Breaking of internal waves and turbulent dissipation in an anticyclonic mode Water Eddy

Fernández-Castro, Bieito; Evans, Gwyn ORCID: https://orcid.org/0000-0002-6328-4093; Frajka-Williams, Eleanor ORCID: https://orcid.org/0000-0001-8773-7838; Vic, Clément; Naveira-Garabato, Alberto C.. 2020 Breaking of internal waves and turbulent dissipation in an anticyclonic mode Water Eddy. Journal of Physical Oceanography, 50 (7). 1893-1914. 10.1175/JPO-D-19-0168.1

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Abstract/Summary

A four-month glider mission was analyzed to assess turbulent dissipation in an anticyclonic eddy at the western boundary of the subtropical North Atlantic. The eddy (radius ≈ 60 km) had a core of low potential vorticity between 100–450 m, with maximum radial velocities of 0.5 m s−1 and Rossby number ≈ −0.1. Turbulent dissipation was inferred from vertical water velocities derived from the glider flight model. Dissipation was suppressed in the eddy core (ε ≈ 5×10−10 W kg−1) and enhanced below it (> 10−9 W kg−1). Elevated dissipation was coincident with quasi-periodic structures in the vertical velocity and pressure perturbations, suggesting internal waves as the drivers of dissipation. A heuristic ray-tracing approximation was used to investigate the wave-eddy interactions leading to turbulent dissipation. Ray-tracing simulations were consistent with two types of wave-eddy interactions that may induce dissipation: the trapping of near-inertial wave energy by the eddy’s relative vorticity, or the entry of an internal tide (generated at the nearby continental slope) to a critical layer in the eddy shear. The latter scenario suggests that the intense mesoscale field characterizing the western boundaries of ocean basins might act as a ‘leaky wall’ controlling the propagation of internal tides into the basins’ interior.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JPO-D-19-0168.1
ISSN:	0022-3670
Date made live:	14 May 2020 13:53 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/527721

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