Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere
Isostatic geoid anomalies are usually interpreted using a flat-earth, one-dimensional idealization. Isostatic anomalies on the spherical, self-gravitating earth differ from this idealization because: (1) degree one terms in the spherical harmonic expansion vanish; (2) each term in the spherical harm...
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ftcaltechauth:oai:authors.library.caltech.edu:3bm1w-zv286 2024-06-23T07:46:04+00:00 Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere Hager, Bradford H. 1983-04 https://doi.org/10.1016/0012-821X(83)90025-0 unknown Elsevier https://doi.org/10.1016/0012-821X(83)90025-0 oai:authors.library.caltech.edu:3bm1w-zv286 eprintid:84529 resolverid:CaltechAUTHORS:20180125-135055796 info:eu-repo/semantics/closedAccess Other Earth and Planetary Science Letters, 63(1), 97-109, (1983-04) info:eu-repo/semantics/article 1983 ftcaltechauth https://doi.org/10.1016/0012-821X(83)90025-0 2024-06-12T05:04:53Z Isostatic geoid anomalies are usually interpreted using a flat-earth, one-dimensional idealization. Isostatic anomalies on the spherical, self-gravitating earth differ from this idealization because: (1) degree one terms in the spherical harmonic expansion vanish; (2) each term in the spherical harmonic expansion is multiplied by (l + 2)/(l + 0.5) relative to the flat-earth case; (3) mass in cones rather than straight-sided columns is constant; and (4) further deformation of the earth is induced by the gravitational attraction of the deformation caused by the isostatic potential anomaly. When the effect of each of these is quantified, the second, third, and fourth nearly cancel, leaving the degree one, "over the horizon" effect providing the most important difference. Calculations of model isostatic geoid anomalies for the spherical analogues (developed here) of the plate and boundary layer thermal models show that this effect can bias estimates of geoid slopes by over 20%, although the effect is usually less than 5%. The geoid anomalies for these two models are quite different over old ocean basins, but they are unlikely to be distinguishable on the basis of global geoid observations owing to the presence of other larger perturbations in the geoid. Stripping the effects of plate aging and a hypothetical uniform, 35 km thick, isostatically-compensated continental crust from the observed geoid emphasizes that the largest-amplitude geoid anomaly is the geoid low of almost 120 m over West Antarctica. This anomaly is a factor of two greater in amplitude than the low of 60 m over Sri Lanka. © 1983 Elsevier B.V. Received 17 November 1982, Revised 5 January 1983. This paper resulted from discussions with Clive Lister, who pointed out that the earth is round, that topography is three-dimensional, and that one-dimensional, fiat-earth geoid models are not necessarily applicable. Tony Dahlen pointed out the second-order nature of the definition of isostasy and provided a preprint of his paper. Bill Haxby provided a very ... Article in Journal/Newspaper Antarc* Antarctica West Antarctica Caltech Authors (California Institute of Technology) Lister ENVELOPE(-60.083,-60.083,-62.483,-62.483) West Antarctica Earth and Planetary Science Letters 63 1 97 109 |
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Open Polar |
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Caltech Authors (California Institute of Technology) |
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ftcaltechauth |
language |
unknown |
description |
Isostatic geoid anomalies are usually interpreted using a flat-earth, one-dimensional idealization. Isostatic anomalies on the spherical, self-gravitating earth differ from this idealization because: (1) degree one terms in the spherical harmonic expansion vanish; (2) each term in the spherical harmonic expansion is multiplied by (l + 2)/(l + 0.5) relative to the flat-earth case; (3) mass in cones rather than straight-sided columns is constant; and (4) further deformation of the earth is induced by the gravitational attraction of the deformation caused by the isostatic potential anomaly. When the effect of each of these is quantified, the second, third, and fourth nearly cancel, leaving the degree one, "over the horizon" effect providing the most important difference. Calculations of model isostatic geoid anomalies for the spherical analogues (developed here) of the plate and boundary layer thermal models show that this effect can bias estimates of geoid slopes by over 20%, although the effect is usually less than 5%. The geoid anomalies for these two models are quite different over old ocean basins, but they are unlikely to be distinguishable on the basis of global geoid observations owing to the presence of other larger perturbations in the geoid. Stripping the effects of plate aging and a hypothetical uniform, 35 km thick, isostatically-compensated continental crust from the observed geoid emphasizes that the largest-amplitude geoid anomaly is the geoid low of almost 120 m over West Antarctica. This anomaly is a factor of two greater in amplitude than the low of 60 m over Sri Lanka. © 1983 Elsevier B.V. Received 17 November 1982, Revised 5 January 1983. This paper resulted from discussions with Clive Lister, who pointed out that the earth is round, that topography is three-dimensional, and that one-dimensional, fiat-earth geoid models are not necessarily applicable. Tony Dahlen pointed out the second-order nature of the definition of isostasy and provided a preprint of his paper. Bill Haxby provided a very ... |
format |
Article in Journal/Newspaper |
author |
Hager, Bradford H. |
spellingShingle |
Hager, Bradford H. Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
author_facet |
Hager, Bradford H. |
author_sort |
Hager, Bradford H. |
title |
Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
title_short |
Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
title_full |
Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
title_fullStr |
Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
title_full_unstemmed |
Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
title_sort |
global isostatic geoid anomalies for plate and boundary layer models of the lithosphere |
publisher |
Elsevier |
publishDate |
1983 |
url |
https://doi.org/10.1016/0012-821X(83)90025-0 |
long_lat |
ENVELOPE(-60.083,-60.083,-62.483,-62.483) |
geographic |
Lister West Antarctica |
geographic_facet |
Lister West Antarctica |
genre |
Antarc* Antarctica West Antarctica |
genre_facet |
Antarc* Antarctica West Antarctica |
op_source |
Earth and Planetary Science Letters, 63(1), 97-109, (1983-04) |
op_relation |
https://doi.org/10.1016/0012-821X(83)90025-0 oai:authors.library.caltech.edu:3bm1w-zv286 eprintid:84529 resolverid:CaltechAUTHORS:20180125-135055796 |
op_rights |
info:eu-repo/semantics/closedAccess Other |
op_doi |
https://doi.org/10.1016/0012-821X(83)90025-0 |
container_title |
Earth and Planetary Science Letters |
container_volume |
63 |
container_issue |
1 |
container_start_page |
97 |
op_container_end_page |
109 |
_version_ |
1802643797849407488 |