Temperature and sound-speed measurements from diffuse hydrothermal vent plumes at the Southern Juan de Fuca Ridge

Abstract

An array of sensors was deployed for 2 weeks at the Southern Juan de Fuca Ridge during the NOAA VENTS’90 field experiment. The instrument measured temperature at six heights on each of four moorings, and temperature, velocity, sound speed, and Reynolds’ stress on each of two tripods. The instruments were placed close to the seafloor to detect effluent from diffuse hydrothermal flow that was advanced horizontally by ambient currents. Temperature and sound-speed measurements were compared during intervals when no plume was evident, and when effects of plumes were clearly detected. The data showed that energy flux from diffuse vents was approximately 125±75 MW from a source to the north of the instrument array, and 12±8 MW from a small source to the east. The largest error in the data was due to estimation of the plume width. A sensor array that would reduce this error in future work will be described. Such an array could be suitable for a long-term vent field monitor.