L’appropriation des normes de participation dans les institutions internationales : Le cas du développement durable dans les grands barrages

Le processus d’internalisation des normes au sein des institutions n’est pas homogène, variant selon divers facteurs. L’article se penche sur des acteurs, liés directement ou indirectement à la construction de grands barrages, peu sensibles aux enjeux sociaux du développement durable. Comment expliquer les différences entre ces institutions dans la prise en compte des critères sociaux ? L’hypothèse est que l’identité d’une organisation et sa capacité « disciplinaire » ou « idéologique » à tenir compte des facteurs sociaux déterminent la qualité de l’évaluation et de la gestion des impacts sociaux des grands barrages, rejoignant l’argument de Young voulant que la structure d’une institution internationale joue un rôle capital dans sa capacité à mettre en oeuvre et à promouvoir des normes.The process of internalisation of norms within different institutions is not homogenous, its speed and depth depending on several factors. Using the case of sustainable development in dams, this article analyses actors – here, dam promoters – whose institutional or disciplinary culture does not lend them to easily take these norms into account. The hypothesis is that the “identity” and the disciplinary or ideological capacity of these “technical” institutions play an important role in the internalisation of non technical, social, norms. This follows Young’s recent arguments concerning the role the internal structure of international institutions plays in internalising and spreading environmental norms

Longterm increases in western Mediteranean salinities and temperatures: a mixture of anthropogenic and climate sources

The deep water of the western Mediterranean Sea is known to have become warmer and saltier since about the 1950s. The causes of these changes have, however, not yet been sactisfactorily determined. Previous studies speculated on decreasing precipitation, greenhouse warming and/or anthropogenic reduction of the freshwater flux into the eastern Mediterranean. Here we report on results from a new oceanographic database of the western Mediterranean Sea together with determinations of longterm changes of the fresh water budget. We analyzed temperature and salinity data of the past 40 years to detect deviations from the longterm average. Certain areas and depth ranges are showing increases in temperature or salinity some of which have been found earlier and some which are new. From the regional and vertical distribution we conclude that the observed increases of temperature and salinity in the western Mediterranean Sea are caused both by changes in atmospheric conditions as described by the NAO‐index and by the regulation of Spanish rivers

Validation expérimentale d'une commande aux perturbations singulières d'un système pile à combustible/super capacités

International audienceCet article traite du problème de la gestion d'énergie d'un système pile à combustible (PaC) à hydrogène associé à des supers condensateurs (SCs) avec de fortes variations de la charge (cf. traction d'un véhicule électrique). La théorie des perturbations singulières est utilisée pour le contrôle et la coordination de deux convertisseurs statiques, l'un associé à la PaC et l'autre aux SCs sous les contraintes suivantes : charge variable et inconnue, en présence des pertes des 2 convertisseurs et une variation du courant de la PaC ne devant pas dépasser 4A/s. La convergence des tensions de la charge et des SCs est analysée en utilisant la théorie de Lyapunov. Des résultats expérimentaux du système PaC-SCs, sont présentés sur un benchmark représentatif de l'application véhicule électrique. Ils permettent de montrer l'intérêt de l'approche utilisée et de souligner les difficultés introduites par la présence des pertes des 2 convertisseurs

Action palliative par le convertisseur statique en cas de défaillance d'un générateur PAC modulaire de puissance

International audienceLa montée en puissance des piles à combustible se heurte à des difficultés d'ordre mécanique et fluidique, limitant l'assemblage en série de cellules unitaires pour les piles de forte puissance. Aussi, à l'heure actuelle, est-il plus aisé de concevoir des générateurs pile à combustible associant plusieurs piles unitaires, dits " multi-stack ". L'approche multi-stack permet en outre de gérer d'éventuelles défaillances pouvant intervenir sur l'une des piles en fonctionnement. Cet article présente des actions de soulagement de la pile défaillante possibles par intervention sur les convertisseurs statiques de puissance d'interface et permettant le rétablissement de cette pile défaillante vers son état sain

Are there superposed Mohos in the south-western Alps? New seismic data from fan-profiling reflections

International audienceThe Moho preserves imprints of the regional geodynamic evolution of the lithosphere. As such, its detailed topography in divergence or convergence zones has a strong bearing on any geodynamic model. This is still more critical where 3D effects are expected, as in the case of the Alpine chain which exhibits in its western part a short radius of curvature while its trend rotates by 180°. The deep structure of this zone, characterized by a peculiar imbrication of highdensity material of lower crust or mantle origin, remains a puzzle. In September 1999 a new controlled-source-seismology experiment was carried out in the south-western Alps, in the area between the Pelvoux, Dora Maira and Argentera massifs. Five shots were recorded with 130 seismic stations deployed on a total of nine fan- and one in-line profiles. It aimed at getting information on the Moho depth in a hitherto blank area, and discussing the existence of the hypothetical Briançonnais mantle flake mapped in 1986 by the ECORS-CROP experiment. Fan profiles recorded at critical distance for reflections from the European Moho allowed us to map in detail the thickening of the crust from the Mediterranean coastline (27 km) to the root zone (55 km). The zone just south of the Pelvoux massif is characterized by a rather flat, 40-km-deep Moho, which distorts the isobaths in thickening the crust along the Durance valley. Beneath the Argentera massif and just north of it, we evidence a strong dip of the Moho down to 51 km, whereas previous maps predicted depths of 40–46 km only. A new, detailed map of the European Moho can be drawn, which integrates depth data measured at ~ 300 reflection midpoints. However the experiment could not establish the continuity of the Briançonnais mantle flake over a large area in the internal Alps. We observed several reflectors in the 15–31-km depth range. One of them is the Ubaye reflector, a 20-km-long, 23–31-km-deep structure. It might correspond to the Briançonnais mantle flake, although it is located much farther south than the reflector mapped in 1986. New investigations will be necessary to state whether its origin is crustal or due to wedging of mantle material

Three hundred eighty thousand year long stable isotope and faunal records from the Red Sea : influence of global sea level change on hydrography

Stable isotope and faunal records from the central Red Sea show high-amplitude oscillations for the past 380,000 years. Positive δ18O anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the Arabian Sea was reduced due to a reduced geometry of the Bab el Mandeb Strait. Salinities as high as 53‰ and 55‰ are inferred from pteropod and benthic foraminifera δ18O, respectively, for the last glacial maximum. During this period all planktonic foraminifera vanished from this part of the Red Sea. Environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level. The foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka. Spectral analysis of the planktonic δ18O record documents highest variance in the orbital eccentricity, obliquity, and precession bands, indicating a dominant influence of climatically - driven sea level change on environmental conditions in the Red Sea. Variance in the precession band is enhanced compared to the global mean marine climate record (SPECMAP), suggesting an additional influence of the Indian monsoon system on Red Sea climates

Recent trends of SST in the Western Mediterranean basins from AVHRR Pathfinder data (1985-2007)

Climate change in the Mediterranean region cannot be understood without taking into account changes in the Mediterranean Sea, which is an important source of moisture and heat for the Mediterranean climate system. Many research papers have been published in the last two decades increasing our knowledge about long-term trends and inter-annual variability of temperature and salinity in the Western Mediterranean. Although recent changes have been better documented, there remain uncertainties because different results are obtained depending on the period of time analyzed or the geographic region selected. This paper analyses the regional, seasonal and decadal variability of sea surface temperature in the Western Mediterranean basins (Northern (Ligurian Sea and Gulf of Lions), Balearic, Algerian and Alboran) by means of thermal satellite images. Monthly data from the PO.DAAC (Physical Oceanography Distributed Active Archive Center) have been processed for the period 19852007. Results show an averaged warming linear trend of 0.03 °C/yr. This rate is higher during the spring (0.06 °C/yr) in all the basins and the highest values were registered in the Northern basin in June. The study suggests that an early warming of the Sea is occurring in all the basins during the spring, with an increment of 0.51 °C in the mean SST of April, May and June over the two decades studied. The analysis of thermal anomalies confirms the warming trend with a dominance of negative anomalies during 19851996 and a dominance of positive anomalies during the last decade (19972007). Intense anomalies are more frequent in the Northern basin

Geometrical optimization and electrical performance comparison of thin-film tandem structures based on pm-Si:H and µc-Si:H using computer simulation

International audienceThis article investigates the optimal efficiency of a photovoltaic system based on a silicon thin film tandem cell using polymorphous and microcrystalline silicon for the top and bottom elementary cells, respectively. Two ways of connecting the cells are studied and compared: (1) a classical structure in which the two cells are electrically and optically coupled; and (2) a new structure for which the "current-matching" constraint is released by the electrical decoupling of the two cells. For that purpose, we used a computer simulation to perform geometrical optimization of the studied structures as well as their electrical performance evaluation. The simulation results show that the second structure is more interesting in terms of efficiency

Seasonal heat content changes in the western Mediterranean Sea as a means for evaluating surface heat flux formulations

The semienclosed western Mediterranean Sea has proven to be a useful location to evaluate surface heat flux estimates. In the past the directly measured average oceanic heat transport from the Atlantic into the Mediterranean Sea through the Strait of Gibraltar of similar to 5.2 +/- 1.3 W m(-2) has been compared to estimates of the average heat flux across the surface of the Mediterranean Sea. On long timescales both should closely balance each other. By using a monthly temperature climatology of the western Mediterranean Sea we offer the possibility to extend the comparison to the seasonal timescale. This gives additional information with which different surface heat flux data sets can be evaluated. The seasonal heat content changes of the western Mediterranean and the advective exchange of heat through the Straits of Gibraltar and Sicily are estimated on the basis of a new extensive hydrographic data set and of published values for the volume transports. To demonstrate the method, a limited number of surface heat flux data sets are compared with the oceanographically calculated counterpart. The comparison reveals that some heat fluxes do not only agree well for the long-term averages but also for the seasonal timescale, whereas others show larger deviations. The remaining rms discrepancies of +/-10.2 W m(-2) for the best heat flux data set are smaller than the uncertainty of the oceanographic estimate and of a reasonable magnitude compared to the uncertainty of the long-term average of similar to 5 W m(-2)

A dynamic explanation for the origin of the western Mediterranean organic-rich layers

The eastern Mediterranean sapropels are among the most intensively investigated phenomena in the paleoceanographic record, but relatively little has been written regarding the origin of the equivalent of the sapropels in the western Mediterranean, the organic-rich layers (ORLs). ORLs are recognized as sediment layers containing enhanced total organic carbon that extend throughout the deep basins of the western Mediterranean and are associated with enhanced total barium concentration and a reduced diversity (dysoxic but not anoxic) benthic foraminiferal assemblage. Consequently, it has been suggested that ORLs represent periods of enhanced productivity coupled with reduced deep ventilation, presumably related to increased continental runoff, in close analogy to the sapropels. We demonstrate that despite their superficial similarity, the timing of the deposition of the most recent ORL in the Alboran Sea is different than that of the approximately coincident sapropel, indicating that there are important differences between their modes of formation. We go on to demonstrate, through physical arguments, that a likely explanation for the origin of the Alboran ORLs lies in the response of the western Mediterranean basin to a strong reduction in surface water density and a shoaling of the interface between intermediate and deep water during the deglacial period. Furthermore, we provide evidence that deep convection had already slowed by the time of Heinrich Event 1 and explore this event as a potential agent for preconditioning deep convection collapse. Important differences between Heinrich-like and deglacial-like influences are highlighted, giving new insights into the response of the western Mediterranean system to external forcing