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Discussions following the publication of “Levantine Intermediate Water characteristics: an astounding general misunderstanding!” (Millot 2013a) confirmed that this warm salty (similar results with cool fresh) intermediate water was generally thought to be characterized, even after significant mixing, by a homogeneous core (i.e. a dσ/dz minimum) while we think it could be characterized by a dσ/dz maximum. Additional computations specify our feelings and suggest that only such a hypothetical dσ/dz maximum can provide information about the characteristics of these intermediate waters, in this case only the local immersion of the core, since the associated s depends essentially on the σ values of all the surrounding waters encountered upstream, while the Θ and S maxima evolve continuously. Because we are convinced that such studies have a global importance and deserve much more interest than they have received up to now, we hope that these additional computations and data analyses will motivate really theoretical studies that could be easily checked with a consequent data set available all over the Mediterranean Sea in particular., Discusiones a partir de la publicación de “Levantine Intermediate Water characteristics: an astounding general misunderstanding!” (Millot 2013a) confirmaron que esta masa de agua intermedia caliente y salada (igualmente válido para un agua fría y dulce) se había considerado siempre caracterizada, incluso tras ser significativamente mezclada, por un núcleo homogéneo (o sea un mínimo de dσ/dz), mientras que nosotros pensamos que podría caracterizarse por un máximo de dσ/dz. Cálculos adicionales especifican esta idea y sugieren que únicamente este hipotético máximo de dσ/dz puede proporcionar información sobre las características de dicha masa de agua, en este caso sólo la profundidad local del núcleo, mientras que la σ asociada depende esencialmente de los valores de σ de todas las aguas arriba circundantes, mientras que los máximos de Θ y S evolucionan continuamente. Dado que estamos convencidos que estos estudios tienen una importancia global y merecen mucho más interés que el recibido hasta ahora, esperamos que estos cálculos adicionales y análisis de datos motivarán estudios teóricos que podrían ser fácilmente verificados con conjuntos de datos disponibles en particular en todo el Mediterráneo.

Levantine Intermediate Water (LIW) is a warm salty water formed in one out of four main zones of dense water formation in the Mediterranean Sea. LIW spreads as a density current and first appears on a ϴ-S diagram as a sharp peak that then smoothens out, often leading to the so-called “scorpion-tail” image with a ϴ (S) maximum above (below) the expected core. Both maxima have always been considered, somewhat fuzzily (even by us), as LIW characteristics without having ever been analysed theoretically. We question neither the “scorpion-tail” image nor the “core-method” nor qualitative analyses of either LIW or other waters characterized by similar extrema. But data from the Strait of Gibraltar demonstrate that characterizing and/or delimiting LIW by these maxima gives LIW a much greater importance than it actually merits so all quantitative analyses of LIW musts be reconsidered. Calculations made as simple as possible to simulate a warm salty layer of intermediate water (IW) mixing with waters lying above and below suggest that these maxima i) can be understood only when all three waters are considered together, ii) can evolve in different ways, iii) generally tend to move from the core of the IW layer outwards, and hence iv) can neither characterize nor delimit the IW in any way. Actual simulations with more sophisticated parameterizations are obviously needed. In addition, we suggest that what has to date been called LIW in the western basin in fact represents all intermediate waters formed in all zones of dense water formation in the eastern basin, i.e. not only Levantine waters but also, in particular, Aegean/Cretan waters. To provide a logical counterpart to WIW (Western Intermediate Water), we therefore suggest that, from the Channel of Sicily downstream, LIW should be renamed Eastern Intermediate Water (EIW)., El Agua Levantina Intermedia (LIW) es una masa de agua caliente y salada que se forma en el Mediterráneo Oriental. Se esparce como una corriente de densidad y aparece en un diagrama ϴ-S como un pico pronunciado que se va suavizando, produciendo a menudo una imagen de “cola de escorpión” con un máximo de ϴ (S) por encima (por debajo) del nivel esperado de su núcleo. Ambos máximos se han considerado siempre, de forma algo difusa, como características definidoras de LIW sin haber sido analizados nunca teóricamente. No cuestionamos aquí ni la imagen de “cola de escorpión” ni el “método del núcleo” ni los análisis cualitativos de LIW ni de otras masas de agua caracterizadas por extremos similares. Pero datos obtenidos en el Estrecho de Gibraltar demuestran que caracterizar y/o limitar LIW por estos máximos otorga a esta masa de agua una importancia mucho mayor que la que tiene en realidad, con lo cual todos los análisis cuantitativos de LIW hechos hasta ahora deben ser reconsiderados. Cálculos hechos de la forma más simple posible para simular una capa de agua intermedia (IW) caliente y salada mezclándose con las aguas que tiene por encima y por debajo sugieren que estos máximos i) sólo pueden entenderse cuando se consideran las tres aguas conjuntamente, ii) pueden evolucionar de formas distintas, iii) generalmente tienden a desplazarse desde el núcleo de la capa de IW hacia afuera, y en consecuencia iv) no pueden caracterizar ni delimitar a la propia IW de ninguna manera. Obviamente estas conclusiones hay que confirmarlas con simulaciones completas que usen parametrizaciones más sofisticadas. Además sugerimos que lo que hasta ahora se ha llamado LIW en la cuenca occidental, en realidad representa al conjunto de las aguas intermedias formadas en todas las zonas de formación de agua densa de la cuenca oriental, es decir no sólo en la Levantina sino también, y en particular, en la Egea/Cretense. Para tener un equivalente de la WIW (Agua Intermedia Occidental), sugerimos que a partir del Canal de Sicilia, el agua intermedia procedente de la cuenca oriental sea llamada EIW (Agua Intermedia Oriental) en lugar de LIW.

The schema of the Atlantic Water (AW, 100-200 m thick) circulation in the eastern basin of the Mediterranean Sea elaborated in the 1990s (and widely referred to nowadays) mainly shows jets meandering offshore across the whole basin. However, all previous schemata (since the 1910s) and an analysis of infrared (IR) satellite images in the 1990s show counterclockwise circulation at basin scale. A former controversy about the circulation was elucidated in the western basin where IR images helped describe the mesoscale features and demonstrate their role in the circulation. This motivated the detailed analysis of IR daily and weekly composites (~1000) from 1996 to 2000, and of monthly composites since 1985. We show that AW circulates along the upper part of the continental slope in a counterclockwise direction around the whole basin. In the south and all year long, this circulation is unstable and generates mesoscale anticyclonic eddies that spread AW offshore; in the north dense water formation induces larger seasonal variability. These mesoscale eddies, as well as the Etesian-induced eddies Ierapetra and Pelops, can be followed for years, sometimes several hundreds of km away from where they are formed, and they can merge and/or interact with the alongslope circulation., Los esquemas de circulación del Agua Atlántica (AW, 100-200 m de grosor) en el Mediterráneo oriental elaborados en los años 1990 (y abundantemente citados en la actualidad) presentan principalmente una corriente en chorro ondulante atravesando el centro de la cuenca. Por el contrario, todos los esquemas anteriores (desde los años 1910) y un análisis de imágenes infrarojas (IR) de satélite en los noventa presentan una circulación antihoraria a escala de la cuenca. Una controversia anterior sobre la circulación en la cuenca occidental fue resuelta gracias a que las imágenes IR ayudaron a describir los fenómenos de mesoescala y demostrar su papel en la circulación. Esto motivó un análisis detallado de imágenes IR compuestas diarias y semanales (~1000) durante 1996-2000 y mensuales desde 1985. Aquí demostramos que el AW en general circula sobre la parte superior del talud continental, de forma antihoraria por toda la cuenca. En el sur, y a lo largo de todo el año, esta circulación es inestable y genera remolinos anticiclónicos de mesoescala que esparcen el AW hacia alta mar; en el norte la formación de agua densa induce una gran variabilidad estacional. Estos remolinos de mesoescala, así como los inducidos por los vientos Etesios (Ierapetra y Pelops), pueden ser seguidos durante años, a veces por varios centenares de quilómetros a partir de su lugar de formación, y pueden unirse y/o interaccionar con la circulación a lo largo del talud.

The overall counterclockwise alongslope circulation of Atlantic Water (AW) in the western basin of the Mediterranean Sea is now generally accepted. As the eastern basin displays similar general features, why is it generally assumed to function in a different way, and why is AW now said to circulate across the interior of the eastern basin? Relatively huge mesoscale anticyclonic eddies induced by the instability of the AW circulation in the south of the western basin have lifetimes up to several years. It is possible that they extend down to the sea bottom and play a major role in the distribution of all water masses. Why have apparently similar eddies generated in the eastern basin never received specific attention? Once formed, Mediterranean Waters (MWs) must spread and circulate before outflowing. Why have simple dynamical arguments for understanding the circulation of AW, such as the Coriolis effect, rarely been considered for the circulation of MWs? In this paper we address these major aspects of water circulation in the Mediterranean Sea. In order to be as objective and convincing as possible, and to write a paper that can be understood by as broad a readership as possible, we have chosen to present only raw data sets that can be easily interpreted by the reader without any help from the author. Based on the evidence provided by these data sets, we specify the current debates and list what we think are the main unanswered questions., En la cuenca occidental del mar Mediterráneo, la existencia de una circulación global ciclónica del Agua Atlántica (AW) siguiendo el talud continental es actualmente un hecho comúnmente aceptado; ya que la cuenca oriental muestra unas características globales similares, por qué en genral se supone que funciona de forma distinata?, y ¿por qué se dice que el AW circula por el interior de la cuenca oriental? Remolinos de mesoescala considerablemente grandes, inducidos por la inestabilidad de la circulación del AW en el sur d ela cuenca occidental, llegan apermanecer hasta varios años, posiblemente se extienden hasta el fondo, y tienen un papel fundamental en la distribución de todas las masas de agua; ¿por qué remolinos aparentemente similares generados en la cuenca oriental nunca han recibido ninguna atención? Una vez formadas, las distintas guas mediterráneas (MWs) tienen que esparcirse y circular antes de llegar a salir de su cuenca; ¿por qué los arguemntos dinámicos simples que permiten entender la circulación del AW, tales como el efecto de Coriolis, han sido muy raramente considerados para explicar la circulación de las MWs? Estos son los aspectos fundamentales de la circulación del mar Mediterráneo que analizamos aquí. Para ser lo más objetivo y convincentes posible, y escribir un artículo comprensible para el mayor número de lectores, hemos elegido prrsentar sólo conjuntos de datos sin procesar que puedan ser fácilmente interpretados por el lector sin ninguna ayuda por parte del autor. En base a las evidencias proporcionadas por estos conjuntos de datos, detallamos los debates actuales y enumeramos las que consideramos principales preguntas sin responder.

A large number of several-month current time series is now available in the western Mediterranean Sea, and harmonic and spectral analyses provide spatially coherent information about the major tidal (M2, S2, N2 and K1) currents in the region. When they are significant, these currents are generally barotropic, they mainly rotate clockwise and their ellipses have orientations that are strongly dependent on the local bathymetry. From the Alboran Sea to the Algerian Basin, the Ibiza Channel and as far as the Sardinian Channel, the velocities of the semidiurnal components continuously decrease from a few 10(-2) m/s in the west to 10(-3) m/s and even less in the east. The phases increase eastward from the Alboran Sea to 3-4 degrees E in the western Algerian Basin, and can then be considered as constant as far as similar to 9 degrees E in the Sardinian Channel. Such a phase variation is consistent with numerical models and results from the presence of an amphidromic zone near 0-2 degrees E. Eastward of similar to 9 degrees E, the phases should increase again, under the influence of another amphidromic zone located in the Sicily Channel. In both the Gulf of Lions and the Ligurian Sea, the velocities are extremely low and the ellipse characteristics are erratic, again in agreement with the models. In the Corsican Channel, where relatively shallow depths induce an increase of barotropic currents, the semi-diurnal components have a phase roughly opposed to that in the southwestern part of the sea. Considering the amphidromic zone in the Sicily Channel, this out-of-phase relationship is consistent with the occurrence of a zone of maximum elevation in the eastern Tyrrhenian Sea. The K1 currents in the Corsican Channel are lower than the M2 ones, but much larger than any other tidal current. They are exactly in phase with the elevation in the whole sea. All these results also prove that low tidal currents can be discerned in records made by simple instruments.

Special issue PRIMO-0.-- 30 pages, 18 figures, In the western Mediterranean Sea, the Northern Current is one of the major veins and is formed by the junction, in the Ligurian Sea, of the currents flowing northward along each side of Corsica; it is recognized as an entity along the continental slope as far as the Catalan Sea; surrounding the central zone where dense water formation occurs in winter. The seasonal and mesoscale variabilities of the Northern Current are analysed from a fortnightly hydrological survey carried out off Nice to a distance of similar to 55 km, from October 1990 to July 1991, and from similar to 30 current time series collected as deep as 2000 m, on four moorings set within a similar to 30 km coastal band from December 1990 to May 1991, in the framework of the PRIMO-O experiment. The hydrological surveys have mainly evidenced the spreading of Levantine Intermediate Water (LIW) in an on-offshore direction, the transformation of Modified Atlantic Water (MAW) into Winter Intermediate Water (WIW) in the deep winter, as well as the advection of less modified MAW. From a dynamic point of view, the seasonal variability is mainly depicted as a well-defined episode of narrowing, deepening and shoreward shift, from late January to mid-March, of a generally wide and shallow Northern Current. Currents have clearly appeared to be similar and highly correlated in an upper layer, the thickness of which is at least a hundred metres (between similar to 60 and 150 m), irrespective of the location of the points and of the season. This layer is expected to extend up to the surface. The flux of the Northern Current (between 0 and similar to 300 m) has ranged within 1-1.6 Sv from autum to summer, in agreement with the known values; relatively high values have been maintained during a rather long winter season. In accordance with other observations which have provided a description of a complete annual cycle, mesoscale activity is found to increase from autumn to deep winter and then displays a continuous decrease until summer at least. Mesoscale events have appeared to extend vertically over some few hundred metres, and the EOF decomposition has shown quasi no rotation of the fluctuations with depth. So, such events should have a relatively simple vertical structure, corresponding mainly to the first baroclinic mode with its zero-crossing at 400-500 m. Currents are relatively well represented by the barotropic and first baroclinic modes, the latter being predominant and more energetic, especially in winter. However, consequently to the variations of the Northern Current in width and depth, our most seaward point (similar to 30 km) is either outside or more or less within this current, so that the dynamic regime is generally more complex there. Nevertheless, the observed mesoscale events become, in deep winter, the barotropic ones of the central zone governed by vigorous convection. The fluctuations have generally shorter time scales in winter than in spring., Due to dramatic winter transformations, the Northern Current is mainly observed to be altered by instability processes, leading to meanders. Indeed, an important finding, based on the standard deviation ellipses and spectral analysis, is that its major fluctuations clearly appear to be quasi transverse within its own core. Moreover, from the polarization of energy, the signature of steep and large mesoscale meanders is clearly evidenced at 10-20 days. These meanders have far greater energy in winter than in spring, when they have slightly shorter periods (similar to 10 days). As previously observed, shorter fluctuations at 3-6 days with smaller amplitudes than those of the meanders at 10-20 days are also associated with a meandering current; they are expected to be intensified from spring-summer to the deep winter. In spring, while the flow is more stable, the predominant fluctuations resemble pulses of the current that may be expected to extend horizontally to a few tens of kilometres. Fundamental to coastal oceanographic problems is the fact that the circulation is actually unforeseeable in the coastal zone of similar to 10 km, where the main mesoscale phenomena have periods slightly shorter than in the core of the current. The major seasonal and mesoscale features of the Northern Current, especially the high flux values maintained during a relatively long winter season, i.e. during the period of dense water formation, its occasional narrowness and shoreward shift, and the extension of the central zone in deep winter, are probably very closely linked. Thus, as a hypothesis for further experimental and theoretical work, we suggest that the winter dense water formation should be effectively one of the major forcings of the circulation in the northern part of the western Mediterranean Sea

The French-Algerian Médiprod V campaign was conducted off the Algerian coasts between 0° and 5° E on hoard the R.V., “Le Suroît” and "Benyahia” .from 27 May to 27 June 1986. The hydrological, chemical and biological data are presented in this report ; current measurements (current-meters and drifting buoys) will be published elsewhere. In a first part are presented some of the data collected by R.V., "Le Suroît", with a CTD an a rosette during 96 stations down to 800 m at about ten variable depths. Other data have been collected with a multiparametric and continuous sampling system (SHET, 64 stations 0-190 M and 400 milles of transect at 45 m ; processing and analysis on hand), and with 0-200 m nets during 125 CTD or SHET stations. In a second part are exposed some of the results already obtained from these data., La campagne franco-algérienne Médiprod V s'est déroulée au large des côtes algériennes entre 0° et 5° E du 27 mai au 27 juin 1986 avec les N.O. "Le Suroît” et "Benyahia”. Elle a permis la collecte d'observations hydrologiques, chimiques et biologiques, présentées dans ce volume, et d'observations courantométriques (mouillages de courantomètres et bouées dérivantes) qui seront présentées par ailleurs. Dans une première partie sont présentées certaines mesures faites par le N.O. “Le Suroît”, avec une CTD et une rosette lors de 96 stations, entre 0 et 800 m à une dizaine d'immersions variables. D'autres données ont été collectées avec un système d'échantillonnage multiparamétrique en continu (SHET, 64 stations entre 0 et 190 m et 400 milles de trajet à environ 45 m de profondeur) dont le traitement et l'analyse sont en cours ; enfin, des traits de filets ont été réalisés entre 0 et 200 m lors de 125 stations CTD ou SHET. Dans une deuxième partie, sont exposés certains des résultats déjà obtenus à partir de ces observations.

Continental shelf dynamics have been observed since 1974 in the Gulf of Lions (NorthWestern Mediterranean Sea), with the principal aim of understanding the sumrner circulation in this region. From satellite infrared data, current meters, thermistor chains, and tidal gauge records, it appears that the major events occurring on the continental shelf take the form of wind-induced mesoscale phenomena. These phenomena, which are connected with strong and transient coastal upwellings, are generated by NorthWesterly winds, the mistral and the tramontane, which are highly transient in speed, with a stable direction and a short lifetime. These specifie features have enabled us to investigate the transient response of the sea on about ten such occasions per typical summer. The present paper clearly shows the importance of the coastline configuration for upwelling generation. Sorne hours after the onset of the wind, actual cool water source-points appear at the surface, along straight coastal segments sorne ten-twenty nautical miles in length. These cool areas then spread out, white warm waters remain in the vicinity of capes and small hays. Fundamental data from satellite observations are combined with in situ measurements to highlight the main features of wind-induced summer circulation. These features comprise high spatial and temporal variabilities of the current and temperature fields, together with complex advective circulations organized like cells around the upwelling areas., (Méditerranée nord-occidentale) dans le but de comprendre la dynamique d'été de cette région. Des vues infrarouge prises par satellite, et des mesures in situ du courant, de la température et de la pression sur le fond montrent que le vent induit des phénomènes d'échelle moyenne de grande amplitude sur le plateau continental. Ces phénomènes sont associés à des upwellings côtiers particulièrement intenses et transitoires. Ils sont engendrés par le mistral et la tramontane, vents de Nord-Ouest caractérisés par une augmentation très rapide de leur vitesse, une direction stable, une durée de vie de quelques jours. Ces particularités permettent d'étudier la réponse transitoire de la mer pendant environ dix cmÎps de vent par été. Cette analyse montre clairement l'importance du dessin de la côte dans la genèse de l'upwelling et le développement particulièrement rapide de ce phénomène. Quelques heures après le début du coup de vent, de véritables points-sources d'eau froide apparaissent à la surface, le long de portions de côte rectilignes sur quelques dizaines de kilomètres. Ces zones froides s'étendent ensuite, pendant que des eaux plus chaudes persistent aux abords des caps et des baies. Les informations fondamentales obtenues par satellite sont confrontées aux observations in situ pour dresser un schéma cohérent de la circulation induite par le vent. Les caractères particuliers de cette dynamique sont une grande variabilité spatiale et tempprelle des champs de courant et de température, et des circulations horizontales complexes organisées en cellules autour des zones d'upwelling.