical scale that are less prone to breaking, so that even though the total energy increases, these more‐energetic waves don't increase total ocean mixing. This mechanism serves to protect sea ice from accelerating decline that could occur if sea ice loss resulted in more ocean mixing and thus higher oceanic heat fluxes. Key Points: Over 100–300 m depth at daily and seasonal timescales, increasing near‐inertial energy was associated with sea ice declineThere is no evidence of increased turbulence over 100–300 m depth coincident with sea ice decline and the increase of near‐inertial energySea ice conditions impact the vertical scales of internal wave energy, explaining why vertical mixing has not changed under sea ice decline [ABSTRACT FROM AUTHOR]
- Published
- 2022
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