The Seasonal and Interannual Variability of the Ligurian Sea

Understanding the variability of the Ligurian Sea is potentially leading to solve the long standing questions about how deep is the Liguro-Proven¸cal Current (LPC)? What drives the circulation across the Corsica Channel? What are the time scales of this variability and how well can geostrophy describe the circulation across the Ligurian basin? Seven free floating devices called MERMAID have been deployed in the Ligurian Sea from 2012 to 2015, surfacing every 4-5 days on average. The instruments positioning data constituted a valuable source to estimate the LPC depth and speed at 1500 m below the sea surface. The Corsica Channel is a choke point to monitor the exchanges between the Tyrrhe- nian Sea and Ligurian Sea. The water flux across the Channel has been monitored for more than 30 years, constituting one of the longest world time series. In the present work the water flux from 1985 to 2010 constitutes the focus to relate atmospheric and marine variables in the Ligurian Sea and Tyrrhenian Sea. The study highlights the permanent influence of the atmospheric Sea Surface Pressure (SSP) on the exchange between the two basins and the crucial role of the Sea Level Anomaly (SLA) on the opposite sides of the Corsica Channel. On a seasonal time scale the water flux variability well relates with SSP, SLA, Ekman transport and meridional wind stress. The interannual variability results instead from changes in SLA. The novel discoveries about deep LPC velocities and Corsica Channel transport are useful constraints for Inverse Box Model (IBM). The IBM, has been run for the first time incorporating data collected during 9 cruises. The oceanographic cruises took place from 2002 to 2012. The IBM results shed light on the importance of the Capraia Channel, almost completely absent in literature. The inversions also outlined the Western Corsica Channel current variability neglected in literature. Through the IBM technique, a modern estimation of the Ligurian Sea circulation and geostrophic transport transport has been generated. This study ultimately contributes to the fundamental knowledge of the Ligurian Sea circulation, implementing state of the art observations and reanalysis data.