Fernandez-Castro, Bieito and Evans, Dafydd Gwyn and Frajka-Williams, Eleanor and Vic, Clement and Naveira Garabato, Alberto
abstract: A 4-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 and 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 quasiperiodic 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 basin’s interior.
@article{FernandezCastro-etal-2020,
author = {Fernandez-Castro, Bieito and Evans, Dafydd Gwyn and Frajka-Williams, Eleanor and Vic, Clement and {Naveira~Garabato}, Alberto},
title = {Breaking of internal waves and turbulent dissipation in an anticyclonic mode water eddy},
year = {2020},
journal = {J. Phys. Ocean.},
volume = {50},
number = {7},
pages = {1893--1914},
doi = {10.1175/JPO-D-19-0168.1}
}
