HR: 09:30h
AN: U41A-07    [PDF]
TI: Thermal coupling between the convecting mantle and core from the view of thermo-chemical mantle convection
AU: * Nakagawa, T
EM: takashi@ess.ucla.edu
AF: Department of Earth and Space Sciences, University of California, Los Angeles, 3806 Geology Building, BOX951567, Los Angeles, CA 90095-1567 United States
AU: Tackley, P
EM: ptackley@ess.ucla.edu
AF: Department of Earth and Space Sciences, University of California, Los Angeles, 3806 Geology Building, BOX951567, Los Angeles, CA 90095-1567 United States
AU: Tackley, P
EM: ptackley@ess.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 3806 Geology Building, BOX951567, Los Angeles, CA 90095-1567 United States
AB: Our previous studies have investigated the suitability of parameterized convection for describing a compositionally-heterogeneous mantle, and developed a coupled mantle-core thermal evolution model in which the mantle has various complexities but the core heat balance is simple, without the effects of radiogenic heat sources and a magnetic field [Nakagawa and Tackley, 2002 at AGU Fall Meeting; Nakagawa and Tackley, 2003 at IUGG General Assembly]. Recently, several heat balance models for the core that include the effects of radioactive heat sources and the magnetic field have been proposed [Buffett, 2003; Labrosse, 2003]. However, those models use a parameterized mantle convection model to calculate CMB heat flux. Here, we develop a coupled core-mantle model that combines a _grealistic_h thermochemical mantle convection model (including the lateral variation of compositional anomalies, phase changes, melting and plate-like behavior) with a core heat balance model that includes inner core growth, the ohmic dissipation and radioactive elements. The numerical model is the same as that of Nakagawa and Tackley [2003] but thermal evolution of the core is based on Buffett [2002], modified to include variable ohmic dissipation, adiabatic heat flux through the CMB and radioactive heat elements. This coupled model is used to calculate the age and radius of the inner core, and the heat flux through the surface and CMB in order to constain core-mantle thermal evolution by comparing the Earth. The two end-member compositonal assumptions are that heterogeneity comes from intial layering, or that heterogeneity is generated through melting over Earth_fs history (assumes both constant buoyancy ratio and depth-dependent buoyancy ratio). The core model either: (1) assumes no magnetic field, (2) includes the effect of a magnetic field and (3) includes effects of magnetici field and radioactive heat elements. The final compositional anomalies take the form of isolated piles for both initial conditions. The effect of ohmic dissipation and radioactive elements in the core is expected to be to a smaller inner core compared to the no magnetic field scenario. Detailed findings will be presented.
DE: 1212 Earth's interior--composition and state (8105)
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8125 Evolution of the Earth
DE: 8130 Heat generation and transport
SC: U
MN: 2003 Fall Meeting