Italian-Croatian Workshop on Spreading of the NAdDW in the Southern Adriatic in 2012

In February 2012, the North Adriatic experienced a cold spell with large decrease of surface temperature associated with severe cold and dry Bora wind. The result was the formation of extremely dense shelf water, further promoted by the low discharge of the Po river in the preceding autumn.

CNR-ISMAR set up a rapid response experiment (ODW) to study the occurrence, amount, timing and properties of the newly formed DSW, which was expected to cascade in the Southern Adriatic in the following weeks after its migration southwards as a bottom-hugging gravity current. The ODW experiment was designed with an integrated approach, including modelling simulations, mooring deployments and quick-response oceanographic cruises.

Since 2006 the OGS E2-M3A observatory, located in the centre of the south Adriatic depression, is used to study the long-term variability associated with large circulation modes, as well as the effects of dense water formation events in the south Adriatic.

IOF  deployed  two  ADCPs  in  March  2012  along  the  Palagruža  Sill  and,  though  permanent  monitoring programmes, performed a number of cruises at the sill and in coastal Croatian waters in winter and spring of 2012. In addition, permanent monitoring programmes along the sill have been executed for more than 60 years,  providing  an  unique  dataset  for  monitoring  of  the  dense  water  dynamics  and  outflow  towards  the southeast.
Numerical modelling experiments were executed by a number of research groups with different atmosphere-ocean modelling systems (ROMS/Aladin, COAWST), aiming for reproduction of the dense water  formation during the 2012 event.

Overall, experiments allowed us to obtain much information about properties and amount of the newly formed NAdDW, as well as pathways and timing of transfer toward the Southern Adriatic Sea. However, it was not sufficiently investigated the vein of dense water coming from the overflow of the Middle Adriatic through the Pelagosa sill. In contrast, both numerical simulations and geological evidences in our possession suggested that this vein is quantitatively significant.

In March 2014 and April 2015, two oceanographic cruises were conducted in joint-venture by CNR-ISMAR, IOF and OGS acquiring CTD and LADCP profiles along transects between the Pelagosa sill and the northern slope of the South Adriatic and deploying a mooring in Croatian waters to obtain an one-year time series of physical and dynamical characteristics of the water masses, and the particle flux and composition along the probable pathway of the dense water coming from the Central Adriatic.

The workshop will make a summary of the results achieved so far and explore the possibility of gain added value by bringing together data from the different groups to explore further aspects of the processes studied still poorly understood.