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The Mediterranean Forecasting Systems produces operational analyses, reanalyses and 10-day forecasts for many Essential Ocean Variables (EOVs), from currents, temperature to wind waves and pelagic biogeochemistry. The products are available at a horizontal resolution of 1/24 degrees (approximately 4 km) and 141 unevenly spaced vertical levels. The core of the Mediterranean Forecasting System is constituted by the physical (PHY), the biogeochemical (BIO) and the wave (WAV) components coupled offline, consisting of both numerical models and data assimilation modules. The 3 components together constitute the so-called Mediterranean Monitoring and Forecasting Center (Med-MFC) of the Copernicus Marine Service. Daily 10-day forecasts are produced by the PHY, BIO and WAV components as well as analyses, while reanalyses are produced for the past 30 years about every ~3 years and extended (yearly). The modelling systems, their coupling strategy and evolution is illustrated in detail. For the first time, the quality of the products is documented in terms of skill metrics evaluated on a common three-year period (2018–2020), giving the first complete assessment of uncertainties for all the Mediterranean environmental variable analyses.

The Mediterranean Sea is a semi-enclosed basin with an excess amount of evaporation compared to the water in-flux through precipitation at the surface and river runoff on the land boundaries. The deficit in the water budget is balanced by the inflow in the Straits of Gibraltar and Dardanelles connecting the Mediterranean with the less saline Atlantic Ocean and the Marmara Sea, respectively. There is evidence that the Mediterranean region will be a hotspot with the warming Earth (Tuel and El Tahir, 2020) which will possibly change the water cycle significantly, but with a large uncertainty (Cos et al., 2022). Therefore, it is inevitable to monitor the evolution of the essential ocean variables (EOVs) to respond to the associated risks and mitigate the related problems. In this work, we evaluate the evolution of the salinity content and anomaly in the Mediterranean Sea during the last decades using the Copernicus Marine Service products. The results show an increasing mean salinity with a stronger trend in the eastern basin. The spread of the products implies a larger variability in the western basin while the standard deviation is lower in the eastern side, especially in the Ionian and the Levantine basins.

Understanding the causes of the variability of the North Atlantic and Mediterranean overturning circulations, and the possible correlation between them is important to disentangle the processes which link the two ocean basins. In this study, we hypothesize that the Gibraltar inflow transport is the main driver of the basin-mean sea surface height variability in the Mediterranean Sea and that they are both anti-correlated to the Atlantic Meridional Overturning Circulation (AMOC) in the North Atlantic.We analyze here the AMOC and the Mediterranean mean sea surface height (SSH) in an ensemble of eddy-permitting global ocean reanalyses and the Gibraltar inflow transport using an eddy-resolving Mediterranean Reanalysis over the period 1993-2019. In this contribution, firstly we extend the results obtained in past literature with observations (2004-2017 period) and confirm the anti-correlation between the Mediterranean mean sea level and the upper branch of the AMOC at 26.5°N over the 1993-2019 period. Secondly, for the first time, we examine the correlation of the different components of the AMOC and the Gibraltar inflow transport and find significant anti-correlations at interannual time scales.We show that during years of weaker/stronger AMOC and higher/lower SSH in the Mediterranean Sea, a stronger/weaker Azores Current results in stronger/weaker Gibraltar inflow transport. We argue that the anticorrelation between AMOC and the mean sea level of the Mediterranean Sea is explained by the anticorrelation between AMOC and the Gibraltar inflow transport which in turn is changed by the wind driven Azores current strength.

The Copernicus Marine Service (CMEMS) Mediterranean Monitoring and Forecasting Center (MED-MFC) adopts state of the art knowledge in scientific modeling development to operationally produce Near Real Time (NRT) and Multi-year products (MYP) for the Mediterranean Sea dynamics, from currents to waves, and biogeochemistry since 2015.The modelling systems are based on community models (NEMO, WAM and BFM), and assimilate observational In-situ and satellite CMEMS data.During the last 6 years, the MED-MFC systems have been substantially improved with regard to: increased resolution, improved physical, biogeochemical and wave representations thanks to modelling and data assimilation upgrades. All the systems are aligned in terms of grid resolution (1/24o), bathymetry and share the same atmospheric and river forcing fields, moreover the wave and biogeochemical systems are forced by the MED-MFC physical fields.The consortium also assured a continuous improvement of the accuracy of the products and their quality is continuously monitored by means of comparison with respect to available insitu and satellite observations.The focus of this work is to present the integrated MED-MFC modelling systems and the available products, their innovative skill assessment, their evolutions during the 1st phase of Copernicus including major recent scientific achievements. An overview of the future upgrades for the period 2022-2024 are also presented.

Ocean forecast for the IBI (Iberian-Biscay-Ireland) region are provided in near real time within the framework of the Copernicus Marine Environment Monitoring Service (CMEMS). They are produced with a physical–biogeochemical coupled model over the north-east Atlantic Ocean from the Canary Islands to Iceland, including the North Sea and the western Mediterranean. The physical system, composed of a NEMO model at 1/36° resolution (around 2km, ORCA grid subset), has started operating in the early 2010s and continuously evolved with regular releases. Its ocean model is corrected through the assimilation of in-situ observations (T and S profiles) and satellite data (Sea Surface temperature, SST and altimetry) with the Assimilation System of Mercator (SAM) which is based on the SEEK Kalman filter. A CMEMS release is planned for 29th of November this year and a new version of the system will be operational. We will describe here the last evolution of the system focusing on the data assimilation updates. Changes in the model equivalent for the satellite Sea Level Anomaly (SLA) using a new formulation for the barotropic part leads to a better estimation of the innovation. The impact of this change and a discussion on the Mean Dynamic Topography (MDT) used will be developed.

Design of numerical experiments assimilating in situ physical and BGC observations to assess and enhance their impact in CMEMS ocean monitoring and forecasting systems.

In order to be able to forecast the weather and estimate future climate changes in the ocean, it is crucial to understand the past and the mechanisms responsible for the ocean variability. This is particularly true in a complex area such as the Mediterranean Sea with diverse dynamics like deep convection and overturning circulation. To this end, effective tools are ocean reanalyses or reconstructions of the past ocean state. Here we present a new physical reanalysis of the Mediterranean Sea at high resolution, developed in the Copernicus Marine Environment Monitoring Service (CMEMS) framework. The hydrodynamic model is based on the Nucleus for European Modelling of the Ocean (NEMO) combined with a variational data assimilation scheme (OceanVar). The model has a horizontal resolution of 1/24° and 141 unevenly distributed vertical z* levels. It provides daily and monthly temperature, salinity, current, sea level and mixed layer depth as well as hourly fields for surface velocities and sea level. ECMWF ERA-5 atmospheric fields force the model and daily boundary conditions in the Atlantic are taken from a global reanalysis. The reanalysis covers the 33 years from 1987 to 2019. Initialized from SeaDataNet climatology in January 1985, it reaches a nominal state after a 2-years spin-up. In-situ data from CTD, ARGO floats and XBT are assimilated into the model in combination with satellite altimetry observations. This reanalysis has been validated and assessed through comparison to in-situ and satellite observations as well as literature climatologies. The results show an overall improvement of the comparison with observations and a better representation of the main dynamics of the region compared to a previous, lower resolution (1/16°), reanalysis. Temperature and salinity RMSD are decreased by respectively 14 and 18%. The salinity biases at depth of the previous version are corrected. Climate signals show continuous increase of the temperature and salinity, confirming estimates from observations and other reanalysis. The new reanalysis will allow the study of physical processes at multi-scales, from the large scale to the transient small mesoscale structures and the selection of climate indicators for the basin.

Ocean reanalyses are becoming increasingly important to reconstruct and provide an overview of the ocean state from the past to the present-day. In this article, we present a Black Sea reanalysis covering the whole satellite altimetry era. In the scope of the Copernicus Marine Environment Monitoring Service, the Black Sea reanalysis system is produced using an advanced variational data assimilation method to combine the best available observations with a state-of-the-art ocean general circulation model. The hydrodynamical model is based on Nucleus for European Modeling of the Ocean, implemented for the Black Sea domain with a horizontal resolution of 1/27°× 1/36°, and 31 unevenly distributed vertical levels. The model is forced by the ECMWF ERA5 atmospheric reanalysis and climatological precipitation, whereas the sea surface temperature is relaxed to daily objective analysis fields. The model is online coupled to OceanVar, a 3D-Var ocean data assimilation scheme, to assimilate sea level anomaly along-track observations and in situ vertical profiles of temperature and salinity. Temperature fields present a continuous warming in the layer between 25 and 150 m, where the Black Sea Cold Intermediate Layer resides. This is an important signal of the Black Sea response to climate change. Sea surface temperature shows a basin-wide positive bias and the root mean square difference can reach 0.75°C along the Turkish coast in summer. The overall surface dynamic topography is well reproduced as well as the reanalysis can represent the main Black Sea circulation such as the Rim Current and the quasi-permanent anticyclonic Sevastopol and Batumi eddies. The system produces very accurate estimates of temperature, salinity and sea level which makes it suitable for understanding the Black Sea physical state in the last decades. Nevertheless, in order to improve the quality of the Black Sea reanalysis, new developments in ocean modeling and data assimilation are still important, and sustaining the Black Sea ocean observing system is crucial.

Eight years of glider data are used to characterize the temporal and spatial variability of a region in the western Mediterranean that will constitute one of the targets for the calibration phase of the Surface Water and Ocean Topography (SWOT) satellite mission. The characteristic horizontal dimension of mesoscale instabilities in the Mallorca channel is 6.0 km. The temporal evolution of intermediate water masses is dominated by an increase over time of the characteristic temperature values. Western Mediterranean and Levantine Intermediate waters display an increase of the temperature extrema of 0.064 ± 0.002 and 0.044 ± 0.002 °C/year between 2011 and 2018, respectively. At the layer of Levantine Intermediate water the salinity temporal regression reveals a mean trend of 0.010 year. Temperature annual cycle shows an averaged temperature gradient of ∼6 °C in 6 months at the upper layer, with a disconnection with the annual cycle at 100-m depth. The circulation across the channel is dominated by high-frequency variability. The signature of eddies with radius ranging from 5 to 18 km is apparent in 16% of the transects analyzed and mainly in spring and summer, with a dominance of subsurface cyclonic eddies. Two-way flow controls the annual cycle of the water transport through the channel with prevalence of the inflow of Atlantic water. Variations of water transport over timescales of weeks to months can be similar to those identifiable as seasonal changes., This study is a contribution to the PRE‐SWOT project (CTM2016‐78607‐P) funded by the Spanish National Research Program and the European Regional Development Fund (MINECO‐FEDER). Glider data are freely available at the SOCIB website (https://doi.org/10.25704/jd07-sv9).

In order to be able to predict the future ocean climate and weather, it is crucial to understand what happened in the past and the mechanisms responsible for the ocean variability. This is particularly true in a complex area such as the Mediterranean Sea with diverse dynamics such as deep convection and thermohaline circulation or coastal hydrodynamics. To this end, effective tools are reanalyses or reconstructions of the past ocean state. Here we present a new physical reanalysis of the Mediterranean Sea at high resolution, developed in the Copernicus Marine Environment Monitoring Service (CMEMS) framework. The hydrodynamic model is based on the Nucleus for European Modelling of the Ocean (NEMO) combined with a variational data assimilation scheme (OceanVar).The model has a horizontal resolution of 1/24° and 141 vertical z* levels and provides daily and monthly 3D values of temperature, salinity, sea level and currents. Hourly ECMWF ERA-5 atmospheric fields force the model and daily boundary conditions in the Atlantic are taken from the global CMCC C-GLORS reanalysis. 39 rivers model the freshwater input to the basin plus the Dardanelles. The reanalysis covers 33-years, initialized from SeaDataNet climatology in January 1985, getting to a nominal state after a two-years spin-up and ending in 2019. In-situ data from CTD, ARGO floats and XBT are assimilated into the model in combination with satellite altimetry data.This reanalysis has been validated and assessed through comparison to in-situ and satellite observations as well as literature climatologies. The results show an overall improvement of the skill and a better representation of the main dynamics of the region compared to the previous, lower resolution (1/16°) reanalysis. Temperature and salinity RMSE is decreased by respectively 12% and 20%. The deeper biases in salinity of the previous version are corrected and the new reanalysis present a better representation of the deep convection in the Gulf of Lion. Climate signals show continuous increase of the temperature due to climate change but also in salinity.The new reanalysis will allow the study of physical processes at multi-scales, from the large scale to the transient small mesoscale structures.

The Mediterranean Analysis and Forecasting System operationally produces analyses and 10 days forecasts of the main physical parameters for the entire Mediterranean Sea and its Atlantic Ocean adjacent areas in the framework of the Copernicus Marine Environment Monitoring Service (CMEMS).The system is composed by the hydrodynamic model NEMO (Nucleus for European Modelling of the Ocean) 2-way coupled with the third-generation wave model WW3 (WaveWatchIII) and forced by ECMWF (European Centre for Medium-range Weather Forecasts) atmospheric fields. The forecast initial conditions are produced by the OceanVar, a 3D variational data assimilation system which daily assimilates Sea Level Anomaly, vertical profiles of Temperature and Salinity from ARGO and XBT (upon availbility) observations. Moreover a heat flux correction using satellite SST is imposed.The system has been recently upgraded by including tidal waves, so that the tidal potential is calculated across the domain for the Mediterranean Sea 8 major constituents: M2, S2, N2, K2, K1, O1, P1, Q1. In addition, tidal forcing is applied along the lateral boundaries in the Atlantic Ocean by means of tidal elevation estimated using the FES2014 global tidal model and tidal currents evaluated using TUGO (Toulouse Unstructured Grid Ocean) model. Moreover the data assimilation scheme now accounts for the tidal signal in the altimeter tracks.The system has been validated comparing model results with satellite and in situ observations. A specific harmonic analysis has been performed comparing model sea level amplitudes and phases with respect to: tide gauges, TPXO global tidal model and literature, showing an overall good skill of all the considered tidal constituents. Moreover the ability of the system to predict sea level has been evaluated comparing the model solutions with respect to tide gauges in areas where recent extreme events occurred such as Venice Lagoon “Acqua Alta” in November 2019, Western Mediterranean Sea during Gloria storm in January 2020, Ionian Sea during Medicane Ianos in September 2020.

Ocean reanalyses are becoming increasingly important to reconstruct and provide an overview of the ocean state from the past to the present-day. These products require advanced scientific methods and techniques to produce a more accurate ocean representation. In the scope of the Copernicus Marine Environment Monitoring Service (CMEMS), a new Black Sea (BS) reanalysis, BS-REA (BSE3R1 system), has been produced by using an advanced variational data assimilation method to combine the best available observations with a state-of-the-art ocean general circulation model. The hydrodynamical model is based on Nucleus for European Modeling of the Ocean (NEMO, v3.6), implemented for the BS domain with horizontal resolution of 1/27° x 1/36°, and 31 unevenly distributed vertical levels. NEMO is forced by atmospheric surface fluxes computed via bulk formulation and forced by ECMWF ERA5 atmospheric reanalysis product. At the surface, the model temperature is relaxed to daily objective analysis fields of sea surface temperature from CMEMS SST TAC. The exchange with Mediterranean Sea is simulated through relaxation of the temperature and salinity near Bosporus toward a monthly climatology computed from a high-resolution multi-year simulation, and the barotropic Bosporus Strait transport is corrected to balance the variations of the freshwater flux and the sea surface height measured by multi-satellite altimetry observations. A 3D-Var ocean data assimilation scheme (OceanVar) is used to assimilate sea level anomaly along-track observations from CMEMS SL TAC and available in situ vertical profiles of temperature and salinity from both SeaDataNet and CMEMS INS TAC products. Comparisons against the previous Black Sea reanalysis (BSE2R2 system) show important improvements for temperature and salinity, such that errors have significantly decreased (about 50%). Temperature fields present a continuous warming in the layer between 25-150 m, within which there is the presence of the Black Sea Cold Intermediate Layer (CIL). SST exhibits a positive bias and relatively higher root mean square error (RMSE) values are present in the summer season. Spatial maps of sea level anomaly reveal the largest RMSE close to the shelf areas, which are related to the mesoscale activity along the Rim current. The BS-REA catalogue includes daily and monthly means for 3D temperature, salinity, and currents and 2D sea surface height, bottom temperature, mixed layer fields, from Jan 1993 to Dec 2019. The BSE3R1 system has produced very accurate estimates which makes it very suitable for assessing more realistic climate trends and indicators for important ocean properties.

The Mediterranean Analysis and Forecasting System is a numerical ocean prediction system that operationally produces analyses and 10 days forecasts of the main physical parameters for the entire Mediterranean Sea and its Atlantic Ocean adjacent areas in the framework of the Copernicus Marine Environment Monitoring Service (CMEMS). The system is composed by the hydrodynamic model NEMO (Nucleus for European Modelling of the Ocean) 2-way coupled with the third-generation wave model WW3 (WaveWatchIII) and forced by ECMWF (European Centre for Medium-range Weather Forecasts) atmospheric fields. The forecast initial conditions are produced by a 3D variational data assimilation system which considers a daily assimilation cycle of Sea Level Anomaly, vertical profiles of Temperature and Salinity from ARGO and ship CTDs and heat flux corrections with satellite SST. The system has been recently upgraded by increasing the grid resolution from 1/16 to 1/24 degree in the horizontal, thus becoming fully mesoscale resolving and from 72 to 141 vertical levels; by increasing the number of fresh water river inputs and by updating the data assimilation scheme. Additional developments will be implemented in the next release of the operational system (April 2019) by including an upgraded SST relaxation to satellite observations close to midnight and the implementation of the Dardanelles strait as a lateral open boundary condition. The focus of this work is to present the latest modeling system upgrades and the related improvements achieved by showing the model skill assessment including comparison with independent (insitu coastal moorings) and quasi-independent (insitu vertical profiles and satellite) datasets.

Hydrographic changes in the western Mediterranean Sea (WMED), which is connected to the North Atlantic through the Strait of Gibraltar, may affect the global ocean thermohaline circulation. The Western Intermediate Water (WIW) is a regional water mass which is formed through winter convection processes in the north WMED. The variations of WIW characteristics are hardly detectable by the conventional criterion as defined in the literature and have been poorly addressed. This study introduces an innovative geometry-based method to properly detect WIW. New insights into changes in WIW properties are obtained by applying this method to glider data in the Ibiza Channel and numerical simulation in the whole WMED. Seasonal and interannual variations as well as positive trends in temperature and salinity leading to negative trend in density are highlighted in the Balearic Sea and Gulf of Lion. The basin-scale simulation also shows the spatio-temporal variability of WIW characteristics in the WMED under the influence of the location of formation site, local and regional atmospheric fluctuations, vertical mixing, horizontal advection and mixing with surrounding waters.

Este artículo contiene 30 páginas, 14 figuras., The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstreamservices in response to the needs of the heavily populatedMediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level ofMediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN’s Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system.

Algerian eddies are the strongest and largest propagating mesoscale structures in the Western Mediterranean Sea. They have a large influence on the mean circulation, water masses and biological processes. Over 20 years of satellite altimeter data have been analyzed to characterize the propagation of these eddies using automatic detection methods and cross-correlation analysis. We found that, on average, Algerian eddy trajectories form two subbasin scale anticlockwise gyres that coincide with the two Algerian gyres which were described in the literature as the barotropic circulation in the area. This result suggests that altimetry sea surface observations can provide information on subsurface currents and their variability through the study of the propagation of deep mesoscale eddies in semienclosed seas. The analysis of eddy sea level anomalies along the mean pathways reveals three preferred areas of formation. Eddies are usually formed at a specific time of the year in these areas, with a strong interannual variability over the last 20 years.

This paper describes the high-resolution Western Mediterranean Sea Operational Forecasting System (WMOP) developed at the Balearic Islands Coastal Observing and Forecasting System (SOCIB). The system runs on a daily basis driven by high-resolution atmospheric forcing, providing 3-day forecasts of physical oceanic variables with a 2 km horizontal resolution, thus representing the ocean variability from mesoscale to basin scale from the Gibraltar Strait to the Sardinia Channel. A systematic regional monitoring and validation system has been developed using multi-platform observations, allowing the evaluation of both the overall realism of the predictions and the specific errors in each sub-basin., This paper is a contribution to Medclic program, a collaboration between “la Caixa” Foundation and SOCIB.

© 2015, Copyright © Taylor & Francis Group, LLC. We present an initial assessment of SARAL/AltiKa data in the coastal band. The study focuses on the Ibiza Channel where the north-south water exchanges play a key role in controlling the circulation variability in the western Mediterranean. In this area, the track 16 of SARAL/AltiKa intercepts the domain covered by a coastal high-frequency (HF) radar system, which provides surface currents with a range up to 60 km. We evaluate the performance of the SARAL/AltiKa Ssalto/Duacs delayed-time along-track products compared to the HF radar surface velocity fields. SARAL/AltiKa data are retrieved at a distance of only 7 km from the coast, putting in evidence the emerging capabilities of the new altimeter. The derived velocities resolved the general features of the seasonal mesoscale variability with reasonable agreement with HF radar fields (significant correlations of 0.54). However, some discrepancies appear, which might be caused by instrumental hardware radar errors, ageostrophic velocities as well as inaccurate corrections and editing in the altimeter data. Root mean square (rms) differences between the estimated SARAL/AltiKa and the HF radar velocities are about 13 cm/s. These results are consistent with recent studies in other parts of the ocean applying similar approaches to Topex/Poseidon and Jason-1 missions and using coastal altimeter corrections., This study has been carried out as part of the MyOcean2 project (EU N° FP7-SPA.2011.1.5-01-Grant Agreement 283367) project. Additional funding from Conselleria d'Educació, Cultura i Universitat (Local Government of the Balearic Islands) and FEDER funds (CAIB-51/2011) is acknowledged

We present an innovative approach to the generation of remotely sensed high-resolution sea surface topography that improves coastal and mesoscale dynamic characterization. This new method is applied for the period 2002-2010 in the northwestern Mediterranean Sea, an area marked by a small Rossby radius. The spectral content of the new mapped data is closer to that of the along-track signal and displays higher levels of energy in the mesoscale bandwidth with the probability distribution of the new velocity fields 30% closer to drifters estimations. The fields yield levels of eddy kinetic energy 25% higher than standard altimetry products, especially over regions regularly impacted by mesoscale instabilities. Moreover, qualitative and quantitative comparisons with drifters, glider and satellite sea surface temperature observations further confirm that the new altimetry product provides, in many cases, a better representation of mesoscale features (more than 25% improvement in correlation with glider data during an experiment).

New altimetry products in semi-enclosed seas are of major interest given the importance of the coastal-open ocean interactions. This study shows how reprocessed altimetry products in the Mediterranean Sea from Archiving, Validation and Interpolation of Satellite Oceanographic data (AVISO) have improved the representation of the surface circulation over the 1993-2012 period. We focus on the Alboran Sea, which is the highest mesoscale activity area of the western Mediterranean. The respective impacts of the new mean dynamic topography (MDT) and mapped sea level anomaly (MSLA) on the description of the Western Alboran Gyre (WAG) are quantitatively evaluated. The temporal mean and variability of the total kinetic energy have been significantly increased in the WAG considering both the new MDT and MSLA (by more than 50%). The new MDT has added 39% to the mean kinetic energy, while the new MSLA has increased the eddy kinetic energy mean (standard deviation) by 53% (30%). The new MSLA has yielded higher variability of total (eddy) kinetic energy, especially in the annual frequency band by a factor of 2 (3). The MDT reprocessing has particularly increased the low-frequency variability of the total kinetic energy by a factor of 2. Geostrophic velocities derived from the altimetry products have also been compared with drifter data. Both reprocessed MDT and MSLA products intensify the velocities of the WAG making them closer to the in situ estimations, reducing the root mean square differences and increasing the correlation for the zonal and meridional components. The results obtained using refined coastal processing of altimetry products and new observational data are very encouraging to better understand the ocean circulation variability and coastal-open ocean interactions, and for potential improvements in other sub-basins, marginal seas and coastal global ocean.

In order to understand potential predictability of the ocean and climate at the decadal time scales, it is crucial to improve our understanding of internal variability at this time scale. Here, we describe a 20-year mode of variability found in the North Atlantic in a 1,000-year pre-industrial simulation of the IPSL-CM5A-LR climate model. This mode involves the propagation of near-surface temperature and salinity anomalies along the southern branch of the subpolar gyre, leading to anomalous sea-ice melting in the Nordic Seas, which then forces sea-level pressure anomalies through anomalous surface atmospheric temperatures. The wind stress associated to this atmospheric structure influences the strength of the East Greenland Current across the Denmark Strait, which, in turn, induces near-surface temperature and salinity anomalies of opposite sign at the entrance of the Labrador Sea. This starts the second half of the cycle after approximatively 10 years. The time scale of the cycle is thus essentially set by advection of tracers along the southern branch of the subpolar gyre, and by the time needed for anomalous East Greenland Current to accumulate heat and freshwater anomalies at the entrance of the Labrador Sea. The Atlantic meridional overturning circulation (AMOC) does not play a dominant role in the mode that is confined in the subpolar North Atlantic, but it also has a 20-year preferred timescale. This is due to the influence of the propagating salinity anomalies on the oceanic deep convection. The existence of this preferred timescale has important implications in terms of potential predictability of the North Atlantic climate in the model, although its realism remains questionable and is discussed.

© 2015 COSPAR. Published by Elsevier Ltd. All rights reserved. In situ water levels in the Guadalquivir River estuary mouth show the effect of strong river freshwater discharges on the monthly means of the sea level on a yearly basis. Accurate altimeter products oriented toward coastal zones are increasing the number of potential applications at different spatiotemporal scales. The present work is focused on the analysis of the sea-level variability in the eastern shelf of the Gulf of Cadiz (between North Africa and the southwestern side of the Iberian Peninsula), adjacent to the Guadalquivir River estuary. Sixteen years (1994-2009) of along-track and standard AVISO maps of sea-level anomalies (SLAs) have been used to generate a new high-resolution product with increased spatiotemporal resolution. The use of a bathymetry constraint and smaller correlation scales in the methodology developed to generate high-resolution altimeter products improves the characterization of the mesoscale signals in the coastal strip adjacent to the estuary due to strong river freshwater discharges. This has been confirmed by the analysis of along-track SLA data in the vicinity of the estuary. The daily evolution (2 weeks) of the sea level obtained in the event of December 2009 might be related to the river plume extension observed by optical Moderate Resolution Imaging Spectrometer (MODIS) images. The spatiotemporal distribution of the altimeter tracks available in the study area might compromise the mapping capabilities to capture coastal and fine-scale features., This work has been partially supported by the ALCOVA Project (CTM2012-37839) funded by the Spanish Ministerio de Economía y Competitividad and FEDER

Satellite altimetry is a key component of the global observing system and plays a major role in the study of the mesoscale processes that drive most of the ocean circulation variability at middle and high latitudes. However, satellite altimetry alone provides only surface information at a limited spatio-temporal resolution. To address these limitations and to better describe the mesoscale three-dimensional variability, it is necessary to complement altimetry data with additional remote and in situ measurements. This study provides an update of the recent advances in the study of the mesoscale variability using a combination of altimetry and other independent observations, with an emphasis on the results obtained for the western Mediterranean Sea. The circulation in this area is complex because of the presence of multiple interacting scales, including basin-scale, sub-basin–scale and mesoscale structures. Thus, characterizing these processes requires high-resolution observations and multi-sensor approaches. Accordingly, multi-platform experiments and analyses have been designed and undertaken in the different sub-basins of the western Mediterranean Sea. These studies have demonstrated the advantages of synergetic approaches that use a combination of observation techniques and are able to resolve different spatio-temporal scales with the aim of better understanding mesoscale dynamics., La altimetría satelitaria es una componente clave del sistema de observación global y juega un papel importante en el estudio de los procesos de mesoescala que impulsan la mayor parte de la variabilidad de la circulación oceánica en las latitudes medias y altas. Sin embargo, la altimetría por satélite sólo proporciona información superficial y con una resolución espacio- temporal limitada. Para hacer frente a estas limitaciones, es necesario complementar los datos de altimetría con otras medidas. Este estudio proporciona una actualización de los avances recientes en el estudio de la variabilidad de mesoescala utilizando una combinación de observaciones altimétricas con otros datos independientes en el Mediterráneo Occidental. La circulación en esta zona es compleja debido a la presencia de múltiples escalas interactuando entre ellas: cuenca, sub-cuenca y estructuras de mesoescala. Por tanto, la caracterización de estos procesos requiere de alta resolución en las observaciones y de enfoques multi-sensoriales. En este trabajo, presentamos una revisión de diversos experimentos multi-plataforma que se han diseñado y llevado a cabo en los diferentes sub-cuencas del Mediterráneo occidental durante los últimos años. Estos estudios han demostrado las ventajas de los enfoques sinérgicos y métodos innovadores que utilizan una combinación de técnicas de observación, y que son capaces de mejorar nuestra comprensión de la dinámica de mesoescala.

Tintoré, Joaquín et al., Capítulo en: MORENO-DÍAZ, Roberto; PICHLER, Franz; QUESADA-ARENCIBIA, Alexis (eds.). Computer Aided Systems Theory-EUROCAST 2013 : 14th International Conference, Las Palmas de Gran Canaria, Spain, February 10-15, 2013. Revised Selected Papers, Part II. Berlin: Springer, 2013, p.341-348 (Lecture Notes in Computer Science ; 8112), New monitoring technologies are key components of ocean observatories, also called marine research infrastructures being implemented in the worlds oceans. As a result, new capabilities to characterise, in quasi-real time, the ocean state and its variability at small scales exist today. The challenge is the integration of theses multiplatform observing and forecasting systems to (a) monitor the variability at small scales (e.g. mesoscale/weeks) in order to (b) resolve the sub-basin/seasonal and inter-annual variability and by this (c) establish the decadal variability, understand the associated biases and correct them. The challenge is also to change focus and now monitor from small to large scales. SOCIB is leading this new small to large-scale multi-platform approach in ocean observation. Some examples are presented and discussed together with initial ideas on the optimal design of an observational network in the world oceans, responding to science priorities, technology development and response to strategic society needs

International audience; Oceanic mesoscale plays a key role in modulating large-scale circulation, heat fluxes and primary production enhancement. Such hydrodynamic processes are also crucial at regional scales where the associated currents are known to significantly influence water-mass mixing and exchanges between the coastal zone and the open ocean. Nevertheless, the characterization of coastal mesoscale dynamics from along-track altimetric observations is complicated from a technical and algorithmic point of view and thus requires continuous developments (refer to the CTOH-XTRACK processor, PISTACH and COASTALT initiatives). Moreover, the high spatial/temporal variability and complexity associated with coastal mesoscale processes make them difficult to be studied with sparse in-situ observations and highly-smoothed standard altimetric products which lack the high resolution often required to correctly represent regional features. Alternative options rely on generating satellite altimetric maps specifically adapted to the coastal domain and also on developing methodologies based on the fusion of multi-sensor platforms in conjunction with numerical simulations. In this respect, optimal interpolation methods for improving the coastal circulation description have been developed over the North Western Mediterranean Sea (NWM), an area marked by a relatively low signal to noise ratio compared to the global ocean. We have also used vertical Empirical Orthogonal Functions (from a numerical model and in-situ measurements) in order to rebuild realistic coastal geostrophic currents both at surface and throughout the water column. Our approach characterizes the main coastal mesoscale features which can be confirmed by comparison with several independent in-situ measurements done by the MIO and IMEDEA laboratories (drifters, ADCP, gliders...). In particular, the developed methods are able to improve the accuracy of surface geostrophic current compared to standard AVISO product. Even better results can be obtained when complementary geophysical information (from bathymetry, sea surface temperature, tide gauges) are integrated in the optimal interpolation scheme. The high resolution 3D currents were then coupled with a Lagrangian code to simulate particle trajectories and therefore better interpret the influence of coastal mesoscale circulation on 3D exchanges between the Gulf of Lion continental shelf and the NWM open sea. Finally, the long-term statistical analysis (> 10 years) of these current fields was exploited to better characterize potential inter-annual changes in the coastal mesoscale activity of the NWM.

New monitoring technologies are being progressively implemented in open-ocean and coastal observatories. The Mediterranean Sea is a well-known, reduced-scale ocean, an ideal natural laboratory to study global ocean processes, in particular those associated with meso- and submesoscale variability, interactions with mean flows and associated ecosystem response. SOCIB, the Balearic Islands Coastal Ocean Observing and Forecasting System, is one of such observatories, a multiplatform distributed and integrated system, a facility of facilities that extends from the nearshore to the open sea. SOCIB profits from the strategic position of the Balearic Islands at the Atlantic/Mediterranean transition area, one of the “hot spots” of biodiversity in the world’s oceans, and also of societal needs in islands where preservation of the environment is essential to assure both residents’ welfare and the competitiveness of the tourist sector. SOCIB is unique in that, from peer-reviewed excellence, its mission and objectives are science-, technology-, and society-driven. These types of new marine infrastructures, because of their critical mass and sustained funding, are presently establishing new ways of international cooperation, leading to major science breakthroughs, innovations in oceanographic instrumentation, and new ways of more efficient and science-based coastal and ocean management. We describe the major elements and structure of SOCIB and present some recent scientific, technological, and society-related results that are of relevance at a global ocean scale.