The influence of tectonic plates on mantle convection patterns, temperature and heat flow

Abstract

SUMMARY The dynamic coupling between plate motion and mantle convection is investigated in a suite of Cartesian models by systematically varying aspect ratios and plate geometries. The aim of the study presented here is to determine to what extent plates affect mantle flow patterns, temperature and surface heat flux. To this end, we compare numerical convection models with free‐slip boundary conditions to models that incorporate between one and six plates, where the geometries of the plates remain fixed while the plate velocities evolve dynamically with the flow. We also vary the widths of the plates and the computational domain in order to determine what constraint these parameters place on the mean temperature, heat flux and plate velocity of mantle convection models. We have investigated the influence of plates for three whole‐mantle convection cases that differ in their heating modes (internally heated and basally heated) and rheologies (isoviscous and depth‐dependent viscosity). We present a systematic investigation of over 30 models that exhibit increasingly complex behaviour in order to understand highly time‐dependent systems using the insight gained from simpler models. In models with aspect ratios from 0.5 to 12 we find that for the same heating mode, variations in temperature can be as much as 40 per cent when comparing calculations with unit‐width plates to models incorporating plates with widths equal to five times the model depth. Mean surface heat flux may decrease by 60 per cent over the same range of plate widths. We also find that internally heated mantle convection models incorporating plates exhibit novel behaviour that, we believe, has not been described previously in mantle convection studies. Specifically, in internally heated models, plate motion is characterized by episodic reversals in direction driven by changes in the mantle circulation from clockwise to counterclockwise and vice versa. These flow reversals occur in internally heated convection and are caused by a build‐up of heat in the interiors of wide convection cells close to mantle downwellings. We find that flow reversals occur rapidly and are present in both single‐plate and multiple‐plate models that include internal heating. This behaviour offers a possible explanation for why the Pacific plate suddenly changed its direction some 43 Ma.

Thermal response of the mantle following the formation of a “super‐plate”

“…However, many previous studies omit the inclusion of oceanic plates. Oceanic plates inhibit the formation of instabilities in the upper thermal boundary layer and affect convective wavelength [Lowman et al, 2001]. Moreover, larger oceanic plates retain more heat in a convecting system [Monnereau and Quéré, 2001;Lowman et al, 2001].…”

The feedback between surface mobility and mantle compositional heterogeneity: Implications for the Earth and other terrestrial planets

“…Eqs. (1)-(3) are solved using MC3D, a hybrid spectral and finite-difference code (e.g., Gable et al, 1991;Gait and Lowman, 2007;Lowman et al, 2011). MC3D is second order accurate in time and space.…”

Numerical model of the supercontinental cycle stages: Integral transfer of the oceanic crust material and mantle viscous shear stresses

“…Ogawa, 2003). The dynamic coupling between moving oceanic plates and mantle convection is investigated by Lowman et al (2001). Tackley (2000) has examined self-consistent generation of tectonic plates in three-dimensional simulations.…”