A Composite Spectrum of Vertical Shear in the Upper Ocean

Results from three separate velocity profilers operated nearly simultaneously in the northwest Atlantic in 1975 are used to form a composite shear spectrum over vertical wavelengths from 100 m down to a few centimeters. This exercise constitutes an intercomparison of the three different measurement techniques and reveals a shear spectrum which is approximately fiat at a WKB-scaled level from k = 0.01 cpm through k0 ≈ 0.1 cpm, then falls as k−1 to a buoyancy wavenumber k0 = (N3/ε)1/2 determined by the local average Väisälä frequency N and the volume-averaged dissipation rate ε. Various consequences of the observed shear spectral shape are explored.