We perform an Observing System Simulation Experiment that simulates the satellite sampling and the mapping procedure on the sea surface of the high‐resolution model CROCO‐MED60v40, to investigate the reliability and the accuracy of the eddy detection. The main result of this study is a strong cyclone‐anticyclone asymmetry of the eddy detection on the altimetry products AVISO/CMEMS in the Mediterranean Sea. Large‐scale cyclones having a characteristic radius larger than the local deformation radius are much less reliable than large‐scale anticyclones. We estimate that less than 60% of these cyclones detected on gridded altimetry product are reliable, while more than 85% of mesoscale anticyclones are reliable. Besides, both the barycenter and the size of these mesoscale anticyclones are relatively accurate. This asymmetry comes from the difference of stability between cyclonic and anticyclonic eddies. Large mesoscale cyclones often split into smaller sub‐mesoscale structures having a rapid dynamical evolution. The numerical model CROCO‐MED60v40 shows that this complex dynamic is too fast and too small to be accurately captured by the gridded altimetry products. The spatio‐temporal interpolation smoothes out this sub‐mesoscale dynamics and tends to generate an excessive number of unrealistic mesoscale cyclones in comparison with the reference field. On the other hand, large mesoscale anticyclones, which are more robust and which evolve more slowly, can be accurately tracked by standard altimetry products. We also confirm that the AVISO/CMEMS products induce a bias on the eddy intensity. The azimuthal geostrophic velocities are always underestimated for large mesoscale anticyclones.

Abstract. This study proposes an approach to estimate the ocean sea surface height signature of coherent internal tides from a 25-year along-track altimetry record, with a single inversion over time, resolving both internal tide contributions and mesoscale eddy variability. The inversion is performed on a reduced-order basis of topography and practically achieved with a conjugate gradient. The particularity of this approach is to mitigate the potential aliasing effects between mesoscales and internal tide estimation from the uneven altimetry sampling (observing the sum of these components) by accounting for their statistics simultaneously, while other methods generally use a prior mesoscale. The four major tidal components are considered (M2, K1, S2, O1) over the period 1992–2017 on a global configuration. From the solution, we use altimetry data after 2017 for independent validation in order to evaluate the performance of the simultaneous inversion and compare it with an existing model.

Abstract. This study proposes an approach to estimate the Ocean Sea Surface Height signature of coherent internal tidesfrom 25 years of along-track altimetry record, with a single inversion over time, resolving both internal tide contributions andmesoscale eddy variability. The inversion is performed through reduced-order basis with conjugate gradient resolution. Theparticularity of this approach is to mitigate the potential aliasing effects between mesoscales and internal tide estimation fromthe uneven altimetry sampling (observing the sum of these components) by accounting of their statistics simultaneously, while other methods generally use a prior for mesoscales. The four major tidal components are considered (M2,K1,S2,O1) over theperiod 1992–2017 on a global configuration. From the solution, we use altimetry data after 2017 for an independent validation,to evaluate the benefits of the simultaneous inversion, and also to compare the skills with an existing model.