Geophysical Research Letters, 26(7), 947-950, 1999
Generation of plumes under a localized high viscosity lid on 3-D spherical shell convection
Masaki Yoshida, Yasuyuki Iwase, and Satoru Honda
Abstract
We present results of numerical simulations of incompressible infinite Prandtl number convection
in a spherical shell with a single localized high viscosity lid (HVL) on the top surface
to understand the possible effects of the continental lithosphere on plume generation.
The temperature under the HVL increases rapidly after the instantaneous emplacement
of the HVL on constant viscosity convection with both internal and bottom heatings.
Later, upwellings at the bottom surface merge into a large scale flow and, as a result,
a large plume emerges under the HVL. The time-scale of these phenomena depends
on the physical properties of the mantle such as the existence of phase changes.
Our model cases, whose Rayleigh number is 106, show that the large plume is formed
on a time-scale of 1 Gyr. A simple scaling argument suggests that this time-scale may be reduced
by a several times, if the actual Rayleigh number is around 107.
Although the temperature structure shows a complicated 3-D pattern,
it is dominated by an l=1 pattern controlled by the plume position, that is, the position of the HVL.