What kinds of vertical ocean mixing measuring instruments are available? This answer How to measure ocean vertical velocity? tells about the measurement of vertical velocity by ADCP, but they give very noisy vertical velocities and hence almost unusable (at least in my case in the Bay of Bengal in India). Also I am interested in vertical velocities in the upper ocean with mixed layer depths of 30 to 50 meters and this is where many different things happen (e.g. fish, air bubbles etc.). Has anyone done direct vertical speed measurements in the upper ocean? I am unable to find a good lead.
I am assuming you know how to get to mixing from velocity field since you are talking about the noise in the ADCP data. The way people get the small fluctuation and vertical mixing profiles that are highly trusted are with "micro-structure" sampling technique.
Please follow this link for more detail on that technique. https://earthobservatory.nasa.gov/blogs/fromthefield/2012/10/04/what-is-ocean-microstructure-and-why-study-it/