Shear and Richardson number in a mode-water eddy

Measurements of stratification and shear were carried out as part of the EDDIES tracer release experiment in mode-water eddy A4 during the summer of 2005. These measurements were accomplished using both shipboard instrumentation and a drifting mooring. A strong relationship between shear intensity and distance from the center of the eddy A4 was observed with the shipboard ADCP. Diapycnal diffusivity at the SF₆ tracer isopycnal prior to and during the release was estimated from the drifting mooring to be 2.9×10⁻⁶ m² s⁻¹. Diffusivity increased by an order of magnitude to 3.2×10⁻⁵ m² s⁻¹ during the period of the final tracer survey in early September, which was similar to the value estimated from the tracer analysis for the whole experiment (3.5×10⁻⁵ m² s⁻¹, Ledwell, J.R., McGillicuddy Jr., D.J., Anderson, L.A., 2008. Nutrient flux into an intense deep chlorophyll layer in a mode-water eddy. Deep-Sea Research II, this issue doi:10.1016/j.dsr2.2008.02.005]].