Home > Publications > Detailed internal wave mixing above a deep-ocean slope

H. van Haren and L. Gostiaux

Detailed internal wave mixing above a deep-ocean slope

Journal of Marine Research, 70(1) (2012)

Turbulent vertical eddy diffusivity (Kz) and dissipation rate (ε) are estimated between 0.5 and 50 m above the sloping side of Great Meteor Seamount, Canary Basin, using 101 moored temperature sensors, 1-mK precision, sampling at 1 Hz.

Effectively, detailed observed time-depth temperature images are split in two: a statically stable and a turbulence image.

Tides dominate the temperature variations, but the local bottom slope is sub-critical to semidiurnal frequencies. Averaged over a fortnight, the observed overall time-depth mean Kz = 2±1×10-3 m2 s-1 and ε = 1.5±0.7×10-7 W kg-1. Variations with time and depth are large, by up to four orders of magnitude. A tidal period shows multiple vigorous overturning events, the largest found away from the bottom during the downslope phase but just prior to arrival of an upslope moving, equally vigorous bore. The strength of the bore may be controlled by the intensity of the mixing just prior to it. The bore itself is turbulent from the bottom upward, up to some 40 m above it. Its mixing is most efficient providing large fluxes in extremely thin layers. In the mean, the canonical relationship Kz N-2 is retrieved, but other, even inverse relationships are also found over shorter periods of time and at particular heights above the bottom.

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