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Role of temperature-dependent viscosity and surface plates in spherical shell models of mantle convection

Zhong, Shijie and Zuber, Maria T. and Moresi, Louis and Gurnis, Michael (2000) Role of temperature-dependent viscosity and surface plates in spherical shell models of mantle convection. Journal of Geophysical Research B, 105 (B5). pp. 11063-11082. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20130212-083631328

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Abstract

Layered viscosity, temperature-dependent viscosity, and surface plates have an important effect on the scale and morphology of structure in spherical models of mantle convection. We find that long-wavelength structures can be produced either by a layered viscosity with a weak upper mantle or temperature-dependent viscosity even in the absence of surface plates, corroborating earlier studies, However,combining the layered viscosity structure with a temperature-dependent viscosity results in structure with significantly shorter wavelengths. Our models show that the scale of convection is mainly controlled by the surface plates, supporting the previous two-dimensional studies. Our models with surface plates: layered and temperature-dependent viscosity, and internal heating explain mantle structures inferred from seismic tomography. The models show that hot upwellings initiate at the core-mantle boundary (CMB) with linear structures, and as they depart from CMB, the linear upwellings quickly change into quasi-cylindrical plumes that dynamically interact with the ambient mantle and surface plates while ascending through the mantle. A linear upwelling structure is generated again at shallow depths (<200 km) in the vicinity of diverging plate margins because of the surface plates. At shallow depths, cold downwelling sheets form at converging plate margins. The evolution of downwelling sheets depends on the mantle rheology. The temperature-dependent viscosity strengthens the downwelling sheets so that the sheet structure can be maintained throughout the mantle. The tendency for linear upwelling and downwelling structures to break into plume-like structures is stronger at higher Rayleigh numbers. Our models also show that downwellings tp first-order control surface plate motions and the locations and horizontal motion of upwellings. Upwellings tend to form at stagnation points predicted solely from the buoyancy forces of downwellings. Temperature-dependent viscosity greatly enhances tb: ascending velocity of developed upwelling plumes, and this may reduce the influence of global mantle flow on the motion of plumes. Our results can explain the anticorrelation between hotspot distribution and fast seismic wave speed anomalies in the lower mantle and may also have significant implications to the observed stationarity of hotspots.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2000JB900003 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2000JB900003/abstractPublisherArticle
ORCID:
AuthorORCID
Moresi, Louis0000-0003-3685-174X
Gurnis, Michael0000-0003-1704-597X
Additional Information:© 2000 by the American Geophysical Union. Received July 16, 1999; revised January 1, 2000; accepted January 6, 2000. Computations were performed on a Cray T3E at GSFC of NASA and a HP Exemplar at CACR of Caltech. S.Z. started this project shortly before leaving Caltech. S.Z. would like to thank RSES at ANU for a visiting fellowship and CSIRO for arranging a visit to AGCRC. We thank Marc Parmentier, R. van der Hilst, and T. Ratcliff for discussions, B. H. Hager for reading the manuscript, and S. Solomatov, P. Tackley, and an anonymous reviewer for their reviews. This represents contribution 8630 of the Division of Geological and Planetary Sciences, Caltech.
Group:Seismological Laboratory
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences8630
Record Number:CaltechAUTHORS:20130212-083631328
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130212-083631328
Official Citation:Zhong, S., M. T. Zuber, L. Moresi, and M. Gurnis (2000), Role of temperature-dependent viscosity and surface plates in spherical shell models of mantle convection, J. Geophys. Res., 105(B5), 11063–11082, doi:10.1029/2000JB900003
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36864
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Feb 2013 21:48
Last Modified:24 Oct 2017 18:20

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