ORCID Profile
0000-0002-3486-4793
Current Organisation
Magellium (France)
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Publisher: Research Square Platform LLC
Date: 06-07-2021
DOI: 10.21203/RS.3.RS-177716/V1
Abstract: This study analyzes the interannual variability of the water mass transport measured by satellite gravity missions in regard to eight major climate modes known to influence the Earth’s climate from regional to global scales. Using sparsity promoting techniques (i.e., LASSO), we automatically select the most relevant predictors of the climate variability among the eight candidates considered. The El Niño–Southern Oscillation, Southern Annular Mode and Arctic Oscillation are shown to account for a large part the interannual variability of the water mass transport observed in extratropical ocean basins (up to 40%) and shallow seas (up to 70%). A combination of three Pacific and one Atlantic modes is needed to account for most (up to 60%) of the interannual variability of the terrestrial water storage observed in the North Amazon, Parana and Zambezi basins. With our technique, the impact of climate modes on water mass changes can be tracked across distinct water reservoirs (oceans, continents and ice-covered regions) and we show that a combination of climate modes is necessary to explain at best the natural variability in water mass transport. The climate modes predictions based on LASSO inversions can be used to reduce the interannual variability in satellite gravity measurements and detect processes unrelated with the natural variability of climate but with similar spatio-temporal signatures. However, significant residuals in the satellite gravity measurements remain unexplained at interannual time scales and more complex models solving the water mass balance should be employed to better predict the variability of water mass distributions.
Publisher: Copernicus GmbH
Date: 08-03-2023
DOI: 10.5194/EGUSPHERE-2023-312
Abstract: Abstract. An oscillation of about 6 years has been reported in Earth’s fluid core motions, magnetic field, rotation, and crustal deformations. Recently, a 6-year cycle has also been detected in several climatic parameters (e.g., sea level, surface temperature, precipitation, land ice, land hydrology, and atmospheric angular momentum). Here we suggest that the 6-year oscillations detected in the Earth’s deep interior, mantle rotation, and atmosphere are linked together, and that the core processes previously proposed as drivers of the 6-year cycle in the Earth’s rotation, cause in addition the atmosphere to oscillate together with the mantle, inducing fluctuations in the climate system with similar periodicities.
Publisher: Copernicus GmbH
Date: 23-03-2023
Abstract: Abstract. We investigate the performances of Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite gravimetry missions in assessing the ocean mass budget at the global scale over 2005–2020. For that purpose, we focus on the last years of the record (2015–2020) when GRACE and GRACE Follow-On faced instrumental problems. We compare the global mean ocean mass estimates from GRACE and GRACE Follow-On to the sum of its contributions from Greenland, Antarctica, land glaciers, terrestrial water storage and atmospheric water content estimated with independent observations. Significant residuals are observed in the global mean ocean mass budget at interannual timescales. Our analyses suggest that the terrestrial water storage variations based on global hydrological models likely contribute in large part to the misclosure of the global mean ocean mass budget at interannual timescales. We also compare the GRACE-based global mean ocean mass with the altimetry-based global mean sea level corrected for the Argo-based thermosteric contribution (an equivalent of global mean ocean mass). After correcting for the wet troposphere drift of the radiometer on board the Jason-3 altimeter satellite, we find that mass budget misclosure is reduced but still significant. However, replacing the Argo-based thermosteric component by the Ocean Reanalysis System 5 (ORAS5) or from the Clouds and the Earth's Radiant Energy System (CERES) top of the atmosphere observations significantly reduces the residuals of the mass budget over the 2015–2020 time span. We conclude that the two most likely sources of error in the global mean ocean mass budget are the thermosteric component based on Argo and the terrestrial water storage contribution based on global hydrological models. The GRACE and GRACE Follow-On data are unlikely to be responsible on their own for the non-closure of the global mean ocean mass budget.
Publisher: American Meteorological Society
Date: 15-09-2020
Abstract: Because of increased emissions of greenhouse gases oceans are warming, causing sea level to rise as the density of seawater falls. Predicting the rates of steric expansion is challenging because of the natural variability of the ocean and because observations are insufficient to adequately cover the ocean basins. Here, we investigate the ability of one ocean reanalysis, two objective analyses, and one combination of satellite geodetic measurements to accommodate data gaps and to reconstruct typical patterns of the steric sea level variability at interannual and multidecadal time scales. Six climate indices are used to identify robust features of the internal variability, using a Least Absolute Shrinkage and Selection Operator (LASSO) regression to select significant predictors of the steric variability. Spatially consistent fingerprints are revealed for all climate indices in the ocean reanalysis dataset, allowing the recovery of most of the steric variability observed in the tropical and North Pacific, as well as large fractions of the Atlantic and Indian Ocean signals. Robust climate mode fingerprints are also identified with high spatial resolution but limited temporal coverage in the geodetic observations. The objective analyses fail to detect many of the patterns expected from climate modes, especially before the Argo era. Climate indices constitute valuable yet underexploited tools to assess the performance of different techniques to reconstruct steric sea levels at interannual and multidecadal scales. Such progress will increase confidence in the historical reconstructions of steric sea levels, which is necessary to improve the closure of regional and global sea level budgets and to validate the predictions of climate models.
Publisher: Elsevier BV
Date: 02-2019
Publisher: Copernicus GmbH
Date: 08-08-2022
Publisher: Springer Science and Business Media LLC
Date: 14-09-2021
DOI: 10.1007/S00382-021-05953-Z
Abstract: This study analyzes the interannual variability of the water mass transport measured by satellite gravity missions in regard to eight major climate modes known to influence the Earth’s climate from regional to global scales. Using sparsity promoting techniques (i.e., LASSO), we automatically select the most relevant predictors of the climate variability among the eight candidates considered. The El Niño–Southern Oscillation, Southern Annular Mode and Arctic Oscillation are shown to account for a large part the interannual variability of the water mass transport observed in extratropical ocean basins (up to 40%) and shallow seas (up to 70%). A combination of three Pacific and one Atlantic modes is needed to account for most (up to 60%) of the interannual variability of the terrestrial water storage observed in the North Amazon, Parana and Zambezi basins. With our technique, the impact of climate modes on water mass changes can be tracked across distinct water reservoirs (oceans, continents and ice-covered regions) and we show that a combination of climate modes is necessary to explain at best the natural variability in water mass transport. The climate modes predictions based on LASSO inversions can be used to reduce the inter-annual variability in satellite gravity measurements and detect processes unrelated with the natural variability of climate but with similar spatio-temporal signatures. However, significant residuals in the satellite gravity measurements remain unexplained at inter-annual time scales and more complex models solving the water mass balance should be employed to better predict the variability of water mass distributions.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-8001
Abstract: We investigate the performances of GRACE and GRACE Follow-On satellite gravimetry missions in assessing the ocean mass budget at global scale over 2005-2020. For that purpose, we focus on the last years of the record (2015-2020) when GRACE and GRACE Follow-On faced instrumental problems. We compare the global mean ocean mass estimates from GRACE and GRACE Follow-On to the sum of its contributions from Greenland, Antarctica, land glaciers, terrestrial water storage and atmospheric water content estimated with independent observations. Significant residuals are observed in the global mean ocean mass budget at interannual time scales. Our analyses suggest that the terrestrial water storage variations based on global hydrological model likely contributes to a large part to the misclosure of the global mean ocean mass budget at interannual time scales. We also compare the GRACE-based global mean ocean mass with the altimetry-based global mean sea level corrected for the Argo-based thermosteric contribution (an equivalent of global mean ocean mass). After correcting for the wet troposphere drift of the radiometer on-board the Jason-3 altimeter satellite, we find that mass budget misclosure is reduced but still significant. However, replacing the Argo-based thermosteric component by the ORAS5 ocean reanlaysis or from CERES top of the atmosphere observations leads to closure of the mass budget over the 2015-2020 time span. We conclude that the two most likely sources of error in the global mean ocean mass budget are the thermosteric component based on Argo and the terrestrial water storage contribution based on global hydrological models. The GRACE and GRACE Follow-On data are unlikely to be responsible on their own for the non-closure of the global mean ocean mass budget.
Publisher: Elsevier BV
Date: 04-2016
Publisher: Wiley
Date: 24-08-2022
Publisher: Oxford University Press (OUP)
Date: 10-01-2011
Publisher: Oxford University Press (OUP)
Date: 19-05-2017
DOI: 10.1093/GJI/GGX142
Publisher: American Geophysical Union (AGU)
Date: 24-03-2014
DOI: 10.1002/2013GL059134
Publisher: American Geophysical Union (AGU)
Date: 06-2013
DOI: 10.1002/WRCR.20235
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-7746
Abstract: A cycle of about 6 years has long been observed in the Earth& #8217 s magnetic field, length of day, dynamic oblateness, polar motions and surface displacements and attributed to dynamical processes occurring in the core and at the core mantle boundary. Recently, a 6-year cycle has also been detected in the rate of change of the global mean sea level and the ice-mass contributions from Greenland and continental glaciers. In this study, we report new observations of a 6-year cycle in the terrestrial water storage estimates based on the satellite gravity missions GRACE and GRACE-FO, consistent with precipitation and global hydrological models. The causes for such oscillations in the climate system are still unexplained, but raise the question of the respective contributions of the Earth& #8217 s deep interior and external surface fluid envelopes to the 6-year cycles reported in many geodetic variables. Indeed, while some of these 6-year fluctuations are convincingly attributed to Earth& #8217 s deep interior processes, for some other variables, climate-related processes occurring in the surface fluid envelopes or at the Earth& #8217 s surface may be more likely. This issue is exacerbated by an opposition of phase discovered between the angular momentum of the atmosphere and the length of day at around 6 years, suggesting that dynamical processes occurring in the Earth& #8217 s core induce a rotation of the solid Earth and the atmosphere as a single system. An overview of the 6-yr cycle observed in different variables of the Earth System may therefore help to better understand potential links between the solid Earth and climate.
Publisher: Copernicus GmbH
Date: 08-08-2022
DOI: 10.5194/EGUSPHERE-2022-716
Abstract: Abstract. We investigate the continuity and stability of GRACE and GRACE Follow-On satellite gravimetric missions by assessing the ocean mass budget at global scale over 2005–2020, focusing on the last years of the record (2015–2020) when GRACE and GRACE Follow-On faced instrumental problems. For that purpose, we compare the global mean ocean mass estimates from GRACE and GRACE Follow-On to the sum of its contributions from Greenland, Antarctica, land glaciers and terrestrial water storage estimated with independent observations. A significant residual trend of -1.60 ± 0.36 mm/yr over 2015–2018 is observed. We also compare the gravimetry-based global mean ocean mass with the altimetry-based global mean sea level corrected for the thermosteric contribution. We estimate and correct for the drift of the wet tropospheric correction of the Jason-3 altimetry mission computed from the on-board radiometer. It accounts for about 40 % of the budget residual trend beyond 2015. After correction, the remaining residual trend amounts to -0.90 ± 0.78 mm/yr over 2015–2018 and -0.96 ± 0.48 mm/yr over 2015–2020. GRACE and GRACE Follow-On data might be responsible for part of the observed non-closure of the ocean mass budgets since 2015. However, we show that significant interannual variability is not well accounted for by the data used for the other components of the budget, including the thermosteric sea level and the terrestrial water storage. Besides, missing contributions from the evolution of the deep ocean or the atmospheric water vapour may also contribute.
Publisher: Copernicus GmbH
Date: 04-08-2023
Abstract: Abstract. An oscillation of about 6 years has been reported in Earth's fluid core motions, magnetic field, rotation, and crustal deformations. Recently, a 6-year cycle has also been detected in several climatic parameters (e.g., sea level, surface temperature, precipitation, land hydrology, land ice, and atmospheric angular momentum). Here, we suggest that the 6-year oscillations detected in the Earth's deep interior, rotation, and climate are linked together and that the core processes previously proposed as drivers of the 6-year cycle in the Earth's rotation additionally cause the atmosphere to oscillate together with the mantle, inducing fluctuations in the climate system with similar periodicities.
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-50
Abstract: & & & We investigate the continuity and stability of GRACE and GRACE Follow-On satellite gravimetric missions by assessing the ocean mass budget at global scale over 2005& #8211 , focusing on the last years of the record (2015& #8211 ) when GRACE and GRACE Follow-On faced instrumental problems. For that purpose, we compare the global mean ocean mass estimates from GRACE and GRACE Follow-On to the sum of its contributions from Greenland, Antarctica, land glaciers and terrestrial water storage estimated with independent observations. A significant residual trend of -1.60 & #177 0.36 mm/yr over 2015& #8211 is observed. We also compare the gravimetry-based global mean ocean mass with the altimetry-based global mean sea level corrected for the thermosteric contribution. We estimate and correct for the drift of the wet tropospheric correction of the Jason-3 altimetry mission computed from the on-board radiometer. It accounts for about 40 % of the budget residual trend beyond 2015. After correction, the remaining residual trend amounts to -0.90 & #177 0.78 mm/yr over 2015& #8211 and -0.96 & #177 0.48 mm/yr over 2015& #8211 . GRACE and GRACE Follow-On data might be responsible for part of the observed non-closure of the ocean mass budgets since 2015. However, we show that significant interannual variability is not well accounted for by the data used for the other components of the budget, including the thermosteric sea level and the terrestrial water storage. Besides, missing contributions from the evolution of the deep ocean or the atmospheric water vapour may also contribute.& & &
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-25
Abstract: & & The GRACE (Gravity Recovery And Climate Experiment) and GRACE Follow-On (FO) satellite gravity missions enable global monitoring of the mass transport within the Earth& #8217 s system, leading to unprecedented advances in our understanding of the global water cycle in a changing climate. This study focuses on the quantification of changes in terrestrial water storage based on an ensemble of GRACE and GRACE-FO solutions and two global hydrological models. Significant changes in terrestrial water storage are detected at pluriannual and decadal time-scales in GRACE and GRACE-FO satellite gravity data, that are considerably underestimated by global hydrological models. The largest differences (more than 20 cm in equivalent water height) are observed in South America (Amazon, Sao Francisco and Parana river basins) and tropical Africa (Congo, Zambezi and Okavango river basins). Significant differences (a few cm) are observed worldwide at similar time-scales, and are generally well correlated with precipitation. While the origin of such differences is unknown, part of it is likely to be climate-related and at least partially due to inaccurate predictions of hydrological models. Slow changes in the terrestrial water cycle may indeed be overlooked in global hydrological models due to inaccurate meteorological forcing (e.g., precipitation), unresolved groundwater processes, anthropogenic influences, changing vegetation cover and limited calibration/validation datasets. Significant differences between GRACE satellite measurements and hydrological model predictions have been identified, quantified and characterised in the present study. Efforts must be made to better understand the gap between both methods at pluriannual and decadal time-scales, which challenges the use of global hydrological models for the prediction of the evolution of water resources in changing climate conditions.& &
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-26
Abstract: & & The natural climate variability is responsible for large fluctuations in the climate system over a broad range of time and space scales. The characterization of such oscillations (accelerations, trends, seasonal signals) is critical to understand the causes of change in the climate system and improve future climate scenarios. In this study, we report an oscillation with a pseudo-periodicity around 6 years in many climate variables, including the surface mass anomalies retrieved from GRACE and GRACE Follow-On missions. Changes in terrestrial water storage are shown to exhibit a 6-year oscillation at tropical latitudes in the Southern hemisphere (North of South America, tropical Africa, North of Australia). Similar oscillations have been detected in the precipitation, but were found to be underestimated by global hydrological models such as ISBA-CTRIP or WGHM. These discoveries echo the recent detection of a 6-year cycle in the global mean sea level and the ice mass balance of the Greenland ice-sheet and continental glaciers, as well as in regional climate indices (Atlantic Multidecennal Oscillation, North Atlantic Oscillation, Pacific Decadal Oscillations) by Moreira et al., (2021). The causes for such short-term oscillations in the climate system are still unexplained but we note that a 6-year cycle has also been reported in the length of day (LOD) & span lang=& quot en-US& quot & and robustly attributed to liquid core dynamics. While the 6-year cycle in LOD, geomagnetic field and core dynamics may be unrelated to the 6-year oscillation detected in several climate parameters, we briefly discuss potential mechanisms that could link deep Earth and surface processes.& /span& & / & & & & & / & & & & span lang=& quot en-US& quot & Moreira, L., Cazenave, A., & Palanisamy, H. (2021). Influence of interannual variability in estimating the rate and acceleration of present-day global mean sea level. & /span& & span lang=& quot en-US& quot & & em& Global and Planetary Change& /em& & /span& & span lang=& quot en-US& quot & , & /span& & span lang=& quot en-US& quot & & em& & /em& & /span& & span lang=& quot en-US& quot & , 103450.& /span& & / &
Publisher: Copernicus GmbH
Date: 29-08-2023
DOI: 10.5194/SP-2023-28
Publisher: Copernicus GmbH
Date: 25-10-2023
Publisher: American Geophysical Union (AGU)
Date: 02-2022
DOI: 10.1029/2021JB022489
Abstract: Several different basis functions have been used to represent the Earth's gravity field in order to generate estimates of mass variations on Earth from the analysis of data of the Gravity Recovery and Climate Experiment ( grace ) and its successor grace Follow‐On missions, including spherical harmonics, mass concentration elements (mascons) and slepian functions. Each approach depends inherently upon accurate modeling of the orbits of the pair of satellites as they revolve around the Earth, so that the observations of inter‐satellite changes in range (or, more specifically, range rate) can be exploited to identify mass variations. We have developed software using a classical orbit modeling approach, mascons and 24‐hr orbit integration, to estimate simultaneously corrections to orbital parameters and the temporal gravity field from grace data. Rather than using the range rate, we use the range acceleration as the inter‐satellite observable as it aids in localizing the mass variations. Level‐1 B range acceleration observations contain high levels of high‐frequency noise that inhibits their usefulness for this purpose. Instead, we generate range acceleration observations by numerical differentiation of the Level‐1B range rate prefit residuals. Simulations show that the gravity signal is not attenuated in this process. Our monthly estimates of mass anomalies from grace data (2003–2016) agree well with previous studies, both spatially and temporally. When converted to spherical harmonics our time series of C 2,0 , derived from grace data alone, are close to the independent estimates from satellite laser ranging, but the overall solution is improved by substituting the SLR C 2,0 .
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-14931
Abstract: The Earth energy imbalance (EEI) at the top of the atmosphere is responsible for the accumulation of energy in the climate system. While necessary to better understand the Earth& #8217 s warming climate, measuring the EEI is challenging as it is a globally integrated variable whose variations are small (0.5-1 W.m& #8722 ) compared to the amount of energy entering and leaving the climate system (~ 340 W.m-2). Accuracies better than 0.1 W.m& #8722 are needed to evaluate the temporal variations of the EEI at decadal and longer time-scales. The CERES experiment provides EEI time variations with a typical uncertainty of & #177 0.1 W.m& #8722 and shows a trend in EEI of 0.50 +/- 0.47 W.m& #8722 per decade over the period 2005-2019. The combination of space altimetry and space gravimetry measurements provides an estimate of the ocean heat content (OHC) change which is an accurate proxy of EEI (because % of the excess of energy stored by the planet in response to the EEI is accumulated in the ocean in the form of heat).& In Marti et al. (2021), the global OHC was estimated at global scales based on the combination of space altimetry and space gravimetry measurements over 2002-2016. Changes in the EEI were then derived with realistic estimates of its uncertainty. Here we present the improvements brought to the global OGC and EEI over an extended period (2002-2021), such as the calculation of the expansion efficiency of heat over the total water column, the improvement of ocean mass solution, the empirical correction of the wet tropospheric correction of Jason-3 altimeter measurements (Barnoud et al., 2022). The space geodetic GOHC-EEI product based on space altimetry and space gravimetry is available on the AVSIO website at 0.24400/527896/a01-2020.003. & References: Barnoud A., Picard B., Meyssignac B., Marti F., Ablain M., Roca R. Reducing the uncertainty in the satellite altimetry estimates of global mean sea level trends using highly stable water vapour climate data records. Submitted to JGR: Oceans. Marti, F., Blazquez, A., Meyssignac, B., Ablain, M., Barnoud, A., Fraudeau, R., Jugier, R., Chenal, J., Larnicol, G., Pfeffer, J., Restano, M., and Benveniste, J.: Monitoring the ocean heat content change and the Earth energy imbalance from space altimetry and space gravimetry, Earth Syst. Sci. Data, 14, 229& #8211 , 0.5194/essd-14-229-2022, 2022.
Publisher: Copernicus GmbH
Date: 16-12-2022
DOI: 10.5194/EGUSPHERE-2022-1032
Abstract: Abstract. The GRACE (Gravity Recovery And Climate Experiment) and GRACE Follow-On (FO) satellite gravity missions enable global monitoring of the mass transport within the Earth’s system, leading to unprecedented advances in our understanding of the global water cycle in a changing climate. This study focuses on the quantification of changes in terrestrial water storage based on an ensemble of GRACE and GRACE-FO solutions and two global hydrological models. Significant changes in terrestrial water storage are detected at pluriannual and decadal time -scales in GRACE and GRACE-FO satellite gravity data, that are generally underestimated by global hydrological models. The largest differences (more than 20 cm in equivalent water height) are observed in South America (Amazon, Sao Francisco and Parana river basins) and tropical Africa (Congo, Zambezi and Okavango river basins). Significant differences (a few cm) are observed worldwide at similar timescales, and are generally well correlated with precipitation. While the origin of such differences is unknown, pa rt of it is likely to be climate-related and at least partially due to inaccurate predictions of hydrological models. Slow changes in the terrestrial water cycle may indeed be overlooked in global hydrological models due to inaccurate meteorological forcin g (e.g., precipitation), unresolved groundwater processes, anthropogenic influences, changing vegetation cover and limited calibration/validation datasets. Significant differences between GRACE satellite measurements and hydrological model predictions have been identified, quantified and characterised in the present study. Efforts must be made to better understand the gap between both methods at pluriannual and decadal time-scales, which challenges the use of global hydrological models for the prediction of the evolution of water resources in changing climate conditions.
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.
Location: France
No related grants have been discovered for Julia Pfeffer.