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Special issue Ten Years of Remote Sensing at Barcelona Expert Center.-- 18 pages, 11 figures, 1 table, 1 appendix .-- Altimetric data was produced by the GlobCurrent Data User Element project and is available through its web site: http://www.globcurrent.org. Infrared images are available through the Insitut de Ciències del Mar (CSIC) at https://coo.icm.csic.es/site-page/satellite-data as well as Sea Surface Salinity Maps, Surface currents in the Alboran Sea are characterized by a very fast evolution that is not well captured by altimetric maps due to sampling limitations. On the contrary, satellite infrared measurements provide high resolution synoptic images of the ocean at high temporal rate, allowing to capture the evolution of the flow. The capability of Surface Quasi-Geostrophic (SQG) dynamics to retrieve surface currents from thermal images was evaluated by comparing resulting velocities with in situ observations provided by surface drifters. A difficulty encountered comes from the lack of information about ocean salinity. We propose to exploit the strong relationship between salinity and temperature to identify water masses with distinctive salinity in satellite images and use this information to correct buoyancy. Once corrected, our results show that the SQG approach can retrieve ocean currents slightly better to that of near-real-time currents derived from altimetry in general, but much better in areas badly sampled by altimeters such as the area to the east of the Strait of Gibraltar. Although this area is far from the geostrophic equilibrium, the results show that the good sampling of infrared radiometers allows at least retrieving the direction of ocean currents in this area. The proposed approach can be used in other areas of the ocean for which water masses with distinctive salinity can be identified from satellite observations, This research was funded by European Space Agency grant number 4000109513/13/I-LG and by Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund grants numbers ESP2015-67549-C3-1-R and CTM2016-79474-R. JIF was funded by Fundación General CSIC through Programa ComFuturo, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Special volume: Planet Ocean. Scientia Marina 80(Suppl.1) 2016.-- 9 pages, 2 figures, 4 tables, [EN] Phytoplankton blooms are events of production and accumulation of phytoplankton biomass that influence ecosystem dynamics and may also have effects on socio-economic activities. Among the biological factors that affect bloom dynamics, prey selection by zooplankton may play an important role. Here we consider the initial state of development of an algal bloom and analyse how a reduced grazing pressure can allow an algal species with a lower intrinsic growth rate than a competitor to become dominant. We use a simple model with two microalgal species and one zooplankton grazer to derive general relationships between phytoplankton growth and zooplankton grazing. These relationships are applied to two common grazing response functions in order to deduce the mathematical constraints that the parameters of these functions must obey to allow the dominance of the lower growth rate competitor. To assess the usefulness of the deduced relationships in a more general framework, the results are applied in the context of a multispecies ecosystem model (ERSEM), [ES] Las proliferaciones de fitoplancton son eventos de producción y acumulación de biomasa de fitoplancton que tienen una fuerte influencia tanto en la dinámica del ecosistema como en actividades socioeconómicas. Entre los factores biológicos que afectan la dinámica de las proliferaciones fitoplanctónicas, la selección de presas por el zooplancton puede jugar un papel importante. En este trabajo consideramos el estado inicial de desarrollo de una proliferación algal considerando que la presión de la predación puede permitir a una especie de algas con una menor tasa de crecimiento intrínseco que un competidor, ser dominante. Utilizamos un modelo sencillo con dos especies de microalgas y un herbívoro (zooplancton) para deducir relaciones generales entre el crecimiento del fitoplancton y la predación. Estas relaciones se aplican a dos funciones de respuesta de predación para deducir las limitaciones matemáticas que los parámetros de estas funciones deben obedecer. Para evaluar la utilidad de las relaciones deducidas en un marco más general, los resultados se aplican a un modelo de múltiples especies del ecosistema marino (ERSEM), We acknowledge the support from the BIOHAB (Biological Control of Harmful Algal Blooms in European Coastal waters) project funded by the European Commission Programme on Environment and Sustainable Development of Marine Ecosystems (ESD, FP-V, Key Action 3) under contract EVK3-CT-1999-00015. JS acknowledges a CSIC JAE-Doc contract co-funded by the FSE

The circulation in the Algerian Basin is characterized by the presence of fresh-core eddies that propagate along the coast or at distances between 100 and 200 km from the coast. Enhancements in the processing of the Soil Moisture and Ocean Salinity (SMOS) data have allowed to produce, for the first time, satellite sea surface salinity (SSS) maps in the Mediterranean Sea that capture the signature of Algerian eddies. SMOS data can be used to track them for long periods of time, especially during winter. SMOS SSS maps are well correlated with in situ measurements although the former has a smaller dynamical range. Despite this limitation, SMOS SSS maps capture the key dynamics of Algerian eddies allowing to retrieve velocities from SSS with the correct sign of vorticity.

Special issue Physical, chemical and biological observations and modelling of oil spills in the Mediterranean Sea.-- 18 pages, 15 figures, 3 tables, An exhaustive validation of some of the operational ocean forecast products available in the Gibraltar Strait and the Alboran Sea is here presented. The skill of two ocean model solutions (derived from the Eulerian ocean forecast systems, such as the regional CMEMS IBI and the high resolution PdE SAMPA) in reproducing the complex surface dynamics in the above areas is evaluated. To this aim, in-situ measurements from the MEDESS-GIB drifter buoy database (comprising the Lagrangian positions, derived velocities and SST values) are used as the observational reference and the temporal coverage for the validation is 3 months (September to December 2014). Two metrics, a Lagrangian separation distance and a skill score, have been applied to evaluate the performance of the modelling systems in reproducing the observed trajectories. Furthermore, the SST validation with in-situ data is carried out by means of validating the model solutions with L3 satellite SST products. The Copernicus regional IBI products are evaluated in an extended domain, beyond the Alboran Sea, and covering western Mediterranean waters. This analysis reveals some strengths of the presented regional solution (i.e. realistic values of the Atlantic Jet in the Strait of Gibraltar area, realistic simulation of the Algerian Current). However, some shortcomings are also identified, with the major one being related to the simulated geographical position and intensity of the Alboran Gyres, particularly the western one. This performance limitation affects the IBI-modelled surface circulation in the entire Alboran Sea. On the other hand, the SAMPA system shows a more accurate model performance and it realistically reproduces the observed surface circulation in the area. The results reflect the effectiveness of the dynamical downscaling performed through the SAMPA system with respect to the regional IBI solution (in which SAMPA is nested), providing an objective measure of the potential added values introduced by the SAMPA downscaling solution in the Alboran Sea, As the MEDESS-GIB experiment the model validation exercise presented here was performed as part of the MEDESS4MS Project activities (Project ref. 2S-MED11-01), supported by the European Regional Development Fund in the framework of the MED Programme. [...] D. Conti is currently receiving a PhD fellowship (FPI/1543/2013) granted by the Conselleria d׳Educació, Cultura i Universitats from the Government of the Balearic Islands co-financed by the European Social Fund (Grant no. FPI/1543/2013)

Special volume: Planet Ocean. Scientia Marina 80(Suppl.1) 2016.-- 18 pages, 22 figures, 1 table, [EN] Since the mid-1980s, physical oceanographers at the Institute of Marine Sciences have been involved in the use of Lagrangian drifters as a complementary technology for their oceanographic research. As Lagrangian observations became more feasible, these researchers continued developing their own drifters in what was to be the seed of current technological activities at the Physical and Technological Oceanography Department. In this paper we overview the work done during the last 30 years with special focus on Lagrangian developments from the initial activities to the latest developments. In addition to basic oceanography research applications, Lagrangian technological developments include prototypes for measuring surface and subsurface ocean properties, for tracking purposes in search and rescue operations and pollution events, and for monitoring ice motion and thickness in the Arctic. The paper emphasizes original and unpublished technical aspects related to the latest development, [ES] Desde mediados de la década de los 80, los oceanógrafos físicos en el Instituto de Ciencias del Mar se involucraron en el uso de boyas Lagrangianas como una tecnología complementaria para su investigación oceanográfica. A medida que las observaciones Lagrangianas se volvieron más factibles, los investigadores continuaron desarrollando sus propios flotadores en lo que se convirtió en la semilla de las actuales actividades tecnológicas llevadas a cabo en el Departamento de Oceanografía Física y Tecnológica. En este artículo se presenta una visión general del trabajo realizado durante los últimos 30 años, con especial énfasis en el uso de flotadores a la deriva y desarrollos propios desde su inicio hasta las aplicaciones más recientes. Además de estudios básicos de investigación oceanográfica, los desarrollos tecnológicos llevados a cabo incluyen prototipos para medir las propiedades superficiales y sub-superficiales, para tareas de seguimiento en operaciones de búsqueda y rescate y eventos de contaminación marina o para monitorizar el grosor de la capa de hielo y su movimiento en el Ártico. En este trabajo se hace hincapié en aspectos técnicos originales e inéditos relacionados con los últimos desarrollos, These include MIDAS-4 (ESP2005-06823-C05-1), MIDAS-5 (ESP2007-65667-C04-1), MIDAS-6 (AYA2010-22062-C05-01), CANOA (CTM2005-00444/MAR), MOC-2 (CTM2008-06438-C02-01), TIC-MOC (CTM2011- 28867), the Malaspina project (CSD2008-00077) and project ACI2009-0977 of the Spanish National Programme of Internationalization of R+D. E. García-Ladona, J. Salvador, P. Fernández and J.A. Jiménez wish to thank the TOSCA (G-MED09-425) and MEDESS-4MS (MED 2S-MED11-01) projects (INTERREG-IV MED programme) for funding many activities related to the ICM-PK1 drifter development; J. A. Jiménez was under contract by both projects. Financial support from the Fundación General CSIC (Programa ComFuturo) is acknowledged

García Sotillo, Marcos ... et al.-- 9 pages, 5 figures, 2 tables, On 9 September 2014, an intensive drifter deployment was carried out in the Strait of Gibraltar. In the frame of the MEDESS-4MS Project (EU MED Program), the MEDESS-GIB experiment consisted of the deployment of 35 satellite tracked drifters, mostly of CODE-type, equipped with temperature sensor sampling at a rate of 30 min. Drifters were distributed along and on both sides of the Strait of Gibraltar. The MEDESS-GIB deployment plan was designed as to ensure quasi-synoptic spatial coverage. To this end, four boats covering an area of about 680NM2 in 6 h were coordinated. As far as these authors know, this experiment is the most important exercise in the area in terms of number of drifters released. Collected satellite-tracked data along drifter trajectories have been quality controlled and processed to build the presented MEDESS-GIB database. This paper reports the MEDESS-GIB data set that comprises drifter trajectories, derived surface currents and in situ SST measurements collected along the buoys tracks. This series of data is available through the PANGAEA (Data Publisher for Earth and Environmental Science) repository, with the following doi:10.1594/PANGAEA.853701. Likewise, the MEDESS-GIB data will be incorporated as part of the Copernicus Marine historical products. The MEDESS-GIB data set provides a complete Lagrangian view of the surface inflow of Atlantic waters through the Strait of Gibraltar and thus, very useful data for further studies on the surface circulation patterns in the Alboran Sea, and their links with one of the most energetic Mediterranean Sea flows: the Algerian Current, The MEDESS-GIB experiment was performed as part of the MEDESS-4MS Project activities (Project ref. 2S-MED11-01), supported by the European Regional Development Fund in the framework of the MED Programme. D. Conti is currently a PhD fellowship (FPI/1543/2013) granted by the Conselleria d’Educació, Cultura i Universitats from the Government of the Balearic Islands co-financed by the European Social Fund. J. M. Sayol is thankful for the financial support of CSIC and FSE with the JAE-pre PhD scholarship program

In this work we report short-term measurements of the thermohaline structure and velocity field inside a narrow submarine canyon by means of a yo-yo–like profiler. An Aqualog profiler was deployed inside the Besòs Canyon in the northwestern Mediterranean continental margin, providing a unique data set on the vertical evolution of water column characteristics with unprecedented fine-scale spatial and temporal resolution. The observations reported here show a very dynamic transient short-term response with a complex vertical structure not observed previously in any submarine canyon of this region. The vertical distribution of water masses was characteristic of the western Mediterranean basin with Atlantic waters (AW) at the surface, Western Intermediate waters (WIW) in the middle and Levantine Intermediate (LIW) waters below. Turner angle and empirical orthogonal functions show that double-diffusive and isopycnal mixing are the main dominant processes at small scales. The interfaces of the three layers exhibit highly vertical excursions in relatively short times. At the surface, deepening of AW was observed, associated with flow intensification events. Deeper in the water column, within the submarine canyon confinement, the WIW-LIW interface uplifts about 100-150 m. These motions are associated with relatively up- and down-canyon–enhanced current events (up to 15-20 cm s-1 at 500 and 800 m depths) along the canyon axis. The time scales of the vertical variability were concentrated in a broad band around the semi-diurnal and local inertial frequencies within the WIW and LIW layers. En este trabajo se muestran medidas a corto plazo de la estructura termohalina y del campo de velocidad dentro de un estrecho cañón submarino a través de un perfilador tipo yo-yo. Este perfilador Aqualog se desplegó dentro del cañón del Besòs en el noroeste del margen continental del Mediterráneo, proporcionando un conjunto de datos único sobre la evolución vertical de las características de la columna de agua, con una resolución espacial y temporal a escala fina sin precedentes. Las observaciones aportadas aquí muestran una respuesta de un periodo transitorio muy dinámico con una estructura vertical compleja no observada anteriormente en ningún cañón submarino de esta región. La distribución vertical de las masas de agua es característica de la cuenca mediterránea occidental con aguas del Atlántico (AW) en la superficie, aguas occidentales Intermedias (WIW) debajo de estas y aguas de Levante Intermedio (LIW) por debajo. Los ángulos de Turner calculados y sus EOFs muestran que la estabilidad a la difusión y mezcla isopicna son los principales procesos dominantes a escalas pequeñas. Las interfaces de las tres capas exhiben excursiones notablemente verticales en tiempos relativamente cortos. En la superficie, la profundización de AW se observó asociada a eventos de intensificación del flujo. A más profundidad en la columna de agua, dentro del régimen de cañón submarino, la interfase WIW-LIW se eleva unos 100-150 m. Tales movimientos se asocian al flujo de agua hacia arriba y hacia abajo del cañón (hasta 15-20 cm s-1 a 500 y 800 m de profundidad) a lo largo del eje del cañón. Las escalas de tiempo de variabilidad vertical aparecen concentradas en una amplia banda de frecuencias alrededor de los periodos inerciales semidiurnos y locales dentro de las capas WIW y LIW.

14 pages, 9 figures, Nowadays Earth observation satellites provide information about many relevant variables of the ocean-climate system, such as temperature, moisture, aerosols, etc. However, to retrieve the velocity field, which is the most relevant dynamical variable, is still a technological challenge, specially in the case of oceans. New processing techniques, emerged from the theory of turbulent flows, have come to assist us in this task. In this paper, we show that multifractal techniques applied to new Sea Surface Temperature satellite products opens the way to build maps of ocean currents with unprecedented accuracy. With the application of singularity analysis, we show that global ocean circulation patterns can be retrieved in a daily basis. We compare these results with high-quality altimetry-derived geostrophic velocities, finding a quite good correspondence of the observed patterns both qualitatively and quantitatively; and this is done for the first time on a global basis, even for less active areas. The implications of this findings from the perspective both of theory and of operational applications are discussed, This is a contribution to the EU MERSEA project (AIP3-CT-2003-502885) and to the Spanish projects OCEANTECH (PIF 2006 project) and MIDAS-4 (ESP2005-06823-C05-1)

15 pages, 9 figures, 1 table.-- Issue title: "Earth Observations for Terrestrial Biodiversity and Ecosystems", In the recent years, the power of employing singularity analysis of scalar variables to perform pattern recognition in complex images has been evidenced. This approach is particularly useful when the image under study corresponds to a scalar variable submitted to a turbulent flow because, in that case, the arrangement of singularity manifolds corresponds to the multifractal hierarchy from the underlying turbulent flow. In this paper we will show how this intimate connection between Image Processing and Physics, when applied to Microwave Sea Surface Temperature images, allows to uncover global circulation patterns in the ocean at a daily basis with the resolution of 1/4 of degree. Using this technique, details not evidenced in the non-processed image are revealed. The emerging patterns provide a description of the global oceanic currents much richer than the usual global circulation scheme; in particular, instabilities, eddy generation and filamentation are distinctly identified. A pattern extraction of this kind is useful in order to measure and track mesoscale oceanic phenomena, opening the way to many operational and reanalysis applications, A. Turiel and J. Ballabrera-Poy are supported by Ramón y Cajal contracts from the Spanish Ministry of Education and Science. J. Solé is supported by a post-doc grant funded by EU Streps Project SEEDS. This is a contribution to CSIC OCEANTECH project (PIF2006), to the Spanish projects ESEOO (VEM2003-20577-C14-10) and MIDAS-4 (ESP2005-06823-C05-1), and to the European MERSEA project (EU AIP3-CT-2003-502885)

Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE-SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow. In the canyon, suspended sediment concentration, downward particle fluxes, chlorophyll and particulate C and N were significantly higher up-canyon from about 1200 m depth than offshore, defining, along with the different hydrodynamics, two canyon domains: one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf-slope front. The higher near-bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows. During the deployment period, the increase in downward particle fluxes occurred by mid-November, when a severe storm took place. On the canyon walls at 1200 m depth, suspended sediment concentrations, downward particle fluxes, chlorophyll and particulate C and N were higher on the southern wall than on the northern wall inversely to the current's energy. This could be caused by an upward water supply on the southern canyon wall and/or the mean flow interacting with the canyon bathymetry. In the swimmers collected by the sediment traps, the dominant species was an elasipod holothurian, which has not been recorded in other canyons or elsewhere in the Mediterranean, indicating particular speciation. © 2005 Elsevier Ltd. All rights reserved.

Deep slope currents and particulate matter concentrations were studied on the Barcelona continental margin in and around the Foix submarine canyon from May 1993 to April 1994. This year-long moored experiment revealed that near-bottom slope currents are strongly influenced by the bottom topography, being oriented along isobaths and along the canyon axis. The deep slope current fluctuations are controlled by the local inertial motion (18.3 h) and also by low-frequency oscillations at periods of 6–10 days, related to the passage of atmospheric pressure cells. Particulate matter concentrations recorded during the experiment do not show a clear seasonal variability, except outside the canyon, where significant peaks of particulate matter concentrations were recorded only during the winter-fall deployment. In addition, the temporal evolution of suspended particulate matter concentration is not linked to changes in the cross-slope or along-slope current components and did not show a clear relationship with river avenues or wave storm events. This suggests that suspended particulate matter exported from the shelf is dispersed on the slope by advective processes, which attenuate the signal of the shelf-slope sediment transfer. Mean particulate matter concentrations differed among sampling sites, but the magnitude of the mean horizontal suspended particle flux reflects a quite similar value in the whole study area, ranging from 2.53 to 4.05 mg m −2 s −1 . These horizontal suspended particle fluxes are 27 (canyon head) to 360 (open slope) times higher than the settling particle fluxes measured at the same sampling sites, indicating that the suspended particulate transport on the Barcelona continental slope dominates over the settling particle fluxes, even inside the Foix submarine canyon.

Transport and mixing properties of surface currents can be detected from altimetric data by both Eulerian and Lagrangian diagnostics. In contrast with Eulerian diagnostics, Lagrangian tools like the local Lyapunov exponents have the advantage of exploiting both spatial and temporal variability of the velocity field and are in principle able to unveil subgrid filaments generated by chaotic stirring. However, one may wonder whether this theoretical advantage is of practical interest in real-data, mesoscale and sub-mesoscale analysis, because of the uncertainties and resolution of altimetric products, and the non-passive nature of biogeochemical tracers. Here we compare the ability of standard Eulerian diagnostics and the finite-size Lyapunov exponent in detecting instantaneous and climatological transport and mixing properties in the south-western Mediterranean. By comparing with sea-surface temperature patterns, we find that the two approaches provide similar results for slowly evolving eddies like the first Alboran gyre. However, the Lyapunov exponent is also able to predict the (sub-)mesoscale filamentary processes occurring along the Algerian current and above the Balearic Abyssal Plain. Such filaments are also observed, with some mismatch, in sea-surface temperature patterns. Climatologies of Lyapunov exponents do not show any compact relation with other Eulerian diagnostics, unveiling a different structure even at the basin scale. We conclude that filamentation dynamics can be detected by reprocessing available altimetric data with Lagrangian tools, giving insight into (sub-)mesoscale stirring processes relevant to tracer observations and complementing traditional Eulerian diagnostics. (C) 2008 Elsevier Ltd. All rights reserved.

[1] Oceans and 2D turbulence present similar characteristics, as for instance the dominant role played by eddies in energy and matter transport. However, providing a complete justification of this analogy is difficult, as it requires knowledge of the ocean's dynamic state at different instants and over large scales. Recently, new techniques coming from the Microcanonical Multifractal Formalism have made it possible to infer the streamlines from the analysis of satellite images of some scalar variables. In this paper, we will show that this information is enough to characterize the scaling properties of the energy cascade, which is manifested as a multifractal signature; further, the multifractal signature is obtained at each location in a local basis. Different scalars obtained from satellite measurements such as Sea Surface Temperature or Surface Chlorophyll Concentration present essentially the same multifractal structure, which is interpreted as a consequence of the pervading character of the turbulent advection at the scales of observation.

10 pages, 4 figures We demonstrate the potential of monitoring coherent wave fronts on the tropical ocean surface using an advanced detection algorithm applied to visible sunglint-affected imagery from geostationary satellites. Data from MeteoSat are processed with the advanced analysis technique to reveal transient wave activity near and to the west of the Mascarene Ridge of the western Indian Ocean. The technique is based on a wavelet-based singularity analysis which enhances the subtle but highly coherent wave patterns in the meteorological satellite data. It is likely that the patterns represent internal ocean waves, a pathway to ocean mixing and climate. The prospect for using this detection algorithm in greatly expanded satellite global surveys of wave activity is outlined This is a contribution to the IMAGEN (Spanish R+D Plan: REN2001-0802-C02-02) and MERSEA projects (EU AIP3-CT-2003-502885). A. Turiel is funded by a Ramón y Cajal contract from the Spanish Ministry of Education. J. Isern-Fontanet is funded by a post-doctoral grant by the Spanish Ministry of Education. J. Young’s visit to ICM was provided by a sabbatical and Graduate School WARF funding from the University of Wisconsin-Madison. We thank EUMETSAT for leaving us their data

18 pages, 11 figures, supporting information http://onlinelibrary.wiley.com/doi/10.1029/2006JC003878/suppinfo, In this paper we investigate the validity of the multifractal formalism to study sea surface temperature (SST). It is shown that SST patterns observed in moderate resolution SST images have anomalous scaling properties characteristic of a multifractal structure. The most probable origin of the observed structures is the turbulent character of the oceanic flow as they evolve slowly and are very persistent in times compatible with ocean mesoscale dynamics (several days). The spectrum of singularity exponents indicates that the dynamics of the processes leading to the geometrical arrangement of the SST patterns is quite general over the available range of scales. As a consequence, multifractal techniques can be used to extract properties of the underlying flow. In particular, the geometry of the SST multifractal components is closely linked with the ocean flow, which allows to build a reasonable guess of the streamfunction (defined as the maximum singular streamfunction (MSS)) from a single SST image. Thus the ocean surface velocity field can be easily inferred, with some limitations. As multifractal analysis is in essence a geometrical approach, the method is able to retrieve a high resolution velocity field, well localized in space, but with some indetermination on the modulus and sense of velocity vectors. To solve this, a general framework for the integration of extra information is proposed, what is illustrated with an example merging MSS with altimetric data, This is a contribution to the EU MERSEA project (AIP3-CT-2003-502885) and to the Spanish projects ESEOO (VEM2003-20577-C14-10) and MIDAS-4 (ESP2005-06823-C05-1). A. Turiel is funded by a Ramón y Cajal fellowship from the Spanish Ministry of Education. The AVHRR Oceans Pathfinder SST data were obtained from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the NASA Jet Propulsion Laboratory, Pasadena, California. The altimeter products were produced by the CLS Space Oceanography Division as part of the Environment and Climate EU ENACT project (EVK2-CT2001-00117) and with support from CNES

12 pages, 8 figures, The Balearic Basin is defined as a wide region of the western Mediterranean located in between the Liguro-Provençal and Algerian basins. The dynamics of the Liguro-Provençal Basin, in the north, is dominated by the dense water formation process associated with a permanent circulation along the continental slope: the Northern Current. The Algerian Basin, in the south, is dominated by intense mesoscale eddies and their interactions with the unstable Algerian Current. The Balearic Basin is a transition region between these two different dynamic regimes. It includes the Catalan Sea, located between the Balearic Islands and the Iberian peninsula, and the wide Gulf of Valencia in the south of this sea. Some new ideas about the surface circulation variability have been inferred from a series of NOAA satellite advanced very high resolution radiometer images, taken mainly from the autumn-winter period during 1981–1988, and also from various in situ data. The Northern Current, which flows southward along the Iberian peninsula slope, is covered in summer by a warm surface layer spreading over the whole Catalan Sea. This local warming creates one of the most intense thermal fronts in the western Mediterranean, the Pyrenees Front. Near the Balearic Islands, the flow through the sills of recent Atlantic water, partially deflected by anticyclonic eddies from the Algerian Current, creates the Balearic Front and contributes to its mesoscale variability. This variability appears to be much more intense than previously described. The Balearic Front is clearly recognized as the westward continuation of the North Balearic Front, already defined in the open sea as the northern limit of the recent Atlantic water reservoir. Finally, the Gulf of Valencia is frequently influenced by water entering from the Algerian Basin, which appears to be important in the disruption of the Northern Current and the formation of the Balearic Current, the geostrophic flow associated with the Balearic Front