The Tyrrhenian Sea plays a key role in Mediterranean circulation. However, the seasonal evolution and coastal circulation patterns of its surface circulation remain only partially resolved by previous observations, particularly at mesoscale and submesoscale. In this study, we investigate the seasonal and coastal variability of Tyrrhenian Sea surface circulation by combining high-resolution wide-swath altimetry from the Surface Water and Ocean Topography (SWOT) mission with conventional multi-mission altimetry, satellite-derived Sea Surface Temperature (SST), and coastal tide gauge observations. Compared to conventional gridded altimetry, SWOT-enhanced products exhibit higher Absolute Dynamic Topography (ADT) gradients, with mean seasonal increases of 4–6% in winter-spring and up to 12–15% in summer-autumn. Surface velocity fields also exhibit generally higher spatial variability (3–10% in most seasons) and stronger mean velocities, with mean seasonal increases of up to 14% relative to conventional gridded altimetry. These differences result in a finer spatial depiction of frontal systems, coastal jets, and mesoscale circulation features. These patterns are consistent with independent tide gauge records and the spatial agreement between altimetry-derived structures and SST frontal gradients in representative seasonal case studies. While confirming the well-known seasonal cyclonic circulation, which is stronger in winter-spring and weaker in summer, our results indicate that SWOT-enhanced altimetry offers a more detailed spatial representation of fine-scale coastal and mesoscale circulation features than conventional gridded altimetry. Overall, these findings highlight the potential of SWOT-enhanced altimetry to improve the spatial characterization of Mediterranean upper-ocean circulation and its fine-scale variability, providing a valuable framework for future studies of coastal dynamics and mesoscale processes.
Fortunato et al. (Tue,) studied this question.