Multi-platform experiments, numerical simulations and data science techniques for generation of new altimetric products: focus on mesoscale and sub- mesoscale variability (MANATEE – OSTST proposal)

Trabajo presentado en la Ocean Surface Topography Science Team Meeting (OSTST), celebrada online del 19 al 23 de octubre de 2020

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Altimetry for the future: building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

What are the effects of environmental factors on Co speciation at magnetite surface?

International audienceMagnetite nanoparticles are abundant in the environment and are notably used for environmental applications due to their unique magnetic, adsorption and redox properties. The stoichiometry of magnetite (Fe(II)/Fe(III)) is dependent on environmental factors (pH, presence of organic ligands, redox conditions), which largely affects magnetite nanoparticles physico-chemical properties, such as redox reaction, but also adsorption of contaminants. However, the joint effects of environmental factors and magnetite stoichiometry on magnetite-metal cations interaction are elusive. This study focuses on Co as an important contaminant, and because Co-doped magnetite nanoparticles are of high interest for nanotechnology applications. Magnetite nanoparticles (~10nm) with different stoichiometries were synthesized by coprecipitation, and partially oxidized using H2O2 to obtain the desired stoichiometry. Batch studies were carried out with different [Co], using three different stoichiometries (0.1, 0.3 and 0.5), at different pH values, and in the presence or the absence of natural organic matter (OM) or atmospheric O2(g). Experimental and modeling results, and XAS and XMCD analysis revealed that interactions between Co and magnetite varied, with favored oligomer formation and surface precipitation at higher stoichiometries. It was also highlighted that the formation of different species of Co depended on environmental conditions with the adsorption of monomers favored at low pH and in the presence of organic matter, and the partial oxidation of Co(II) to Co(III) in aerobic conditions. These results will help to predict the behavior and fate of Co in the environment and to understand the impact of environmental factors for an appropriate use of magnetite nanoparticles for environmental applications, or to synthesize Co-modified magnetite nanoparticles using water as solvent for high technology applications

Investigation of magnetite-Co interactions by soft XAS and XMCD

International audienceMagnetite (Fe3O4) nanoparticles (MNs) are largely known as strong adsorbents for dissolved contaminants such as divalent transition metals (e.g. Co2+). Therefore, MNs play an important role on the behaviour and fate of trace contaminants, and are commonly used in wastewater treatment technologies, for instance. In addition, surface modification of MNs using Co2+ (either adsorbed ions or surface CoO(s) precipitates) affects MNs magnetic properties, which leads to a broad range of high technology applications. However, the mechanisms involved between magnetite and transition metals are still poorly understood in aqueous solution.Stoichiometric MNs (i.e. with Fe(II)/Fe(III) = 0.5) were synthesized by co-precipitation and adsorption studies were performed with different Co concentrations at pH = 8 and [NaCl] = 0.01 M. The Co adsorption isotherm was found non-linear over the 5 orders of magnitude in aqueous [Co] investigated. This could tentatively be modelled assuming the formation of (i) adsorbed or incorporated of Co2+ at loadings ([Co]s ≤ 1 Co/nm²), (ii) small Co polymers at intermediate loadings (1 ≤ [Co]s ≤ 10 Co/nm²) and (iii) precipitation of Co(OH)2(s) onto the magnetite surface for highest Co concentrations. Soft X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) at the Co and Fe L2,3 absorption edges confirmed the occurrence of three types of surface modification. From low to high surface loadings, these techniques revealed (i) the presence of Co2+ in octahedral coordination environment with a similar magnetic behavior to cobalt ferrite (CoFe2O4) or adsorbed Co2+ ions, (ii) a magnetically-silent Co2+ species and (iii) an antiferromagnetic Co(OH)2 phase, whose occurrence coincided with that of modelled species.This study provides a detailed understanding of the Co sorption and surface precipitation mechanisms onto magnetite, as well as the chemical and magnetic properties of these particles. These results might not only be used to better understand the effect of magnetite on the behaviour and fate of metal contaminants in the environment, but also to optimize the synthesis procedures of Co-modified MNs using water as solvent for high technology applications

Investigating SWOT capabilities to detect meso and submesoscale eddies in the western Mediterranean

International audienceThe primary oceanographic objective of the future Surface Water Ocean Topography (SWOT) altimetric satellite is to characterize the mesoscale and submesoscale ocean circulation. The aim of this study is to assess the capabilities of SWOT to resolve the meso and submesoscale in the western Mediterranean. With ROMS model data as inputs for the SWOT simulator, pseudo-SWOT data were generated. These data were compared with the original ROMS model data and ADT data from present day altimetric satellites to assess the temporal and spatial resolution of SWOT in the western Mediterranean. We then addressed the removal of the satellite's noise in the pseudo-SWOT data using a Laplacian diffusion. We investigated different parameters of the filter by looking at their impact on the spatial spectra and RMSEs calculated from the simulator outputs. To further assess the satellites capabilities, we derived absolute geostrophic velocities and relative vorticity. Our numerical experiments show that the noise patterns affect the spectral content of the pseudo-SWOT fields below 60 km. The Laplacian diffusion improves the recovery of the spectral signature of the altimetric field, especially down to 30 km. With the help of this filter, we manage to observe small scale oceanic features in pseudo-SWOT data, and in its derived variables

Investigation of magnetite-Co interactions by soft XAS and XMCD

International audienceMagnetite (Fe3O4) nanoparticles (MNs) are largely known as strong adsorbents for dissolved contaminants such as divalent transition metals (e.g. Co2+). Therefore, MNs play an important role on the behaviour and fate of trace contaminants, and are commonly used in wastewater treatment technologies, for instance. In addition, surface modification of MNs using Co2+ (either adsorbed ions or surface CoO(s) precipitates) affects MNs magnetic properties, which leads to a broad range of high technology applications. However, the mechanisms involved between magnetite and transition metals are still poorly understood in aqueous solution.Stoichiometric MNs (i.e. with Fe(II)/Fe(III) = 0.5) were synthesized by co-precipitation and adsorption studies were performed with different Co concentrations at pH = 8 and [NaCl] = 0.01 M. The Co adsorption isotherm was found non-linear over the 5 orders of magnitude in aqueous [Co] investigated. This could tentatively be modelled assuming the formation of (i) adsorbed or incorporated of Co2+ at loadings ([Co]s ≤ 1 Co/nm²), (ii) small Co polymers at intermediate loadings (1 ≤ [Co]s ≤ 10 Co/nm²) and (iii) precipitation of Co(OH)2(s) onto the magnetite surface for highest Co concentrations. Soft X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) at the Co and Fe L2,3 absorption edges confirmed the occurrence of three types of surface modification. From low to high surface loadings, these techniques revealed (i) the presence of Co2+ in octahedral coordination environment with a similar magnetic behavior to cobalt ferrite (CoFe2O4) or adsorbed Co2+ ions, (ii) a magnetically-silent Co2+ species and (iii) an antiferromagnetic Co(OH)2 phase, whose occurrence coincided with that of modelled species.This study provides a detailed understanding of the Co sorption and surface precipitation mechanisms onto magnetite, as well as the chemical and magnetic properties of these particles. These results might not only be used to better understand the effect of magnetite on the behaviour and fate of metal contaminants in the environment, but also to optimize the synthesis procedures of Co-modified MNs using water as solvent for high technology applications

Investigating SWOT capabilities to detect meso and submesoscale eddies in the western Mediterranean

International audienceThe primary oceanographic objective of the future Surface Water Ocean Topography (SWOT) altimetric satellite is to characterize the mesoscale and submesoscale ocean circulation. The aim of this study is to assess the capabilities of SWOT to resolve the meso and submesoscale in the western Mediterranean. With ROMS model data as inputs for the SWOT simulator, pseudo-SWOT data were generated. These data were compared with the original ROMS model data and ADT data from present day altimetric satellites to assess the temporal and spatial resolution of SWOT in the western Mediterranean. We then addressed the removal of the satellite's noise in the pseudo-SWOT data using a Laplacian diffusion. We investigated different parameters of the filter by looking at their impact on the spatial spectra and RMSEs calculated from the simulator outputs. To further assess the satellites capabilities, we derived absolute geostrophic velocities and relative vorticity. Our numerical experiments show that the noise patterns affect the spectral content of the pseudo-SWOT fields below 60 km. The Laplacian diffusion improves the recovery of the spectral signature of the altimetric field, especially down to 30 km. With the help of this filter, we manage to observe small scale oceanic features in pseudo-SWOT data, and in its derived variables

Étude des interactions magnétite-Co : des traces de Co dans l'environnement aux nanoparticules cœur-coquille Fe3O4@Co(OH)2 avec applications magnétiques

National audienceLes nanoparticules de magnétite (NM), Fe3O4, sont largement connues comme de puissants adsorbants pour les contaminants dissous tels que les métaux de transition divalents (par exemple Co2+). Les NM jouent donc un rôle important dans le comportement et le devenir des contaminants à l'état de traces et sont couramment utilisées pour la dépollution des eaux, par exemple. En outre, la modification de la surface des NM à l'aide de Co2+ affecte les propriétés magnétiques des NM, ce qui conduit à une large gamme d'applications de haute technologie. Cependant, les mécanismes impliqués entre la magnétite et les métaux de transition sont encore mal compris en solution aqueuse. Cette étude vise donc à mieux comprendre les mécanismes de sorption du Co et de précipitation en surface sur la magnétite, ainsi que les propriétés chimiques et magnétiques de ces nanoparticules. Pour ce faire, des NM stœchiométriques (ratio Fe(II)/Fe(III) = 0.5) ont été synthétisés par coprécipitation et des études d'adsorption ont été réalisées avec différentes concentrations de Co à pH = 8 et [NaCl] = 0,01 M. L'isotherme d'adsorption du Co s'est avéré non-linéaire sur les 5 ordres de grandeur de [Co] en solution aqueuse. Ceci a pu être modélisé en supposant la formation (i) de Co2+ adsorbé ou incorporé à de faibles charges ([Co]s ≤ 1 Co/nm²), (ii) de petits polymères de Co à des charges intermédiaires (1 ≤ [Co]s ≤ 10 Co/nm²) et (iii) la précipitation de Co(OH)2(s) sur la surface de la magnétite pour les concentrations de Co les plus élevées. La spectroscopie d'absorption des rayons X (XAS) et le dichroïsme circulaire magnétique des rayons X (XMCD) sur les bords d'absorption du Co et du Fe L2,3 ont confirmé l'existence de trois types de modification de la surface. Ces résultats pourraient être utilisés non seulement pour mieux comprendre l'effet de la magnétite sur le comportement et le devenir des contaminants métalliques dans l'environnement, mais aussi pour optimiser les procédures de synthèse des NMs modifiées par le Co en utilisant l'eau comme solvant pour des applications de haute technologie.

Étude des interactions magnétite-Co : des traces de Co dans l'environnement aux nanoparticules cœur-coquille Fe3O4@Co(OH)2 avec applications magnétiques

National audienceLes nanoparticules de magnétite (NM), Fe3O4, sont largement connues comme de puissants adsorbants pour les contaminants dissous tels que les métaux de transition divalents (par exemple Co2+). Les NM jouent donc un rôle important dans le comportement et le devenir des contaminants à l'état de traces et sont couramment utilisées pour la dépollution des eaux, par exemple. En outre, la modification de la surface des NM à l'aide de Co2+ affecte les propriétés magnétiques des NM, ce qui conduit à une large gamme d'applications de haute technologie. Cependant, les mécanismes impliqués entre la magnétite et les métaux de transition sont encore mal compris en solution aqueuse. Cette étude vise donc à mieux comprendre les mécanismes de sorption du Co et de précipitation en surface sur la magnétite, ainsi que les propriétés chimiques et magnétiques de ces nanoparticules. Pour ce faire, des NM stœchiométriques (ratio Fe(II)/Fe(III) = 0.5) ont été synthétisés par coprécipitation et des études d'adsorption ont été réalisées avec différentes concentrations de Co à pH = 8 et [NaCl] = 0,01 M. L'isotherme d'adsorption du Co s'est avéré non-linéaire sur les 5 ordres de grandeur de [Co] en solution aqueuse. Ceci a pu être modélisé en supposant la formation (i) de Co2+ adsorbé ou incorporé à de faibles charges ([Co]s ≤ 1 Co/nm²), (ii) de petits polymères de Co à des charges intermédiaires (1 ≤ [Co]s ≤ 10 Co/nm²) et (iii) la précipitation de Co(OH)2(s) sur la surface de la magnétite pour les concentrations de Co les plus élevées. La spectroscopie d'absorption des rayons X (XAS) et le dichroïsme circulaire magnétique des rayons X (XMCD) sur les bords d'absorption du Co et du Fe L2,3 ont confirmé l'existence de trois types de modification de la surface. Ces résultats pourraient être utilisés non seulement pour mieux comprendre l'effet de la magnétite sur le comportement et le devenir des contaminants métalliques dans l'environnement, mais aussi pour optimiser les procédures de synthèse des NMs modifiées par le Co en utilisant l'eau comme solvant pour des applications de haute technologie.