The Batchelor spectrum and dissipation in the upper ocean

Observations of vertical temperature microstructure at ocean station P during the mixed layer experiment (Mile) indicate that the shape of the high‐frequency temperature gradient spectrum depends on the relative strengths of turbulence and stratification. For low Cox number 〈( dT / dz ) 2 〉/〈 dT / dz 〉 2 the linear range of the Batchelor spectrum is not well approximated by observed spectra, while for high Cox number a remarkably close correspondence to the Batchelor spectrum is found. Dissipation rates calculated by the temperature gradient spectrum cutoff wave number method show a dramatic contrast in turbulence between low and high wind speed periods separated by only 3 hours, showing that the response of the mixed layer and transition zone to wind forcing is rapid. Some indication is found that the thermocline may also respond rapidly to surface forcing.