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Role of plates and temperature-dependent viscosity in phase change dynamics

Zhong, Shijie and Gurnis, Michael (1994) Role of plates and temperature-dependent viscosity in phase change dynamics. Journal of Geophysical Research B, 99 (B8). pp. 15903-15917. ISSN 0148-0227. doi:10.1029/94JB00545.

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The effects of plates and slabs on phase change dynamics have been investigated with convection models. Two complementary methods to simulate plates are used: material property and imposed surface velocity methods with temperature-dependent viscosity. For a wide range of model parameters, plates and slabs exert a significant control on phase change dynamics. As plate length (and hence plate age and convection cell aspect ratio) increases, both the propensity for slab penetration and the mass flux across an endothermic phase change increase. When cold downwellings are stiffened with a temperature-dependent rheology, slab penetration is enhanced, but total mass flux changes little. Plates organize large-scale flow and thermal structure and thereby affect phase change dynamics. As plates become larger, the resulting largerscale structures are influenced less by endothermic phase changes, thus reducing the degree of layering. A model showing completely layered convection for a plate of unit length becomes unlayered when the plate is 3 or 5 times longer. For a given Clapeyron slope, the proportion of time for slab penetration increases from zero for cases with small plates to more than 0.5 for cases with large plates. The degree of layering, plate velocity, and mass flux are controlled by large-scale structures, while slab penetration may be more related to small-scale features. Therefore, whether or not subducted slabs penetrate the phase change may not necessarily indicate that convection is entirely layered or entirely unlayered. The episodicity of convection induced by an endothermic phase change strongly depends on plate length, rheology, and Clapeyron slope. A large plate and a stiff slab both weaken the episodicity of convection. Only for a certain range of Clapeyron slopes can the phase change induce a strong episodic thermal convection.

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Gurnis, Michael0000-0003-1704-597X
Additional Information:© 1994 by the American Geophysical Union. Manuscript Accepted: 18 Feb 1994. Manuscript Received: 1 September 1993; revised January 31, 1994. We appreciate the discussions with S. Weinstein and reviews by S. King, G. Davies, and an anonymous reviewer. Many of the computations were carried at the Pittsburgh Supercomputer Center. Funded by the David and Lucile Packard Foundation and NSF grant EAR-8957164.
Group:Seismological Laboratory
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Issue or Number:B8
Record Number:CaltechAUTHORS:20130506-081344460
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Official Citation:Zhong, S., and M. Gurnis (1994), Role of plates and temperature-dependent viscosity in phase change dynamics, J. Geophys. Res., 99(B8), 15903–15917, doi:10.1029/94JB00545.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38280
Deposited By: Ruth Sustaita
Deposited On:06 May 2013 15:28
Last Modified:09 Nov 2021 23:36

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