The impact of Cyclone Ianos on the hydrodynamics of the Ionian Sea

Mediterranean cyclones are intense weather systems that strongly influence both atmospheric and oceanic conditions. Cyclone Ianos, which developed over the Ionian Sea between 15 and 20 September 2020, has been widely studied for its coastal impacts; however, its influence on open-ocean hydrodynamics remains less understood. This study examines the impact of Cyclone Ianos on the upper-ocean structure and circulation of the Ionian Sea, with particular focus on the cyclonic eddy formed at peak storm intensity (17 September), based on simulations with the Regional Ocean Modelling System (ROMS). Results indicate a sea surface temperature decrease of 2–3°C, a salinity reduction of ~0.1 PSU, and a sea surface height increase of 1–2 cm across the basin. A well-defined cyclonic eddy developed under wind stress and Coriolis forcing, with surface currents deflected to the right of the wind, consistent with Ekman dynamics. While the storm’s influence weakened below 30–40 m, a persistent counterclockwise eddy remained. Analysis of its vertical and horizontal structure provides new insight into how Mediterranean cyclones generate coherent open-ocean features. These findings improve understanding of storm-driven hydrodynamic processes and their implications for marine ecosystems, particularly nutrient upwelling and biological productivity.