Convection under a lid of finite conductivity in wide aspect ratio models: effect of continents on the wavelength of mantle flow

Cécile Grigné (1) , Stéphane Labrosse (2) , Paul J. Tackley (1)

1 Institut für Geophysik [Zürich]
2 LST - Laboratoire de Sciences de la Terre

Mantle convection in the Earth and Mars are dominated by large-scale flow, and this can be due at least in part to the effect of thermally insulating continent-like heterogeneities. Indeed, the presence of a finitely conducting lid on top of a convective isoviscous fluid at infinite Prandtl number induces the formation of a zone of hot upwelling centered beneath the lid and a large horizontal cellular circulation on each side of the lid. In a previous paper, this lateral cellular circulation was limited in size by the dimensions of the model. We now use very large aspect ratio models in order for this circulation to be unhampered. The large-scale circulation consists of the constructive superposition of hot and cold plumes attracted to and expelled from, respectively, the conductive lid. The width of the cellular circulation increases with the Rayleigh number of the fluid, and we propose a scaling law to explain this expansion. Scaling laws for the velocity of the plumes and heat transfer by this large-scale circulation are also developed. Although the model used is much simpler than actual planetary mantles, the driving mechanism for the large-scale circulation must operate in a similar fashion. Important implications in terms of heat transfer can therefore be predicted.

Domaines: Géophysique [physics.geo-ph]; Géophysique [physics.geo-ph]; Milieux et Changements globaux

Cécile Grigné, Stéphane Labrosse, Paul J. Tackley. Convection under a lid of finite conductivity in wide aspect ratio models: effect of continents on the wavelength of mantle flow. Journal of Geophysical Research : Solid Earth, 2007, 112 (B8), pp.B08403. ⟨10.1029/2006JB004297⟩. ⟨hal-00583852⟩