Node and junction box services and interfaces for a local sea bottom observatory

Peer Reviewe

Multidisciplinary investigation on cold seeps with vigorous gas emissions in the Sea of Marmara (MarsiteCruise): Strategy for site detection and sampling and first scientific outcome

MarsiteCruise was undertaken in October/November 2014 in the Sea of Marmara to gain detailed insight into the fate of fluids migrating within the sedimentary column and partially released into the water column. The overall objective of the project was to achieve a more global understanding of cold-seep dynamics in the context of a major active strike-slip fault. Five remotely operated vehicle (ROV) dives were performed at selected areas along the North Anatolian Fault and inherited faults. To efficiently detect, select and sample the gas seeps, we applied an original procedure. It combines sequentially (1) the acquisition of ship-borne multibeam acoustic data from the water column prior to each dive to detect gas emission sites and to design the tracks of the ROV dives, (2) in situ and real-time Raman spectroscopy analysis of the gas stream, and (3) onboard determination of molecular and isotopic compositions of the collected gas bubbles. The in situ Raman spectroscopy was used as a decision-making tool to evaluate the need for continuing with the sampling of gases from the discovered seep, or to move to another one. Push cores were gathered to study buried carbonates and pore waters at the surficial sediment, while CTD-Rosette allowed collecting samples to measure dissolved-methane concentration within the water column followed by a comparison with measurements from samples collected with the submersible Nautile during the Marnaut cruise in 2007. Overall, the visited sites were characterized by a wide diversity of seeps. CO2- and oil-rich seeps were found at the westernmost part of the sea in the Tekirdag Basin, while amphipods, anemones and coral populated the sites visited at the easternmost part in the Cinarcik Basin. Methane-derived authigenic carbonates and bacterial mats were widespread on the seafloor at all sites with variable size and distributions. The measured methane concentrations in the water column were up to 377 μmol, and the dissolved pore-water profiles indicated the occurrence of sulfate depleting processes accompanied with carbonate precipitation. The pore-water profiles display evidence of biogeochemical transformations leading to the fast depletion of seawater sulfate within the first 25-cm depth of the sediment. These results show that the North Anatolian Fault and inherited faults are important migration paths for fluids for which a significant part is discharged into the water column, contributing to the increase of methane concentration at the bottom seawater and favoring the development of specific ecosystems

Maneuvering modelling of ship towed by kite in a seaway

International audienc

Outil d'évaluation d'économies de carburant pour la propulsion par cerf-volant des navires marchands

International audienceA tool dedicated to assess fuel economy induced by kite propulsion has been developed. To produce reliable results, computations must be performed on a period over several years, for several routes and for several ships. In order to accurately represent the impact of meteorological trends variations on the exploitability of the kite towing concept, a time domain approach of the problem has been used. This tool is based on the weather database provided by the ECMWF. Two sailing strategies can be selected for assessing the performance of the kite system. For a given kite area, the simulation can be run either at constant speed or at constant engine power. A validation has been made, showing that predicted consumption is close from in-situ measurement. It shows an underestimation of 11.9% of the mean fuel consumption mainly due to auxiliary consumption and added resistance in waves that were not taken into account. To conclude, a case study is performed on a 2200 TEU container ship equipped with an 800m² kite on a transatlantic route between Halifax and Le Havre. Round trip simulations, performed over 5 years of navigation, show that the total economy predicted is of around 12% at a speed of 16 knots and around 6.5% at a speed of 19 knots

La Bouée MOLIT : un nouveau concept de bouée instrumentée

La validité du concept de station de mesure haute-fréquence Marel a été vérifié par le déploiement d’un réseau constitué de stations de type axisymétrique (Réseau Baie de Seine, Bouée Iroise en rade de Brest). Le mouillage et le comportement de ces bouées en terme d’accessibilité et de maintenance est un handicap pour l’extension vers les zones plus exposées du large. La bouée MOLIT (Mer Ouverte LITtorale) constitue une réponse technique et financière

Une avancée optique pour la mesure de la salinité absolue des océans

rubrique "Cahier technique"National audienceLa salinité est un paramètre clé pour déterminer les propriétés physiques de l'eau de mer. Sa connaissance permet notamment d'étudier la circulation des grands courants marins. Les transports de chaleur et de masse qui leur sont associés sont régis principalement par leurs variations de salinité ou de masse volumique, les deux paramètres étant liés. L'importance que revêt de nos jours l'étude des variations climatiques et des variations de salinité liées par exemple à la fonte de la calotte glacière ainsi que les biais constatés sur la mesure de salinité, ont conduit les océanographes à s'intéresser au développement de nouveaux capteurs fiables, précis et utilisables in situ, pour surveiller l'évolution des phénomènes océaniques

A high pressure and high optical power characterization method designed for underwater optical elements

International audienceThis paper describes two methods for characterizing underwater optical elements under both hyper-baric pressure and high optical power. Commercial optical feedthroughs to be tested were inserted in a hyper-baric vessel and a 600 bar pressure was applied as an optical power of several Watts was sent over the optical fibers. An unexpected decrease of the optical losses was evidenced

A high pressure and high optical power characterization method designed for underwater optical elements

International audienceThis paper describes two methods for characterizing underwater optical elements under both hyper-baric pressure and high optical power. Commercial optical feedthroughs to be tested were inserted in a hyper-baric vessel and a 600 bar pressure was applied as an optical power of several Watts was sent over the optical fibers. An unexpected decrease of the optical losses was evidenced

Development of an optical salinometer for oceanography

Salinity is the essential parameter for ocean dynamics studies. Its definition and using in the equations used to calculate the thermodynamic properties of seawater, were revised in 2010, opening the possibility of new sensors developments. In this context, NOSS (NKE Optical Salinity Sensor) has emerged as one of the first underwater instrument for in situ refractive index measurement in the past years open up the scope of possibilities to access to density parameter. This achievement is the fruit of the cooperation between several institutions and the fruit of several years of developments and trials. NOSS sensor is designed to be deployed in coastal environment and open-ocean waters up to 2000m, especially on profiling floats of the Argo network.La salinité est un paramètre essentiel pour l’étude des propriétés dynamiques des océans. Sa définition et les équations utilisées pour calculer les propriétés thermodynamiques de l’eau de mer, ont été revues en 2010, ouvrant la possibilité de développements de nouveaux capteurs. Dans ce contexte, le NOSS (NKE Optical Salinity Sensor) est apparu, ces dernières années, comme étant le premier instrument utilisable in situ pour réaliser des mesures d’indice de réfraction, ouvrant la voie à la possibilité de mesurer directement la grandeur masse volumique, qui ne peut être que calculée jusqu’à présent. Cette recherche a nécessité plusieurs années de développements et d’essais et une collaboration entre plusieurs institutions. Le Capteur NOSS a été conçu pour être déployé dans des environnements côtiers et hauturiers jusqu’à des profondeurs de 2000 m et, plus spécifiquement, sur des flotteurs dérivants du réseau ARGO

Node and junction box services and interfaces for a local sea bottom observatory

Peer Reviewe