Modification of turbulent dissipation rates by a deep Southern Ocean eddy

• Published in: Geophysical Research Letters
• Main Authors: Sheen, Katy L., Brearley, J. Alexander, Naveira Garabato, Alberto C., Smeed, David A., St. Laurent, Louis C., Meredith, Michael P., Thurnherr, Andreas M., Waterman, Stephanie N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley & Sons 2015
• Subjects: Mixing; Eddy; Turbulent dissipation; Internal waves; Southern Ocean; Ray tracing
• Online Access: https://hdl.handle.net/1912/7380

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 42 (2015): 3450–3457, doi:10.1002/2015GL063216. The impact of a mesoscale eddy on the magnitude and spatial distribution of diapycnal ocean mixing is investigated using a set of hydrographic and microstructure measurements collected in the Southern Ocean. These data sampled a baroclinic, middepth eddy formed during the disintegration of a deep boundary current. Turbulent dissipation is suppressed within the eddy but is elevated by up to an order of magnitude along the upper and lower eddy boundaries. A ray tracing approximation is employed as a heuristic device to elucidate how the internal wave field evolves in the ambient velocity and stratification conditions accompanying the eddy. These calculations are consistent with the observations, suggesting reflection of internal wave energy from the eddy center and enhanced breaking through critical layer processes along the eddy boundaries. These results have important implications for understanding where and how internal wave energy is dissipated in the presence of energetic deep geostrophic flows. Natural Environment Research Council (NERC). Grant Numbers: NE/E007058/1, NE/E005667/1; U.S. National Science Foundation. Grant Numbers: OCE-1231803, OCE-0927583, OCE-1030309; NERC 2015-11-07