Gulf stream variability for acoustic tomography

Abstract

Abstract Fluctuations of sound speed from average conditions in the Slope waters, Gulf Stream, and Sargasso Sea are investigated from historical measurements. The covariance of the sound speed fluctuations is computed as a function of horizontal distance from the north wall of the Gulf Stream in four different vertical layers. Above (below) 500 m the scales are greater (less) in the Slope water than in the Sargasso Sea, indicating a strong anisotropy in the covariance function. The empirical orthogonal functions (EOF's) of the vertical variability are also computed. The EOF's in the Sargasso Sea and Gulf Stream are similar but differ from the EOF's computed for the Slope water. For all three regions the first three EOF's describe about 95% of the variance. These statistical descriptions of sound speed variability are useful for mapping Gulf Stream variability using the techniques of ocean acoustic tomography.