An Analysis of Dumpsite Diffusion Experiments
The oceanic dispersion of industrial waste barged to Deep Water Dumpsite 106 is effected in the first instance by barge-bound eddies (“wake dispersion”), then by naturally occurring mean shear and turbulence. Wake dispersion is very efficient, producing initial dilution up to a factor of 104, and is controlled by the dimensions and the forward speed of the barge. Subsequent dispersion by natural oceanic processes is slow under stratified summer conditions, describable by an effective diffusivity of order 300 cm2 sec−1, or a diffusion velocity in the neighborhood of 0.2 cm sec−1, for the first 12 hours or so after release. A comparison of the observed data with shear-dispersion theory shows that: (a) horizontal dispersion in the upper 10–20 m of a stratified ocean is mainly due to mean shear-vertical mixing interaction; (b) the low observed rates of dispersion may be attributed to the fact that an early phase of shear diffusion was in evidence. Extrapolation to diffusion times of the order of several days should be possible using a constant diffusion velocity, or an effective diffusivity increasing in direct proportion to time.
KeywordsMixed Layer Mixed Layer Depth Surface Mixed Layer Ekman Layer Diffusion Velocity
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