Basic Numerical Simulation of Large-Scale Plume Activity Due to the Circum-Pacific Lithosphere Subduction and Implications for the Elementary Process Associated with the Static-Layered Terrestrial Mantle

Abstract

To unveil the global dynamics of long-term lithosphere subduction along the circum-Pacific Ocean and relationship with large-scale mantle plume activity, we conducted 3-D spherical numerical simulations using a newly developed program. This program is based on the finite difference method with the Boussinesq (incompressible) approximation and temperature-dependent viscosity. To obtain a higher precision time integral, we adopted the Newton method. In addition, the preconditioned ‘Bi-CGSTAB’ (Bi-Conjugate Gradient Stabilized) method was incorporated to solve the Jacobian matrix of five finite difference equations for the velocity vector, pressure, and temperature. The preconditions used were matrix-matrix multiplication and incomplete LU factorization. We subsequently modeled circum-Pacific lithosphere subduction using the initial condition of a cool ring, at the base of the upper mantle along the equatorial great circle, imposed on the horizontally uniform temperature field with thermal boundary layers. The results indicated major upwellings at latitudes ± 30~40° as a response function. Secondary rising systems at both polar regions were clear. Our result numerically manifests part of the Green function-like elementary processes of large-scale passive flows within the static layered terrestrial mantle.