HR: 08:35h
AN: T41H-03    [Abstracts]
TI: A critical analysis of Earth's heat loss and secular cooling
AU: * Labrosse, S
EM: labrosse@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu Cedex 05, Paris, 75252 France
AU: Jaupart, C
EM: jaupart@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu Cedex 05, Paris, 75252 France
AB: Earth's rate of heat loss is about twice as large as the amount of heat generated by radioactive decay, which provides a strong constraint on mantle convection models. Here, we evaluate how theoretical models compare with heat flow data. Most studies rely on a parameterized law for convective heat transfer, of the form $Q=f(l)Ra^{1/3}T^{4/3}$, where non-dimensional heat flux $Q$ is written as a function of Rayleigh number $Ra$ and non-dimensional temperature $T$. Coefficient $f$ is controlled by the planform of mantle convection and depends on dominant wavelength $l$. Earth's heat loss depends on mantle temperature and maximum lithospheric age, as well as a shape function for the heat flux distribution. The spatial distribution of heat flux density at the surface is also characteristic of the planform and regime of convection. Comparing the observed distribution to theoretical predictions for a range of convection models illustrates the peculiar characteristics of Earth's convective regime. Earth's heat loss is sensitive to the maximum lithospheric age and to the distribution shape function. The simplest model, such that neither has changed by large amounts over geological history, predicts small secular cooling rates and yields the observed difference between present-day heat loss and heat production.
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8125 Evolution of the Earth
DE: 8130 Heat generation and transport
DE: 5418 Heat flow
DE: 5430 Interiors (8147)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting