Emmanuelle Sultan

IntroductionWhile crucial to ensuring the production of accurate and high-quality data—and to avoid erroneous conclusions—data quality control (QC) in environmental monitoring datasets is still poorly documented.MethodsWith a focus on annual inter-laboratory comparison (ILC) exercises performed in the context of the French coastal monitoring SOMLIT network, we share here a pragmatic approach to QC, which allows the calculation of systematic and random errors, measurement uncertainty, and individual performance. After an overview of the different QC actions applied to fulfill requirements for quality and competence, we report equipment, accommodation, design of the ILC exercises, and statistical methodology specially adapted to small environmental networks (<20 laboratories) and multivariate datasets. Finally, the expanded uncertainty of measurement for 20 environmental variables routinely measured by SOMLIT from discrete sampling—including Essential Ocean Variables—is provided.Re...

Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years (2010-2019) of data from 6 levels of meteorological instrumentation mounted on a 45-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface environment. Large seasonal differences are evident in the monthly mean temperature and wind data, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occu...

Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years (2010-2019) of data from 6 levels of meteorological instrumentation mounted on a 45-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface environment. Large seasonal differences are evident in the monthly mean temperature and wind data, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occu...

En vue de reactualiser nos connaissances de la circulation de grande echelle dans l'Ocean Indien sur, un modele inverse aux differences finies est applique aux donnees hydrologiques disponibles a l'heure actuelle. La vitesse geostrophique au niveau de reference est ajustee par des contraintes de conservation de flux de masse, de chaleur et de vorticite potentielle. Trois resultats majeurs ressortent de cette etude. 1) Les differents systemes de circulation de l'ocean Indien sud sont bien mis en evidence avec, pour chacun d'eux, un fort controle topographique lie a la complexite de la bathymetrie dans cette region. La nature barotrope du gyre de Weddell est prouvee avec une extension vers l'est limitee par la branche sud du Courant Circumpolaire Antarctique. 2) La circulation au fond au nord de 50°S suit les courants de bords ouest avec une tendance cyclonique. Au sud de 50°S, l'origine de l'eau de fond soit etre validee par des etudes complementaires. 3) La position de la cellule meridienne de circulation thermohaline est estimee entre 26°S et 32°S par 1400m de profondeur et elle est concentree a l'est du Seuil du Mozambique. Elle met en jeu 15 Sv (1Sv=10 millions m3/s) ce qui correspond a de tres fortes vitesses verticales. A 32°S, a l'est du Seuil du Mozambique, 15Sv sont vehicules par un important Sous-courant des Aiguilles. Le gain de chaleur vers le Sud a 32° est de 0. 33PW (1PW=10 [exposant 15] W). Le modele inverse aux differences finies est un outil robuste de synthese et d'analyse pour la circulation du fond au sud de 50°S et pour la zone tropicale. L'impact de l'intensite du Courant des Aiguilles sur l'intensite de la cellule meridienne de circulation pourrait etre quantifiee avec d'autres simulations.

ABSTRACT a b s t r a c t Studying the foraging strategies of top predators can provide information on both how animals interact with their environment and the distribution of their prey. We studied the winter foraging behaviour of Weddell seals in Adé lie Land, East Antarctica, and the influence of abiotic parameters (bathymetry, hydrology, sea ice, light intensity) on their foraging behaviour. A total of six seals were fitted with Conductivity Temperature Depth Satellite Relayed Data Loggers (CTD-SRDL) at Dumont D'Urville ($ 671S, 1401E) during the austral winters in 2007 and 2008. The tags transmitted positions and dive information over 169 731 day, providing a total of 20,400 dive profiles and 2350 CTD profiles. Significant environmental influences on seal diving behaviour and habitat use were detected. Seals dived deeper, longer and increased their foraging effort during the day than at night with intermediate values for twilight. During the winter season the maximum dive depth decreased in association with an increase in dive duration, but foraging effort was unchanged. Seals spent more time at the bottom of their dives in shallow waters associated with relatively smooth bathymetry and dominated by Antarctic Surface Water. Considering the whole winter, Weddell seals tended to favour enriched, warmer and less dense water masses following their seasonal appearance on the shelf (Antarctic Surface Water and Modified Circumpolar Deep Water). Our results are consistent with seals feeding primarily on Pleuragramma antarcticum during winter, tracking their vertical diel migrations and foraging in areas associated with bathymetric and hydrographic features likely to concentrate prey patches.

We report on the hydrographic observations collected on the Antarctic continental shelf between 138°E and 146°E as part of the CEAMARC and ALBION projects in December 2007–January 2008. A total of 140 quasi-synoptic CTD (Conductivity–Temperature–Depth) casts were analysed to map the spatial distribution of the summer hydrographic properties. Seven distinct hydrographic regimes were identified based on regional topographic features and

Historical hydrological data of the South Indian Ocean are combined with dynami- cal constraints in a finite difference inverse model. The gridded data set (1 degree in latitude, 2 degrees in longitude) results from an EOF decomposition on the vertical and an objective analysis on the horizontal. The wind used is both from the ERS1 and the ECMWF fields. To compute the geostrophic currents, the level of no motion is adjusted by the inverse model under three constraints : the mass conservation, the conservation of potential vorticity and the heat conservation. The meridional overturn- ing circulation is then estimated. It is to be located between 26rS and 32rS at 1400m. The meridional overturning circulation is concentrated east of the Mozambic Ridge. It amounts is compared with other estimations and corresponds to important upwellings. The impact of the intensity of the Aghulas Under Current on the meridional overturn- ing is discussed, as the consequence on the heat fluxes.

. Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years of data from 6 levels of meteorological instrumentation mounted on a 42-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface atmospheric environment (Genthon et al., 2021,a,b). Monthly temperature and wind data demonstrate the large seasonal differences in the near-surface boundary layer dynamics, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer leading to near-uniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual time scales. Analysis of observational uncertainty and comparison to reanalysis data from ERA-5 indicate that wind speed is particularly difficult to measure at this location. Data are distributed on PANGAEA data repository, see data availability section.

ABSTRACT a b s t r a c t Studying the foraging strategies of top predators can provide information on both how animals interact with their environment and the distribution of their prey. We studied the winter foraging behaviour of Weddell seals in Adé lie Land, East Antarctica, and the influence of abiotic parameters (bathymetry, hydrology, sea ice, light intensity) on their foraging behaviour. A total of six seals were fitted with Conductivity Temperature Depth Satellite Relayed Data Loggers (CTD-SRDL) at Dumont D'Urville ($ 671S, 1401E) during the austral winters in 2007 and 2008. The tags transmitted positions and dive information over 169 731 day, providing a total of 20,400 dive profiles and 2350 CTD profiles. Significant environmental influences on seal diving behaviour and habitat use were detected. Seals dived deeper, longer and increased their foraging effort during the day than at night with intermediate values for twilight. During the winter season the maximum dive depth decreased in association with an increase in dive duration, but foraging effort was unchanged. Seals spent more time at the bottom of their dives in shallow waters associated with relatively smooth bathymetry and dominated by Antarctic Surface Water. Considering the whole winter, Weddell seals tended to favour enriched, warmer and less dense water masses following their seasonal appearance on the shelf (Antarctic Surface Water and Modified Circumpolar Deep Water). Our results are consistent with seals feeding primarily on Pleuragramma antarcticum during winter, tracking their vertical diel migrations and foraging in areas associated with bathymetric and hydrographic features likely to concentrate prey patches.

ABSTRACT Summer repeated hydrographic surveys and four years of mooring observations are used to characterize for the first time the interannual variability of the bottom water in the Mertz Glacier Polynya (MGP) on the East Antarctic shelf (142°E – 146°E). Until 2010, large interannual variability was observed in the summer bottom salinity with year-to-year changes reaching 0.12 in Commonwealth Bay, the region with the highest sea ice production. The summer variability was shown to be linked to the efficiency of the convection during the preceding winter. The recent freshening of the bottom waters subsequent to the Mertz Glacier calving was well beyond the range of the pre-calving interannual variability. Within two years after the event, the bottom water of the shelf became too light to possibly contribute to renewal of the Antarctic Bottom Water. Rough estimates of the fresh water budget of the Adélie Depression indicate that the freshening necessary to compensate for net sea ice production in the MGP did not change drastically after the Mertz calving. The year-to-year salinity changes appeared to respond to the MGP activity. Yet, prior to the calving, the convective system in the polynya was also partly controlled by the late winter bottom salinity through a mechanism leading to a sequence of alternatively fresher and more saline bottom waters over the period 2007-2010. Exceptional events like the Mertz calving seem to be able to switch over the system into a less stratified state where convection responds more directly to changes in the surface forcing.

We report on the hydrographic observations collected on the Antarctic continental shelf between 138°E and 146°E as part of the CEAMARC and ALBION projects in December 2007–January 2008. A total of 140 quasi-synoptic CTD (Conductivity–Temperature–Depth) casts were analysed to map the spatial distribution of the summer hydrographic properties. Seven distinct hydrographic regimes were identified based on regional topographic features and

More than 10 years of surface sea level anomalies and geostrophic currents from TOPEX/Poséïdon and Jason altimetric data are used to describe the low frequency variability of the tropical Atlantic circulation through Empirical Orthogonal Function analysis. The seasonal variability clearly agrees with previous studies based on climatological data. It shows the tropical Atlantic response to seasonal fluctuations of the overlying wind system. More interesting is the capability, using altimetry, to reach for the first time on a basin scale the year-to-year variability from measurements. Abnormal events occur in 1996-1997 and in 2001 with different spatial scales regarding both large scale zonal distribution and regional variability located in the north-western basin. Analysis of overlying winds and fluxes together with in-situ measurements from Atlantic equatorial moorings confirm this long term variability. Attempt to link these events to climatic indexes (El Niño-Southern Oscillation,...