Articles | Volume 6, issue 4
Research article
21 Oct 2015
Research article |  | 21 Oct 2015

The hydrothermal power of oceanic lithosphere

C. J. Grose and J. C. Afonso

Abstract. We have estimated the power of ventilated hydrothermal heat transport, and its spatial distribution, using a set of recently developed plate models which highlight the effects of axial hydrothermal circulation and thermal insulation by oceanic crust. Testing lithospheric cooling models with these two effects, we estimate that global advective heat transport is about 6.6 TW, significantly lower than most previous estimates, and that the fraction of that extracted by vigorous circulation on the ridge axes (< 1 My old) is about 50 % of the total, significantly higher than previous estimates. These new estimates originate from the thermally insulating properties of oceanic crust in relation to the mantle. Since the crust is relatively insulating, the effective properties of the lithosphere are "crust dominated" near ridge axes (a thermal blanketing effect yielding lower heat flow) and gradually approach mantle values over time. Thus, cooling models with crustal insulation predict low heat flow over young seafloor, implying that the difference of modeled and measured heat flow is due to the heat transport properties of the lithosphere, in addition to ventilated hydrothermal circulation as generally accepted. These estimates may bear on important problems in the physics and chemistry of the Earth because the magnitude of ventilated hydrothermal power affects chemical exchanges between the oceans and the lithosphere, thereby affecting both thermal and chemical budgets in the oceanic crust and lithosphere, the subduction factory, and the convective mantle.

Short summary
Due to a thermal insulation effect of oceanic crust, the seafloor heat flux is predicted to be low over young lithosphere (compared to other cooling models). Consequently, the amount of heat extracted from oceanic lithosphere by ventilated hydrothermal circulation is predicted to be significantly lower than previous models. About 50% of total hydrothermal power is extracted on ridge axes.