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Keywords:

  • Kelvin-Helmholtz billow;
  • deep-ocean mixing;
  • internal waves

[1] Detailed overturning is observed between 0.5 and 50 m above the sloping side of Great Meteor Seamount, Canary Basin, using 100 moored temperature sensors, 1 mK accurate, sampling at 1-Hz. While previously reported frontal bores of 40-m amplitude can form with vigorous near-bottom motions and sediment resuspension at the beginning of the upslope phase of large, e.g., tidal, carrier waves, the downslope phase presented here is more “permanently” turbulent away from the bottom. This turbulence is inferred from high-resolution temperature space-time series, which reveal ubiquitous “finger-like” structures. It occurs during the clear-water tidal phase, with low amounts of acoustic scatterers. The high-frequency finger-like motions σ ≫ N, N the buoyancy frequency, are observed simultaneously with local mode-2 near-N inertio-gravity waves and overall shear ∣S∣ ≈ N. They show large temperature variations, 5–10 m vertical amplitudes and occasionally develop Kelvin-Helmholtz billows. The typical (Eulerian) period of these firstly observed deep-ocean billows amounts 50 ± 10 s.