Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity
International audience The Earth's surface was depressed under the weight of ice during the last glaciations. Glacial Isostatic Adjustment (GIA) induces the slow recession of the trough that is left after deglaciation and is responsible for a contemporary uplift rate of more than 1 cm/yr around...
Published in: | Earth and Planetary Science Letters |
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Online Access: | https://insu.hal.science/insu-03581287 https://doi.org/10.1016/j.epsl.2016.07.034 |
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ftsorbonneuniv:oai:HAL:insu-03581287v1 2024-09-15T17:43:56+00:00 Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity Métivier, Laurent Caron, Lambert Greff-Lefftz, Marianne Pajot-Métivier, Gwendoline Fleitout, Luce Rouby, Hélène Université Paris Cité (UPCité) Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) Laboratoire de géologie de l'ENS (LGENS) Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL) 2016 https://insu.hal.science/insu-03581287 https://doi.org/10.1016/j.epsl.2016.07.034 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.epsl.2016.07.034 insu-03581287 https://insu.hal.science/insu-03581287 BIBCODE: 2016E&PSL.452.146M doi:10.1016/j.epsl.2016.07.034 ISSN: 0012-821X Earth and Planetary Science Letters https://insu.hal.science/insu-03581287 Earth and Planetary Science Letters, 2016, 452, pp.146-156. ⟨10.1016/j.epsl.2016.07.034⟩ gravity gradients GIA mantle viscosity deformation modelling Laurentia [SDU]Sciences of the Universe [physics] info:eu-repo/semantics/article Journal articles 2016 ftsorbonneuniv https://doi.org/10.1016/j.epsl.2016.07.034 2024-07-25T23:47:51Z International audience The Earth's surface was depressed under the weight of ice during the last glaciations. Glacial Isostatic Adjustment (GIA) induces the slow recession of the trough that is left after deglaciation and is responsible for a contemporary uplift rate of more than 1 cm/yr around Hudson Bay. The present-day residual depression, an indicator of still-ongoing GIA, is difficult to identify in the observed topography, which is predominantly sensitive to crustal heterogeneities. According to the most widespread GIA models, which feature a viscosity of 2- 3 ×10 21 Pa s on top of the lower mantle, the trough is approximately 100 m deep and cannot explain the observed gravity anomalies across North America. These large anomalies are therefore usually attributed to subcontinental density heterogeneities in the tectosphere or to slab downwelling in the deep mantle. Here, we use observed gravity gradients (GG) to show that the uncompensated GIA trough is four times larger than expected and that it is the main source of the North American static gravity signal. We search for the contribution to these GGs from mantle mass anomalies, which are deduced from seismic tomography and are mechanically coupled to the global mantle flow. This contribution is found to be small over Laurentia, and at least 82% of the GGs are caused by GIA. Such a contribution from GIA in these GG observations implies a viscosity that is greater than 10 22 Pa s in the lower mantle. Our conclusions are a plea for GIA models with a highly viscous lower mantle, which confirm inferences from mantle dynamic models. Any change in GIA modelling has important paleoclimatological and environmental implications, encouraging scientists to re-evaluate the past ice history at a global scale. These implications, in turn, affect the contribution of bedrock uplift to the contemporaneous mass balance over Antarctica and Greenland and thus the present-day ice-melting rate as deduced from the GRACE space mission. Additionally, studies of the ... Article in Journal/Newspaper Antarc* Antarctica Greenland Hudson Bay HAL Sorbonne Université Earth and Planetary Science Letters 452 146 156 |
institution |
Open Polar |
collection |
HAL Sorbonne Université |
op_collection_id |
ftsorbonneuniv |
language |
English |
topic |
gravity gradients GIA mantle viscosity deformation modelling Laurentia [SDU]Sciences of the Universe [physics] |
spellingShingle |
gravity gradients GIA mantle viscosity deformation modelling Laurentia [SDU]Sciences of the Universe [physics] Métivier, Laurent Caron, Lambert Greff-Lefftz, Marianne Pajot-Métivier, Gwendoline Fleitout, Luce Rouby, Hélène Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity |
topic_facet |
gravity gradients GIA mantle viscosity deformation modelling Laurentia [SDU]Sciences of the Universe [physics] |
description |
International audience The Earth's surface was depressed under the weight of ice during the last glaciations. Glacial Isostatic Adjustment (GIA) induces the slow recession of the trough that is left after deglaciation and is responsible for a contemporary uplift rate of more than 1 cm/yr around Hudson Bay. The present-day residual depression, an indicator of still-ongoing GIA, is difficult to identify in the observed topography, which is predominantly sensitive to crustal heterogeneities. According to the most widespread GIA models, which feature a viscosity of 2- 3 ×10 21 Pa s on top of the lower mantle, the trough is approximately 100 m deep and cannot explain the observed gravity anomalies across North America. These large anomalies are therefore usually attributed to subcontinental density heterogeneities in the tectosphere or to slab downwelling in the deep mantle. Here, we use observed gravity gradients (GG) to show that the uncompensated GIA trough is four times larger than expected and that it is the main source of the North American static gravity signal. We search for the contribution to these GGs from mantle mass anomalies, which are deduced from seismic tomography and are mechanically coupled to the global mantle flow. This contribution is found to be small over Laurentia, and at least 82% of the GGs are caused by GIA. Such a contribution from GIA in these GG observations implies a viscosity that is greater than 10 22 Pa s in the lower mantle. Our conclusions are a plea for GIA models with a highly viscous lower mantle, which confirm inferences from mantle dynamic models. Any change in GIA modelling has important paleoclimatological and environmental implications, encouraging scientists to re-evaluate the past ice history at a global scale. These implications, in turn, affect the contribution of bedrock uplift to the contemporaneous mass balance over Antarctica and Greenland and thus the present-day ice-melting rate as deduced from the GRACE space mission. Additionally, studies of the ... |
author2 |
Université Paris Cité (UPCité) Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) Laboratoire de géologie de l'ENS (LGENS) Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL) |
format |
Article in Journal/Newspaper |
author |
Métivier, Laurent Caron, Lambert Greff-Lefftz, Marianne Pajot-Métivier, Gwendoline Fleitout, Luce Rouby, Hélène |
author_facet |
Métivier, Laurent Caron, Lambert Greff-Lefftz, Marianne Pajot-Métivier, Gwendoline Fleitout, Luce Rouby, Hélène |
author_sort |
Métivier, Laurent |
title |
Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity |
title_short |
Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity |
title_full |
Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity |
title_fullStr |
Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity |
title_full_unstemmed |
Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity |
title_sort |
evidence for postglacial signatures in gravity gradients: a clue in lower mantle viscosity |
publisher |
HAL CCSD |
publishDate |
2016 |
url |
https://insu.hal.science/insu-03581287 https://doi.org/10.1016/j.epsl.2016.07.034 |
genre |
Antarc* Antarctica Greenland Hudson Bay |
genre_facet |
Antarc* Antarctica Greenland Hudson Bay |
op_source |
ISSN: 0012-821X Earth and Planetary Science Letters https://insu.hal.science/insu-03581287 Earth and Planetary Science Letters, 2016, 452, pp.146-156. ⟨10.1016/j.epsl.2016.07.034⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.epsl.2016.07.034 insu-03581287 https://insu.hal.science/insu-03581287 BIBCODE: 2016E&PSL.452.146M doi:10.1016/j.epsl.2016.07.034 |
op_doi |
https://doi.org/10.1016/j.epsl.2016.07.034 |
container_title |
Earth and Planetary Science Letters |
container_volume |
452 |
container_start_page |
146 |
op_container_end_page |
156 |
_version_ |
1810491166132535296 |