Scaling Laws for Regional Stratification at the top of Earth’s Core

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1029/2020GL087715.

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Authors

Jonathan Mound , Christopher J. Davies 

Abstract

Seismic and geomagnetic observations have been used to argue both for and against a global stratified layer at the top of Earth’s outer core. Recently, we used numerical models of turbulent thermal convection to show that imposed lateral variations in core-mantle boundary (CMB) heat flow can give rise to regional lenses of stratified fluid at the top of the core while the bulk of the core remains actively convecting. Here we develop theoretical scaling laws to extrapolate the properties of regional stratified lenses measured in simulations to the conditions of Earth’s core. We estimate that regional stratified lenses in Earth’s core have thicknesses of up to a few hundred kilometres and Brunt-Vaisala frequencies of hours, consistent with independent observational constraints. The location, thickness, and strength of the stratified regions would change over geological time scales in response to the slowly evolving CMB heat flux heterogeneity imposed by mantle convection.

DOI

https://doi.org/10.31223/osf.io/r52wc

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Keywords

Geodynamics, core stratification, Earth's outer core, fluid dynamics - scaling laws

Dates

Published: 2019-12-04 08:24

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License

CC BY Attribution 4.0 International

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