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ITRF2014, Earth figure changes, and geocenter velocity: Implications for GIA and recent ice melting / Laurent Métivier in Journal of geophysical research : Solid Earth, vol 125 n° 2 (February 2020)  

Public [article]  inJournal of geophysical research : Solid Earth > vol 125 n° 2 (February 2020) . - n° e2019JB018333 Titre : ITRF2014, Earth figure changes, and geocenter velocity: Implications for GIA and recent ice melting Type de document : Article/Communication Auteurs : Laurent Métivier , Auteur ; Hélène Rouby , Auteur ; Paul Rebischung , Auteur ; Zuheir Altamimi , Auteur Année de publication : 2020 Projets : 2-Pas d'info accessible - article non ouvert / Article en page(s) : n° e2019JB018333 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] ajustement glacio-isostatique [Termes IGN] figure de la Terre [Termes IGN] fonte des glaces [Termes IGN] harmonique sphérique [Termes IGN] International Terrestrial Reference Frame [Termes IGN] manteau terrestre [Termes IGN] mouvement du géocentre [Termes IGN] vitesse de déplacement Résumé : (auteur) Using a selection of Global Navigation Satellite System vertical velocities from the latest solution of the International Terrestrial Reference Frame (ITRF) ITRF2014, we calculate the degree-1 and degree-2 spherical harmonics coefficients (SHC) of the solid Earth figure changes at different dates, with realistic errors that take into account the inhomogeneity of the network. We find that the SHC are globally close to zero except the zonal coefficients, which show values notably larger than those derived from different glacial isostatic adjustment (GIA) models and which have tended to increase during the time span of observations. We show that these differences are most probably due to global recent ice melting (RIM). Assuming elastic RIM deformation, we then investigate the Earth's geocenter velocity and the geoid oblateness time evolution (J2-rate) derived from our SHC estimations. The obtained geocenter velocity reaches 0.9 ± 0.5 mm/year in 2013 with a z-component of 0.8 ± 0.4 mm/year, which is slightly larger than previous estimations. We compare our J2-rate estimations with observations. Our estimations show a similar acceleration in J2 after 2000. However, our estimates are notably larger than the observations. This indicates either that the J2-rate due to GIA processes is lower than expected (as proposed by Nakada et al., 2015, 2016) or that the deformation induced by RIM is not purely elastic, or both. Finally, we show that viscous relaxation or phase transitions in the mantle transition zone may only partly explain this discrepancy. This raises the question of the accuracy of current mass estimations of RIM and GIA models. Numéro de notice : A2020-363 Affiliation des auteurs : UMR IPGP-Géod (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2019JB018333 Date de publication en ligne : 02/01/2020 En ligne : https://doi.org/10.1029/2019JB018333 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98263 [article]

A generalized theory of the figure of the Earth : on the global dynamical flattening / Chenjun Liu in Journal of geodesy, vol 93 n° 3 (March 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 3 (March 2019) . - pp 319 - 331 Titre : A generalized theory of the figure of the Earth : on the global dynamical flattening Type de document : Article/Communication Auteurs : Chenjun Liu, Auteur ; Chengli Huang, Auteur ; Yu Liu, Auteur ; Mian Zhang, Auteur Année de publication : 2019 Article en page(s) : pp 319 - 331 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie [Termes IGN] aplatissement [Termes IGN] croute terrestre [Termes IGN] isostasie [Termes IGN] manteau terrestre [Termes IGN] moment d'inertie [Termes IGN] noyau terrestre [Termes IGN] rotation de la Terre Résumé : (Auteur) A generalized theory of the figures of the Earth’s interior to a third-order precision of ellipticity is proposed in accompanying paper in which all the odd degree and nonzero order spherical harmonic terms are included. As both the direct and indirect contributions of the asymmetric crust are included, this theory makes a significant improvement for calculating the asymmetric equilibrium figures of the real Earth comparing with the traditional theories which can only deal with the ideal symmetric Earth. The principal moments of inertia (PMOI: A, B, C) and global dynamical flattening (H) are important quantities in studying the rotating Earth. Precession and gravity observations give observation value of H (Hobs≈1/305.4559) with very high precision, while its theoretical calculated value (Htheory≈1/308.5) from traditional theories and a starting symmetric Earth model (like PREM model) is about 1% less than Hobs. Using the new theory in accompanying paper and replacing the homogeneous outermost crust and oceanic layers in PREM with CRUST1.0 model, we recalculate the equilibrium figures of the Earth’s interior and finally get new values of PMOI and Htheory (≈1/304.7167) whose consistency with Hobs are significantly improved to 0.24%. Furthermore, the asymmetric figures of some interesting boundaries, like inner core boundary, core-mantle boundary, are also given as by-products of this work as these boundaries’ figures are key input for studies of their topographic effect on global rotation and geodynamics, like nutation, normal modes, especially like free core nutation. Numéro de notice : A2019-151 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1163-x Date de publication en ligne : 22/06/2018 En ligne : https://doi.org/10.1007/s00190-018-1163-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92490 [article]

Reconciling upper mantle seismic velocity and density structure below ocean basins / Isabelle Panet (2019)

Public Titre : Reconciling upper mantle seismic velocity and density structure below ocean basins Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Barbara Romanowicz, Auteur ; Marianne Greff-Lefftz, Auteur Editeur : Saint-Mandé : Institut national de l'information géographique et forestière - IGN Année de publication : 2019 Projets : 1-Pas de projet / Conférence : AGU 2019 Fall Meeting 09/12/2019 13/12/2019 San Francisco Californie - Etats-Unis programme sans actes Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] déformation de la croute terrestre [Termes IGN] données bathymétriques [Termes IGN] données GRACE [Termes IGN] fond marin [Termes IGN] geoïde marin [Termes IGN] géophysique interne [Termes IGN] Indien (océan) [Termes IGN] manteau terrestre [Termes IGN] Pacifique (océan) [Termes IGN] structure géologique [Termes IGN] vitesse de déplacement Résumé : (auteur) Imaging the spatial pattern of mantle flows and constraining their mass is one of the keys to understand the character of mantle convection inside the Earth, and its interactions with plate motions. The horizontal planform of the flows, their heterogeneity and mass transport at depth, are reflected in variations of the gravity field and seismic velocities, as well as deformations of the Earth's surface. Over ocean basins, these observables show an elusive medium-scale structure. A 1500-2000 km wavelength directional fabric following the present-day absolute plate motion is present in the Pacific Ocean in GRACE satellite gravity data (Hayn et al., 2012), while 2000-km wavelength slow shear velocity anomalies sharing a similar orientation are found in seismic tomography at upper mantle depths below the oceans (SEMUM2, French et al., 2013). Today, the dynamic processes at the origin of these observations remain unresolved. Here, we develop a joint analysis of satellite gravity and bathymetry data together with the SEMUM2 seismic tomography model, in order to advance our understanding of upper to mid-mantle flows below the oceans. First, we enhance and reconstruct the medium-scale gravity and seafloor topography signals aligned with the present-day plate motion from an analysis of the rates of gravity vector variations and seafloor slopes. Then, we compare the obtained signals with the spatial distribution of shear velocity anomalies at depth. We show that slow velocity anomalies coincide with geoid lows, depressions in the seafloor topography, and mass excess in the mantle, in the Pacific ocean and part of the Indian ocean. We first consider a purely thermal interpretation of the seismic velocity variations, associated with medium-scale convective rolls in the upper to mid-mantle, a process able to only explain the observed geometry of anomalies. Investigating whether the needed mass excess arises from lithospheric or deeper sources, such as at the level of the 660-km interface, we conclude that it lies more likely within the slow velocity anomalies themselves, suggesting hot and dense structures. We finally discuss the possible meaning and implications of these results. Numéro de notice : C2019-058 Affiliation des auteurs : Géodésie+Ext (mi2018-2019) Thématique : POSITIONNEMENT Nature : Poster nature-HAL : Poster-avec-CL DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96896

Contribution actuelle de la calotte Antarctique à la variation du niveau marin / Clémence Chupin (2018) 

Public Titre : Contribution actuelle de la calotte Antarctique à la variation du niveau marin Type de document : Mémoire Auteurs : Clémence Chupin, Auteur Editeur : Le Mans : Ecole Supérieure des Géomètres et Topographes ESGT Année de publication : 2018 Autre Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Importance : 83 p. Format : 21 x 30 cm Note générale : bibliographie Mémoire d'ingénieur ESGT, master PPMD Photogrammétrie, Positionnement et Mesure de Déformation Langues : Français (fre) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse spatio-temporelle [Termes IGN] Antarctique [Termes IGN] bilan de masse [Termes IGN] calotte glaciaire [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] données GRACE [Termes IGN] élasticité [Termes IGN] fonte des glaces [Termes IGN] géoïde local [Termes IGN] image Envisat-ASAR [Termes IGN] levé gravimétrique [Termes IGN] manteau terrestre [Termes IGN] montée du niveau de la mer [Termes IGN] rhéologie [Termes IGN] viscosité Index. décimale : MPPMD Mémoires du mastère spécialisé Photogrammétrie, Positionnement et Mesures de Déformation Résumé : (auteur) Avec ses 14 millions de km2, la calotte Antarctique représente le plus grand réservoir d’eau douce de la planète, ce qui en fait un contributeur non négligeable de l’augmentation du niveau marin. Les dernières estimations de son bilan de masse évalue la perte de glace de la calotte à 2.720 ± 1.390 Gt entre 1992 et 2017, ce qui correspond à une hausse du niveau marin d’environ 7.6 ± 3.9 mm [Shepherd et al., 2018]. L’objectif de ce stage est d’utiliser ce bilan de masse moyen pour quantifier l’amplitude des variations du niveau marin. Grâce aux données d’altimétrie et de gravimétrie satellitaire, un modèle des variations spatio-temporelles du bilan de masse est également construit. Le logiciel SELEN ensuite permet de calculer la variation du niveau marin induite par ces deux modèles de fonte. Note de contenu : Introduction 1- Antarctique & niveau marin 2- Modélisation de la variation spatio-temporelle de l’Antarctique 3- Estimation des variations du niveau marin Conclusion Numéro de notice : 21856 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Mémoire ingénieur ESGT Organisme de stage : Laboratoire Geoazur (CNRS) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91420

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Inverting Glacial Isostatic Adjustment signal using Bayesian framework and two linearly relaxing rheologies / Lambert Caron in Geophysical journal international, vol 209 n° 2 (May 2017)  

Public [article]  inGeophysical journal international > vol 209 n° 2 (May 2017) . - pp 1126 - 1147 Titre : Inverting Glacial Isostatic Adjustment signal using Bayesian framework and two linearly relaxing rheologies Type de document : Article/Communication Auteurs : Lambert Caron, Auteur ; Laurent Métivier , Auteur ; Marianne Greff-Lefftz, Auteur ; Luce Fleitout, Auteur ; Hélène Rouby , Auteur Année de publication : 2017 Projets : TOSCA / Article en page(s) : pp 1126 - 1147 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] ajustement glacio-isostatique [Termes IGN] anomalie de pesanteur [Termes IGN] calotte glaciaire [Termes IGN] élasticité [Termes IGN] gravimétrie spatiale [Termes IGN] manteau terrestre [Termes IGN] méthode de Monte-Carlo par chaînes de Markov [Termes IGN] rhéologie Résumé : (Auteur) Glacial Isostatic Adjustment (GIA) models commonly assume a mantle with a viscoelastic Maxwell rheology and a fixed ice history model. Here, we use a Bayesian Monte Carlo approach with a Markov chain formalism to invert the global GIA signal simultaneously for the mechanical properties of the mantle and the volumes of the ice sheets, using as starting ice models two previously published ice histories. Two stress relaxing rheologies are considered: Burgers and Maxwell linear viscoelasticities. A total of 5720 global palaeo sea level records are used, covering the last 35 kyr. Our goal is not only to seek the model best fitting this data set, but also to determine and display the range of possible solutions with their respective probability of explaining the data. In all cases, our a posteriori probability maps exhibit the classic character of solutions for GIA-determined mantle viscosity with two distinct peaks. What is new in our treatment is the presence of the bi-viscous Burgers rheology and the fact that we invert rheology jointly with ice history, in combination with the greatly expanded palaeo sea level records. The solutions tend to be characterized by an upper-mantle viscosity of around 5 × 1020 Pa s with one preferred lower-mantle viscosities at 3 × 1021 Pa s and the other more than 2 × 1022 Pa s, a rather classical pairing. Best-fitting models depend upon the starting ice history and the stress relaxing law. A first peak (P1) has the highest probability only in the case with a Maxwell rheology and ice history based on ICE-5G, while the second peak (P2) is favoured for ANU-based ice history or Burgers stress relaxation. The latter solution also may satisfy lower-mantle viscosity inferences from long-term geodynamics and gravity gradient anomalies over Laurentia. P2 is also consistent with large Laurentian and Fennoscandian ice-sheet volumes at the Last Glacial Maximum (LGM) and smaller LGM Antarctic ice volume than in either ICE-5G or ANU. Exploration of a bi-viscous linear relaxing rheology in GIA now seems logical due to a new set of requirements to satisfy observations of transient post-seismic flow seen so ubiquitously in space gravimetry and other global geodetic data. Numéro de notice : A2017-402 Affiliation des auteurs : LaSTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggx083 Date de publication en ligne : 27/02/2017 En ligne : https://doi.org/10.1093/gji/ggx083 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86108 [article]

Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity / Laurent Métivier in Earth and planetary science letters, vol 452 (October 2016)  

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Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism / Grace E. Shephard in Geophysical research letters, vol 43 n° 8 (28 April 2016)    

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Joint analysis of GOCE gravity gradients data of gravitational potential and of gravity with seismological and geodynamic observations to infer mantle properties / Marianne Greff-Lefftz in Geophysical journal international, vol 205 n° 1 (April 2016)  

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Gravimetric and magnetic anomalies produced by dissolution-crystallization at the core-mantle boundary / Mioara Mandea in Journal of geophysical research : Solid Earth, vol 120 n° 9 (September 2015)    

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Gravité de la Terre : des mesures aux modèles, une image de la dynamique interne / Isabelle Panet (2015)

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Mapping the mass distribution of Earth's mantle using satellite-derived gravity gradients / Isabelle Panet in Nature geoscience, vol 7 n° 2 (February 2014)  

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Europe's Goce gravity satellite probes Earth's mantle [interview of Isabelle Panet] / Jonathan Amos in BBC News - Science & Environment, sans n° (2014)    

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Wavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations / M. Hayn in Geophysical journal international, vol 189 n° 3 (June 2012)  

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Pacific geoid anomalies revisited in light of thermochemical oscillating domes in the lower mantle / Cécilia Cadio in Earth and planetary science letters, vol 306 n° 1-2 (June 2011)  

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Signature des séismes dans le champ de pesanteur / Isabelle Panet in XYZ, n° 127 (juin - août 2011)

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