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...
Published in: | Earth and Planetary Science Letters |
---|---|
Main Author: | |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
Elsevier
1983
|
Subjects: | |
Online Access: | https://authors.library.caltech.edu/84529/ https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796 |
id |
ftcaltechauth:oai:authors.library.caltech.edu:84529 |
---|---|
record_format |
openpolar |
spelling |
ftcaltechauth:oai:authors.library.caltech.edu:84529 2023-05-15T14:01:44+02:00 Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere Hager, Bradford H. 1983-04 https://authors.library.caltech.edu/84529/ https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796 unknown Elsevier Hager, Bradford H. (1983) Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere. Earth and Planetary Science Letters, 63 (1). pp. 97-109. ISSN 0012-821X. doi:10.1016/0012-821X(83)90025-0. https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796 <https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796> Article PeerReviewed 1983 ftcaltechauth https://doi.org/10.1016/0012-821X(83)90025-0 2021-11-18T18:44:53Z 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. Article in Journal/Newspaper Antarc* Antarctica West Antarctica Caltech Authors (California Institute of Technology) West Antarctica Earth and Planetary Science Letters 63 1 97 109 |
institution |
Open Polar |
collection |
Caltech Authors (California Institute of Technology) |
op_collection_id |
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. |
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://authors.library.caltech.edu/84529/ https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796 |
geographic |
West Antarctica |
geographic_facet |
West Antarctica |
genre |
Antarc* Antarctica West Antarctica |
genre_facet |
Antarc* Antarctica West Antarctica |
op_relation |
Hager, Bradford H. (1983) Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere. Earth and Planetary Science Letters, 63 (1). pp. 97-109. ISSN 0012-821X. doi:10.1016/0012-821X(83)90025-0. https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796 <https://resolver.caltech.edu/CaltechAUTHORS:20180125-135055796> |
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_ |
1766271775272861696 |