Acoustic imaging of hydrothermal plumes, East Pacific Rise, 21°N, 109°W

Abstract

We report the first observations based on acoustic imaging of large‐scale structure and time variability of buoyant plumes emanating from black smoker‐type seafloor hot springs. Three‐dimensional plume reconstructions were made from a digital data set of acoustic backscattering information recorded on a prototype submersible‐mounted sonar system. The acoustic images of two adjacent black smokers depict volume and show zones of flow organization (meters to tens of meters) in the lower 40 m of the buoyant plumes. The two plumes coalesce, bend in the prevailing current, exhibit short‐term (minutes) variation in cross section, and rapid (seconds) turbulent eddy variations at small scales (< 1 m). The plume imaging system is being developed for determination of plume dynamics, flux determinations when combined with chemical and thermal measurements, and long‐term monitoring of the activity of seafloor hydrothermal fields.

A method for Doppler acoustic measurement of black smoker flow fields

“…We report here on development of a Doppler method to measure the vertical velocity field of hydrothermal plumes. This velocity measurement, in concert with sonar measurements of plume structure (via mapping of the acoustic backscattering strength) such as those we have reported previously [ Rona et al , 1991; Bemis et al , 2000; Rona et al , 2001], is important to the understanding of plume behavior. The goal of this paper is to demonstrate the method using a limited set of data.…”

The relative effects of particles and turbulence on acoustic scattering from deep-sea hydrothermal vent plumes

“…Although the application of using backscattering techniques to probe hydrothermal plumes has been available for a long time Rona et al, 1991;Bemis et al, 2002), the mechanism within the plume dominating the backscattering of acoustic signals is still unclear. In this section, the turbulent effect (measured by forward scattering from temperature fluctuations) will be used to quantify the volume backscattering strength for comparison to the effect of particles.…”

“…Acoustic scintillation and acoustic remote imaging are the two major active techniques that have been applied in many cases of hydrothermal investigation during the past two decades (Di Iorio et al, 2005;Rona et al, 1991;Rona et al, 2002;Rona et al, 2006).…”

“…In the experiment conducted by Rona et al (1991), a monostatic sonar was used to scan the plume with high frequency pulsed acoustic waves. The shape of the plume was visualized by measuring the intensity of the backscattered signals.…”

Evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of El Hierro (Canary Islands, Spain)

“…However, studies made with standard sonar instruments showed the potential of acoustics to allow estimation of the volume of large submarine volcanic plumes (Orr and Hess 1978;Hay 1984;Palmer et al 1986; Thomson et al 1989;Rona et al 1991).…”