PMEL Earth-Ocean Interactions Program logo National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory Earth-Ocean Interactions Program
Modeling Research Group:

Principal Investigator:

Bill Lavelle j.william.lavelle@lavelle-associates.org

  Modeling Effects of Hydrothermal Venting on the Benthic Ocean
 

Goal:
Bring analytic and numerical models to bear on the understanding of physical, chemical, and sedimentological processes active at or near ridge crest spreading centers.

Accomplishments:
Development of a variety of analytic and numerical models to look at circulation and transport in hydrothermal regions. The primary three-dimensional time-dependent numerical models are: the non-hydrostatic Very Large Eddy Simulation (VLES) model Hot_Cross which allows the convection from hot vents to be studied; and the hydrostatic free-surface model Gaia that has been used to investigate flow and tracer transport over ridge topography. An outline of the problem areas studied is shown below.

View Animation Gallery

  
  Modeling Focuses  
  Local Scale Convection-  
  icon buoyant plumes model

Buoyant plumes in cross flows
Aluminum Entrainment and Transport results for aluminum originating in focused and diffuse vents and in the background ocean are depicted. Hot_Cross allows wavering, wispy, and occasionally bifurcated plumes to be quantitatively described.

 
 

event plume icon

 Event Plumes
Line Source Event Plumes-An event plume is formed by the sudden, short-lived release of heat from line-segment sources, fissures created during tectonic events.		  
     
  Regional Scale Flow and Transport-
  
 

Axial valley transport icon

 Transport in the axial valley
Effects of Current Variability on Plume Distribution-The time-varying nature of composite plumes in the North Cleft axial valley has been examined using an analytic model and measured currents.		  
 

Ridge flow icon

 Flow over Ridges and Seamounts
The influence of ridge topography on flow and on the regional transport of hydrothermal discharge is being investigated with Gaia.		  
     
  Geochemical Transport-
  
  particle transport icon Particle Transport and Deposition
Deposition of hydrothermal manganese occurs preferentially within 100 km of the ridge axis (triangles). The process involves two stages: bacterial scavenging of dissolved Mn followed by the scavenging of bacteria by rapidly settling macroaggregates. 		 
     
  Hydrographic-Tracer Relationships-  
  tracer icon Tracers
Volume integrals of megaplume heat anomalies and thus the estimate of heat released during a megaplume event depend on anomaly definition. Total heat flux estimates based on temperature anomalies defined as the difference between plume and ambient values for points of equal density do not represent the actual total flux from hydrothermal events.		  
     
  Future Plans  
 

Examine transport of hydrothermal plumes off the ridge using the regional scale circulation model and regional current data, particularly in relation to the plume measured following the large, recent event at Axial volcano. Extend studies of circulation and transport of hydrothermal signals from ridge crest to even larger length scales.