Comparison of sphericalshell and planelayer mantle convection thermal structure in viscously stratified models with mixedmode heating: implications for the incorporation of temperaturedependent parameters
O'Farrell, K.A., J.P. Lowman, and H.P. Bunge (2013),
Comparison of sphericalshell and planelayer mantle convection thermal structure in viscously stratified models with mixedmode heating: implications for the incorporation of temperaturedependent parameters,
GEOPHYSICAL JOURNAL INTERNATIONAL, 192, 456472, doi:10.1093/gji/ggs053.
 Abstract
 Planelayer geometry convection models remain a useful tool for investigating planetary mantle dynamics but yield significantly warmer geotherms than sphericalshell systems. Comparisons of uniform property planelayer and sphericalshell models have provided insight into the role of geometry on temperature in convecting systems but the inclusion of firstorder terrestrial characteristics is needed to quantitatively assess the influence of system geometry on more relevant mantle models. Here, we analyse the mean temperatures of over 160 sphericalshell and planelayer convection models featuring a uniform uppermantle viscosity and a lower mantle that increases in viscosity by a factor of 30 or 100. With the imposition of the stratified viscosity, an effective Rayleigh number, Ran(), is defined based on the average viscosity of the mantle. We derive equations for the relationship between the mean temperature, theta, Ran() and the nondimensional internal heating rate, H, for both convection in a spherical shell with Earthlike mantle geometry and planelayer solution domains. These equations predict the mean temperatures in the corresponding systems to an accuracy of a few percent or better. Our equations can be combined to derive the appropriate heating rate for a planelayer convection model to emulate the temperatures in a mixed heating mode sphericalshell convection model with effective Rayleigh number comparable to the Earth's value, or greater. When comparing cases with the same internal heating rate and effective Rayleigh number, we find that the increased lower mantle viscosity amplifies the mean temperature ratio of the planelayer and sphericalshell systems relative to isoviscous convection. These findings imply that the disagreement between sphericalshell mantle convection and planelayer geometry mantle convection thermal structure must be particularly accounted for in planelayer geometry models featuring variable viscosities.
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 BibTeX

@article{id2022,
author = {K.A. O'Farrell and J.P. Lowman and H.P. Bunge},
journal = {GEOPHYSICAL JOURNAL INTERNATIONAL},
pages = {456472},
title = {{Comparison of sphericalshell and planelayer mantle convection thermal structure in viscously stratified models with mixedmode heating: implications for the incorporation of temperaturedependent parameters}},
volume = {192},
year = {2013},
url = {http://gji.oxfordjournals.org/content/192/2/456},
doi = {10.1093/gji/ggs053},
}
 EndNote

%0 Journal Article
%A O'Farrell, K.A.
%A Lowman, J.P.
%A Bunge, H.P.
%D 2013
%V 192
%J GEOPHYSICAL JOURNAL INTERNATIONAL
%P 456472
%T Comparison of sphericalshell and planelayer mantle convection thermal structure in viscously stratified models with mixedmode heating: implications for the incorporation of temperaturedependent parameters
%U http://gji.oxfordjournals.org/content/192/2/456