Ollitrault Michel

• Researcher at Institut Français de Recherche pour l'Exploitation de la Mer

Hobnails with reliefs under the head are a clue to the presence of Roman soldiers, while the design proper and the size may allow a more precise datation. Larger nails, possibly for carts, and with the same symbols, were found in the Jura region (antique Sequania). They could be linked with the salt transport, not excluding a military context. Thes...

The vertically integrated potential energy of an incompressible stratified fluid formulated in density coordinates can be simply written as a weighted vertical sum of the squares of the vertical displacements of density surfaces, a general expression valid for arbitrary displacements. The sum of this form of potential energy and kinetic energy is t...

The evolution and dispersion of intermediate water masses in the ocean interior is studied. To this purpose an empirical statistical model of Lagrangian tracers at a constant depth level is developed. The model follows the transfer operator based on 10-day deep displacements of Argo floats at ~1,000 m depth. An asymptotic analysis of the model show...

The time-mean Argo float displacements and the World Ocean Atlas 2009 temperature–salinity climatology are used to obtain the total, top to bottom, mass transports. Outside of an equatorial band, the total transports are the sum of the vertical integrals of geostrophic- and wind-driven Ekman currents. However, these transports are generally diverge...

The mean ocean circulation near 1000-m depth is estimated with 100-km resolution from the Argo float displacements collected before 1 January 2010. After a thorough validation, the 400 000 or so displacements found in the 950-1150 dbar layer and with parking times between 4 and 17 days allow the currents to be mapped at intermediate depths with unp...

During the first decade of the 21 st century, approximately 6000 Argo floats have been launched over the World Ocean, gathering temperature and salinity data of the top 2000 m, at a 10-day or so sampling period. Meanwhile their deep displacements over 8 or 9 days can be used to map the ocean circulation at their drifting depth (mostly around 1000 m...

Argo hydrographic profiles collected from 2004 to 2011 in the southeast Atlantic sector of the Southern Ocean are used in combination with hydrographic transects to describe the characteristics of Antarctic Intermediate Water (AAIW) in the region. Making use of the recently developed ANDRO velocity data set, we estimate the evolution of the dynamic...

Subsurface float measurements at 800 m depth carried out from 1994 to 2003 in the Brazil Basin are used to characterise the equatorward Intermediate Western Boundary Current (IWBC) and its connections to the ocean interior. Transversally, the boundary flow is less than 100 km wide, and most intense at 10-20 km from the 800 m isobath. Its average ve...

Mean total (barotropic + baroclinic) mass transports of the oceanic top 1000 dbar are estimated for two regions of the South Atlantic between 18°S and 47°S. These transports are obtained by using Gravest Empirical Mode (GEM) fields calculated from historical hydrography with temperature and position data from quasi-isobaric subsurface floats deploy...

a b s t r a c t A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three ind...

1] Acoustic float data collected near 800 m depth, are used to map zonal mean currents within the Antarctic Intermediate Water (AAIW) tongue in the equatorial Atlantic. Alternating zonal jets of 2° latitudinal width are revealed between 6°S and 6°N. Displacements from profiling floats drifting near 1000 m depth, also reveal similar zonal jets at th...

As two fluid particles separate in time, the entire spectrum of eddy motions is being sampled from the smallest to the largest scales. In large-scale geophysical systems for which the Earth rotation is important, it has been conjectured that the relative diffusivity should vary respectively as D-2 and D-4/3 for distances respectively smaller and la...

This study combines float data from different projects collected between 1991 and 2003 in the South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity space–time averages are calculated for various grid resolutions and with cells deformed to match the bathymetry, f/H or f/h (with H being the water depth and h being the t...

Quasi-Lagrangian trajectories of 26 sound fixing and ranging (SOFAR) floats have been collected near a depth of 700 m in the Central North Atlantic between 1983 and 1989, aiming at studying the influence of the Mid-Atlantic ridge on the large-scale intermediate circulation. Launched as tight clusters (18 km near neighbor distance) on either side of...

Part I of this paper has given a descriptive view of the trajectories of 26 SOFAR floats drifting near 700-m depth in the central North Atlantic during the mid-1980s, as part of the TOPOGULF experiment. Here an Eulerian analysis of the 53.4 collected float years is performed by grouping data in 2 latitude 4 longitude boxes. The mean circulation lac...

The Antarctic Intermediate Water is a low-salinity, oxygen-rich water mass that spreads northward in the South Atlantic Ocean in the 700-1200 m depth range. The circulation of this water mass and its role in the global thermohaline circulation are the subjects of intense debates. During the World Ocean Circulation Experiment (WOCE), hydrographic se...

The subsurface oceanic circulation is an important part of the Earth climate system. Subsurface currents tradi-tionally are inferred indirectly from distributions of tempera-ture and dissolved substances, occasionally supplemented by current meter measurements. Neutrally-buoyant floats how-ever, now enable us to obtain for the first time directly m...

MARVOR is a multicycle subsurface RAFOS type float developed by IFREMER, in partnership with TEKELEC. The first 20 serial MARVORs were launched in February 1994 in the Brazil Basin for 30 2-month cycles at 800 dbar depth within the framework of the SAMBA experiment. The SAMBA experiment, a component of WOCE, will use a total of 100 MARVOR floats ov...

Subsurface floats (named SOFAR) have been used since mid-seventies to track water particles, providing Lagrangian description of oceanic circulation. Recently, the reverse concept - floats called RAFOS that are listening and sources that are fixed - have become increasingly popular among the oceanographic community because their size and cost can b...

An inverse method is used to evaluate the information contained in sediment data for the Atlantic basin during the Last Glacial Maximum (defined here as the time interval 18–21 kyr before present). The data being considered are an updated compilation of the isotopic ratios 18 O/ 16 O (18 O) and 13 C/ 12 C (13 C) of fossil shells of benthic foramini...

The TOPEX/POSEIDON altimeter will provide the temporal mean seal level. So, secondly, we propose to compute the difference between these two surfaces (mean sea level minus general circulation dynamic topography). The result will be an estimate of the marine geoid, which is time invariant for the 5-year period under consideration. If this geoid is p...

A 2.5-meter diameter, heave pitch and roll buoy, has been developed by CNEXO and NEREIDES Company. The ARGOS satellite system is used for data transmission. To be compatible with the ARGOS message length, raw data had to be processed on-board. This led us to use a digital band pass recursive filter technique, to obtain estimates of energy and mean...

A network of 3 wave buoys was deployed between the Glenans Archipelago and the mouth of the Gironde river (France) to determine potential wavepower resources. The buoys were fitted with accelerometers and spectral analyzers generating a sea state spectrum every hour, transmitted to the ARGOS system. The mean annual power per meter calculated from t...

In February 1994, during the SAMBA1 croise, 9 CTD casts were done and 22 subsurface floats (20 MARVORs, 1 VCM and 1 ALFOS) 1aunched near 800 dbar in the Brazil basin, within the framework of the SAMBA experiment. SAMBA (SubAntarctic Motions in the Brazil BAsin), is a component of the WOCE float program, and aims at describing the absolute general c...

From July 1983 to June 1989, the TOPOGULF experiment took place in the North Atlantic, to investigate the large scale and mesoscale circulations in the area of the Mid-Atlantic Ridge (MAR). The TOPOGULF experiment comprised hydrographic (CTD, O2 and nutrient data) sections, long-term current meter measurements, tracking of lagrangian surlace and su...

Depuis le début des années 70, des flotteurs dérivant librement en profondeur s'utilisent pour décrire les mouvements des "particules" d'eau. En effet ces flotteurs se stabilisent naturellement à une immersion donnée où ils sont alors entraînés par les mouvements des masses d'eaux environnantes.