Deep ocean acoustic Doppler current profiling

A standard 300-kHz self-contained acoustic Doppler current profiler (ADCP) which was mounted with a CTD on a rosette sampler and used to obtain relative velocity profiles over the full ocean depth range is described. The unknown motion of the ADCP-CTD package is removed by averaging individual vertical shear profiles in depth bins and then integrating over the water column to get a velocity profile relative to an unknown constant of integration. The resulting profile is useful at scales of a few hundred metres, but has errors that accumulate to 10-20 cm/s over a few thousand metres. Errors at low wavenumber are found to be considerably larger than the calculated lower bound, but the information at higher wavenumbers is still of scientific value