HR: 0800h
AN: V21D-0754    [Abstracts]
TI: Quantitative Effect of Variable Entrainment on the Hydrothermal Heat Outputs Deduced From the Heights Reached by Submarine Buoyant Plumes
AU: Kaminski, E
EM: kaminski@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005, France
AU: * Carazzo, G
EM: carazzo@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005, France
AU: Tait, S
EM: tait@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005, France
AB: In the absence of direct measurements of the heat flux released by hydrothermal vent activity, the large submarine plumes associated provide a key information to estimate thermal outputs. Physical models of turbulent plumes have shown that the maximum height reached by a plume in a stratified environment can be related only to its source buoyancy flux, the stratification of the surrounding fluid and the efficiency of the mixing between both fluids. If one assumes that the mixing is constant along the distance from the source and if the ambient stratification is known, the maximum height reached by the plume provides directly the source heat flux. These models have been adapted to predict the rise of buoyant hydrothermal plumes as a function of the source heat flux in the ambient seawater of the Atlantic and the Pacific Oceans. Five plumes heights detected above the TAG vent field in the Mid-Atlantic Ridge (26° N) have been used to calculate the heat and vent fluxes emitted from this hydrothermal system. We will show that these estimations are erroneous by a factor 3 because of the simple assumption that the mixing is constant with depth. We present a new model of turbulent entrainment highlighting the fundamental effect of the plume buoyancy on the mixing. The stratification of the ambient seawater induces a negative buoyancy close to the maximum height which can considerably reduce the turbulent entrainment. We re- evaluate the thermal ouput of the TAG hydrothermal field to 2850 MW. This generic approach can be applied to any submarine hydrothermal system for which the density stratification in the ambient seawater is known.
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting