On the linear dependence of temperature structure and acoustic backscatter at the western edge of the Gulf Stream using optimal least-squares filtering.

Abstract

A quantitative approach, Wiener optimal least-squares filtering, was used to determine the linear correlation between physical and biological structure along the western edge of the Gulf Stream. Temperature, vertical temperature gradient, and diurnal effects on the vertical distribution of biological sound scatterers in the top 200 m of Gulf Stream frontal regions were studied. Coordinated temperature and 70- and 120-kHz acoustic backscatter data were obtained 105 km northeast of Cape Hatteras along a transect perpendicular to the Gulf Stream front. The data show that temperature is a better predictor of 70- and 120-kHz scattering than is temperature gradient at the fine scale. Diurnal differences suggest biological influences can override temperature preferences by nekton and zooplankton. A universal filter is developed to determine a consistent temporal relationship between acoustic scatterers and temperature structure. Application of this technique is a unique means of quantitatively determining relationships of acoustic scatterers to physical structure in the ocean.