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Auteur Hélène Rouby
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Affiner la recherche Interroger des sources externesPast and present ITRF solutions from geophysical perspectives / Laurent Métivier in Advances in space research, vol 65 n° 12 (15 June 2020)
Titre : Past and present ITRF solutions from geophysical perspectives Type de document : Article/Communication Auteurs : Laurent Métivier Année de publication : 2020 Projets : TOSCA / Article en page(s) : pp 2711 - 2722 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] ajustement glacio-isostatique
[Termes IGN] champ de vitesse
[Termes IGN] fonte des glaces
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] positionnement par GNSS
[Termes IGN] vitesseRésumé : (auteur) Questions about the accuracy of the origin of the different versions of International Terrestrial Reference Frame (ITRF), have been regularly raised. In particular the origin drift between ITRF2000 and ITRF2005 (and subsequent ITRF solutions) is well-known to be problematic. Here, we look forward a sort of geophysical evaluation of ITRF solutions. We investigate GNSS vertical velocities provided by the last four ITRF solutions (ITRF2000 to ITRF2014; Altamimi et al., 2005, 2007, 2011, 2016) that we compare with different Global Isostatic Adjustment (GIA) model predictions. We find that each new ITRF solution appears to be more and more consistent with all GIA predictions, except ITRF2014 whose consistency with the GIA models depends on the date of observation. Indeed, GNSS observations and GIA predictions appear consistent at global scale at a level of ~4 mm/yr using ITRF2000 data, ~2.5–3 mm/yr using ITRF2005 data, and ~2 mm/yr using ITRF2008 data (global weighted root mean squares). For ITRF2014, the consistency between GNSS observations and GIA predictions is extremely high in 2000 (~1.5 mm/yr) but seems then to decrease with time (~2 mm/yr in 2013). This discrepancy is due to the recent ice melting effect that is not accounted for in GIA models, but clearly evidenced by ITRF2014 vertical velocities during the last years of observations, in particular in Greenland. Numéro de notice : A2020-364 Affiliation des auteurs : UMR IPGP-Géod (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2020.03.031 date de publication en ligne : 06/04/2020 En ligne : https://doi.org/10.1016/j.asr.2020.03.031 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96828
in Advances in space research > vol 65 n° 12 (15 June 2020) . - pp 2711 - 2722[article]
Titre : ITRF2014 and Earth figure changes: evidence of global viscous relaxation in recent ice melting Earth’s response? Type de document : Article/Communication Auteurs : Laurent Métivier Editeur : Munich [Allemagne] : European Geosciences Union EGU Année de publication : 2018 Collection : Geophysical Research Abstracts, ISSN 1607-7962 num. 20 Conférence : EGU 2018, General Assembly 08/04/2018 13/04/2018 Vienne Autriche OA Abstracts only Note générale : EGU2018-7567 Langues : Anglais (eng) Résumé : (auteur) The latest solution of the International Terrestrial Reference Frame, entitled ITRF2014, presents particularly large vertical velocities across Greenland, South East Alaska and the Antarctic Peninsula, compared with the previous solution ITRF2008. We investigate here the geophysical origin of this evolution of the ITRF velocity field. From a selection of ITRF2014 GNSS vertical velocities we determine solid Earth figure changes and Earth’s geocenter motion at different dates. By exploring various geophysical models, we show that our estimations can be well explained by the deformation due to Glacial Isostatic Adjustment (GIA) and Recent Ice Melting (RIM). However, we also show that the obtained solid Earth oblateness is not consistent with J2-rate observations if we assume purely elastic RIM deformations.We explore here different rheological scenarios that may explain this discrepancy, including low viscosities in the asthenosphere and/or the D” layer, or possible phase transitions in the mantle transition zone. Numéro de notice : C2018-071 Affiliation des auteurs : LaSTIG LAREG (2012-mi2018) Thématique : POSITIONNEMENT Nature : Poster nature-HAL : Poster-avec-CL DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91463
Titre : ITRF2014 plate motion model Type de document : Article/Communication Auteurs : Zuheir Altamimi Année de publication : 2017 Projets : 1-Pas de projet / Article en page(s) : pp 1906 - 1912 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] ajustement glacio-isostatique
[Termes IGN] déformation de la croute terrestre
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] modèle de déformation tectonique
[Termes IGN] modèle de déplacement de plaque
[Termes IGN] pôle de rotation
[Termes IGN] station permanente
[Termes IGN] vitesse
[Termes IGN] vitesse de déplacementRésumé : (Auteur) For various geodetic and geophysical applications, users need to have access to a plate motion model (PMM) that is consistent with the ITRF2014 frame. This paper describes the approach used for determining a PMM from the horizontal velocities of a subset of the ITRF2014 sites away from plate boundaries, Glacial Isostatic Adjustment regions and other deforming zones. In theory, it would be necessary to include in the inversion model a translational motion vector (called in this paper origin rate bias, ORB) that would represent the relative motion between the ITRF2014 origin (long-term averaged centre of mass of the Earth as sensed by SLR) and the centre of tectonic plate motion. We show that in practice, the magnitude of the estimated ORB is strongly dependent on the selection of ITRF2014 sites used for the PMM adjustment. Its Z-component can in particular range between 0 and more than 1 mm yr−1 depending on the station network used, preventing any geophysical interpretation of the estimated value. Relying on rigorous statistical criteria, the site selection finally adopted for the ITRF2014-PMM adjustment leads to a relatively small ORB (0.30 ± 0.18 mm yr−1 in the Z-component), which is statistically insignificant at the 2-sigma level, but also according to an F-ratio test. Therefore we opted for an ITRF2014-PMM without estimating the ORB, which in turn accommodates geodetic applications that require access to the ITRF2014 frame through pure plate rotation poles. Numéro de notice : A2017-403 Affiliation des auteurs : LaSTIG LAREG (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggx136 date de publication en ligne : 30/03/2017 En ligne : https://doi.org/10.1093/gji/ggx136 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86077
in Geophysical journal international > vol 209 n° 3 (June 2017) . - pp 1906 - 1912[article]
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 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] rhéologieRésumé : (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
in Geophysical journal international > vol 209 n° 2 (May 2017) . - pp 1126 - 1147[article]
Titre : Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity Type de document : Article/Communication Auteurs : Laurent Métivier Année de publication : 2016 Article en page(s) : pp 146 - 156 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] Amérique du nord
[Termes IGN] anomalie de pesanteur
[Termes IGN] déformation de la croute terrestre
[Termes IGN] gradient de gravitation
[Termes IGN] manteau terrestre
[Termes IGN] paléocontinent
[Termes IGN] viscositéRésumé : (auteur) 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 2–3×1021 Pa s2–3×1021 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 1022 Pa s1022 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 thermo-chemical structure of the lithosphere/crust under North America that exploit gravity or geodetic data should be corrected for a GIA model, which is not the case today.Numéro de notice : A2016-906 Affiliation des auteurs : IGN+Ext (2012-2019) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.epsl.2016.07.034 date de publication en ligne : 16/08/2016 En ligne : http://dx.doi.org/10.1016/j.epsl.2016.07.034 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83034
in Earth and planetary science letters > vol 452 (October 2016) . - pp 146 - 156[article]Permalink
