ORCID Profile
0000-0003-0259-209X
Current Organisation
Université de Strasbourg
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Publisher: Oxford University Press (OUP)
Date: 08-07-2022
DOI: 10.1093/GJI/GGAC264
Abstract: We analyse Global Navigation Satellite System (GNSS) data from Svalbard to understand how uplift rates are controlled by the elastic and viscoelastic response of the solid Earth to changes in glacier mass on annual, interannual, decadal, centennial and millennial timescales. To reveal local patterns of deformation, we filter the GNSS time-series with an enhanced common-mode filtering technique where the non-tidal loading signal is incorporated. This technique reduces the estimated uncertainties for 5-yr time-series from 0.8 to 0.3 mm yr–1. Analysis of the GNSS data with different software–GAMIT, GipsyX, and GINS–produce consistent results that all indicate large temporal variations in uplift. For ex le, at the Ny-Ålesund GNSS station, uplift varies between 6 and 12 mm yr–1 for different 5-yr periods, and also shows a significant increase in the last 15 yr. We show that this increase is due to climate change-related ice mass loss in Svalbard. We constrain recent glacier retreat on Svalbard using a series of digital elevation models, and then correct the GNSS-derived uplift records for the elastic signal from these ice mass changes. The residual uplift signal is relatively constant, confirming the hypothesis that current ice mass changes exert a strong influence on GNSS observations. The relatively constant record of residual uplift can be used to constrain other geophysical signals such as the viscoelastic response of the solid Earth to ice loading during the Little Ice Age and the Last Glacial Period. We review uplift results from previous viscoelastic modelling studies and show that the residual signal cannot yet be fully explained. Our new uplift results thus motivate the need for new viscoelastic modelling of the glacial isostatic adjustment process in Svalbard.
Publisher: Wiley
Date: 24-08-2022
Publisher: EDP Sciences
Date: 2016
Publisher: American Geophysical Union (AGU)
Date: 09-2010
DOI: 10.1029/2010GC003214
Publisher: Elsevier BV
Date: 12-2009
Publisher: American Geophysical Union (AGU)
Date: 05-2012
DOI: 10.1029/2011JB009102
Publisher: Oxford University Press (OUP)
Date: 10-01-2011
Publisher: MDPI AG
Date: 10-11-2021
DOI: 10.3390/RS13224523
Abstract: Thanks to the increasing number of permanent GNSS stations in Europe and their long records, we computed position solutions for more than 1000 stations over the last two decades using the REPRO3 orbit and clock products from the IGS CNES-CLS (GRGS) Analysis Center. The velocities, which are mainly due to tectonics and glacial isostatic adjustment (GIA), and the annual solar cycle have been estimated using weighted least squares. The interannual variations have been accounted for in the stochastic model or in the deterministic model. We demonstrated that the velocity and annual cycle, in addition to their uncertainties, depend on the estimation method we used and that the estimation of GPS draconitic oscillations minimises biases in the estimation of annual solar cycle displacements. The annual solar cycle extracted from GPS has been compared with that from loading estimates of several hydrological models. If the annual litudes between GPS and hydrological models match, the phases of the loading models were typically in advance of about 1 month compared to GPS. Predictions of displacements modelled from GRACE observations did not show this phase shift. We also found important discrepancies at the interannual frequency band between GNSS, loading estimates derived from GRACE, and hydrological models using principal component analysis (PCA) decomposition. These discrepancies revealed that GNSS position variations in the interannual band cannot be systematically interpreted as a geophysical signal and should instead be interpreted in terms of autocorrelated noise.
Publisher: Authorea, Inc.
Date: 03-2023
DOI: 10.22541/ESSOAR.167768139.90331914/V1
Abstract: Space gravity measurements have been mainly used to study the temporal mass variations at the Earth’s surface and within the mantle. Nevertheless, mass variations due to the Earth’s core might be observable in the gravity field variations as measured by GRACE(-FO) satellites. Earth’s core dynamical processes inferred from geomagnetic field measurements are characterized by large-scale patterns associated with low spherical harmonic degrees of the potential fields. To study these processes, the use of large spatial and inter-annual temporal filters is needed. To access gravity variations related to the Earth’s core, surface effects must be corrected, including hydrological, oceanic or atmospheric loading (Newtonian attraction and mass redistribution). However, these corrections for surface processes add errors to the estimates of the residual gravity field variations enclosing deep Earth’s signals. As our goal is to evaluate the possibility to detect signals of core origin embedded in the residual gravity field variations, a quantification of the uncertainty associated with gravity field products and geophysical models used to minimise the surface process signatures is necessary. Here, we estimate the dispersion for GRACE solutions as about 0.34 cm of Equivalent Water Height (EWH) or 20% of the total signal. Uncertainty for hydrological models is as large as 0.89 to 2.10 cm of EWH. We provide estimates of Earth’s core signals whose litudes are compared with GRACE gravity field residuals and uncertainties. The results presented here underline how challenging is to get new information about the dynamics of the Earth’s core via high-resolution, high-accuracy gravity data.
Publisher: Elsevier BV
Date: 09-2018
Publisher: Oxford University Press (OUP)
Date: 19-05-2017
DOI: 10.1093/GJI/GGX142
Publisher: Springer Science and Business Media LLC
Date: 14-02-2020
No related grants have been discovered for Jean-Paul Boy.