Elizaveta Svilova

A film editor, director, writer, and archivist, Elizaveta Svilova was an intellectual and creative force in early Soviet montage. She is best known for her extensive collaborations with her husband, Dziga Vertov, on seminal early documentary films, and especially for instances when she appeared on camera demonstrating the act of editing itself. The fact that Vertov’s filmic theory and practice focused on montage as the fundamental guiding force of cinema confirms the crucial role Svilova’s groundbreaking experimentation played in early Soviet film and global film history. Her career, which spanned far beyond her collaborations with her husband, significantly advanced the early principles of cinematic montage

A Connectivity-Based Eco-Regionalization Method of the Mediterranean Sea

International audienceEcoregionalization of the ocean is a necessary step for spatial management of marine resources. Previous ecoregionalization efforts were based either on the distribution of species or on the distribution of physical and biogeochemical properties. These approaches ignore the dispersal of species by oceanic circulation that can connect regions and isolates others. This dispersal effect can be quantified through connectivity that is the probability, or time of transport between distinct regions. Here a new regionalization method based on a connectivity approach is described and applied to the Mediterranean Sea. This method is based on an ensemble of Lagrangian particle numerical simulations using ocean model outputs at 1/12u resolution. The domain is divided into square subregions of 50 km size. Then particle trajectories are used to quantify the oceanographic distance between each subregions, here defined as the mean connection time. Finally the oceanographic distance matrix is used as a basis for a hierarchical clustering. 22 regions are retained and discussed together with a quantification of the stability of boundaries between regions. Identified regions are generally consistent with the general circulation with boundaries located along current jets or surrounding gyres patterns. Regions are discussed in the light of existing ecoregionalizations and available knowledge on plankton distributions. This objective method complements static regionalization approaches based on the environmental niche concept and can be applied to any oceanic region at any scale

Circulation côtière en Méditerranée Nord Occidentale (courantométrie par radar HF et couplage avec un modèle numérique)

Le radar HF est actuellement le seul instrument courantométrique permettant d'obtenir une description synoptique à haute résolution spatiale et temporelle de la circulation côtière de surface. Un système radar déployé depuis 2010 en Méditerranée sur les côtes varoises offre pour la première fois une description exhaustive de la circulation, encore peu documentée dans cette zone.La cartographie des courants se fait classiquement en combinant les mesures d'au moins deux radars. Cependant des résultats significatifs ont été obtenus avec un seul radar concernant : l'identification de tourbillons méso-échelle ; la signature de phénomènes périodiques affectant la circulation superficielle dans les bandes diurne, inertielle et semi-diurne ; et les caractéristiques et les instabilités du Courant Nord Méditerranéen (CN).L'assimilation des mesures radar au moyen d'un lisseur de Kalman d'ensemble dans un modèle régional de la Méditerranée Nord Occidentale a été réalisée pour la première fois dans la zone d étude. Cette méthode, qui contraint les courants de surface en optimisant le vent et les forçages aux frontières ouvertes, améliore la description de la veine du CN en vitesse et positionThe HF radar is the sole instrument being able to monitor the surface coastal current at very high spatial and temporal resolution. A radar system deployed since 2010 on the Var coast (Western Mediterranean Sea) provides for the first time a comprehensive picture of the circulation, which remains poorly documented in this area.Surface current mapping is conventionally performed by combining measurements of at least two radars. However, significant results were obtained with a single radar concerning: the identification of mesoscale vortices; the signature of periodic phenomena affecting the surface circulation in the diurnal, inertial and semi-diurnal bands; and the features and instabilities of the North Mediterranean Current (NC).The assimilation of radar measurements using an ensemble Kalman smoother in a regional model of the North-Western Mediterranean Sea was performed for the first time in the study area. This method, which constraints the surface currents by wind and open boundary conditions optimisation, improves the simulation of the NC vein in terms of speed and position.TOULON-Bibliotheque electronique (830629901) / SudocSudocFranceF

Measurements within the Pacific-Indian oceans throughflow region

Two hydrographic ... and trichlorofluoromethane (F-11) sections were carried out between the Australian continental shelf and Indonesia, in August 1989, on board the R.V. "Marion Dufresne". The sections lie in the easternmost part of the Indian Ocean where the throughflow between the Pacific Ocean and the Indian Ocean emerges. They allow us to describe the features of the water-property and circulation fields of the throughflow at its entrance in the Indian Ocean. Between the Australian continental shelf and Bali, the Subtropical and Central waters are separated from the waters of the Indonesian seas by a sharp hydrological front, located around 13°30S, below the thermocline down to 700 m. Near the coast of Bali, upwelling occurs in the near-surface layer under the effect of the Southeast monsoon; at depth, between 300 m to more than 800 m, a water mass of Northern Indian Ocean origin was present. (D'après résumé d'auteur

Variational analysis of drifter positions and model outputs for the reconstruction of surface currents in the central Adriatic during fall 2002

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C04004, doi:10.1029/2007JC004148.In this paper we present an application of a variational method for the reconstruction of the velocity field in a coastal flow in the central Adriatic Sea, using in situ data from surface drifters and outputs from the ROMS circulation model. The variational approach, previously developed and tested for mesoscale open ocean flows, has been improved and adapted to account for inhomogeneities on boundary current dynamics over complex bathymetry and coastline and for weak Lagrangian persistence in coastal flows. The velocity reconstruction is performed using nine drifter trajectories over 45 d, and a hierarchy of indirect tests is introduced to evaluate the results as the real ocean state is not known. For internal consistency and impact of the analysis, three diagnostics characterizing the particle prediction and transport, in terms of residence times in various zones and export rates from the boundary current toward the interior, show that the reconstruction is quite effective. A qualitative comparison with sea color data from the MODIS satellite images shows that the reconstruction significantly improves the description of the boundary current with respect to the ROMS model first guess, capturing its main features and its exchanges with the interior when sampled by the drifters.Four of the authors are supported by the Office of Naval Research, V.T. and A.G. under grants N00014-05-1-0094 and N00014-05-1-0095, P.M.P. under grant N00014-03-1-0291, and S.C. under grant N00014-05-1-0730. CNR-ISMAR activity was partially supported by P.O.R. ‘‘CAINO’’ (Regione Puglia), VECTOR (Italian MIUR) project, and ECOOP (EU project)

Persistent Transport Barrier on the West Florida Shelf

Analysis of drifter trajectories in the Gulf of Mexico has revealed the existence of a region on the southern portion of the West Florida Shelf (WFS) that is not visited by drifters that are released outside of the region. This so-called ``forbidden zone'' (FZ) suggests the existence of a persistent cross-shelf transport barrier on the southern portion of the WFS. In this letter a year-long record of surface currents produced by a Hybrid-Coordinate Ocean Model simulation of the WFS is used to identify Lagrangian coherent structures (LCSs), which reveal the presence of a robust and persistent cross-shelf transport barrier in approximately the same location as the boundary of the FZ. The location of the cross-shelf transport barrier undergoes a seasonal oscillation, being closer to the coast in the summer than in the winter. A month-long record of surface currents inferred from high-frequency (HF) radar measurements in a roughly 60 km $\times$ 80 km region on the WFS off Tampa Bay is also used to identify LCSs, which reveal the presence of robust transient transport barriers. While the HF-radar-derived transport barriers cannot be unambiguously linked to the boundary of the FZ, this analysis does demonstrate the feasibility of monitoring transport barriers on the WFS using a HF-radar-based measurement system. The implications of a persistent cross-shelf transport barrier on the WFS for the development of harmful algal blooms on the shoreward side of the barrier are considered.Comment: Submitted to Geophysical Research Letter

Lagrangian transport through an ocean front in the North-Western Mediterranean Sea

We analyze with the tools of lobe dynamics the velocity field from a numerical simulation of the surface circulation in the Northwestern Mediterranean Sea. We identify relevant hyperbolic trajectories and their manifolds, and show that the transport mechanism known as the `turnstile', previously identified in abstract dynamical systems and simplified model flows, is also at work in this complex and rather realistic ocean flow. In addition nonlinear dynamics techniques are shown to be powerful enough to identify the key geometric structures in this part of the Mediterranean. In particular the North Balearic Front, the westernmost part of the transition zone between saltier and fresher waters in the Western Mediterranean is interpreted in terms of the presence of a semipermanent ``Lagrangian barrier'' across which little transport occurs. Our construction also reveals the routes along which this transport happens. Topological changes in that picture, associated with the crossing by eddies and that may be interpreted as the breakdown of the front, are also observed during the simulation.Comment: 34 pages, 6 (multiple) figures. Version with higher quality figures available from http://www.imedea.uib.es/physdept/publications/showpaper_en.php?indice=1764 . Problems with paper size fixe

Oceanic three-dimensional Lagrangian Coherent Structures: A study of a mesoscale eddy in the Benguela ocean region

We study three dimensional oceanic Lagrangian Coherent Structures (LCSs) in the Benguela region, as obtained from an output of the ROMS model. To do that we first compute Finite-Size Lyapunov exponent (FSLE) fields in the region volume, characterizing mesoscale stirring and mixing. Average FSLE values show a general decreasing trend with depth, but there is a local maximum at about 100 m depth. LCSs are extracted as ridges of the calculated FSLE fields. They present a "curtain-like" geometry in which the strongest attracting and repelling structures appear as quasivertical surfaces. LCSs around a particular cyclonic eddy, pinched off from the upwelling front are also calculated. The LCSs are confirmed to provide pathways and barriers to transport in and out of the eddy

Interbasin deep water exchange in the western Mediterranean

Owing to its nearly enclosed nature, the Tyrrhenian Sea at first sight is expected to have a small impact on the distribution and characteristics of water masses in the other basins of the western Mediterranean, The first evidence that the Tyrrhenian Sea might, in fact, play an important role in the deep and intermediate water circulation of the entire western Mediterranean was put forward by Hopkins [1988]. There, an outflow of water from the Tyrrhenian Sea into the Algero Provencal Basin was postulated in the depth range 700-1000 m, to compensate for an observed inflow of deeper water into the Tyrrhenian Sea. However, this outflow, the Tyrrhenian Deep Water (TDW), was undetectable since it would have hydrographic characteristics that could also be produced within the Algero-Provencal Basin. A new data set of hydrographic, tracer, lowered Acoustic Doppler Current Profiler (LADCP), and deep float observations presented here allows us now to identify and track the TDW in the Algero-Provencal Basin and to demonstrate the presence and huge extent of this water mass throughout the western Mediterranean. It extends from 600 m to 1600-1900 m depth and thus occupies much of the deep water regime. The outflow from the Tyrrhenian is estimated to be of the order of 0.4 Sv (Sv=10(6) m(3) s(-1)), based on the tracer balances. This transport has the same order of magnitude as the deep water formation rate in the Gulf of Lions. The Tyrrhenian Sea effectively removes convectively generated deep water (Western Mediterranean Deep Water (WMDW)) from the Algero-Provencal Basin, mixes it with Levantine Intermediate water (LIW) above, and reinjects the product into the Algero-Provencal Basin at a level between the WMDW and LIW, thus smoothing the temperature and salinity gradients between these water masses. The tracer characteristics of the TDW and the lowered ADCP and deep float observations document the expected but weak cyclonic circulation and larger flows in a vigorous eddy regime in the basin interio