Deformation of internal boundaries in a viscoelastic earth and topographic coupling between the mantle and core

Abstract

Deformation in a two‐layer self‐gravitating, viscoelastic Maxwell earth is solved analytically and the behaviour of the internal interface which is non‐monotonic in time is shown to be due to the buoyancy effect across the interface. Deformation inside realistic earth models is calculated using the new normal mode method. Some modes with long relaxation times which do not contribute significantly to surface deformations are found to be significant for deformations inside the mantle. Flow patterns inside the mantle and the topograph at the core‐mantle boundary (CMB) due to surface glacial loads have been calculated. Glacial induced topography at the CMB, unless suitably located, is shown to be too small to significantly alter the total coupling mechanism and thus flow in the fluid core. If there is any causal relationship between climatic changes and geomagnetic reversals, then it is probably due to the transfer of rotational energy from the mantle to the core. A revised estimate of 100 m drop in sea level is required to cause changes in the flow pattern in the core. Copyright © 1990, Wiley Blackwell. All rights reserved