ORCID Profile
0000-0003-2931-9034
Current Organisations
Université Nice Sophia Antipolis, Géoazur
,
University of Tasmania
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Publisher: Springer Science and Business Media LLC
Date: 03-09-2012
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: Elsevier
Date: 2018
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-6911
Abstract: The Antarctic Ice Sheet (AIS) is the largest ice sheet on Earth that has known important mass changes during the last 26 kyrs. These changes deform the Earth and modify its gravity field, a process known as Glacial Isostatic Adjustment (GIA). GIA is directly influenced by the mechanical properties and internal structure of the Earth and is monitored using Global Navigation Satellite System positioning or gravity measurements. However, GIA in Antarctica remains poorly constrained due to the cumulative effect of past and present ice-mass changes, the unknown history of the past ice-mass change, and the uncertainties of the mechanical properties of the Earth. The viscous deformation due to GIA is usually modeled using a Maxwell rheology. However, other geophysical processes employ the Andrade rheology for tidal deformation or Burgers for post-seismic deformation which could result in a more rapid response of the Earth. We investigate the effect of using these different rheologies to model GIA-induced deformation in Antarctica. We use the Love number and Green functions formalism to compute the radial surface displacements and the gravity changes induced by the past and present day ice-mass changes. We use the elastic properties and the radial structure of the Preliminary Reference Earth Model (PREM) and the viscosity profile VM5a given by Peltier et al., 2015 and a modified version of it to account for the recent results published regarding the present-day ice-mass changes. Deformations are computed for each rheological laws mentioned above using ICE6g deglaciation model and altimetry data from various satellite missions over the period 2002 to 2017 to represent the past and present changes of the AIS, respectively.We find that the three rheological laws lead to significant discrepancies in the Earth response. The differences are the largest between Maxwell and Burgers rheologies during the 100 -1000 years following the beginning of the surface-mass change. First using a simple deglaciation model, we find that the deformations rates can be 3 times and 1.5 times greater using the Burgers and Andrade rheologies. However, the ratio between the gravity change rate and the displacement rate are similar for all rheologies (less than 5% difference). Results show that using the Andrade and Burgers rheologies can lead to a 5 and 10m difference in the radial displacement with regards to the Maxwell rheology, on a 200 year period after deglaciation using the ICE6g model. Regarding the response to present changes in Antarctica, the largest discrepancies are obtained in regions with the greatest current melting rates, namely Thwaites and Pine Island Glacier in West Antarctica. Using the Burgers and Andrade rheologies lead to deformations rates respectively 6 times and 2 times greater with respect to Maxwell rheology.
Publisher: MDPI AG
Date: 04-06-2021
DOI: 10.3390/RS13112199
Abstract: Quantifying the mass balance of the Antarctic Ice Sheet (AIS), and the resulting sea level rise, requires an understanding of inter-annual variability and associated causal mechanisms. Very few studies have been exploring the influence of climate anomalies on the AIS and only a vague estimate of its impact is available. Changes to the ice sheet are quantified using observations from space-borne altimetry and gravimetry missions. We use data from Envisat (2002 to 2010) and Gravity Recovery And Climate Experiment (GRACE) (2002 to 2016) missions to estimate monthly elevation changes and mass changes, respectively. Similar estimates of the changes are made using weather variables (surface mass balance (SMB) and temperature) from a regional climate model (RACMO2.3p2) as inputs to a firn compaction (FC) model. Elevation changes estimated from different techniques are in good agreement with each other across the AIS especially in West Antarctica, Antarctic Peninsula, and along the coasts of East Antarctica. Inter-annual height change patterns are then extracted using for the first time an empirical mode decomposition followed by a principal component analysis to investigate for influences of climate anomalies on the AIS. Investigating the inter-annual signals in these regions revealed a sub-4-year periodic signal in the height change patterns. El Niño Southern Oscillation (ENSO) is a climate anomaly that alters, among other parameters, moisture transport, sea surface temperature, precipitation, in and around the AIS at similar frequency by alternating between warm and cold conditions. This periodic behavior in the height change patterns is altered in the Antarctic Pacific (AP) sector, possibly by the influence of multiple climate drivers, like the Amundsen Sea Low (ASL) and the Southern Annular Mode (SAM). Height change anomaly also appears to traverse eastwards from Coats Land to Pine Island Glacier (PIG) regions passing through Dronning Maud Land (DML) and Wilkes Land (WL) in 6 to 8 years. This is indicative of climate anomaly traversal due to the Antarctic Circumpolar Wave (ACW). Altogether, inter-annual variability in the SMB of the AIS is found to be modulated by multiple competing climate anomalies.
Publisher: EDP Sciences
Date: 2016
Publisher: Elsevier BV
Date: 12-2009
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-7781
Abstract: & & The Sun exerts tidal forces that deform the planet Venus, from deformation and mass redistribution in& its interior, involving variation in the gravity field. The deformation of the planet induced by tidal forcing can be observed with the periodic variations of its gravity field and the Love number k2. The planet& #8217 s deformation is linked to its internal structure, most effectively to& its density, rigidity and viscosity.& Hence the tidal Love number k& sub& & /sub& & can be theoretically estimated& for different planetary models.& & & & The terrestrial planet Venus is reminiscent of the Earth twin planet in size and& density, which leads to the assumption that the Earth and Venus have similar internal& structures.& In this work, the calculation of k& sub& & /sub& & is done with& ALMA, a Fortran 90 program from& Spada [2008]& which computes the tidal and load Love& numbers using the& Post-Widder Laplace inversion formula. With a reference Venus model from Dumoulin et al. [2017], we investigate different parameters of the planet& #8217 s layers to calculate its frequency dependent tidal k& sub& & /sub& . We apply a random variation of each layer& #8217 s parameters within certain boundaries, which allows a statistical analysis of the possible Venus models that fall into the observed data (Mass, Moment of Inertia and k2). We test the effect of different parameters in the Venus model on the k& sub& & /sub& & and better understand the different hypotheses for the interior of Venus, as mantle viscosity to core structure (a fluid, solid and part fluid part solid core) .& &
Publisher: Oxford University Press (OUP)
Date: 21-01-2011
Publisher: Elsevier BV
Date: 10-2014
Publisher: Springer Science and Business Media LLC
Date: 12-06-2014
Publisher: Springer Science and Business Media LLC
Date: 14-02-2020
Publisher: Springer International Publishing
Date: 2016
Publisher: Oxford University Press (OUP)
Date: 09-06-2016
DOI: 10.1093/GJI/GGW220
Publisher: Oxford University Press (OUP)
Date: 29-05-2015
DOI: 10.1093/GJI/GGV190
Abstract: Geodetic vertical velocities derived from data as short as 3 yr are often assumed to be representative of linear deformation over past decades to millennia. We use two decades of surface loading deformation predictions due to variations of atmospheric, oceanic and continental water mass to assess the effect on secular velocities estimated from short time-series. The interannual deformation is time-correlated at most locations over the globe, with the level of correlation depending mostly on the chosen continental water model. Using the most conservative loading model and 5-yr-long time-series, we found median vertical velocity errors of 0.5 mm yr−1 over the continents (0.3 mm yr−1 globally), exceeding 1 mm yr−1 in regions around the southern Tropic. Horizontal velocity errors were seven times smaller. Unless an accurate loading model is available, a decade of continuous data is required in these regions to mitigate the impact of the interannual loading deformation on secular velocities.
Publisher: Elsevier BV
Date: 07-2015
Publisher: Elsevier BV
Date: 09-2018
Location: France
Location: France
No related grants have been discovered for Anthony Mémin.