TY - JOUR
T1 - GIA-induced secular variations in the Earth's long wavelength gravity field
T2 - Influence of 3-D viscosity variations
AU - Latychev, Konstantin
AU - Mitrovica, Jerry X.
AU - Tamisiea, Mark E.
AU - Tromp, Jeroen
AU - Christara, Christina C.
AU - Moucha, Robert
N1 - Funding Information:
The authors acknowledge research support from NSERC, CIAR, the Miller Institute for Basic Research in Science and NSF grant EAR-0309576. We also thank John Wahr and an anonymous reviewer for their constructive comments on an earlier version of the manuscript. This is contribution No. 9125 of the Division of Geological and Planetary Sciences of the California Institute of Technology.
PY - 2005/12/1
Y1 - 2005/12/1
N2 - Predictions of present day secular variations in the Earth's long wavelength geopotential driven by glacial isostatic adjustment (GIA) have previously been analyzed to infer the radial profile of mantle viscosity and to constrain ongoing cryospheric mass balance. These predictions have been based on spherically symmetric Earth models. We explore the impact of lateral variations in mantle viscosity using a new finite-volume formulation for computing the response of 3-D Maxwell viscoelastic Earth models. The geometry of the viscosity field is constrained from seismic-to-mographic images of mantle structure, while the amplitude of the lateral viscosity variations is tuned by a free parameter in the modeling. We focus on the zonal J̇ℓ harmonics for degrees ℓ = 2,...,8 and demonstrate that large-scale lateral viscosity variations of two to three orders of magnitude have a modest, 5-10%, impact on predictions of J̇2. In contrast, predictions of higher degree harmonics show a much greater sensitivity to lateral variation in viscosity structure. We conclude that future analyses of secular trends (for degree ℓ > 2) estimated from ongoing (GRACE, CHAMP) satellite missions must incorporate GIA predictions based on 3-D viscoelastic Earth models.
AB - Predictions of present day secular variations in the Earth's long wavelength geopotential driven by glacial isostatic adjustment (GIA) have previously been analyzed to infer the radial profile of mantle viscosity and to constrain ongoing cryospheric mass balance. These predictions have been based on spherically symmetric Earth models. We explore the impact of lateral variations in mantle viscosity using a new finite-volume formulation for computing the response of 3-D Maxwell viscoelastic Earth models. The geometry of the viscosity field is constrained from seismic-to-mographic images of mantle structure, while the amplitude of the lateral viscosity variations is tuned by a free parameter in the modeling. We focus on the zonal J̇ℓ harmonics for degrees ℓ = 2,...,8 and demonstrate that large-scale lateral viscosity variations of two to three orders of magnitude have a modest, 5-10%, impact on predictions of J̇2. In contrast, predictions of higher degree harmonics show a much greater sensitivity to lateral variation in viscosity structure. We conclude that future analyses of secular trends (for degree ℓ > 2) estimated from ongoing (GRACE, CHAMP) satellite missions must incorporate GIA predictions based on 3-D viscoelastic Earth models.
KW - 3-D structure
KW - Geopotential harmonics
KW - Glacial isostatic adjustment
UR - http://www.scopus.com/inward/record.url?scp=28044445885&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=28044445885&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2005.10.001
DO - 10.1016/j.epsl.2005.10.001
M3 - Article
AN - SCOPUS:28044445885
SN - 0012-821X
VL - 240
SP - 322
EP - 327
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 2
ER -