In the "secret" depths of the Adriatic Sea

The Adriatic Sea is considered one of the "cold engines" of the Mediterranean thermohaline circulation, that is the "conveyor belt" that conveys masses of sea water, heat and chemical compounds, connecting coastal areas and deep and abyssal regions, distant between  them even thousands of kilometers.  The mechanism through which the Adriatic performs this function is the formation of "dense water", therefore heavy waters that sink, and which can occur in the winter months, following episodes of intense wind and cold preceded by relatively little rainy periods.

Where these conditions occur (typically in the northern coastal areas, but not only), the water masses see their temperature decrease and their salinity increase, becoming denser than the surrounding waters and therefore tending to move towards the deeper areas of the  pelvis, thus feeding the large circulatory mechanism.

The thick water of Puglia
In correspondence with these events, the continental margin off Puglia, where the depth of the seabed rapidly passes from about 200 to over 1000 meters, is therefore the scene of intense flows of dense water coming from the north and directed towards the regions of the deep Mediterranean,  “Renewing” them with the supply of oxygen and essential nutrients for the abyssal ecosystems.

As part of a long study on the processes of formation and propagation of dense waters, the presence in the Adriatic Sea of ​​oscillatory phenomena called "Continental Shelf Waves (CSW)" was recently demonstrated, theoretically hypothesized since the 1980s but never documented so far.  in these regions.

The fruit of this work, which lasted two years, was published in Scientific Reports magazine and was realized thanks to the H2020 Ceaseless project funded by the European Union and the Ritmare Flag Project of the CNR funded by the Ministry of Education, University and Research.  A "Continental Shelf Wave" can be seen as a modulation of a sea current, characterized by an oscillatory nature with respect to its "average" motion governed by the steep slope of the seabed.  The conclusions of the research were obtained thanks to the joint analysis of the data recorded off the coast of Puglia and the results produced by new mathematical models that simultaneously process the hydrodynamic, atmospheric and wave situation.

Between canyons and mountains
By discovering the presence of the "Continental Shelf Waves" along the Adriatic continental margin and describing their dynamics, the work adds an important new element to the understanding of the processes that control dense water flows and, more generally, exchanges between coastal and  the deep ones.  In fact, by giving the currents a tendentially meandering trend that affects the entire water column and propagating over long distances (over 100 kilometers in the case identified by our study), CSW favor the development of "cascades" of dense water even far away  by the "preferential lanes" dictated by the topography (such as canyons or submarine mountains), alternating with phases of transport in the opposite direction.

The new vision that emerges from this work opens the way to various practical applications in the scientific and socio-economic fields, allowing, among other things, a better quantification of transport phenomena along the continental margin, the optimization of measurement campaigns, and a  better characterization of marine habitats and potential areas for the repopulation of ichthyofauna.