Drivers of the 2019 Marine Heatwaves in the Mediterranean Sea

Marine heatwaves (MHWs) are prolonged discrete anomalously warm water events that
last for more than five successive days and can be described by their duration, intensity, rate of evolution, and spatial coverage. These Episodes of large-scale anomalously high ocean temperatures can have many impacts on marine ecology and ecosystems and major implications for fisheries as well. As a result of the anthropogenic climate change, MHWs have been observed in many parts of the world's oceans and their intensity and frequency are expected to increase in the future. This thesis investigates the 2019 MHWs that have occurred in the Mediterranean Sea, their possible drivers, and their mechanism of formation. The MHWs that occurred in the Mediterranean Sea between June and December 2019 were defined and categorized using the daily NOAA OISST data set and based on a 30-years climatology (1982–2011) baseline. The eastern and western basins of the Mediterranean Sea have shown dissimilarities in the SST and SST anomaly distributions as well as in the characteristics of the MHW events that occurred in them
during the study period. The MHWs occurred more often in the WMED than in the EMED with higher intensities while the EMED marine heatwaves were observed to have a longer duration than the WMED ones. In both basins, the MHWs characteristics were linked to the changes in the heat flux anomaly, mixed layer depth, air temperature, mean sea level pressure, and winds. The high anomalous sea surface temperature of the marine heatwaves was associated with high heat flux anomaly, shallow mixed layer, high air temperature, high-pressure system, and low wind speed.