The Mediterranean Sea is a critical hotspot for climate and biodiversity, where dense water formation and its spreading significantly influence thermohaline circulation and biogeochemical exchanges. In this context, the Adriatic Observatory Network serves as a leading example of a basin-scale observatory to study ecosystem dynamics across the Adriatic and Ionian Seas, integrating different infrastructures and producing FAIR (Findable, Accessible, Interoperable, Reusable) data. This network has unveiled a previously unexplored aspect occurred in 2017, with potential impact on the Mediterranean basin scale circulation. In 2016-2017, the central Mediterranean experienced significant heat loss, reduced freshwater input, and a persistent cyclonic phase of the Northern Ionian Gyre, which drove salt water into the Adriatic. These conditions facilitated dense water formation in the northern and southern Adriatic by shelf and open-ocean convection. The dense water formed in the north flows southward along the western continental slope, in part cascading into the southern Adriatic Pit, where it mixes with resident waters to form the Adriatic deep water, which then spreads into the Ionian Sea. Our findings revealed that another part of the northern dense water flows directly towards the strait of Otranto without being further altered on the way. These two water masses follow two different fates after their outflow into the Ionian Sea: southward along the Hellenic Trench and westward towards the Gulf of Taranto, respectively. The westward flow contributes to the reversal of the Northern Ionian Gyre, while the southward sinking affects the deep layers of the Hellenic Trench and the Levantine Basin.