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This work is a contribution to CSIC PTI Teledetect.-- 23 pages, 11 figures.-- Data Availability Statement: HYCOM reanalysis outputs (GLBu0.08/expt_19.1) analyzed in this study can be found at hycom.org/data/glbu0pt08/expt-19pt1, Satellite altimeters provide quasi-global measurements of sea surface height, and from those the vertically integrated geostrophic velocity can be directly estimated, but not its vertical structure. This study discusses whether the mesoscale (30–400 km) dynamics of three regions in the South Atlantic can be described by the surface quasi-geostrophic (SQG) theory, both at the surface and in depth, using outputs from an ocean general circulation model. At these scales, the model surface eddy kinetic energy (EKE) spectra show slopes close to k−5/3 (k−3) in winter (summer), characterizing the SQG and quasi-geostrophic (QG) turbulence regimes. We use surface density and temperature to (a) reconstruct the stream function under the SQG theory, (b) assess its capability of reproducing mesoscale motions, and (c) identify the main parameters that improve such reconstruction. For mixed layers shallower than 100 m, the changes in the mixed-layer depth contributes nine times more to the surface SQG reconstruction than the EKE, indicating the strong connection between the quality of the reconstruction and the seasonality of the mixed layer. To further explore the reconstruction vertical extension, we add the barotropic and first baroclinic QG modes to the surface solution. The SQG solutions reproduce the model density and geostrophic velocities in winter, whereas in summer, the interior QG modes prevail. Together, these solutions can improve surface correlations (>0.98) and can depict spatial patterns of mesoscale structures in both the horizontal and vertical domains. Improved spatial resolution from upcoming altimeter missions poses a motivating scenario to extend our findings into future observational studies, We would like to acknowledge the financial support of Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq (130215/2018-0) and Fundação de Amparo à Pesquisa do Estado de São Paulo—FAPESP (2019/02968-9, 2019/13830-8, and 2017/09659-6). This work was supported in part by the Spanish R&D project L-BAND (ESP2017-89463-C3-1-R), which is funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe,” and project INTERACT (PID2020-114623RB-C31), which is funded by MCIN/AEI/10.13039/501100011033. We also acknowledge the financial support from the Spanish government through the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S). [...] This work supports the SWOT-Brésil project, in preparation for the future SWOT wide-swath altimetry mission. SWOT-Brésil project is financed by CNES/INSU via the French TOSCA programme

24 pages, 10 figures, 3 tables, Sea surface currents probably are the most relevant essential ocean variable affecting diverse societal challenges concerning the marine environmental (as, for example, safe and efficient navigation, marine pollution and ecological connectivity). This work introduces a climatological Atlas (monthly resolution) of currents in the Mediterranean and Canary–Iberian–Biscay basins, based on today's state of the art reanalyses of the ocean circulation. The focus is on surface and subsurface reanalyses (here understood as z∼0.5 and z∼15 m, respectively) provided by the Copernicus Marine Environment Monitoring Service (CMEMS). The climatological values are computed from the median of the empirical probability density functions and the Atlas also includes the variance matrix and a bimodality index to have quantitative information on their variability. For both domains, the subsurface climatological fields are reasonably consistent with circulation schemes proposed in the previous literature but clearly improving the time and space resolution of the emerging patterns. For the Canary–Iberian–Biscay domain, the monthly climatological surface currents capture accurately the characteristic seasonal signal and its transition between a favourable and non-favourable upwelling regime. In the Mediterranean basin, differences between the near-surface and the 15 m velocity fields suggest a non-negligible role of winds over the variability of the uppermost ocean layer, specially in the Eastern Mediterranean basin. This is, up to our knowledge, the first time that such near-surface climatological patterns are computed. It has been found that, in general, the resulting patterns agree with surface drifter trajectories. In several regions, interannual variability foster bimodal and multimodal probability distributions. The Atlas has been conceived with the purpose of providing a first quantitative assessment on the surface circulation, thus being a complementary tool of real-time ocean forecasting systems. The Atlas is distributed following the FAIR principles and is accompanied with a digital version, with enhanced visualization capabilities for both research and assessment, This is a contribution made with support of COSMO project funded by the Spanish Ministry of Economy, Industry and Competitiveness (Code: CTM2016-79474-R) and MEDOSMOSIS (Code: 6MED20_4.1_SP_005) funded by the INTERREG-MED program. S. González-Motos was under contract of COSMO project. The support of MEDOSMOSIS has been crucial to extend the work to the whole Mediterranean basin., The authors would like to thank the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

25 pages, 18 figures, 3 tables, 1 appendix, The encountering of the subtropical Brazil Current (BC) and the subantarctic Malvinas Current (MC) along the western margin of the Argentine Basin forms the Brazil-Malvinas Confluence (BMC), one of the most intense open-ocean fronts in the world ocean and a site for the formation of intermediate water masses. Here, we provide a comprehensive description of the BMC based on physical and biogeochemical data – hydrographic stations, profiling floats and subsurface drifters – gathered in March 2015. We use these data in order to characterize the impinging and outflowing currents and to describe the cross- and along-frontal thermohaline structure. In addition, we compare the in-situ measurements with both climatological data and the Mercator Ocean eddy-resolving reanalysis. The hydrographic sections illustrate the contrasting properties between the two western boundary currents: warm, salty, nutrient- and oxygen-poor oligotrophic subtropical waters carried southward by the BC and the cold, fresh, oxygen- and nutrient-rich subantarctic waters carried northward by the MC. The frontal system is also characterized by the presence of thermohaline intrusions, with the cross-frontal gradients and along-front velocities sharpening as the colliding currents shape the frontal system. We also observe brackish waters spreading on top of the frontal jet as a result of both the confluence dynamics and off-shelf advection favored by north-easterly winds. These low-salinity waters are positively correlated with surface ageostrophic speeds over the frontal jet. The cruise data illustrates the high regional and mesoscale variability as compared with climatological conditions, and further document the submesoscale subsurface complexity, which is not properly captured by available operational models, We acknowledge support from the Spanish Government through grants CTM2011-28867 (TIC-MOC project), CTM2014-56987-P (VA-DE-RETRO project) and RTI2018-100844-B-C33 (SAGA project), and through the funding of PhD scholarships for D.O.E. (FPU2013-02884), C.H. (CSIC JAE-Predoc program), S.R.G. (BES-2012-055970) and I.V.C. (BES-2015-071314). We also recognize the institutional support of the Spanish Government through the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S)

15 pages, 9 figures, 1 appendix, The multifractal theory of turbulence is used to investigate the energy cascade in the northwestern Atlantic Ocean. The statistics of singularity exponents of horizontal velocity gradients computed from in situ measurements at 2-km resolution are used to characterize the anomalous scaling of the velocity structure functions at depths between 50 and 500 m. Here, we show that the degree of anomalous scaling can be quantified using singularity exponents. Observations reveal, on one side, that the anomalous scaling has a linear dependence on the exponent characterizing the strongest velocity gradient and, on the other side, that the slope of this linear dependence decreases with depth. Since the observed distribution of exponents is asymmetric about the mode at all depths, we use an infinitely divisible asymmetric model of the energy cascade, the log–Poisson model, to derive the functional dependence of the anomalous scaling with the exponent of the strongest velocity gradient, as well as the dependence with dissipation. Using this model we can interpret the vertical change of the linear slope between the anomalous scaling and the exponents of the strongest velocity gradients as a change in the energy cascade. This interpretation assumes the validity of the multifractal theory of turbulence, which has been assessed in previous studies, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

16 pages, 12 figures, 2 tables, Knowledge of ocean surface current at high resolutions is crucial for many applications. In addition to the classic satellite altimetry retrieval from sea surface height (SSH), ocean surface currents can be retrieved from sea surface temperature (SST) observations using a transfer function between SST and SSH. Previous works showed the potential of microwave SST observations to reconstruct ocean surface currents using a synergistic approach: an optimal transfer function that combines the phase of SST with the SSH amplitude spectra. This synergistic approach revealed that surface quasi geostrophy (SQG) reconstruction can be enhanced and opened up the possibility to improve spatial resolution of ocean currents retrieved from altimeters observations if infrared SST observations are considered. However, before applying this synergistic approach to satellite observations, we need to analyze and characterize the spectral properties of the transfer function. This spectral characterization of the transfer function allows to exploit the synergy between SST and SSH observations that have different measurement topology and different spatial resolution. Here, we performed a feasibility study using the daily outputs of the operational Mercator global analysis and forecast system at (1/12)° in the western coast of Australia (27–35°S, 107–113°E) spanning from 26 November 2012 to 26 November 2016. Results showed that the mean transfer function in this region presents two well different bands: one characterized by a negative slope slightly steeper (α = −1.2) than the k−1 predicted by the SQG solution for scales smaller than 270 km and another characterized by a plateau for wavelengths larger than 270 km. In addition, the results revealed that the inhomogeneity in dynamics of the flow limits global solutions. Finally, we showed that information contained along the track is enough for a synoptic reconstruction of the flow in this region, which shows the feasibility of applying this methodology to real satellite observations, This work was mainly supported by the ESA Scientific Exploitation of Operational Missions (SEOM) Living Planet Fellowship OCEANUS. This work was also partially supported by public funds (Ministère de l'Education Nationale, de l'Enseignement Supérieur et de la Recherche, FEDER, Région Bretagne, Conseil Général du Finistère, Brest Métropole) and by Institut Mines Télécom, received in the framework of the VIGISAT project managed by “Groupement Bretagne Télédétection” (BreTel). J. I. F. acknowledges the support by the European Space Agency through the GlobCurrent Data User Element project (4000109513/13/I‐LG), by the Convocatoria Programa Estatal de I+D+i Orientada a los Retos de la Sociedad del año 2016 in the framework of COSMO project (CTM2016‐79474‐R) and from Fundación General CSIC (Programa ComFuturo). This study has been conducted using E.U. Copernicus Marine Service Information (Product identifier: GLOBAL_ANALYSIS_FORECAST_PHY_001_024), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Orúe-Echevarría, Dorleta ... et al.-- 10 pages, 7 figures,4 tables, supplementary material https://doi.org/10.1016/j.dib.2018.12.004, This oceanographic dataset was gathered during the TIC-MOC cruise, which was designed to characterize the dynamics of the Brazil-Malvinas Confluence. The cruise was carried on board the R/V Hespérides, with departure from Ushuaia and arrival to Salvador de Bahía. A total of 66 conductivity-temperature-depth (CTD) stations were completed between 8 and 22 March 2015, offshore from the continental platform and within 45°S-35°S and 61°W-50°W. At each station, water samples were collected, which were used to calibrate the CTD salinity-oxygen sensors and to determine inorganic nutrient concentrations, and the horizontal current was measured. Along its track, the vessel recorded surface temperature and salinity, as well as the horizontal flow down to about 700 m. Lastly, eight position-transmitting drifters were launched and two profiling floats were deployed and later recovered, This research has been supported by the Spanish Government, through projects TIC-MOC (CTM2011-28867) and VA-DE-RETRO (CTM2014-56987-P) and through the funding of PhD scholarships for D.O.E. (FPU2013–02884), S.R.G. (BES-2012–055970) and C.H. (CSIC JAE-Predoc program)

Blooms of the benthic dinoflagellate Ostreopsis have been related to sporadic acute respiratory symptoms and general malaise in people exposed to marine aerosols on some Mediterranean beaches. However, the direct link between recurrent Ostreopsis blooms and health problems has not been clearly established. In order to establish and elucidate the connection, we conducted a joint ecology and epidemiology study in an Ostreopsis hot spot. Throughout the bloom, which extended from the end of June until the end of October 2013, 81% of the human cohort that we studied experienced at least one Ostreopsis -related symptom. Paradoxically, the time when the effects were greatest was during a short time window in early August. This corresponded to the transition from the exponential growth to the stationary phase of the bloom. Negligible symptoms were reported from August to mid-October, during the stationary period of the proliferation, when O . cf. ovata maintained high concentrations of epiphytic cells. No clear patterns in the landward wind component were noted during the time when health effects were greatest. Our main hypothesis is that the irritants present in the aerosol are produced during a particular physiological phase of the Ostreopsis cells during the bloom.

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.

Ocean currents play a key role in Earth’s climate, they are of major importance for navigation and human activities at sea, and impact almost all processes that take place in the ocean. Nevertheless, their observation and forecasting are still difficult. First, direct measurements of ocean currents are difficult to obtain synoptically at global scale. Consequently, it has been necessary to use Sea Surface Height and Sea Surface Temperature measurements and refer to dynamical frameworks to derive the velocity field. Second, the assimilation of the velocity field into numerical models of ocean circulation is difficult mainly due to lack of data. Recent experiments assimilating coastal-based radar data have shown that ocean currents will contribute to increase the forecast skill of surface currents, but require to be applied in multi-data assimilation approaches to allow better identification of the thermohaline structure of the ocean. In this paper we review the current knowledge on these fields and provide global and systematic view on the technologies to retrieve ocean velocities in the upper ocean and the available approaches to assimilate this information into ocean model.

Ocean currents are a key component to understanding many oceanic and climatic phenomena and knowledge of them is crucial for both navigation and operational applications. Currently, they are derived from Sea Surface Height (SSH) measurements provided by altimeters. However, distances between tracks and the limited number of available altimeters lead to errors in the accurate location of oceanic currents. In this study, we investigate the capability of Sea Surface Temperature (SST) observations to reconstruct surface currents at a global scale. The methodology we use consists of estimating the stream function by taking the phase from SST and the spectrum of SSH and then comparing it with altimetric measurements. Results reveal that SST provided by microwave radiometers can be used to retrieve ocean currents during winter near the major extratropical current systems, which are characterized by an intense mesoscale activity and the presence of strong thermal gradients. We have also found that surface ocean current reconstruction based on Surface Quasi-Geostrophic approach can be improved if the information about the energy spectrum provided by altimeters is used. This points to the development of a new method of reconstructing ocean currents based on the combination of the phase of SST images with the energy spectrum derived from along-track altimetric measurements.

The real transfer function and the phase shift between sea surface height (SSH) and sea surface buoyancy (SSB) were estimated from the output of a realistic eddy-resolving model of the Mediterranean Sea circulation. The analysis of their temporal evolution unveiled the existence of a clear seasonal cycle closely related to that of the mixed layer depth. The phase shifts between SSH and SSB attain their minimum for deep mixed layers, which is different from zero. Besides, the spectral slope of the transfer function at scales shorter than 100 km fluctuates between k−1 and k−2. For deep mixed layers, it is close to k−1, as predicted by the surface quasigeostrophic (SQG) solution. At longer wavelengths, it is approximately constant under the different environmental conditions in all of the subbasins analyzed with the exception of the Gulf of Lions. The capability to observe sea surface temperature (SST) from satellites motivated the extension of this analysis to SST and SSH. Results showed a similar qualitative behavior but with larger phase shifts. In spite of the presence of a phase shift, even for deep mixed layers, results revealed that it is still possible to reconstruct surface dynamics from SST using a transfer function, provided that the mixed layer is deep enough. For the present study, a threshold value of 70 m was enough to identify the appropriate environmental conditions. In addition, the results revealed that a precise estimation of the transfer function significantly improves the reconstruction of the flow in comparison with the application of the classical SQG solution.

International audience; The potentiality of retrieving high spatial resolution velocity fields by exploiting the synergy between nearly simultaneous observations of infrared SST and along-track altimetry is shown here through a case study in the Gulf Stream region. The presented approach relies on the characterization of a transfer function between the SST observations and the streamfunction of the flow and allows to improve the spatial resolution and the effective scales of the retrieved velocity field.

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

16 pages, 9 figures, A realistic 4-year dataset of the surface velocity field of the western Mediterranean Sea obtained with the Mediterranean Forecasting System and the GFDL-MOM model was used to obtain the finite-scale Lyapunov exponents (FSLE) and finite-size diffusion coefficients. Dispersive properties and Lagrangian parameters in four sub-basins are discussed, and a comparison is made between the FSLE and the Eulerian Okubo–Weiss parameter obtained for the same area with the same dataset. An additional comparison is made with the FSLE calculated from independent datasets obtained from 15 drifters launched in the Algerian basin during October of 1996, This work is a contribution to the IMAGEN project (REN-2001-0802-C02-02). Numerical simulations were done within the MFSTEP project (EVK3-CT-2002-00075)

12 pages, 9 figures, Velocity probability density functions (PDFs) are a key tool to study complex flows and are of great importance to model particle dispersion. The PDFs of geostrophic velocities derived from sea level anomalies maps for the Mediterranean Sea have been computed and analyzed, guided by recent results found in studies of two-dimensional and geostrophic turbulence. At the basin scale results show that the geostrophic velocity PDF derived from SLA maps is non-Gaussian. To understand the origin of this non-Gaussianity, a topological partition of the flow based on the Okubo–Weiss parameter is applied to separate the contribution of coherent vortices from the background field. After such separation the non-Gaussian part of the PDF appears mostly associated with the presence of such structures. Only about 20% of the vortices identified in the dataset are mainly responsible for this deviation. These vortices, called intense vortices in previous works, are those vortices with values of the amplitude larger than or equal to two standard deviations of the Okubo–Weiss parameter and correspond to vortices with a radius on the order of 40 km, This is a contribution to the IMAGEN project funded by the Spanish R D Plan (REN2001-0802-C02-02) and MERSEA project funded by the European Union (AIP3-CT-2003-502885). Altimetric maps for the period analyzed were elaborated upon and provided by CLS (Toulouse, France) under contract to the MATER project funded by the European Commission (MAS3-CT96-0051)

17 pages, 12 figures, 2 tables, The presence of coherent vortices makes observed mesoscale fields of the ocean resemble two-dimensional turbulence. Using this analogy, a common definition of a coherent structure has been used to study the statistical properties of Mediterranean Sea vortices observed by satellite altimeters over a 7-yr period. A vortex has been defined as the simply connected region with values of the Okubo–Weiss parameter W < −0.2σW, where σW is the spatial standard deviation of W, and the same sign of vorticity. This definition is shown to be appropriate to detect and characterize, statistically, properties such as size, mean kinetic energy, and amplitude of vortices in the Mediterranean basin from sea level anomaly maps corresponding to the period from October 1992 to October 1999. The distribution of such properties for the Mediterranean vortices suggests a heuristic criterion to extract and select very coherent and long-lived vortices from the whole set of structures identified in altimetric maps. Such coherent vortices appear to be selected for amplitudes greater than 2σW, where the amplitude has been defined in terms of the Okubo–Weiss parameter rather than vorticity, and strongly correspond to those reported from observations with independent data. Systematic locating and tracking of such vortices provide, for the first time, a general picture of their preferential paths in the Mediterranean basin, which are characterized by complex but rather well defined patterns, This is a contribution to the IMAGEN project funded by the Spanish R+D Plan (REN2001-0802-C02-02) and MERSEA project funded by the European Union 6th Framework Program (AIP3-CT-2003-502885). Jordi Isern-Fontanet has been partially supported by contracts from IMAGEN and MERSEA projects. Altimetric maps for the period analyzed were elaborated and provided by CLS (Toulouse, France) under contract of the MATER project funded by the European Union MAST Program (MAS3-CT96-0051)

A procedure is presented to detect eddy cores from sea level anomaly (SLA) maps obtained from altimetric measurements. The method is based on finding the sign of Q, which is an invariant of the velocity gradient tensor (=u). This parameter, commonly used in studies of two-dimensional turbulence, measures the relative contribution of deformation and vorticity. Vortex cores are associated with regions with large and positive values of Q. It is shown that this parameter is adequate to detect marine eddies in altimetric maps and, when the geometry of streamline contours in SLA maps is unclear, the Q . 0 criterion appears to work more consistently. The performance of the methodology is applied, as an example, to altimetric maps of the Algerian Basin in the Western Mediterranean Sea, where two long-lived eddies are tracked. The observed trajectories are in good agreement with Advanced Very High Resolution Radiometer (AVHRR) images.

17 pages, 12 figures, 3 tables, The phytoplankton bloom in the Liguro-Provençal deep convection region represents one of the main fertilization mechanisms in the Mediterranean. This communication examines nano- and microphytoplankton observations, and measurements of primary production and chlorophyll a concentration (Chl a) in the southwestern part of the deep convection region, where such information is scarce. Data were obtained from four cruises, carried out in 2005 (EFLUBIO project) and 2009 (FAMOSO project), covering the seasonality between mid-March and September in the region. Our aims were to constrain primary production estimates and to ascertain the importance of short-term variability on the photosynthetic response of phytoplankton assemblages during bloom, post-bloom and late-summer stratification periods in the area. Overall, the initial slope of the P-E relationship (αB) increased and the Chl a-normalized photosynthetic rate (PmB) decreased with increasing optical depth of sample origin, but there were exceptions. In general, there were marked seasonal trends, with stratification increasing and Chl a concentration, primary production and dissolved inorganic nitrogen and phosphate fluxes decreasing from winter to late summer. Chl a at 5m depth reached a maximum of 7mgm-3 on 25 March 2005, one of the highest values measured in the region. Average surface values (±SD) ranged from respectively 2.4±2.3mgm-3 and 2±0.7mgm-3 in the March 2005 and March 2009 cruises to 0.12±0.01mgm-3 in the September 2009 cruise. Vertically integrated (0-80m) primary production (PPint) attained 1800mgCm-2d-1 in March 2009, with an average of 1024±523mgCm-2d-1, and decreased to a mean of 141±0.43mgCm-2d-1 in September 2009. Superimposed to the seasonal trends, there was a considerable within-cruise variability of biomass and primary production, especially during the spring-winter bloom and post-bloom periods, when PPint could change more than threefold within a few days. These differences were mainly associated with the intense hydrographic mesoscale and sub-mesoscale heterogeneity in the region and with the differences in the physiological and ecological history of the phytoplankton communities inhabiting the different water bodies. In late summer, most PPint variability could be explained by fluctuations in surface incident irradiance. © 2014 Elsevier Ltd., This work was supported by the Spanish Projects EFLUBIOREN2002-04151-C02, FAMOSO (CTM2008-06261-C03) and TURBIMOC (CTM2009-06712-E/MAR), and partially by the Grup de Recerca of the (2009 SGR 588). B.F.-C. holds a FPU fellowship of the Spanish Government

11 pages, 17 figures, The repeated observation of the same signatures of mesoscale and submesoscale features in different ocean variables indicates that some common, non-linear processes affect them to a significant extent. A new method to exploit these common signatures to improve the quality of a noisy variable (i.e. increasing the signal to-noise ratio) using another variable as template has recently been introduced. The method is based on superimposing the multifractal structure of singularity exponents from the template variable to the variable to be enhanced. In this paper, we will discuss the sensitivity of this method to the presence of noise of different types and amplitude. Our results indicate that multifractal methods can be a key to enhancing the existing databases of remote sensing images and give hints about non-linear dynamics of the ocean, We acknowledge ICMAT Severo Ochoa project SEV-2011-0087 for its support in the publication of this work. M. Umbert is funded by an FPI grant from the Spanish Ministry of Economy. This work has been funded by the Spanish Ministry of Economy through the National R+D Plan by means of MIDAS-7 project AYA2012-39356-C05-03, MIDAS-6 project AYA2010-22062-C05 and previous grants

In this work we evaluate surface ocean current reconstruction at a global scale using a new methodology that combines the benefits of microwave and altimetry measurements. The combined method is based on SQG theory and combines the information about the energy spectrum provided by altimeters with SST microwave measurements. We compare ocean surface current reconstruction using the combined method with eSQG reconstruction, taking as a reference surface geostrophic currents derived from altimetry. Results showed that reconstruction of surface currents based on SQG theory can be improved if the information about the energy spectrum provided by altimeters is used. Furthermore, we investigate to which extent the quality of our results is related to the seasonal cycle of the Mixed Layer Depth (MLD). Results confirmed that the reconstruction performs better for deeper mixed layer.

In this work we evaluate surface ocean current reconstruction at a global scale from microwave Sea Surface Temperature (SST) measurements, based on the Surface Quasi- Geostrophic (SQG) theory. One of the main advantages of microwave measurements is that they are not affected by cloud cover, which is an important aspect for global studies and operational applications. A new heuristic method that combines the benefits of microwave and altimetry measurements is also proposed and evaluated. Results showed that reconstruction of surface currents based on SQG theory can be improved if the information about the energy spectrum provided by altimeters is used.

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.

A surface Quasi-Geostrophy based (eSQG) method to diagnose the vertical velocity field from Sea Surface Height (SSH) is assessed using high resolution simulations. These simulations concern a turbulent eddy field with large Rossby numbers and energetic wind-driven motions. Results indicate that low-frequency vertical velocities (and also horizontal motions) can be reconstructed within a range of scales between 20 km and 400 km from the surface down to 500 m. The only information needed is a single high-resolution SSH snapshot and information on the large-scale vertical stratification. Inertial motions are naturally filtered because they do not contaminate SSH as we demonstrate. These results are encouraging and further strengthen previous studies using the eSQG method. They indicate that access to high resolution SSH may represent a major advance to retrieve horizontal and vertical fluxes of any tracer in the upper ocean. Citation: Klein, P., J. Isern-Fontanet, G. Lapeyre, G. Roullet, E. Danioux, B. Chapron, S. Le Gentil, and H. Sasaki (2009), Diagnosis of vertical velocities in the upper ocean from high resolution sea surface height, Geophys. Res. Lett., 36, L12603, doi: 10.1029/2009GL038359.

12 pages, 14 pages, 2 tables, We use data from a hydrographic cruise in November 2003 over Sedlo Seamount, in conjunction with historical hydrographic and altimeter data, to describe the circulation patterns near the seamount and within the region. A mixing model that incorporates two water types and two water masses assesses the water composition within the region, and an inverse model provides estimates of mass transports within different water strata. Eastern North Atlantic Central Water dominates for the upper neutral-density (γn) levels, γn, This work has been carried out in the frame of the EU Project OASIS (EVK3-CT-2002-00073-OASIS). The first author thanks the Direccion General de Universidades e Investigacion del Gobierno de Canarias for supporting his stay at the Institut de Ciencies del Mar (Barcelona) and CANOA Project (CTM2005-0444/MAR) funded by the Spanish Government. 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

2 pages, 2 figures.-- PAMM Special issue: "Sixth International Congress on Industrial Applied Mathematics (ICIAM07) and GAMM Annual Meeting, Zürich 2007", We summarize recent work on the location of Lagrangian structures in velocity fields obtained from realistic simulations and from satellite altimetry of the surface layers of the Mediterranean sea. Finite-size Lyapunov exponents are found to be useful quantities to characterize stretching and compressing structures, and their implications for mixing. Direct calculation of hyperbolic points and their stable and unstable manifolds identifies ocean structures, and allows the use of the tools of lobe dynamics to characterize fluid transport, Parts of this work have been supported by CSIC (grants PI-200650I224 and OCEANTECH), Royal Society-CSIC cooperation agreement (B2003GB03), MEC and FEDER (projects IMAGEN, CONOCE2 and FISICOS), ONR (Grant No. N00014-01-1-0769), and European Commission (projects MERSEA and 024717-DEMETRA)

17 pages, 7 figures, 2 tables, Because of the optimal features of wavelet processing, the use of wavelets for describing and analyzing signals in 2D turbulence has been generalized since a decade ago. In spite of the close analogy between 2D turbulence and geophysical fluid dynamics, few works have tried to generalize the rich framework of wavelet techniques to the study of experimental signals in oceanography. In this paper, the authors extend a prominent wavelet technique designed for the study of direct numerical simulations (DNSs) on 2D turbulence, the coherent vortex simulation, and analyze with it ocean velocity fields obtained from sea surface height maps derived from satellite altimetry. The authors demonstrate the pertinence of this technique to describe altimetry data, resulting in a description of oceanic flows with a reduced number of degrees of freedom. In particular, it is shown that the western Mediterranean circulation is well approximated by a field of extracted coherent vortices when an appropriate wavelet basis is employed as a filter; however, about one-third of the energy is lost in this description, evidencing important differences between results obtained on the frame of 2D turbulence and oceanic data, This is a contribution to the IMAGEN (Spanish R+D Plan: Grant REN2001-0802-C02-02) and MERSEA projects (Grant EU AIP3-CT- 2003-502885). A. Turiel is funded by a Ramón y Cajal fellowship from the Spanish Ministry of Education. The altimeter products were produced by Ssalto/Duacs and distributed by AVISO with support from CNES

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

17 pages, 8 figures, 6 tables, Here we tested whether the dispersal of loggerhead sea turtles in the western Mediterranean was affected by the pattern of surface currents and whether temporary mesoscale eddies were favoured habitats by comparing the distribution of ten satellite-tracked turtles (average straight carapace length = 46.3 cm; range: 37.1-61.1 cm) with satellite images indicative of the position of mesoscale eddies and the Algerian current. The tracking period averaged 120.9 ± 67.0 SD days. The comparison of turtle tracks with satellite images revealed that only 9.5% of the fixes were associated with mesoscale eddies or the Algerian current. However, 28.3% (range: 0-60.0%) of the maximum longitudinal displacement of each turtle occurred while swimming in the Algerian current. Furthermore, accelerated eastward dispersal with the Algerian current was the most likely reason why turtles did not penetrate deep into the Alboran Sea. Conversely, mesoscale eddies were not involved in any net latitudinal or longitudinal displacement of the turtles. Track analysis revealed that only a few turtles were involved in fine habitat search, as the speed of travel and the cosine of the turning angle seldom correlated once the drift associated with the Algerian current and with mesoscale eddies had been removed from the analysis; only the turtles approaching the limits of the Algerian basin modified their swimming behaviour, thus indicating habitat selection. These observations and the results of the simulation experiments revealed that turtle dispersal within the western Mediterranean was a combination of: (1) passive dispersal within a region limited by physical barriers (the Balearic Archipelago, Sardinia, Corsica, and Sicily) and influenced by a strong current (the Algerian current) and (2) fidelity to regions filled with recent Atlantic water. However, turtles fail to recognise and remain in small, discrete mesoscale eddies, thus suggesting that habitat selection in these turtles appears to occur at the scale of hundreds rather than tens of kilometres. © 2007 Elsevier B.V. All rights reserved, This study was funded by the EU project “Protección de Praderas de Posidonia en LICs de Baleares” LIFE00-NAT/E/7303 and the Spanish R+D project IMAGEN (REN2001-0802-C02-02). The Fundació pel Desenvolupament Sostenible (FDS) provided logistic support for the fieldwork. Animals were instrumented under permit #2003/11 issued by the local government of the Balearic Islands (Conselleria de Medi Ambient del Govern de les Illes Balears) on 19 February, 2003. Satellite data were obtained from several sources: AVHRR data (NOAA satellites) from the SAIDIN database at ICM (http://ers.cmima.csic.es/saidin/), MODIS data (Aqua and Terra satellites) from the GES DAAC (http://disc.gsfc.nasa.gov/index.shtml) at NASA and SEAWIFS data (ORBIMAGE satellite) from GES DAAC (http://daac.gsfc. nasa.gov/data/dataset/SEAWIFS/) at NASA. [RH]

International audience; In this paper, we examine the emerging potential offered by satellite microwave radiometer SST measurements to complement altimeter data to quantitatively derive surface ocean currents. The proposed methodology does not follow standard sequential temporal analysis but follows the application of the Surface Quasi-Geostrophic (SQG) theory. Accordingly, under favourable environmental conditions, the implementation for this methodology is simple and robust, and most importantly, solely requires a single SST image. For the present demonstration, altimetric measurements are used to infer a necessary adjustment to match the kinetic energy level for length scales smaller than 300 km. This helps to derive a regional effective Brunt-Väisälä frequency to produce SQG surface current estimates. As demonstrated, the results are very encouraging and strongly invite to consider the systematic use of satellite microwave radiometer measurements.

Special issue Small and mesoscale processes and their impact on the large scale.-- 20 pages, 9 figures, Three Algerian eddies (open sea big anticyclonic eddies in the Algerian basin, western Mediterranean sea) are studied in detail using altimetric and in situ data. To characterize their spatial structure we make use of the Okubo¿Weiss parameter, which allows to separate the flow into vorticity-dominated and deformation-dominated regions. The application of this parameter to geostrophic velocity fields obtained from Sea Level Anomaly maps show that the observed eddies have a spatial structure in close resemblance to that found in coherent vortices of two-dimensional turbulence. These eddies appear to have a rather coherent vorticity-dominated core region surrounded by an outer region dominated by deformation with a very complicated and variable in time structure. This analysis is also applied to CTD data collected across three eddies sampled between 1997 and 1998. From these data eddy cores are equivalently defined as the interior region enclosed by the maximum of azimuthal velocity, and are consistent with the horizontal structures seen in SLA maps. The distinction between the core and the outer region (circulation cell) is particularly important to understand the role of transport and stirring of properties associated to eddies, as illustrated by the observed salinity structure, some selected SST images, and drifter trajectories. The core is characterized by very small isopycnal salinity gradients, while the surrounding cell is characterized by a strong slope of isohalines with respect to isopycnals. Persistent stagnation points are observed around the eddy and correspond to regions of high values of deformation with respect to vorticity. These regions allow analyzing characteristic patterns seen in the corresponding SST images. In addition, drifters trajectories exhibit very different behavior when crossing such regions, This is a contribution to ELISA and ALGERS experiments and to the IMAGEN project funded by the Spanish R+D Plan (REN2001-0802-C02-02). Jordi Isern-Fontanet has been partially supported by contracts from GRAC (2FD97-0588) and IMAGEN projects. Altimetric maps for the period analyzed were elaborated and provided by CLS (Toulouse, France) under contract of the MATER project funded by the European Commission (MAS3-CT96-0051). ELISA1, ELISA4 and ALGERS98 were also partially funded by MATER

12 pages, 10 figures, 1 table, [EN] In May 1998 a big and deep open ocean anticyclonic eddy (AE 98-1) was sampled in the Algerian basin (western Mediterranean sea) in a region south of the Balearic islands. Fifteen surface Lagrangian buoys, tracked by satellite, were released across the eddy and were used for a few months to observe the continuity of the anticyclonic motion and the westward drift of the eddy. This kind of big and intense eddies in the Mediterranean can be detected by satellite altimeter radars. Using a new method, based on the Okubo-Weiss criterion, to identify mesoscale eddies in Sea Level Anomaly maps derived from measurements of the ERS and TOPEX/POSEIDON altimeters, an independent tracking of the same eddy was performed. There is a remarkable agreement between the two results despite the different nature of the information, mainly due to the fact that SLA maps contain interpolated and smoothed measurements while the drifter? trajectories are in situ data obtained from individual drifter fixes. The location of the eddy centre during two months with the two methods agrees within an average distance lower than the spatial resolution of the altimetric maps (0.2º). The size of the eddy, when it is possible to determine it, is also highly coincident in both cases (96.5% in diameter), and its average westwards translation speed is reasonably similar (24% lower from drifters). These results can be considered a good validation of the new tracking method in SLA maps in this specific case, [ES] En mayo de 1998 un gran remolino anticiclónico de mar abierto fue observado al sur de las islas Baleares, en la cuenca Argelina (mar Mediterráneo occidental). Quince boyas superficiales de deriva fueron lanzadas a través del remolino, y su localización por satélite durante varios meses permitió seguir la continuidad del movimiento anticiclónico y el desplazamiento del remolino hacia el oeste. Este tipo de remolinos intensos puede ser detectado mediante radares altimétricos desde satélite. Un nuevo método, basado en el criterio de Okubo-Weiss, ha permitido seguir este mismo remolino en una serie de mapas de anomalías del nivel del mar obtenidos a partir de observaciones de los satélites ERS y TOPEX/POSEIDON. A pesar de que la información de los mapas altimétricos está interpolada y suavizada, y en cambio las trayectorias de los flotadores se han determinado a partir de localizaciones puntuales, se ha encontrado una concordancia notable entre ambos tipos de resultados. La posición del centro del remolino determinada con ambos métodos durante dos meses presenta unas diferencias que en promedio son menores que la resolución espacial de los mapas altimétricos (0.2º). El tamaño del remolino, cuando es posible calcularlo, es altamente coincidente (96.5% del diámetro), mientras que su velocidad de desplazamiento hacia el oeste es razonablemente parecida (24% inferior cuando se calcula a partir de los flotadores). Estos resultados pueden considerarse como una buena validación del nuevo método de seguimiento de remolinos de mesoescala en mapas altimétricos en el caso particular estudiado, The ALGERS98 cruise on board the R/V Hespérides was part of the INTERMESO project funded by the Spanish National Programme on Environment and Natural Resources (AMB95-0901), and a contribution to the European research projects MATER (funded under contract MAS3-CT96-0051) and ALGERS (European Space Agency ERS AO E102/0)

The Algerian Basin dynamics is dominated by the presence of very energetic mesoscale structures. Deep open sea eddies are key features that influence the regional circulation of water masses at all depths. In May 1998, an open sea eddy was sampled near 38j N2 jE by means of CTD, Acoustic Doppler Current Profiler (ADCP) and surface Lagrangian drifters. For the first time, it has been possible to characterise one of these mesoscale structures in its full depth, down to 2800 m. The density distribution indicated the presence of lighter water in the centre of the eddy from the surface to the bottom. The direct velocity measurements in the surface layer, plus the determination of the baroclinic shear from CTD data, evidenced that the anticyclonic motion was present in the whole water depth. D 2002 Elsevier Science B.V. All rights reserved.

This work represents a contribution to the CSIC Thematic Interdisciplinary Platform PTI-POLARCSIC and PTI-TELEDETECT.-- pages, 13 figures, 2 tables, This study assesses the capability of Surface Quasi-Geostrophy (SQG) to reconstruct the three- dimensional (3D) dynamics in four critical areas of the Arctic Ocean: the Nordic, Barents, East Siberian, and Beaufort Seas. We first reconstruct the upper ocean dynamics from TOPAZ4 re- analysis of sea surface height (SSH), surface buoyancy (SSB), and surface velocities (SSV) and validate the results with the geostrophic and total TOPAZ4 velocities. The reconstruction of upper ocean dynamics using SSH fields is in high agreement with the geostrophic velocities, with correlation coefficients greater than 0.8 for the upper 400 m. SSH reconstructions outperform surface buoyancy reconstructions, even in places near freshwater inputs from river discharges, melting sea ice, and glaciers. Surface buoyancy fails due to the uncorrelation of SSB and subsurface potential vorticity (PV). Reconstruction from surface currents correlates to the total TOPAZ4 velocities with correlation coefficients greater than 0.6 up to 200 meters. Due to a lower stratification of the water column, the performance of the SQG approach is better in fall and winter than in the spring and summer. In the second part, we apply the SQG approach validated withthe reanalysis outputs to satellite-derived upper ocean currents and validate the results against in-situ measurements. Our results demonstrate that using surface information from SSH or surface velocities, combined with information on the stratification of the water column, it is possible to effectively reconstruct upper ocean dynamics in the Arctic and Subarctic Seas up to 400 meters. Future remote sensing missions in the Arctic Ocean, such as SWOT, Seastar, WaCM, CIMR, and CRISTAL, will produce enhanced SSH and surface velocities observations, allowing SQG schemes to characterize upper ocean 3D mesoscale dynamics up to 400 meters with higher resolution and lower uncertainties, M. Umbert received funding from H2020 Marie Skłodowska-Curie Actions under Grant Agreement No. 840374. E. De Andres received funding from Margarita Salas fellowship un-´ der Next Generation EU Grant Agreement No. UP2021-035. This work has also been funded by the AEI with the ARCTIC-MON project (PID2021-125324OB-I00). [...] We also received funding from the Spanish government through the ”Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S) and from the ESA Arctic+Salinity project (AO/1-9158/18/I-BG)