Global dynamic topography observations reveal limited influence of large-scale mantle flow

Hoggard, M. J. and White, N. J. and Al-Attar, David (2016) Global dynamic topography observations reveal limited influence of large-scale mantle flow. Nature Geoscience, 9. pp. 456-463. ISSN 1752-0894 EISSN:1752-0908 DOI 10.1038/ngeo2709

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Abstract

Convective circulation of the Earth’s mantle maintains some fraction of surface topography that varies with space and time. Most predictive models show that this dynamic topography has peak amplitudes of about ±2km, dominated by wavelengths of 10⁴km. Here, we test these models against our comprehensive observational database of 2,120 spot measurements of dynamic topography that were determined by analysing oceanic seismic surveys. These accurate measurements have typical peak amplitudes of ±1km and wavelengths of approximately 10³km, and are combined with limited continental constraints to generate a global spherical harmonic model whose robustness has been carefully tested and benchmarked. Our power spectral analysis reveals significant discrepancies between observed and predicted dynamic topography. At longer wavelengths (such as 10⁴km), observed dynamic topography has peak amplitudes of about ±500m. At shorter wavelengths (such as 10³km), significant dynamic topography is still observed. We show that these discrepancies can be explained if short-wavelength dynamic topography is generated by temperature-driven density anomalies within a sub-plate asthenospheric channel. Stratigraphic observations from adjacent continental margins show that these dynamic topographic signals evolve quickly with time. More rapid temporal and spatial changes in vertical displacement of the Earth’s surface have direct consequences for fields as diverse as mantle flow, oceanic circulation and long-term climate change.

Item Type:	Article
Uncontrolled Keywords:	2015AREP, IA70;
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics 08 - Green Open Access
Journal or Publication Title:	Nature Geoscience
Volume:	9
Page Range:	pp. 456-463
Identification Number:	10.1038/ngeo2709
Depositing User:	Sarah Humbert
Date Deposited:	20 Apr 2016 16:55
Last Modified:	15 May 2017 10:00
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3605

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