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Scaling Laws for Regional Stratification at the Top of Earth's Core
Author(s) -
Mound Jonathan E.,
Davies Christopher J.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl087715
Subject(s) - stratification (seeds) , geology , outer core , geophysics , convection , earth's magnetic field , scaling , mantle (geology) , core–mantle boundary , boundary layer , inner core , heat flux , mantle convection , thermal , mechanics , heat transfer , physics , meteorology , geometry , seismology , subduction , tectonics , magnetic field , mathematics , biology , germination , seed dormancy , botany , dormancy , quantum mechanics
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‐Väisälä 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.