Manioc : Portail | resultats 61 - 80 pour la recherche: Gauthier-Villars

Western boundary currents and transports off french-guiana as inferred from pegasus observations
Auteur(s) : Colin, C Bourles, Bernard

Éditeur(s) : Gauthier-Villars
Résumé : Pegasus current measurements carried out along a section located off French Guiana are presented; the section was repeated five times from September 1989 to June 1991 during the NOE (region Nord-Ouest equatoriale)/STACS (Sub Tropical Atlantic Climate Studies) cruises on board the NOAA (National Oceanographic and Atmospheric Administration) research vessels. The data (vertical and horizontal distributions) show, as suggested by earliest observations, the presence of different currents. At the surface, and in winter, the North Brazil Current (NBC) flows northwestward (positive), is strong (120 cm/s), confined in the first 250 m, coastally trapped (within 250 km) and fed by offshore waters; in summer the NBC strengthens (the velocity increases to 150 cm/s), vertically extends (down to 800 m) and veers offshore; the mean NBC mass flux computed from all the sections available is 34 +/- 9 Sv with absolute maximum and minimum respectively in September 1989 (81 +/- 4 Sv) and February 1990 (13 +/- 1 Sv). Subsurface, a southeastward (negative) undercurrent (herein after named Western Boundary UnderCurrent) is present in winter-spring and located in the layer 250-800 m with similar velocities in February 1990 (- 33 cm/s) and June 1991 (- 29 cm/s) but with largest vertical and horizontal extensions in the latter case; in summer (September 1989 and September 1990) this undercurrent is absent; the mean mTBUC mass flux is - 9 +/- 3 Sv; the maximum is observed in June 1991 (- 19 +/- 2 Sv) and the minimum in February 1990 (- 3 +/- 0.4 Sv) and January 1991 (- 5 +/- I Sv). Deeper, the equatorward Deep Western Boundary Current is trapped against the continental shelf (within 100 km of the shelf break), extends downward from 1 200 to 3 000 m depth with the velocity core centred in the 1 700-2 000 m layer, is maximum (- 50 cm/s) in spring-summer and minimum (- 23 cm/s) in winter; the absolute velocity (- 92 cm/s) has been recorded at 2 000 m depth in September 1989 suggesting a strong variability at this level; the mean equatorward DWBC mass flux is - 30 +/- 14 Sv with absolute maximum and minimum respectively in September 1989 (- 59 +/- 6 Sv) and September 1990 (- 7 +/- 1 Sv). The Integrated Mass, Temperature and Salt Fluxes (IMF, ITF and ISF) with the cumulated errors, computed across the whole section and down to 3 000 m depth for the September 1990, January 1991 and June 1991 cruises, are all positive in September 1990 (respectively 1.9 +/- 19 Sv, 3.1 +/- 30.1 PW and 74 +/- 1 845 Tt/s) but all negative both in January 1991 (- 13.3 +/- 17.0 Sv, - 15.6 +/- 26.5 PW and - 478 +/- 1594 Tt/s) and June 1991 (- 3.8 +/- 10.1 Sv, - 4.0 +/- 16.3 PW, - 130 +/- 989 Tt/s) showing a strong variability between the summer and winter periods. The mean IMF, ITF and ISF values (respectively - 5.1 +/- 46.4 Sv, - 5.2 +/- 73 PW and - 178 +/- 4428 Tt/s) are high and negative, indicating the large influence of the DWBC and the associated North Atlantic Deep Water (upper part) off French Guiana at 5 degrees N.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1994 , Vol. 17 , N. 2 , P. 143-157

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00098/20881/18495.pdf
http://archimer.ifremer.fr/doc/00098/20881/

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Algal growth on two sections of a fringing coral reef subject to different levels of eutrophication in Reunion Island
Auteur(s) : Semple, S

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Environmental factors influencing asexual reproductive processes in echinoderms
Auteur(s) : Mladenov, Pv

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Activité tectonique, magmatique et hydrothermale autour des triples jonctions de16°50'S-173°30'E et de l6°30'S-l76°10E dans le bassin nord fidjien (SWPacifique): Campagne HYFIFLUX
Auteur(s) : Auzende, Jean-marie Halbach, P Allspach, A Becker, K Blum, N Bonnier, Olga Van Gerven, M Halbach, M

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Subduction and Tectonics. Discussion on the Results of the IPOD Program in Active Margins
Auteur(s) : Aubouin, J Blanchet, R

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Traceurs organiques dans les dépôts de la vasière Ouest-Gironde (Golfe de Gascogne)
Auteur(s) : Gadel, F Jouanneau, Jm Weber, O Serve, L Comellas, L

Éditeur(s) : Gauthier-Villars
Résumé : Mud fields located In the inner part of shelves in front of large estuaries are preferential environments for the investigation of the mechanisms and evolution in time of the supply of such sedimentary bodies. The study of different constituents of the particulate organic matter trapped in the sediments of the West Gironde mud patch contributes to the knowledge of the input origins. This study was carried out with different techniques, including pyrolysis-gas chromatography-mass spectrometry and high performance liquid chromatography, on samples from a core collected in the centre of the mud field. At the bottom of the core, the increase of sugars, amino-sugars and some aromatic hydrocarbons may indicate a more marine character of organic components. The same appears to be the case at the top of the core, where, despite a finer sedimentation, biochemical characteristics could show a more pronounced marine influence than in the middle part. In the middle part of the core, on the other hand, the increase in phenols could result from an increase in lignin-derived. terrestrial inputs. The increase in pyrolysis-derived cyclopentenone may indicate the same terrestrial influence, because this component has its origin in aliphatic polycarboxylic acids resulting from sail leaching. The continental character of the sedimentation is also reflected in the increase of the silt-clay fractions representative of suspended matter originating in the Gironde estuary, associated with a slight carbonate decrease. The taxonomic significance of some phenols is noteworthy: this is especially the case of the cinnamyls which, in the middle part of the core, emphasize the input of herbaceous debris and of the hydroxybenzyls which, at the bottom, provide evidence of the algal origin of part of the organic material. Thus, by means of pyrolysis results and HPLC phenol analysis, it is possible to establish the more or less continental signature of organic components trapped in the ''Ouest-Gironde'' mud patch. This study of organic matter, which confirms earlier sedimentological and micropaleontological data, constitutes a new approach, adapted to the identification of the origin of carbon sources.
Oceanolica Acta (0399-1784) (Gauthier-Villars), 1997 , Vol. 20 , N. 5 , P. 687-695

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00093/20426/18093.pdf
http://archimer.ifremer.fr/doc/00093/20426/

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Structure et organisation de l'étang de Thau d'après la faune benthique (macrofaune, méiofaune). Relations avec le confinement
Auteur(s) : Guelorget, O Perthuisot, Jp Lamy, N Lefebvre, A

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Répartition des Noelaerhabdaceae (nannofossiles calcaires) dans le Quaternaire moyen et supérieur des océans Atlantique et Pacifique
Auteur(s) : Pujos, A Giraudeau, J

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Nannoplankton and foraminifera biostratigraphy and microfacies of the Cretaceous to Cenozoic post-platform series (Mazagan Escarpment, Morocco)
Auteur(s) : Cepek, P Hagn, H

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Biomasse du mesozooplancton au large de la Guyane française
Auteur(s) : Razouls, C

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ENSO signals in the vicinity of New Caledonia, South Western Pacific
Auteur(s) : Delcroix, T Lenormand, O

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Recyclage des sels nutritifs par le macroplancton-micronecton dans le Pacifique tropical Sud-Ouest
Auteur(s) : Roger, C

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Le récif-barrière et le lagon du Grand Cul-de-Sac Marin (Guadeloupe, Antilles françaises). Géomorphologie et sédiments
Auteur(s) : Guilcher, A Marec, A

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Aspects of the steroid geochemistry of an interfacial sediment from the peruvian upwelling
Auteur(s) : Smith, Dj Eglinton, G Morris, Rj Poutanen, El

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Biogenic silica in the Bay of Bengal during the southwest monsoon
Auteur(s) : Gupta, Gvm Sarma, Vv

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On the variability of yellow substance in the skagerrak and the kattegat
Auteur(s) : Karabashev, Gs Khanaev, Sa Kuleshov, Af

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/

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Bioturbation récente au large de la Nouvelle-Calédonie. Premiers résultats de la campagne Biocal
Auteur(s) : Gaillard, C

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Microheterotrophic utilization of dissolved free amino-acids in depth profiles of southern-california borderland basin waters
Auteur(s) : Carlucci, Af Craven, Db Robertson, Kj Henrichs, Sm

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Western boundary current variability off french-guiana as observed from moored current measurements
Auteur(s) : Colin, C Bourles, B Chuchla, R Dangu, F

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Temporal changes of aeolian saharan input in the cape verde abyssal-plain since the last glacial period
Auteur(s) : Grousset, F Buatmenard, P Boust, D Tian, Rc Baudel, S Pujol, C Vergnaudgrazzini, C

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