Dominant drivers of Past Mediterranean Marine Heatwaves

The Mediterranean Sea, a global climate change hot-spot region, has experienced an increase in marine heatwave (MHW) frequency and intensity since the early 1990s. These extreme events have been associated with a range of local-ecological impacts in the basin, which hosts a large marine biodiversity in addition to 480 million inhabitants along its coasts. According to 21^st century projections, the increasing MHW trends are likely to continue in the Mediterranean Sea. This calls for a deeper understanding of MHW drivers that can lead to a higher degree of MHW predictability. Therefore, this study investigates the dominant physical processes behind an ensemble of past Mediterranean MHWs, using the output of a dedicated, fully-coupled regional climate system model in hindcast mode, over the 1980-2018 period. In particular, we explore the vertical signature of multiple events in a local scale through “online” diagnostics of a mixed layer heat budget, where we disentangle the relative role of local-scale dynamics (e.g air-sea interactions, ocean currents, entrainment, mixing) during their development and decline. Preliminary results indicate a key role of atmosphere heat fluxes, wind forcing and vertical mixing on most events and a predominant horizontal advection presence only at smaller-scale. We present here a statistical overview of the dominant MHW drivers at the regional scale, across seasons and different regions in the Mediterranean basin, providing stakeholders and economy sectors affected by these marine extreme events, with critical information on their causes.