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07.06.2021: Online Ocean Circulation and Climate Dynamics Colloquium
Dr. Elizabeth Fine, Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA (USA): "Decadal observations of internal wave energy, shear, and mixing in the western Arctic Ocean"
online 2 pm
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As Arctic sea ice declines wind energy has increasing access to the upper ocean, with potential consequences for mixing, stratification, and heat fluxes. Here we investigate the relationships between internal wave energy, turbulent dissipation, and ice concentration and draft using data collected in the Beaufort Sea during 2003-2018. The Beaufort Gyre Exploration Project moorings have been deployed in the Canada Basin since 2003 and thus provide opportunities to observe changes in the internal wavefield in response to varying sea ice conditions over this 15 year period. We use velocity and CTD records to estimate near-inertial shear and energy, and apply a finescale parameterization to infer turbulent dissipation rates. All quantities vary widely on monthly and interannual timescales, with significant seasonal cycles in ice concentration, ice draft and near-inertial energy, but not shear or dissipation. We find that near-inertial energy between 50-400 m is inversely correlated with ice cover, so that a decline in sea ice is associated with increased energy in the internal wave field. However, in ice-free conditions this energy enters the ocean at relatively large vertical length scales and is not efficiently transported to the small vertical scales associated with turbulent dissipation. These results help to explain apparently contradictory observations that have shown internal wave energy increasing in ice-free waters, with no corresponding increase in turbulent dissipation.
