The spectral signature of salt fingers

The spectra of either temperature, salinity or vertical velocity which might be measured by a sensor moving through a field of salt fingers are considered. A theoretical calculation is presented which attempts to incorporate the deviations from squareness and perfect orientation of the salt fingers. The resulting spectra rise to a peak close to ω = (√2)kv and decrease rapidly for larger ω, where ω is the temporal frequency of the spectrum, k the dominant wave number of the salt fingers and ν the horizontal velocity of the sensor. A spectrum of vertical velocity of laboratory-generated salt fingers is shown to be in close agreement with the theoretical prediction.