Salinity-driven dynamics in the central Mediterranean in the era of ocean warming

Scientists are closely monitoring the effects of global warming on the oceanic conveyor belt because of its central role in maintaining global climate stability. As the oceans warm up and become more stratified, processes driven by salinity are becoming increasingly important in shaping surface circulation, despite traditionally being considered less significant than wind forcing and sea-level gradients. This study examines salinity-driven dynamics in the Central Mediterranean Sea (CMed) using an integrated approach combining in situ observations (Argo floats and gliders), satellite data and model reanalysis. The CMed is a critical region where the zonal and meridional branches of the Mediterranean overturning circulation converge and deep convection and dense water formation occur. Over recent decades, the region has experienced significant warming and salinification, with salinity levels rising sharply since 2012. This enhanced salinity has directly affected the circulation field and the vertical stability of the water column. In the Southern Adriatic Gyre, the vorticity field is primarily driven by wind forcing and its interannual variability, but is also strongly influenced by horizontal advection from adjacent regions. After 2012, the baroclinic term of the vorticity equation associated with salinity-induced density gradients became increasingly significant, reaching magnitudes comparable to wind stress. Together with advection, these effects shaped the circulation. In the North Ionian Sea, rising upper-layer salinity has intensified the centre–edge salinity gradient during the inflow of fresher, Atlantic-origin waters. This has led to a weakening of the vorticity field and increased water-column stability. These findings highlight the growing importance of salinity in driving thermohaline variability and surface circulation, with significant implications for the dynamics of the Mediterranean Sea in the context of ongoing climate change.