Assessing the interactions between extreme weather systems and the marine environment in the Mediterranean Sea

In this study, the impacts of a specific class of extreme weather systems in the Mediterranean region (Medicanes) on the physical and biogeochemical parameters of the marine environment are thoroughly investigated. A comprehensive analysis based on 14 systems that occurred between 2007 and 2021 was carried out, with a specific focus on the impact on the different regions of the Mediterranean Sea (MS). The analysis showed some consistent patterns in the response of the marine environment to the passage of the system: surface concentrations of Chlorophyll-a (Chl-a), phytoplankton, nutrients, and oxygen tend to increase above the MLD, while temperature tends to decrease. Significant increments of these parameters were observed in the presence of Warm Core Eddies (WCEs) and Cold Core Eddies (CCEs). The interaction with WCEs enhanced the intensity of the weather system and related mixing and upwelling in the upper layer, leading to the increase in Chl-a, phytoplankton, and oxygen concentrations .. Cyclone-induced local mixing injects nutrients into the ocean’s upper layer that can drive significant phytoplankton blooms. Moreover, strong winds frequently lead to a drop in sea surface temperature (SST), which is a key factor in primary productivity. The analysis of mean sea level pressure (MSLP) and wind speed (WS) along the path of the cyclones revealed a sudden drop (rise) in MSLP and rise (drop) in WS at WCEs (CCEs) locations. It is observed that a few medicanes, such as Zissi, Anton, and Xandra, show exceptional behavior. Among them, Zissi exhibited an exceptionally high translational speed. The fast evolution of Zissi resulted in limited interaction with the underlying ocean, which is responsible for its unique characteristics during the event.