Éditeur(s) : HAL CCSD
Résumé : The heterogeneous nature and sometimes karstified carbonate environments has a direct impact on many environmental issues, such as coastal aquifers affected by saltwater intrusion. At the south of the island of Mallorca (Spain), the Llucmajor carbonate platform offers a privileged site for the study of such intrusions including the experimental site of Campos who meets the intrusion at shallow depth. The characterization of heterogeneous properties passes through a preliminary description of the properties of carbonate reservoirs, including those of the porosity. According to the wide range of sizes of heterogeneities from micrometer to hundreds of meters, the use of multiscale methods is required. This thesis focused on the determination of multiscale porosities from the microporosity to karstic porosity, and of relationships between observation scale changes of these properties. At the micron scale, high-resolution X-ray microtomography allows to extract the microporosity and the microporous network connectivity. At lower resolution (mm), X-ray tomography is also used to study the micro- and macro-porous network at the core scale which is already allocated to number of observations and measurements, including petrophysical. At the borehole scale, the wall images are used to identify the dissolved zones from centimeter macropores to plurimetric karstic cavities. At the larger scale, surface geophysics study the lateral extension of the karsts and heterogeneities. Finally, the porous structure of the studied site is integrated with its wide range of scales into the regional geology of the Llucmajor platform. Thus, the hydrogeophysical observatory set up on the site of Campos to monitor the spreading of salt water in the aquifer is integrated in its geological and petrophysical context, in order to refine the interpretation of its variations of salinity measurements during the time.
La nature hétérogène et parfois karstifiée des milieux carbonatés a un impact direct sur nombre de problématiques environnementales, comme celle des aquifères côtiers affectés par une intrusion d'eau salée. Au sud de l'ile de Majorque (Baléares, Espagne), la plate-forme carbonatée de Llucmajor offre un site privilégié pour l'étude de telles intrusions notamment avec le site expérimental de Campos, qui rencontre l'intrusion à faible profondeur. La caractérisation des propriétés hétérogènes du réservoir passe par une description préalable des propriétés des réservoirs carbonatés et notamment celle de la porosité. Au regard de la large gamme d'échelles d'hétérogénéités allant du micromètre à la centaine de mètre, l'utilisation de méthodes multi-échelles est nécessaire. Ce travail de thèse a porté sur la caractérisation multi-échelle de la porosité, allant de la microporosité à la porosité karstique, et l'établissement de relations entre les changements d'échelles d'observation de ces propriétés. A très petite échelle, la microtomographie haute-résolution à rayons X extrait à l'échelle du micron la microporosité et la connectivité des réseaux microporeux. A plus basse fréquence (celle du mm), la tomographie est également utilisée afin d'étudier le réseau micro- et macroporeux à l'échelle des carottes, à laquelle sont réalisées nombre d'observations et de mesures, notamment pétrophysiques. A l'échelle du puits, les images de paroi permettent d'identifier les zones de dissolution allant des macropores centimétriques aux cavités karstiques plurimétriques. A plus grande échelle, la géophysique de surface permet d'étudier l'extension latérale de ces karsts et hétérogénéités. Enfin, la structure poreuse du site étudié sur cette vaste gamme d'échelles est intégrée à la géologie régionale de la plate-forme de Llucmajor. Ainsi, l'observatoire installé sur le site pour surveiller la propagation de l'eau salée dans l'aquifère a pu être replacé dans son contexte géologique et pétrophysique, afin d'affiner l'interprétation de ses mesures de variations de salinité au cours du temps.
https://tel.archives-ouvertes.fr/tel-00633488

tel-00633488
https://tel.archives-ouvertes.fr/tel-00633488
https://tel.archives-ouvertes.fr/tel-00633488/document
https://tel.archives-ouvertes.fr/tel-00633488/file/TheseHebert.pdf

Résumé : Pratiquement inexistante il y a 20 ans, la pêche est devenue un secteur économique porteur d'emplois et créateur de valeur ajoutée, et constitue un enjeu de développement local non négligeable. Les activités de pêche se situent sur les localités suivantes : La Possession, Le Port, St Paul, St Gilles, Etang-Salé, St Leu, St Pierre, Terre-Sainte, Langevin, St Philippe, Ste Rose, St Benoît, Ste Marie, St Denis. La consommation : 18000 tonnes de produits de la mer consommées par an, représentant plus de 80 millions d'€ en valeur, soit une moyenne de 4.40 € / kg par produit, ce qui correspond à une entrée de gamme de congelés en Grandes et moyennes surfaces (GMS), 90% de la population réunionnaise consommatrice de poissons à hauteur de 19 kg/hab./an contre 25 Kg/hab./an en Métropole et 48 aux Antilles Françaises. Sur les 19 kg/hab./an de poissons consommés, seuls 750 grammes sont issus de la production de la pêche réunionnaise. [Extraits]

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/rapport-6491.pdf
http://archimer.ifremer.fr/doc/00000/6491/

Éditeur(s) : HAL CCSD Elsevier
Résumé : The current interpretation of the Messinian Salinity Crisis (MSC) involves the deposition of the so-called “peripheral or marginal” evaporites in onshore basins, as well as the erosion of the margins and the formation of thick evaporites in the deep parts of the basins. The present study focuses on intermediate depth basins, i.e. located between the onshore outcrops and the deep basins. Indeed, the Balearic Promontory shows small stepped basins filled with MSC deposits between its western extremity on the Alicante shelf and its eastern end around the Menorca block. New and already available seismic reflection profiles and onshore data allow us to investigate the nature and geometrical relationships of these deposits in the area between the islands of Ibiza and Mallorca.Our observations suggest the existence of three MSC-related units in this area. The lowermost transparent seismic unit can be interpreted as a 100 to 200-m-thick salt layer deposited in the deepest part of the Central Mallorca Depression. These evaporites pass laterally and upward into a thin-bedded seismic unit, which could be lithologically equivalent to the Upper Evaporites of the deep basins. All around the borders of the Central Mallorca Depression, this bedded seismic unit onlaps a Slope Unit which shows bedded to chaotic and rafted facies. The Messinian continental shelf is eroded and incised by a valley extending from the Palma onshore area to the Mallorca downslope domain.Our results suggest the presence offshore of at least two generations of diachronous MSC deposits. The observation of salt on a continental high and the widespread MSC deposits on the margins of the Central Mallorca Depression call into question the location of halite preferentially in the deep abyssal basins and the significance of the deep basin MSC units that onlap onto the Margin Erosional Surface (MES), as observed all around the passive margins of the Northwest-Mediterranean Basin. The dual terminology used for peripheral/deep MSC evaporites cannot be applied to any of the MSC units found in the study area.
ISSN: 0025-3227

hal-01115656
https://hal.archives-ouvertes.fr/hal-01115656
DOI : 10.1016/j.margeo.2014.10.001

Éditeur(s) : Ieee-inst Electrical Electronics Engineers Inc
Résumé : We validate Soil Moisture and Ocean Salinity (SMOS) sea surface salinity (SSS) retrieved during August 2010 from the European Space Agency SMOS processing. Biases appear close to land and ice and between ascending and descending orbits; they are linked to image reconstruction issues and instrument calibration and remain under study. We validate the SMOS SSS in conditions where these biases appear to be small. We compare SMOS and ARGO SSS over four regions far from land and ice using only ascending orbits. Four modelings of the impact of the wind on the sea surface emissivity have been tested. Results suggest that the L-band brightness temperature is not linearly related to the wind speed at high winds as expected in the presence of emissive foam, but that the foam effect is less than previously modeled. Given the large noise on individual SMOS measurements, a precision suitable for oceanographic studies can only be achieved after averaging SMOS SSS. Over selected regions and after mean bias removal, the precision on SSS retrieved from ascending orbits and averaged over 100 km $times$ 100 km and 10 days is between 0.3 and 0.5 pss far from land and sea ice borders. These results have been obtained with forward models not fitted to satellite L-band measurements, and image reconstruction and instrument calibration are expected to improve. Hence, we anticipate that deducing, from SMOS measurements, SSS maps at 200 km $times$ 200 km, 10 days resolution with an accuracy of 0.2 pss at a global scale is not out of reach.
Ieee Transactions On Geoscience And Remote Sensing (0196-2892) (Ieee-inst Electrical Electronics Engineers Inc), 2012-05 , Vol. 50 , N. 5 , P. 1662-1675

Droits : 2012 IEEE
http://archimer.ifremer.fr/doc/00074/18557/16108.pdf
DOI:10.1109/TGRS.2012.2184546
http://archimer.ifremer.fr/doc/00074/18557/

Éditeur(s) : IEEE
Résumé : Soil Moisture and Ocean Salinity, European Space Agency, is the first satellite mission addressing the challenge of measuring sea surface salinity from space. It uses an L-band microwave interferometric radiometer with aperture synthesis (MIRAS) that generates brightness temperature images, from which both geophysical variables are computed. The retrieval of salinity requires very demanding performances of the instrument in terms of calibration and stability. This paper highlights the importance of ocean salinity for the Earth's water cycle and climate; provides a detailed description of the MIRAS instrument, its principles of operation, calibration, and image-reconstruction techniques; and presents the algorithmic approach implemented for the retrieval of salinity from MIRAS observations, as well as the expected accuracy of the obtained results.
Proceedings of the IEEE (0018-9219) (IEEE), 2010-05 , Vol. 98 , N. 5 , P. 649-665

Droits : 2010 IEEE – All Rights Reserved
http://archimer.ifremer.fr/doc/00004/11482/8066.pdf
DOI:10.1109/JPROC.2009.2033096
http://archimer.ifremer.fr/doc/00004/11482/

Éditeur(s) : Gauthier-Villars
Résumé : Data collected in an area enclosing New Caledonia are analysed both for the open ocean (17 degrees S-27 degrees S, 169 degrees E-170 degrees E; 1972-1992) and for one point in its lagoon (1967-1993), in order to improve our knowledge of the regional environment, with emphasis on seasonal and interannual (i.e. ENSO) variability. Long-term means and seasonal changes in surface wind, sea-surface temperature and salinity, and 0-400 m temperature, salinity and zonal geostrophic current are first described to Set the context. Through comparisons with the Southern Oscillation Index (SOI), it is demonstrated that there are signals in these parameters that are connected with ENSO. During the warm phase of ENSO (SOI < 0, El Nino), we observed saltier-than-average anomalies in sea-surface salinity (similar to 0.2), 0-50 m cold temperature anomalies (similar to 0.5 degrees C) contrasting with the well-known warm eastern equatorial Pacific anomalies, together with westerly (similar to 10 m(2) s(-2)) and southerly (similar to 4 m(2) s-2) wind anomalies over a large part of the studied area. Conversely, anomalies of similar magnitude but of opposite sign were detected during the cold phase of ENSO (SOI > 0; La Nina). The mechanisms which connect these regional anomalies to ENSO evolution at low-latitudes are qualitatively discussed.
Oceanolica Acta (0399-1784) (Gauthier-Villars), 1997 , Vol. 20 , N. 3 , P. 481-491

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00093/20410/18077.pdf
http://archimer.ifremer.fr/doc/00093/20410/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Located on the margin of the west Alboran basin, the Gibraltar Arc (Betic-Rif mountain belt) displays post-Pliocene vertical movements evidenced by uplifted marine sedimentary basins and marine terraces. Quantification of vertical movements is an important clue to understand the origin of present-day relief generation in the Betic-Rif mountain chain together with the causes of the Messinian Salinity Crisis. In this paper, we present the results of a pluridisciplinary study combining an analysis of low temperature thermochronology and Pliocene basins evolution to constrain the exhumation history and surface uplift of internals units of the Rif belt (Northern Morocco). The mean (U-Th)/He apatite ages obtained from 11 samples are comprised between 14.1 and 17.8 Ma and display a wide dispersion, which could be explained by a great variability of apatite chemistries in the analyzed samples. No correlations between altitude and age have been found along altitudinal profile suggesting a rapid exhumation during this period. Thermal modeling using our (U-Th)/He apatite ages and geochronological data previously obtained in the same area (40Ar/39Ar and K/Ar data on biotite, zircon and apatite fission track) allow us to propose a cooling history. The rocks suffered a rapid cooling at 60-100 °C/Ma between 22.5 and 19 Ma, then cooled to temperatures around 40 °C between 19 and 18 Ma. They were re-heated at around 110 °C between 18 and 15 Ma then rapidly cooled and exhumed to reach the surface temperature at around 13 Ma. The re-heating could be related to a renewal in thrusting and burying of the inner zones. Between 15 and 13 Ma the cooling resumed at a rate of 50 °C/Ma indicating an exhumation rate of 0.8 mm/y considering an average 40 °C/km geothermal gradient. This exhumation may be linked to the extension in the Alboran Sea. Otherwise biostratigraphic and sedimentological analysis of Pliocene basins of the internal Rif provided informations on the more recent events and vertical movements. Pliocene deposits of the Rifian coast represent the passive infilling of palaeo-rias between 5.33 and 3.8 Ma. The whole coastal area was uplifted at slow average rates (0.01-0.03 mm/y) in relation with a northeastward tilting of 0.2-0.3° since the Lower-Pliocene. A late Pliocene to present extensional tectonics associated to uplift has been identified all along the coastal ranges of the Internal Zone of the Rif chain. This extension was coeval with the major late Pliocene to Pleistocene extensional episode of the Alboran Sea and appears to be still active nowadays. No significant late Messinian uplift was evidenced, thus calling into question the geodynamic models relating the closure of the marine gateways and the MSC to slab roll back.
ISSN: 0264-3707

hal-01053531
https://hal.archives-ouvertes.fr/hal-01053531
DOI : 10.1016/j.jog.2014.01.006

Éditeur(s) : HAL CCSD
Résumé : International audience
The Rif Chain (Northern Morocco) belongs, with the Betic Cordillera(Southern Spain), to the western termination of the Alpine belt. Deepestunits of the Rif Internal Zones (i.e. Lower Sebtides) outcrop in three areas, from North to South : Ceuta, Cabo Negro and Beni Bousera.The quick exhumation of these units during the Late Oligocene-EarlyMiocene is related with a crustal thinning and the Alboran Sea rifting.Despite Beni Bousera massif has been well investigated, no data areavailable in Ceuta and Cabo Negro areas. This study aims to constrainthe last steps of cooling and exhumation in the Lower Sebtides usingmedium- and low-temperature thermochronological data. Combinationof Ar-Ar on micas, fission tracks and (U-Th)/He on apatites (respectivelyAFT and AHe) from high-grade rocks allows understanding thermalhistory between 450-350°C and surface temperatures. These datasuggest a similar cooling evolution of the Ceuta and Cabo Negro units.Ages obtained with all these methods are comprised in the same interval,between 22 and 18 Ma. These data record an almost instantaneouscooling (between 50 and 200°C/Ma) associated to final exhumation afterthe Oligo-Miocene thermal event affecting these units at shallowdepths (10 km). Low-temperature data suggest that Ceuta and CaboNegro units cooled at surface temperatures before Beni Bousera ones.Since the end of Burdigalian, the Rif internal zones vertical movementsdid not exceed 1km, even during the Messinian Salinity. AFT and AHeages in the whole Sebtides are also slightly older than these obtainedin their Spanish equivalent (Alpujarrides). The Gibraltar arc is dividedinto several independent crustal blocks separated by major fault zonesperpendicular to the coast that could have induced independent verticalmovements during the entire Neogene
24 ème Réunion des sciences de la Terre 2014
Pau, France

insu-01080768
https://hal-insu.archives-ouvertes.fr/insu-01080768

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : The sea surface salinity (SSS) measured from space by the Soil Moisture and Ocean Salinity (SMOS) mission has recently been revisited by the European Space Agency first campaign reprocessing. We show that, with respect to the previous version, biases close to land and ice greatly decrease. The accuracy of SMOS SSS averaged over 10 days, 100 x 100 km(2) in the open ocean and estimated by comparison to ARGO (Array for Real-Time Geostrophic Oceanography) SSS is on the order of 0.3-0.4 in tropical and subtropical regions and 0.5 in a cold region. The averaged negative SSS bias (-0.1) observed in the tropical Pacific Ocean between 5 degrees N and 15 degrees N, relatively to other regions, is suppressed when SMOS observations concomitant with rain events, as detected from SSM/Is (Special Sensor Microwave Imager) rain rates, are removed from the SMOS-ARGO comparisons. The SMOS freshening is linearly correlated to SSM/Is rain rate with a slope estimated to -0.14 mm(-1) h, after correction for rain atmospheric contribution. This tendency is the signature of the temporal SSS variability between the time of SMOS and ARGO measurements linked to rain variability and of the vertical salinity stratification between the first centimeter of the sea surface layer sampled by SMOS and the 5 m depth sampled by ARGO. However, given that the whole set of collocations includes situations with ARGO measurements concomitant with rain events collocated with SMOS measurements under no rain, the mean -0.1 bias and the negative skewness of the statistical distribution of SMOS minus ARGO SSS difference are very likely the mean signature of the vertical salinity stratification. In the future, the analysis of ongoing in situ salinity measurements in the top 50 cm of the sea surface and of Aquarius satellite SSS are expected to provide complementary information about the sea surface salinity stratification.
Ocean Science (1812-0784) (Copernicus Gesellschaft Mbh), 2013 , Vol. 9 , N. 1 , P. 183-192

Droits : Author(s) 2013. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00139/25073/23161.pdf
DOI:10.5194/os-9-183-2013
http://archimer.ifremer.fr/doc/00139/25073/

Éditeur(s) : Gauthier-Villars
Résumé : The variability of ''yellow substance'' in waters of the Skagerrak and the Kattegat was studied during the international Skagex programme in 1990 and 1991. Data on attenuation of light and fluorescence of dissolved organic matter (DOM) in sea water were collected with a spectral transmissiometer and a submersible fluorometer within a depth range of 0-250 m at several stations. More than fifty-fold variations of fluorescence intensity over space and time were due to the combined action of different sources of DOM in the straits. The surface maximum of fluorescing DOM, related to river outflow, was spreading from Oslo fjord to the central Skagerrak in late spring. This maximum may be ecologically important because it diminishes shortwave PAR. In the autumn the brightest DOM fluorescence was found in the Kattegat and along the Norwegian coast in accordance with earlier studies. The local minima of DOM fluorescence are associated with the Jutland current. Both the instability of the current and a ten-fold difference in DOM content between deep layers of the Skagerrak and Kattegat resulted in strong synoptic variability of fluorescence in the transitional area between the straits. Seasonal and synoptic variabilities of ''yellow substance'' were minimal in the southern Kattegat. The vertical gradients of DOM fluorescence were mostly negative at the depth of the thermocline of the open Skagerrak in spring, reaching values of 40-50 % m-1. Fine structure and complex shape were inherent to fluorescence profiles from areas of intensive water mixing. DOM fluorescence closely covaried with attenuation of UV light: the correlation coefficient was + 0.9 for wavelength w <= 350 nm regardless of season. The inverse dependence between wavelength derivative and magnitude of UV attenuation in the straits did not change with season. DOM fluorescence and water salinity were negatively correlated at depths of 25-50 m but they varied independently in the upper 10 m. No significant correlation between fluorescence and nitrates has been found. Estimates of correlation with phosphates ranged from 0.7 to 0.8. In general, the changes of fluorescence were due to variations of DOM content in sea water but not to variability of DOM composition or state. The properties of DOM fluorescence in the Skagerrak-Kattegat area make it a useful natural tracer of water movements suitable for active remote sensing with airborne lidar.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1993 , Vol. 16 , N. 2 , P. 115-125

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00099/21041/18667.pdf
http://archimer.ifremer.fr/doc/00099/21041/

Éditeur(s) : Amer Geophysical Union
Résumé : Sea surface salinity (SSS) measured from space by the Soil Moisture and Ocean Salinity (SMOS) mission is validated in the subtropical North Atlantic Ocean. 39 transects of ships of opportunity equipped with thermosalinographs (TSG) crossed that region from 2010 to 2012, providing a large database of ground truth SSS. SMOS SSS is also compared to Aquarius SSS. Large seasonal biases remain in SMOS and Aquarius SSS. In order to look at the capability of satellite SSS to monitor spatial variability, especially at scales less than 300 km (not monitored with the Argo network), we first apply a monthly bias correction derived from satellite SSS and In Situ Analysis System (ISAS) SSS differences averaged over the studied region. Ship SSS averaged over 25 km is compared with satellite and ISAS SSS. Similar statistics are obtained for SMOS, Aquarius and ISAS products (root mean square error of about 0.15 and global correlation coefficient r of about 0.92). However, in the above statistics, SSS varies due to both large scale and mesoscale (here, for scales around 100 km) variability. In order to focus on mesoscale variability, we consider SSS anomalies with respect to a monthly climatology. SMOS SSS and Aquarius SSS anomalies are more significantly correlated (r > 0.5) to TSG SSS anomaly than ISAS. We show the effective gain of resolution and coverage provided by the satellite products over the interpolated in situ data. We also show the advantage of SMOS (r=0.57) over Aquarius (r=0.52) to reproduce SSS mesoscale features.
Journal Of Geophysical Research-oceans (0148-0027) (Amer Geophysical Union), 2014-12 , Vol. 119 , N. 12 , P. 8878-8896

Droits : 2014. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00210/32150/34082.pdf
DOI:10.1002/2013JC009610
http://archimer.ifremer.fr/doc/00210/32150/

Éditeur(s) : Elsevier
Résumé : A coupled three-dimensional physical-biogeochemical model was developed in order to simulate the ecological functioning of the Rio de la Plata estuary and plume. The biogeochemical model reproduces the nitrogen cycle between five compartments: dissolved inorganic nitrogen, phytoplankton, zooplankton, detritus and dissolved organic nitrogen. The coupling is tested in seasonal climatological configurations and for the particular year 1999. The circulation is forced with Parana and Uruguay rivers discharges, NCEP wind and tide. The biogeochemical model includes loads of inorganic and organic nitrogen from both rivers. The model reproduces the correct tidal amplitudes in the estuary, as well as the most outstanding features of the observed horizontal and vertical structures of the salinity plume. Simulated surface chlorophyll a concentrations exhibit maximum values all year long seaward of the turbidity front, between the 0.5 and 15 isohalines, in agreement with SeaWiFS images of the area. The model simulates well the low primary production in the light-limited highly turbid tidal river (20 gC/m(2)/yr), the high production area in the frontal zone where it can reach 500 gC/m(2)/yr, and the nutrient-limited production in the outer estuary and inner shelf (300 gC/m(2)/yr), with realistic values in each case. According to the 1999 model simulation, the tidal river is the location of organic nitrogen remineralization with a consequent increase of the inorganic pool. At the entrance of the frontal zone, inorganic nitrogen represents about 75% of the whole nitrogen pool, it is reduced to 50% at its sea end-member. The outer estuary has the same sink role for inorganic nitrogen, suggesting that organic nitrogen is the major form exported to the shelf.
Continental Shelf Research (0278-4343) (Elsevier), 2005-03 , Vol. 25 , N. 5-6 , P. 629-653

Droits : 2004 Elsevier Ltd.
http://archimer.ifremer.fr/doc/2005/publication-334.pdf
DOI:10.1016/j.csr.2004.10.003
http://archimer.ifremer.fr/doc/00000/334/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
New investigations in the Neogene Boudinar basin (Morocco) provide new information about the Messinian Salinity Crisis (MSC) and Zanclean reflooding in the southern part of the Alboran realm (westernmost Mediterranean). Based on a new field, sedimentological and palaeontological analyses, the age and the geometry of both the Messinian erosional surface (MES) and the overlying deposits have been determined. The MES is of late Messinian age and was emplaced in subaerial settings. In the Boudinar basin, a maximum of 200 m of Miocene sediments was eroded, including late Messinian gypsum blocks. The original geometry of the MES is preserved only when it is overlain by late Messinian continental deposits, conglomeratic alluvial fans or lacustrine marly sediments. These sediments are interpreted as indicators of the sea-level fall during the MSC. Elsewhere in the basin, the contact between late Messinian and early Pliocene deposits is a low-angle dipping, smooth surface that corresponds to the early Pliocene transgression surface that subsequently re-shaped the regressive MES. The early Pliocene deposits are characterized by: (i) their onlap onto either the basement of the Rif chain or the late Miocene deposits; (ii) lagoonal deposits at the base to offshore marls and sands at the top (earliest Pliocene; 5.33–5.04 Ma interval; foraminifer zone PL1); (iii) marine recovery occurring in the 5.32–5.26 Ma interval; and (iv) the change from lagoonal to offshore environments occurring within deposits tens of metres thick. This information indicates that at least the end of the reflooding period was progressive, not catastrophic as previously thought.
ISSN: 0037-0738

hal-01306672
https://hal.archives-ouvertes.fr/hal-01306672
DOI : 10.1016/j.sedgeo.2015.12.014

Éditeur(s) : Amer Geophysical Union
Résumé : Hydrographic (0-1000 dbar) and direct current measurements (0-600 dbar) along 165-degrees-E (20-degrees-S-10-degrees-N) between January 1984 and July 1991 are used to investigate the mean circulation and its relationships with the distributions of salinity and potential vorticity on isopycnal surfaces. Less well documented mean sections along 142-degrees-E and 137-degrees-E are used to complement the 165-degrees-E analysis. The Equatorial Undercurrent is centered on the equator at 165-degrees-E and on 0.5-degrees-N at 142-degrees-E. No variation in its transport (15.0 x 10(6) m3 s-1) is found between those longitudes. We find indication of the Equatorial Undercurrent at 137-degrees-E-0.75-degrees-N in the geostrophic field. The northern and southern Subsurface Countercurrents are clearly identified by extrema of eastward velocity at 165-degrees-E around 3-degrees-N and 3-degrees-S (250 dbar). No evidence of a southern Subsurface Countercurrent is found at 142-degrees-E. At 137-degrees-E the northern Subsurface Countercurrent is not characterized by a local extrema of eastward velocity: the North Equatorial Countercurrent seems to extend from the surface to 400 dbar with a southward shift of its core. Analysis of the seasonal variability at 165-degrees-E indicates that the Equatorial Undercurrent transport increases by a factor 2 between January (10.7 x 10(6) m3 s-1) and July (21.5 x 10(6) m3 s-1) and the Equatorial Intermediate Current transport is halved (6.3 x 10(6) m3 s-1 in January, 3.5 x 10(6) m3 s-1 in July). hi contrast, the transport of the Subsurface Countercurrents does not vary substantially between those two months. The meridional distributions of salinity and potential vorticity show that the axes of the main eastward currents are associated with strong meridional property gradients, not with property extrema. The eastward currents thus represent a barrier to the northward extension of the high salinity Tropical Water. Relatively weak meridional gradients of salinity and potential vorticity are observed in the westward directed South Equatorial Current and Equatorial Intermediate Current.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 1993-12 , Vol. 98 , N. C12 , P. 22495-22520

Droits : 1993 by the American Geophysical Union.
http://archimer.ifremer.fr/doc/00192/30346/29190.pdf
DOI:10.1029/93JC02513
http://archimer.ifremer.fr/doc/00192/30346/

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Quantitative analyses on calcareous nannofossil assemblages on high temporal resolution (600-800 years) have been carried out from Core KC01B in the Ionian Sea (Eastern Mediterranean) throughout Marine Isotope Stage (MIS) 13-9, between 500 and 300 ka. This is an interval of considerable climate changes, known as the Mid-Brunhes event, which includes MIS 11, considered as a possible analogue for future interglacial conditions. In the Mediterranean core, the interval is characterized by the dominance of Gephyrocapsa spp., as also known from ocean records. Calcareous nannofossil abundance fluctuations have been interpreted in terms of modification of sea surface primary productivity/water stratification and temperature. Specifically, the increase in abundance of Gephyrocapsa caribbeanica and small Gephyrocapsa coupled with decreases of Florisphaera profunda, Syracosphaera spp. and Rhabdosphaera spp. suggests enhanced primary productivity/mixed surface waters during interglacial stages and at the Terminations, which can be interpreted in terms of interaction between climate changes and mesoscale oceanographic circulation. On the other hand, distributions of Calciosolenia spp., Oolithotus spp. and Umbilicosphaera sibogae, which are in phase with delta O-18 curve showing higher abundances at the lighter values of the marine isotope record, are considered as warm-water indicators. Biotic proxies point to peculiar climate dynamics through the MIS 12-11 transition (i.e. Termination V). High productive, cool, low salinity and turbid surface waters characterize the early MIS 11(421-408 ka) and likely reflect enhanced continental humidity/monsoon activity over North Africa and increased runoff into the basin. A late surface water warming with respect to Termination V is established at about 403 ka, during a period of low insolation forcing, almost coeval with the deposition of sapropel S11. A climate optimum, lasting about 15 ky (403-389 ka), is then recorded during a period of low insolation forcing centred at 398 ka. The later part of MIS 11 is characterized by climate deterioration at about 389 ka. Comparison with results from subtropical to polar Atlantic records suggests a remarkable relation between Mediterranean and Atlantic climate regimes.
Quaternary International (1040-6182) (Pergamon-elsevier Science Ltd), 2013-03 , Vol. 288 , P. 97-111

Droits : 2011 Elsevier Ltd and INQUA. All rights reserved.
http://archimer.ifremer.fr/doc/00181/29194/27593.pdf
DOI:10.1016/j.quaint.2011.12.007
http://archimer.ifremer.fr/doc/00181/29194/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A shallow field experimental site for CO2 injection was established at Maguelone (Languedoc, France), in order to test in an integrated manner a suite of surface and downhole hydrogeophysical monitoring methods. The objective is to improve monitoring of gas transport in the shallow subsurface and to determine the sensitivity of CO2 monitoring systems for leakage detection. The site offers a natural laboratory to study the processes associated with CO2 injection in a clastic and clay-rich context saturated with saline fluids. Prior to CO2 injection, three nitrogen (N2) injections were undertaken in 2012 to measure the site response to neutral gas injection. In 2013, a volume of 111 m3 (mass of 220 kg) of CO2 was injected during 3.5 h at 15 m depth. During each experiment, the gas plumes were successfully detected from pressure monitoring, time-lapse induction logging and downhole resistivity monitoring with dipole–dipole array. Increases in resistivity are attributed to free gas propagation (either N2 or CO2) whereas decreases in resistivity correlate with CO2 dissolution in the pore fluid. Chemical analyses confirm this hypothesis with a decrease in pH and an increase in the concentration of dissolved species in the latter case.
ISSN: 1750-5836

hal-01355943
https://hal.archives-ouvertes.fr/hal-01355943
DOI : 10.1016/j.ijggc.2015.12.005

Éditeur(s) : American Geophysical Union
Résumé : The origins and fates of the Atlantic salinity maximum water (SMW), formed through excess evaporation in the tropics and subtropics of both hemispheres, are studied using monthly mean outputs of a numerical simulation of the world ocean climatological circulation. After defining formation domains from the surface salinity field and the vertical stratification, a Lagrangian technique is used to estimate the formation rates and main pathways in each hemisphere and the role of this water in the framework of the warm water return flow of the meridional overturning cell. Formation rates around 9 and 11 Sv are found in the Southern and Northern Hemispheres, respectively. While the export of the southern SMW from its formation area is realized by the western boundary currents, that of the northern SMW mainly results from interior subduction. Equatorward of the formation regions, a fraction of each SMW variety is entrained in the subtropical cells that connect the subtropics to the equatorial region. Poleward of them, both varieties are seen to feed the regions of subtropical mode water (STMW) formation around 35degrees of latitude in both hemispheres. The bulk of the transport associated with each variety eventually turns northward: This amounts to similar to6 Sv of southern SMW gathered in the North Brazil Undercurrent (NBUC), and similar to10 Sv of northern SMW found in the Gulf Stream at 35degreesN, of which 8 Sv have gone through the Caribbean Sea. Of the 13.4-Sv northward transport of the meridional overturning cell estimated by the model at 47degreesN, more than 50% (6.9 Sv) is found to have transited through at least one of the SMW regions. This gives an indication of the likely important role of SMW formation in the observed northward salinity increase of the upper Atlantic Ocean.
Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2002-09 , Vol. 107 , N. C10 , P. NIL_610-NIL_624

Droits : 2002 by the American Geophysical Union
http://archimer.ifremer.fr/doc/2002/publication-769.pdf
DOI:10.1029/2002JC001318
http://archimer.ifremer.fr/doc/00000/769/

Éditeur(s) : Amer Geophysical Union
Résumé : At its seasonal peak the Amazon/Orinoco plume covers a region of 10^6 km2 in the western tropical Atlantic with more than 1m of extra freshwater, creating a near-surface barrier layer (BL) that inhibits mixing and warms the sea surface temperature (SST) to >29oC. Here new sea surface salinity (SSS) observations from the Aquarius/SACD and SMOS satellites help elucidate the ocean response to hurricane Katia, which crossed the plume in early fall, 2011. Its passage left a 1.5psu high haline wake covering >10^5 km2 (in its impact on density, the equivalent of a 3.5oC cooling) due to mixing of the shallow BL. Destruction of this BL apparently decreased SST cooling in the plume, and thus preserved higher SST and evaporation than outside. Combined with SST, the new satellite SSS data provide a new and better tool to monitor the plume extent and quantify tropical cyclone upper ocean responses with important implications for forecasting.
Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2012-10 , Vol. 39 , N. L20603 , P. 1-8

Droits : 2012. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00094/20540/18943.pdf
DOI:10.1029/2012GL053335
http://archimer.ifremer.fr/doc/00094/20540/

Éditeur(s) : Gauthier-Villars
Résumé : Cyprideis torosa (Crustacea, Ostracoda), which is well known for its ability to live in a wide range of salinity and for the variability of its ornamentation, was sampled in the paralic environment. in the Camargue (France) and in the area of Santa-Pola (south-east Spain), in ambient waters whose salinity varies from 1 to 120 g/l. The collected valves. which are smooth, punctuated, reticulated or have nodes on their surface, were analyzed by means of spark-source mass spectrometry. We detected twenty-six chemical elements, and found a clear relationship between the chemical composition, the ornamentation of the valves and the environmental parameters. In the oligohaline environment, the carapaces are thick, reticulated or node-bearing ; they are enriched in Si, Al, Fe, Mn and Ba which are terrigenous elements introduced by fresh water. In an open hypersaline environment, the carapaces are reticulated or punctuated ; they are chemically characterized by P, Sr and Li, typical for concentrated seawater. Finally, in a closed hypersaline environment. the collected individuals are smooth, and their carapaces are very thin ; their content S is related to the abundant organic matter provided by the development of algal and cyanobacterial mats. Salinity and confinement, which are the main parameters characteristic of the studied ecosystems, are also the two factors that control the ornamentation of the valves. The chemical analysis and the field observations reveal that the granulometric characteristics of the microhabitats must be considered because they control the exchanges at the water-sediment interface. The anthropic influences on the chemical composition of the carapace must be emphasized: it is possible to detect industrial and domestic wastes. But the ornamentation of the carapace is not related to these pollutants - chiefly heavy metals (Pb, Ni Sn) - and depends mainly on the open or closed character of the ambient environment. The present method highlights, on the basis of the chemical composition, a relationship between ornamentation and environmental parameters. It is particularly efficient in the interpretation of the morphology of the valves in relation to the palaeoenvironment.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 5 , P. 505-514

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00103/21378/18978.pdf
http://archimer.ifremer.fr/doc/00103/21378/

Éditeur(s) : Oxford university press
Résumé : Fish-aggregating devices (FADs) are increasingly used worldwide to enhance tuna catches. Meanwhile, ecosystem-based management of this fishery is constrained by a paucity of information regarding the interaction of FAD-associated tuna aggregations with their local environment. This paper reports the results of a nine-month study around a FAD moored near Martinique Island, aimed at assessing the effects of the local environment on the variability of monthly estimates of proximate tuna biomass. Dual-frequency, active acoustics provided highresolution quantitative data on the pelagic community around the FAD, from fish to micronekton forage. Geostatistics were used to compute biomass estimates of the tuna aggregation comprising most of the FADassociated fish biomass, with a sampling error of 27%. Environmental variability was summarized by a small set of principal components (PCs) derived from profiles of temperature, salinity and dissolved oxygen vs. depth; and maps of chlorophyll a derived from remotely sensed, sea-surface colour. A generalized linear model was used to relate tuna biomass to environmental PCs and revealed a positive correlation between tuna abundance and: i) a micronekton layer sensed at 38 kHz and potentially consisting of preferred prey at about 180 m depth; and ii) low subsurface salinity (60–80 m). These favourable environmental conditions may be related to thepresence of North Brazilian Current eddies that migrating tuna follow when not temporally associated with the FADs.
ICES Journal of Marine Science (1054-3139) (Oxford university press), 2009-07 , Vol. 66 , N. 6 , P. 1410-1416

Droits : 2009 Oxford university press
http://archimer.ifremer.fr/doc/2008/publication-6162.pdf
DOI:10.1093/icesjms/fsp039
http://archimer.ifremer.fr/doc/00000/6162/