Dominant drivers of Past Mediterranean Marine Heatwaves

Abstract

<p class="western" align="justify">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<sup>st</sup> 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, <span lang="en-US"> this study investigates the dominant physical processes behind an ensemble of past Mediterranean MHWs, u</span>sing the output of <span lang="en-US">a dedicated, fully-coupled regional climate system model in hindcast mode, </span><span lang="en-US">over the 1980-2018 period</span><span lang="en-US">. 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 </span><span lang="en-US">atmosphere heat fluxes, </span><span lang="en-US">wind forcing and vertical mixing on most events and a predominant horizontal advection presence only at smaller-scale. We present here a</span><span lang="en-US"> statistical overview of the dominant MHW drivers at the regional scale, </span><span lang="en-US">across seasons and different regions in the Mediterranean basin, providing </span><span lang="en-US">stakeholders and economy sectors </span><span lang="en-US">affected by these marine extreme events, with critical information on their causes. </span></p>