The relationship between depth, age and gravity in the oceans

Crosby, A. and McKenzie, D. P. and Sclater, J. G. (2006) The relationship between depth, age and gravity in the oceans. Geophysical Journal International, 166 (2). pp. 553-573. ISSN ISSN: 0956-540X, ESSN: 1365-246X DOI 10.1111/j.1365-246X.2006.03015.x

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Abstract

We reassess the applicability of the thermal plate cooling model to the subsidence of the North Pacific, Atlantic and North Indian Ocean Basins. We use a new numerical plate model in which the thermophysical parameters of the lithosphere vary with temperature according to the results of laboratory experiments, and the ridge temperature structure is consistent with the thickness of the oceanic crust. We first attempt to exclude thickened crust from our data set, and then to exclude swells and downwellings by masking regions of the data that remains that have significant gravity anomalies when there exists a clear regional correlation between intermediate-wavelength gravity and topography. We find that the average variation of depth with age is consistent with conventional half-space models until about 90 Myr. Thereafter, the departure from the half-space cooling curve is more rapid than predicted using simple conductive plate cooling models. The depth–age curves in the Pacific and Atlantic show ∼250 m of temporary shallowing between the ages of 90–130 Myr, a result consistent with the outcome of experiments on the initiation of small-scale boundary layer convection. The results do not change significantly if the estimated component of the gravity arising from plate cooling is subtracted prior to calculation of the correlation between gravity and topography. A 90-km-thick conductive plate is nevertheless a reasonable model for the average temperature structure of the oldest part of the Pacific ocean lithosphere. In the Pacific, the broad topographic undulations associated with the Line Island Swell, the Hawaiian Swell and surrounding basins have correlated gravity anomalies and an admittance of approximately 30 mGal km−1 and are likely to result from convective circulation in the upper mantle. In the Northeast Atlantic, the intermediate-wavelength admittance over the Cape Verde swell is similar; in the Northwest Atlantic over the Bermuda Swell it is slightly larger but not as well constrained.

Item Type: Article
Additional Information: This article has been accepted for publication in Geophysical Journal International ©: 2006 The Authors owner as specified on the article] Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 2006 AREP 2006 P IA51
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Geophysical Journal International
Volume: 166
Page Range: pp. 553-573
Identification Number: 10.1111/j.1365-246X.2006.03015.x
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:02
Last Modified: 28 Jan 2016 17:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/226

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