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Glacial isostasy and the interplay between upper and lower mantle lateral viscosity heterogeneities
Author(s) -
Sabadini R.,
Gasperini P.
Publication year - 1989
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl016i005p00429
Subject(s) - geology , mantle (geology) , isostasy , post glacial rebound , viscosity , wavelength , geophysics , mantle convection , lithosphere , glacial period , seismology , physics , tectonics , thermodynamics , paleontology , optics
From the analysis of sea‐level data near the centre of the former Fennoscandian ice sheet and the theoretical predictions of vertically and laterally stratified Earth models, we explore the extent to which lateral viscosity variations could have influenced the estimate of long term mantle viscosity. We follow a finite element scheme in cylindrical symmetry, focusing on the effects of lateral viscosity contrasts of different magnitudes and wavelengths. Sea‐levels are consistent with long wavelength lateral viscosity contrasts of at most 2 orders of magnitude; short wavelength variations, comparable with the lateral extension of the surface load, should be ruled out. Differences in the average viscosities inferred from laterally stratified and uniform mantle models, may be as high as 1 order of magnitude. If we allow for different lateral viscosity patterns in the upper and lower mantle, we find that sea‐levels are consistent with short wavelength variations in the upper mantle of around 2 orders of magnitude, coupled with smoother lateral viscosity contrasts in the lower mantle.