Yu. N. Tokarev
Kovalevskii Institute of the Biology of Southern Seas, National Academy of Sciences of Ukraine, Sevastopol, Ukraine
Received June 8, 1998; in final form, September 9, 1999
Abstract—We studied the possibility of classifying the vertical profiles of the strength of sound volume back-
scattering (SVBS) in the upper productive layer of the Tropical Atlantic, when decomposed into empirical
orthogonal functions (EOF), and of determining the influence of the biological processes of various scales on
the stratification of the SVBS strength. An analysis of the data from 228 stations indicates that, in the eastern
and western parts of the entire study area, the SVBS strength field is characterized with an accuracy of 95% by
different numbers of EOF. The eastern part of the study area, which is distinguished for its higher biological
productivity and greater dynamics of the water masses, has a dominating effect on the dispersion of the SVBS
strength. The 95% accuracy of the approximation of the dispersion of the SVBS strength field at daytime is
reached in the eastern part of the study area by a sum of only five lower modes, while in the western part, the
required number of them is nine. At nighttime, this relation is somewhat equalized (six and seven), while the
dominating contribution of the eastern part of the study area is conserved. The result of the operative analysis
of the hydroacoustic characteristics at frequencies of the order of 80 kHz can be used for the classification (typ-
ification) of the water masses with regard to their biological productivity.
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