Theory applied to the Mid-Atlantic ridge hydrothermal plumes: the finite-difference approach

Abstract

A system of differential equations describing the entrainment of ambient seawater during the rise of a buoyant hydrothermal plume has been solved by an explicit finite-difference method, chosen for its ease of application. An equation for tracer concentration has been added so that concentrations in the neutrally buoyant plume can be calculated for those elements whose background profiles vary over the depth range of the buoyant plume. The height of plume rise can be related directly to the thermal and hydrothermal vent flux. For the TAG vent field, 26°N MAR, five plume layers have been identified. The calculated heat flux is 500–940 MW, and the fluid flux is 0.210–0.392 m 3 s −1. The fluid flux to the neutrally buoyant plume is 1460–2740 m 3 s −1. Calculated plume concentrations of Mn compared with measurements made at TAG in 1988 indicate that there is either 50% removal of manganese in the buoyant plume, or that low-temperature vent-fluids contribute about 50% of the total thermal output of the TAG vent field.