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Lookup NU author(s): Dr Pingping Huang, Dr Nigel Penna, Professor Peter ClarkeORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025 The Author(s). Ocean tide loading (OTL) refers to the Earth's deformational response to periodic ocean mass redistributions driven by astronomical tides. This transient deformation likely involves anelasticity, which is associated with energy dissipation and plays a crucial role in understanding Earth's deformation across various temporal scales. However, anelastic contributions to OTL are minor (submillimetre-to-millimetre scale) relative to elastic OTL deformation and are comparable in magnitude to the influence of lateral heterogeneities in crust and upper mantle elasticity. Because of this, detecting and isolating anelastic OTL deformation remains challenging. Here, by analysing high-accuracy (0.2 – 0.4 mm) Global Positioning System (GPS) data from 255 sites across western Europe, and comparing with OTL forward modelling results from advanced 3-D elastic and anelastic Earth models incorporating sediments, we unambiguously demonstrate anelastic OTL displacements, in both horizontal and vertical directions. Our findings highlight the necessity of incorporating anelasticity into geodynamic models, particularly for processes operating at sub-seismic frequencies, and into a unifying viscoelastic law for modelling Earth deformations across multiple timescales. Furthermore, using GPS observations and realistic 3-D models, we constrain anelastic parameters for Earth's upper mantle. These parameters reveal the weakening or dispersion of upper-mantle shear modulus, by up to 20 % at semi-diurnal tidal frequencies compared to its 1 Hz value in the Preliminary Reference Earth Model (PREM), and constrain the time dependence of this weakening. Our results support the application of OTL observations for constraining Earth's anelasticity in the sub-seismic frequency range.
Author(s): Huang P, Penna NT, Clarke PJ, Klemann V, Martinec Z, Tanaka Y
Publication type: Article
Publication status: Published
Journal: Earth and Planetary Science Letters
Year: 2025
Volume: 671
Print publication date: 01/12/2025
Online publication date: 25/09/2025
Acceptance date: 15/09/2025
Date deposited: 06/10/2025
ISSN (print): 0012-821X
ISSN (electronic): 1385-013X
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.epsl.2025.119644
DOI: 10.1016/j.epsl.2025.119644
Data Access Statement: The raw GPS data used in this study are available from NERC BIGF (http://www.bigf.ac.uk), IGN (http://rgp.ign.fr), EUREF (http://www.epncb.oma.be), and IGS (https://www.igs.org). The GPS-derived and forwardly modelled (using PREM and our optimal 3D anelastic Lyon model with TPXO9.5, Section 4.5) M2 OTL W, S, and U displacements for the 255 sites are provided in Tables S1-S3 of the Supplementary Materials. In addition, a global dataset of M2 OTL predictions from the optimized 3D anelastic Lyon model and TPXO9.5 forcing is available via the GFZ Data Service (Huang et al., 2025).
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