Numerical modeling of hydrothermal plumes in the ocean

Numerical modeling of hydrothermal plumes in the ocean

Hydrothermal vents are openings in the seafloor, typically located along mid-ocean ridges or in back-arc basins, that emit fluid which can be as hot as 400 degrees Celsius or more. This fluid is seawater that slowly seeps through the ocean floor, circulates through the crust, where it heats up and changes its chemical composition through interaction with the rock, and finally gets expelled from a hydrothermal vent. Despite the extreme conditions that reign in hydrothermal vents, their immediate surroundings teem with life. Chemotrophic microorganisms use the high concentration of electron donors in the hydrothermal fluid to obtain energy. These again support diverse organisms such as tube worms, clams, limpets and shrimps. It has also been shown recently that the plumes emitted from hydrothermal vents can reach heights of several hundred meters, thereby fertilizing the surface waters with essential elements for photosynthesis, e.g., iron and manganese. It is becoming more and more clear that hydrothermal vents occupy an important place in global biogeochemical cycles, and several efforts have been made to quantify the element fluxes. However, so far, modeling of the chemistry in hydrothermal plumes has not involved fluid transport, though turbulent mixing is expected to have a strong impact on the chemical reactions.

The aim of this project is the numerical modeling of hydrothermal plumes in the ocean using methods from Computational Fluid Dynamics, in particular, Large Eddy Simulations (LES). We want to fill the gap between chemical modeling and fluid transport simulations. To this end, we will implement a chemistry module in a numerical model of a hydrothermal plume in the ocean and analyze the behavior of passive and active tracers, as well as chemical and microbial kinetics in the plumes.

Our main methods of investigation include Computational Fluid Dynamics, in particular, Large Eddy Simulation, theoretical plume models based on the approach by Morton et al. (1956), and geochemical software, for example Phreeqc.