气候变化领域集成服务门户(CCPortal): A regime diagram for the slurry F-layer at the base of Earth's outer core

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DOI	10.1016/j.epsl.2021.116791
	A regime diagram for the slurry F-layer at the base of Earth's outer core
	Wong J.; Davies C.J.; Jones C.A.
发表日期	2021
ISSN	0012821X
卷号	560
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.
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
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203337
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
推荐引用方式 GB/T 7714	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],2021,560.
APA	Wong J.,Davies C.J.,&Jones C.A..(2021).A regime diagram for the slurry F-layer at the base of Earth's outer core.Earth and Planetary Science Letters,560.
MLA	Wong J.,et al."A regime diagram for the slurry F-layer at the base of Earth's outer core".Earth and Planetary Science Letters 560(2021).