Observatoire de la variabilité interannuelle à décennale en Atlantique Nord

41 páginas, 19 figuras.-- Pascale Lherminier ... et al.-- Merian Cruise N. 2, Leg. 1, Lisbon (Portugal) - Thorshavn (Faroes), May 21 to June 28, 2006Cruise MSM02/1 is the third occurrence of the Ovide hydrological section that was performed in 2002 and 2004, as part of the CLIVAR programme under the name of A25. The Ovide Principal Investigator is Herlé Mercier. A Greenland-Portugal section was previously performed in 1997 under the leadership of S. Bacon (NOCS), slightly south of the Ovide path. The Ovide route crosses Reykjanes Ridge 300 miles north of Charlie-Gibbs Fracture Zone and runs through the West European Basin without having to sample on top of the complex Mid-Atlantic Ridge. The objective of this repeated hydrological section is to monitor the variability of water mass properties and main current transports in the basin, complementing the international observation array relevant for climate studies. The western part of the Ovide section is redundant with AR7E (called also A1) which was done on the odd years and will allow a better analysis of the inter annual variability. The hydrological section includes a hundred surface-bottom stations from coast to coast, collecting profiles of temperature, salinity, oxygen and currents. From the 28 bottles closed at various depth at each stations, samples of sea water are used for salinity and oxygen calibration, and for measurements of biogeochemical components, including tracers, isotopes, nutrients and carbon. From the thermal wind equations, geostrophic transports are deduced from temperature and salinity. Then, direct current observations, preferentially those measured by the ship ADCP, are used to constrain the velocity at the chosen reference level. This is particularly important in the Irminger Sea, where bottom currents are very energetic. This way, the contribution in heat and fresh water of the major currents crossed (mostly perpendicularly) by the Ovide line can be estimated. From north to south, the major currents are the East Greenland/Irminger Current (about 20 Sv southward, 1 Sv = 106 m3s-1), the Deep Western Boundary Current (about 10 Sv southward), the Irminger Current (about 10 Sv northward), and the North Atlantic Current (about 20 Sv northward). Between 1997 and 2004, we already observed a significative variability of these transports (about 30%)The Meridional Overturning Circulation reflects the equilibrium between the warm and salty waters flowing poleward near surface and the cold and relatively fresh water flowing equatorward near the bottom. Measured across Ovide, it is mainly the balance between the North Atlantic Current and the Deep Western Boundary Current. The simple sketch is however complicated by the export into the Labrador Sea and around the Subpolar Gyre of part of the highly variable East Greenland Current. This is why an array of four currentmeter moorings and one ADCP lander was deployed on the East Greenland slope and shelf in 2004, for two year. While temperature and salinity are often the basic parameters to identify water masses, it is useful to use tracers like CFCs to determine when they were ventilated. Oxygen is also a good indicator near the sources, but not conservative. Combining oxygen with nutrients gives useful information on the biological activity and on the remineralization processes. CFCs and nutrients are analysed by the Roscoff team led by Pascal Morin (LCM). The measurements and analyses of pH, alkalinity and pCO2 are performed by a Fiz Perez and Aida Rios from Vigo (IIMV) at every Ovide cruise. In 2006, it was officially part of the CARBO-OCEAN international program, and the objective is to better quantify the role of the North Atlantic in the storage and transport of anthropogenic carbon accumulated in the atmosphere. In 2006, samples were taken to measure isotopes of oxygen (18) and carbon (13) after the cruise. Oxygen isotopes are very useful to determine the proportion of fresh water from different origin (rain/snow, runoff, sea ice).Peer reviewe

Decomposition de la matiere organique dans des eaux de mer cotieres : etude en laboratoire de la biodegradation d'effluents urbains

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Comportement des tensio-actifs anioniques (LAS) et non-ioniques (APE) dans les effluents urbains, les eaux douces et les eaux marines

This report presents the methods of determination, the levels of concentration in urban sewage and in aquatic environment (with special reference to marine environment), and the degradation pathways of linear alkylbenzenesulfonates (LAS) and alkylphenol ethoxylates (APE).Ce rapport présente les méthodes d'analyse, les niveaux de concentration dans les effluents urbains et dans le milieu aquatique (en particulier le milieu marin), ainsi que les voies de dégradation des alkylbenzènesulfonates linéaires (LAS) et des alkylphénols éthoxylés (APE)

Recueil des données OVIDE 2008. Traceurs géochimiques (Eléments nutritifs et fréons)

Le nord de l'Atlantique Nord est le lieu de formation de l'eau profonde Nord Atlantique, composante essentielle de la circulation thermohaline. Le travail faisant l'objet du présent contrat avait pour objet de réaliser des mesures de composants biogéochimiques des masses d'eau le long d'une radiale allant du Groenland au Portugal en 2008 (section OVIDE). Les différentes composantes constituant l'eau profonde Nord Atlantique ont été échantillonnées. Ces mesures complètent des observations déjà effectuées par la même équipe en 2002,2004 et 2006. La mise en perspective temporelle de l'ensemble de ces données donne des informations sur la variabilité des masses d'eau océanique et par extension de la circulation