Deep sea hydrothermal plumes and their interaction with oscillatory flows

Abstract

[1] The acoustic scintillation method is applied to the investigation and monitoring of a vigorous hydrothermal plume from Dante within the Main Endeavour vent field (MEF) in the Endeavour Ridge segment. A 40 day time series of the plume's vertical velocity and temperature fluctuations provides a unique opportunity to study deep sea plume dynamics in a tidally varying horizontal cross flow. An integral plume model that takes into account ambient stratification and horizontal cross flows is established from the conservation equations of mass, momentum and density deficit. Using a linear additive entrainment velocity in the model (E = aU m + bU ? ) that is a function of both the plume relative axial velocity (U m ) and the relative ambient flow perpendicular to the plume (U ? ) gives consistent results to the experimental data, suggesting entrainment coefficients a = 0.1 and b = 0.6. Also from the integral model, the plume height in a horizontal cross flow (U a ) is shown to scale as 1.8B 1/3 U a À1/3 N À2/3 for 0.01 ≤ U a ≤ 0.1 m/s where B is the initial buoyancy transport and N is the ambient stratification, both of which are assumed constant.

Observations of the volume flux of a seafloor hydrothermal plume using an acoustic imaging sonar

“…According to previous laboratory and field measurements [ Fan , ; Rona et al ., ; Xu and DiIorio , ], ambient horizontal cross flows ( U a ) can enhance entrainment. As reported in Thomson et al .…”

“…Hydrothermal plumes, occurring mainly at mid‐ocean ridges, disperse the heat, chemicals, and biological materials from the vents on the seafloor [ Stein and Stein , ; Anderson and Hobart , ; Bickle and Elderfield , ; Jackson et al ., ; Adams et al ., ] and induce unique patterns of deep‐ocean circulations around the vent fields [ Thomson et al ., ]. Traditional hydrothermal‐vent studies have depended on ship and submersible‐based experiments or moored self‐contained instruments to collect data that are mostly snapshots or intermittent time series with limited durations [ Bemis et al ., ; Rona and Trivett , ; Kellogg and McDuff , ; Larson et al ., ; Crone et al ., ; Xu and DiIorio , ]. These data are insufficient to resolve the interaction of a hydrothermal system with the geological changes of a mid‐ocean ridge and the hydrodynamic influences of the deep‐ocean currents, both of which require long‐term continuous time‐series measurements of the plume properties of interest (i.e., temperature, chemical concentration, volume flux, and flow rate).…”

Observation and Modeling of Hydrothermal Response to the 2015 Eruption at Axial Seamount, Northeast Pacific

“…To evaluate this hypothesis, we used an integral plume model to derive the temperature‐plume‐height relationship based on the ambient ocean stratification observed near Axial Seamount. The plume model was adapted from the one described in Xu and DiIorio (). We replaced the linear equation of state in the original Xu and DiIorio model with a hybrid equation of state that calculates density and other thermodynamic properties of plume fluids using the TEOS‐10 thermodynamic equation of seawater (McDougall & Barker, ) for fluids with temperatures <40°C and a thermodynamic equation of NaCl solution (Driesner, ) for fluids with temperatures >40°C.…”

“…The model results above are for a plume rising in a quiescent environment with no ambient flow. Previous studies suggest the presence of background cross flow can enhance a plume's mixing with ambient seawater and hence reduce the plume's rise height (Xu & DiIorio, ). To investigate the sensitivity of our model results to ambient flows, we conducted a second set of simulations, referred to as flow , which had the same base source conditions but with a spatially uniform horizontal flow of 0.1 m/s added to the background.…”

A turbulent convection model with an observational context for a deep-sea hydrothermal plume in a time-variable cross flow

“…[]. Detailed acoustic observations [e.g., Jackson et al ., ; Rona et al ., ] of hydrothermal plumes at the Main Endeavour Field (MEF) on the Endeavour segment of the Juan de Fuca Ridge, a deep sea crustal spreading center, and particularly measurements [ Xu and Di Iorio , ] at the sulfide mound called Dante in the MEF have renewed our interest in how these turbulent plumes respond to time‐variable flow and what model and measurements together can say about source heat flux and dependence on other external variables. In this paper, we report results from a 3‐D, time‐dependent convection model for sources discharging into time‐variable cross flows and compare specific model results to measurements made of the rising turbulent plume above Dante and nearby Grotto.…”