A WHOI program in 1996 and 1997 who goal was to use two independent methods to quantify turbulent mixing in the eastern Brazil Basin. The methods employed were:

• injecting an SF6 tracer and tracking its dissipation over time; and
• making discrete, instantaneous estimates of the turbulence using the HRP instrument.

The experiment involved released approximately 110 kg of sulfur hexafluoride on an isopycnal near 4000 m depth near 21° 40' S, 18° 25' W. The location is over a system of ridge spurs and canyons that run zonally towards the crest of the Mid Atlantic Ridge. The spurs attain depths of nearly 4400 m in the vicinity of the tracer release and the canyon valleys about 5000 m, with both shoaling to the east towards the Ridge crest where individual bathymetric peaks extend to about 2000 m depth.

The tracer was surveyed in 1996 within two weeks of its release, with HRP measurements indicating weak turbulent dissipation at all depths (with a diapycnal diffusivity of about 0. 1 cm² s^-1) in the western half of the Brazil Basin where the bottom is smooth. Mixing rates were much greater over the rough topography, with measured diapycnal diffusivity values of about 0. 5 cm² s^-1 for the depth and region of the tracer cloud (and values greater than twice this near the bottom). A survey cruise in 1997 sampled the distribution of sulfur hexafluoride about 14 months after its release. The average diffusivity over the 14 months on the injection isopycnal was estimated to be at least 1. 5 cm² s^-1, with values of 10 cm² s^-1 estimated near the bottom of the canyons.