Acoustic imaging of black smoker hydrothermal plumes: East Pacific Rise 21°N, 109°W.

Abstract

During the November 1990 dive series of the US Navy DSV Turtle, plumes emanating from high-temperature black smoker-type vents were imaged using a prototype sonar system mounted on the submersible. The study focused on two plumes from adjacent sources that were scanned horizontally in arcuate sectors at increasing angular increments from the vent orifices up to 90°. Multiple data sets were recorded at horizontal ranges of 3–70 m from the base of the plumes and sonar ranges to 200 m with submersible stationary on the seafloor. Computer graphics were used to reconstruct the plumes in cross section and in 3D, revealing coherent plume images up to 100 m above the seafloor. Multiple plume cross sections recorded at the same level show changes in shape and distribution of suspended particulate matter on a time scale of seconds. Whole images show coalescing of the buoyant plumes and deflection by the prevailing current. The work demonstrates the value of acoustic imaging of plumes for initial detection and for characterization of plume dynamics.