Analysis of the effect of a Rossby wave on sound speed in the ocean

The effects of an assumed Rossby wave on density, pressure, current, and sound speed are examined and analyzed. It is shown that the zeroth-mode wave solution has only slight effect on sound speed, while the first-mode solution is significant. A dispersion relation is developed, having as one solution an east-west wavelength of 210 nautical miles and a period of 114 days, for parameters consistent with the Sargasso Sea area. This first-mode solution predicts the gross behavior of observed sound speed versus depth variations, and provides striking agreement with measured curves of constant sound speed. The addition of a second-mode solution to the first leads to a crossover of sound-speed profiles in qualitative agreement with observations.