DOI: 10.1016/j.epsl.2021.116791
论文题名: A regime diagram for the slurry F-layer at the base of Earth's outer core
作者: Wong J. ; Davies C.J. ; Jones C.A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 560 语种: 英语
中文关键词: crystallisation
; F-layer
; inner core
; iron snow
; slurry
英文关键词: Advection
; Chemical elements
; Geodynamics
; Heat transfer
; Iron alloys
; Seismic waves
; Seismology
; Thermal conductivity
; Wave propagation
; Chemical diffusion
; Chemical diffusivity
; Evolution models
; Geophysical properties
; High thermal conductivity
; Inner core boundary
; Seismic observation
; Stratified layers
; F region
; body wave
; crystallization
; geodynamo
; inner core
; outer core
; P-wave
; seismic velocity
英文摘要: Seismic observations of a slowdown in P wave velocity at the base of Earth's outer core suggest the presence of a stably-stratified region known as the F-layer. This raises an important question: how can light elements that drive the geodynamo pass through the stably-stratified layer without disturbing it? We consider the F-layer as a slurry containing solid particles dispersed within the liquid iron alloy that snow under gravity towards the inner core. We present a regime diagram showing how the dynamics of the slurry F-layer change upon varying the key parameters: Péclet number (Pe), the ratio between advection and chemical diffusion; Stefan number (St), the ratio between sensible and latent heat; and Lewis number (Le), the ratio between thermal and chemical diffusivity. We obtain four regimes corresponding to stable, partially stable, unstable and no slurries. No slurry is found when the heat flow at the base of the layer exceeds the heat flow at the top, while a stably-stratified slurry arises when advection overcomes thermal diffusion (Pe≳Le) that exists over a wide range of parameters relevant to the Earth's core. Our results estimate that a stably-stratified F-layer gives a maximum inner-core boundary (ICB) body wave density jump of Δρbod≤534kgm−3 which is compatible with the lower end of the seismic observations where 280≤Δρbod≤1,100kgm−3 is reported in the literature. With high thermal conductivity the model predicts an inner core age between 0.6 and 1.2Ga, which is consistent with other core evolution models. Our results suggest that a slurry model with high core conductivity predicts geophysical properties of the F-layer and core that are consistent with independent seismic and geodynamic calculations. © 2021 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165715
Appears in Collections: 气候变化与战略
There are no files associated with this item.
作者单位: Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, F-75005, France; EPSRC Centre for Doctoral Training in Fluid Dynamics, University of Leeds, Leeds, LS2 9JT, United Kingdom; School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom; School of Mathematics, University of Leeds, Leeds, LS2 9JT, United Kingdom
Recommended Citation:
Wong J.,Davies C.J.,Jones C.A.. A regime diagram for the slurry F-layer at the base of Earth's outer core[J]. Earth and Planetary Science Letters,2021-01-01,560