Variability of marine heatwaves and atmospheric cyclones in the Mediterranean Sea during the last four decades

The Mediterranean Sea has been recognized as a hotspot for marine heatwaves (MHWs) and climate change impacts. Cyclogenesis and the occurrence of tropical-like cyclones (also known as Medicanes) in the Mediterranean appear to have intensified during the last decades. This study investigates the relationship between increased sea surface temperature (SST) levels and low-pressure systems in the Mediterranean Sea over four recent decades (1982-2020), highlighting a strong spatial variability in regions affected by MHWs. Key areas, such as the Ligurian, Tyrrhenian, Ionian, Aegean, and Northern Levantine Seas, demonstrate a notable interaction between MHWs and cyclogenesis. Stronger relations are identified at the west of Cyprus (Northern Levantine), in the northern Ionian Sea, and in the Gulf of Genoa (Ligurian Sea). Conversely, weaker interactions are observed in the southern Mediterranean, where both MHWs and cyclonic activity are weaker. The sea level pressure (SLP) in the Mediterranean and the intensity of the surface MHW revealed decreasing and increasing trends, respectively, during the 39 year period. A marked negative trend in SLP and an increase in SSTs in the northern Aegean point to heightened cyclone activity in this region. MHWs may ampilfy atmospheric systems that increase coastal hazards like flooding, strong winds and heavy precipitation. The study also highlights that periods of intense cyclonic activity often coincide with intense MHW formations, with both phenomena peaking in 2018. The cumulative intensity of the MHWs, measured by their duration and magnitude, correlates with the intensification of low-pressure systems in most of the Mediterranean sub-regions. These findings suggest that monitoring MHWs could improve the understanding and forecasting of cyclogenesis, benefiting both short-term weather predictions and long-term climate assessments.