Insights into exceptional freshening events in the northern Adriatic Sea throughout 2023–2024

The northern Adriatic Sea experienced multiple extreme freshening events in 2023 and 2024, underscoring the intensifying influence of heavy precipitation, river discharge, and coastal flooding in the region. This study combines high-frequency in-situ observations from two autonomous meteo-marine monitoring platforms offshore of Fano and Senigallia with river discharge records, satellite imagery, and Copernicus Marine Service products to examine the evolution, drivers, and ecological implications of these events. The first freshening event in early summer 2023 was linked to consecutive heavy rainfall episodes, including Storm Minerva, which triggered catastrophic flooding across the Emilia-Romagna region in northern Italy. Near-surface salinity declined from ∼ 36 g kg ⁻¹ to below 24 g kg ⁻¹ within two weeks, corresponding to an estimated freshwater input of ∼ 42.5 m ³  h ⁻¹ in the vicinity of the buoy. Events in late 2023 and 2024 were even more abrupt and intense, culminating in late October 2024 with salinity values dropping to ∼ 15 g kg ⁻¹ following Storm Boris. A key distinction between the two years was the marked recovery of Po River discharge in 2024 after a prolonged drought, which significantly amplified freshwater inputs. These events triggered cascading environmental responses, including stratification, turbidity peaks, and phytoplankton blooms including summertime mucilage-forming aggregations, posing risks to aquaculture, water quality, and coastal tourism. By combining autonomous in-situ measurements, satellite observations, and Copernicus reanalysis products, this study demonstrates a robust and cost-effective approach to tracking extreme hydrological events in coastal zones. The integrated dataset not only captures rapid thermohaline and biogeochemical changes near-real time but also places them in a broader environmental context. These findings underscore the value of sustained and interoperable observing systems in supporting early warning capabilities, scientific research, and climate adaptation in vulnerable marine regions such as the northern Adriatic Sea.