The Mediterranean sub-basin circulation is governed by a complex interplay of oceanic
currents, atmospheric fluxes, freshwater inflows, and extreme weather events, all of which are
increasingly influenced by climate change. This thesis examines key oceanographic processes
in the Adriatic and Ionian Seas, focusing on three major aspects: the variability of the
Southern Adriatic Gyre, the critical role of the Po River in shaping hydrodynamics of the
Adriatic Sea, and the impact of Mediterranean cyclones on the Ionian Sea. Using the ROMS model, this study provides an assessment of the dynamic interactions within these marine systems and their sensitivity to alterations in climatic and environmental changes.
The first component of this research investigates the variability of the Southern
Adriatic Gyre, a dominant circulation feature that undergoes seasonal and interannual
fluctuations due to changes in atmospheric and boundary fluxes. Using an ocean dynamics
model, we analyze gyre behavior from 2016 to 2018, revealing that the gyre’s core shifts
laterally by approximately 30–70 km, particularly in winter and fall. This displacement is
accompanied by changes in sea surface height (SSH), with the gyre’s core being 15–20 cm
lower than the surrounding waters, exhibiting higher salinity (0.1 to 0.8 PSU) and lower
temperature (0 to 2°C). Wind stress enhances gyre transport by approximately 30%, whereas
frictional forces, reduce transport by 8%. These findings indicate that changes in atmospheric
conditions, particularly wind stress and heat fluxes, have impacts on modulating gyre stability
and mixing. Given that atmospheric patterns are expected to shift under climate change, the
gyre’s structure and transport dynamics may also undergo long-term alterations, potentially affecting regional circulation.The second part of this research explores the influence of the Po River, the largest freshwater contributor to the Adriatic Sea, on regional heat and salt budgets, as well as
broader hydrodynamic patterns. Although the Po River has been widely recognized as a key
driver of Adriatic circulation, the potential consequences of its reduced discharge due to
climate change remain uncertain. To address this knowledge gap, we compared two
numerical simulations: a control run (WITHPO) that includes natural river discharge
conditions during 2018, and an experimental run (NOPO) that simulates a complete removal
of the Po River’s freshwater input. Our results show that the Po River exerts an influence on
surface temperature, salinity, and SSH variations. In the WITHPO scenario, the northern Adriatic experiences surface temperatures up to 1.5°C warmer throughout the year but can be
colder by 2°C during the spring. Salinity decreases by 0.35 to 1 PSU at the surface due to
freshwater input, with a corresponding effect on vertical stratification. Furthermore, SSH differences between the two scenarios range from 8–10 cm in the fall and winter (lower in
NOPO) to 4–6 cm in spring and summer (higher in WITHPO). The presence of the Po River
enhances the surface outflow from the Adriatic into the Ionian Sea and strengthens deep inflows near the seabed, demonstrating its role in maintaining the exchange processes
between the two basins. These results highlight the vulnerability of the Adriatic’s circulation
to changes in river discharge, with potential consequences for regional marine ecosystems,
fisheries, and coastal communities.
Finally, we examine the role of extreme weather events, particularly Mediterranean
cyclones, in modifying ocean conditions. We focus on Cyclone Ianos, which formed over the
Ionian Sea between 15 and 20 September 2020. While previous studies have primarily examined Ianos’ impact on coastal areas, its broader influence on the Ionian circulation
remains less explored. Our simulations indicate that the cyclone induced substantial changes
in temperature, salinity, and current patterns. A rapid drop of 2–3°C in surface temperatures
and a decrease in salinity by 0.1 PSU was documented, along with SSH increases of 1–2 cm. The cyclone generated a circular surface current, with clear evidence of Ekman transport
influencing the current structure. The relationship between the sea surface circulation
vorticity and the 10-meter wind vorticity revealed that as depth increased, as the storm’s
impact diminished, a counterclockwise eddy formed at a depth of 30–40 m. These findings
demonstrate that Mediterranean cyclones can drive substantial oceanographic changes
beyond coastal areas, influencing vertical mixing and nutrient transport, which are essential
for marine productivity.Overall, this study underscores the interconnectedness of atmospheric forcing, river discharge, and extreme weather events in shaping Mediterranean sub-basin circulation. The
results provide critical insights into how these processes may evolve under climate change
and highlight the potential implications for ocean dynamics. As climate change continues to
alter atmospheric patterns, riverine discharges, and the frequency of extreme events, understanding these mechanisms is essential for predicting future shifts in Mediterranean
circulation and developing strategies for climate adaptation and marine resource
management.