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We describe the circulation and mean sea level variations of the Mediterranean Sea from 2 years of TOPEX/POSEIDON altimetric data. It is first shown that the response of the Mediterranean Sea to atmospheric pressure forcing is close to an inverse barometer (except at high frequencies) which means that the adjustment is accompanied by a flow through the Straits of Sicily and Gibraltar. We then use TOPEX/POSEIDON to study the mean sea level variations, representing steric effects and integrated large‐scale changes of the mass of the Mediterranean Sea. We observe an annual cycle with a fast drop during winter. Steric effects account for about half of the observed variations. The remaining signal is believed to be driven by evaporation minus precipitation (E ‐ P) forcing and internal hydraulic control in the Straits of Gibraltar. Using suboptimal space‐time objective analysis, the classic components of the Mediterranean surface circulation are recovered, despite low signal‐to‐noise ratio (the rms of sea level variability is less than 10 cm). The variable Mediterranean circulation is seen as a complex combination of mesoscale and large‐scale variations. The surface circulation is more complex in the eastern basin than in the western basin. In the east it is composed of subbasin‐scale gyres, such as the so‐called Mersa‐Matruh and Shikmona gyres, which do not have an obvious recurrence period. We also observe an intensification of the large‐scale cyclonic winter circulation in the western and in the Ionian basins. Several mesoscale structures, such as the Alboran gyres and the Ierepetra gyre, show a clear seasonal cycle, with a maximum in summer. The good qualitative and quantitative agreement of the results with previous data from the Mediterranean illustrates the improved accurary of TOPEX/POSEIDON over its predecessors.

Abstract. This work describes the design and validation of a high-resolution (1/36 • ) ocean forecasting model over the "Iberian-Biscay-Irish" (IBI) area. The system has been setup using the NEMO model (Nucleus for European Modelling of the Ocean). New developments have been incorporated in NEMO to make it suitable to open-as well as coastal-ocean modelling. In this paper, we pursue three main objectives: (1) to give an overview of the model configuration used for the simulations; (2) to give a broad-brush account of one particular aspect of this work, namely consistency verification; this type of validation is conducted upstream of the implementation of the system before it is used for production and routinely validated; it is meant to guide model development in identifying gross deficiencies in the modelling of several key physical processes; and (3) to show that such a regional modelling system has potential as a complement to patchy observations (an integrated approach) to give information on non-observed physical quantities and to provide links between observations by identifying broader-scale patterns and processes. We concentrate on the year 2008. We first provide domain-wide consistency verification results in terms of barotropic tides, transports, sea surface temperature and stratification. We then focus on two dynamical subregions: the Celtic shelves and the Bay of Biscay slope and deep regions. The model-data consistency is checked for variables and processes such as tidal currents, tidal fronts, internal tides and residual elevation. We also examine the representation in the model of a seasonal pattern of the Bay of Biscay circulation: the warm extension of the Iberian Poleward Current along the northern Spanish coast (Navidad event) in the winter of 2007-2008.

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A high resolution simulation covering the Iberia–Biscay–Ireland (IBI) region is set-up over July 2007–February 2009. The NEMO model is used with a 1/36&deg; horizontal resolution on 50 <i>z</i>-levels in the vertical. It is forced by the astronomical potential and atmospheric forcing fields which consist of 3-hourly ECMWF analyses. Initial hydrographic conditions are derived from an Atlantic and Mediterranean Sea analyse at 1/12&deg; from Mercator Ocean (PSY2V3 model). At the open boundaries, IBI is forced with PSY2V3 temperature and salinity fields. It is also forced with tidal currents and elevations and inverse barometer elevations. In this study we evaluate the realism of the simulation through comparisons with an extensive observational dataset including climatology, temperature and salinity profiles, satellite SST data, sea surface buoys, tide gauges, altimeter data and HF radar data. A specific interest is given to the procedure used for the validation. General aspects of the simulation and its quality are analysed and particular attention is given to the validation of high frequency processes including the diurnal cycle, barotropic and internal tides, and surges. Finally, we focus on specific aspects of the circulation on the European sea shelves and give a qualitative assessment by studying tidal fronts, and specially the Ushant front, and the winter extension of the Iberian Poleward Current along the Northern Spanish coast during winter 2007–2008

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