Energy and volume flux into the deep ocean: examining diffuse hydrothermal systems

Abstract

Hydrothermal circulation plays an important role in the chemistry of the world's oceans, the biology beneath and at the seafloor---as well as within the ocean itself---and also the geology of the uppermost igneous oceanic crust. Seawater slowly percolates through the crust, reacts with the basaltic rock, transports nutrients and heat, and eventually discharges back into the deep ocean---primarily at low-temperature vents and hydrothermal seeps. This dissertation is concerned with the flux of heat and fluid discharging from the seafloor and how field observations and numerical modeling can be utilized to describe the bulk hydrologic and mechanical properties of this fluid reservoir. Toward this end, heat and volume flux estimates were obtained using (1) a hydrologically sealed sampler which obtained direct measurement of fluid volume and heat flux from a diffuse hydrothermal vent on the seafloor, and (2) turbulence data collected above areas exhibiting low-temperature diffuse hydrothermal venting. Given that field observations near deep-sea hydrothermal vents are frequently modulated on tidal time-scales, a simple thermodynamic model is also proposed which can explain the modulation of temperature observed at some hydrothermal vents.