Abstract. In this paper we document dense water formation throughout the Adriatic shelf and coastal area in January/February 2012, resulting in record-breaking densities observed during and after the event. The unprecedented dense water generation was preconditioned by a dry and warm year which resulted in a significant reduction of coastal freshwaters, superimposed on a long-term basin-wide salinity increase. The final event that triggered the dense water formation was an extended period of cold weather with strong and severe winds. Record-breaking potential density anomalies (above 30 kg m −3 ) were measured at several formation sites. Accumulated surface net heat and water losses in some coastal regions exceeded 1.5 GJ m −2 and 250 kg m −2 over 21 days, respectively. Excessiveness, importance of shelf-type dense water formation and effects on the thermohaline circulation and deep aquatic systems are discussed.

We document dense water formation (DWF) throughout the Adriatic shelf and coastal area in January/February 2012, resulting in record-breaking densities observed during and after the event. The unprecedented dense water generation was preconditioned by a dry and warm year which resulted in a significant reduction of coastal freshwaters, superimposed on a long-term basin-wide salinity increase. The final event that triggered the DWF was an extended period of cold weather with strong and severe winds. Record-breaking potential density anomalies (above 30 kg m^−3) were measured at several DWF sites. Accumulated surface net heat and water losses in some coastal regions exceeded 1.5 GJ m^−2 and 250 kg m^−2 over 21 days, respectively. Excessiveness, importance of shelf-type DWF, effects on the thermohaline circulation and deep aquatic systems, and connection with climate change are discussed

The karstic Zrmanja River discharges into the eastern Adriatic Sea, forming a highly stratified estuary with a sharp halocline that divides upper brackish and lower marine layers. Low orthophosphate concentrations and high Redfield ratios indicate that phosphorus limits phytoplankton growth. In addition, high transparency (avg 6.7 m) and oxygen saturation (avg 98.78%) indicate oligotrophy. Maximum phytoplankton abundance reached 3.4 × 106 cells·l−1 in early spring, a period when the community was composed mainly of diatoms. Dinoflagellates and nanoplanktonic phytoplankton dominated in summer; coccolithophorids and silicoflagellates characterized autumn. Stable conditions in the middle and lower estuary provided a suitable setting for development of microphytoplanktonic diatoms, whereas unstable conditions (frequent salinity variations) at the head of the estuary favored nanophytoplankton. Canonical correspondence analysis identified salinity, temperature, and river inflow as the main factors influencing phytoplankton development. Nutrients strongly limited phytoplankton growth in summer when the river discharge was a minimum.

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