Abstract:

A mechanically scanned sonar operating at 330 kHz has been used to image hydrothermal flows on ocean ridges using two different techniques. Scattering from particulates is used to image smoker plumes [Rona et al., Geophys. Res. Lett. 18, 2233--2236 (1991)], and scintillation of seafloor backscatter is used to image diffuse flows. Results will be presented from cruises on the East Pacific Rise and the northern Cleft segment of the Juan de Fuca Ridge. Plume images have been analyzed to extract physical parameters relevant to plume theory. Observations of diffuse flow employ cross correlation of ping doublets. Scattering theory is used to relate the correlation levels to the variance of temperature fluctuations. [Work supported by the NOAA National Undersea Research Program through the West Coast Undersea Research Center.]