Featuring lithosphere rheology in models of glacial isostatic adjustment

Abstract:

It is common to treat the lithosphere as a purely elastic plate parameterized by its flexural rigidity or effective elastic thickness if glacial isostatic adjustment processes are modeled. Furthermore, the viscous or viscoelastic mantle structure underlying the elastic plate is considered in a spherical, i.e. 1D symmetry. These assumptions downgrade the lithosphere to a thin plate where its rheological characteristics and structural features are neglected; but the assumptions are widely accepted as the horizontal extensions of the classical glacial loads in Scandinavia and North America are too large as to be sensitive to small-scale lateral variations of lithospheric strength. Likewise, the presently observed fading adjustment process due to the loading processes dating back several thousands of years is governed by the large-scale flow of mantle material.

However, recent studies question this assumption and propose to consider the rheological structure of the lithosphere. To analyze the influence of the lithospheric rheology variations, we apply the spectral finite element code VILMA which allows to consider such effects and discuss the impact on the broad scale pattern of GIA.