to quantify the socio-economic uncertainty. Our 6-member scenario simulations display a warming and saltening of the Mediterranean. For the 2070-2099 period compared to , the sea surface temperature anomalies range from +1.73 to +2.97 °C and the SSS anomalies spread from +0.48 to +0.89. In most of the cases, we found that the future Mediterranean thermohaline circulation (MTHC) tends to reach a situation similar to the eastern Mediterranean Transient. However, this response is varying depending on the chosen boundary conditions and socio-economic scenarios. Our numerical experiments suggest that the choice of the near-Atlantic surface water evolution, which is very uncertain in General Circulation Models, has the largest impact on the evolution of the Mediterranean water masses, followed by the choice of the socio-economic scenario. The choice of river runoff and atmospheric forcing both have a smaller impact. The state of the MTHC during the historical period is found to have a large influence on the transfer of surface anomalies toward depth. Besides, subsurface currents are substantially modified in the Ionian Sea and the Balearic region. Finally, the response of thermosteric sea level ranges from +34 to +49 cm (2070-2099 vs. 1961-1990), mainly depending on the Atlantic forcing.

[1] Tropical cyclones form only under specific environmental conditions. Anthropogenic climate change might alter the geographical areas where tropical cyclones can develop. Using an ensemble of regional climate models, we find an increase in the extremes of cyclone intensity over the Mediterranean Sea under a climate change scenario. At least for the most sensitive model, the increase in intensity is clearly associated with the formation of tropical cyclones. Previous studies did not find evidence of changes in the projected areas of formation of tropical cyclones (Intergovernmental Panel on Climate Change, 2007;Walsh, 2004;Lionello et al., 2002). Those studies were based either on relatively low-resolution global climate models or on one particular regional climate model. The use of a multi-model ensemble of relatively high-resolution regional climate models has allowed us to detect for the first time a risk of tropical cyclone development over the Mediterranean Sea under future climate change conditions.

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An exhaustive validation of operational ocean forecast products available in the Gibraltar Strait and the Alboran Sea is presented. The skill of two ocean model solutions (i.e. the regional CMEMS IBI and the local PdE SAMPA ones) in reproducing the complex surface dynamics in the above areas is evaluated. To this aim, in-situ measurements from 35 drifter buoys (the MEDESS-GIB database) are used as observational reference. A Lagrangian separation distance and a skill score have been applied to evaluate the performance of the modeling systems in reproducing the observed trajectories. Furthermore, the SST validation with in-situ data is carried out by means of validating the model solutions with L3 satellite SST products. The IBI products are evaluated in an extended domain, beyond the Alboran Sea, covering western Mediterranean waters. This analysis reveals some strengths of the regional solution (i.e. realistic values of the Atlantic Jet in the Strait, realistic simulation of the Algerian Current), together with some shortcomings (the major one related to the simulated geographical position and intensity of the Alboran Gyres, particularly the western one). On the other hand, the SAMPA system shows a more accurate model performance and it realistically reproduces the observed surface circulation in the area. The results reflect the effectiveness of the dynamical downscaling performed through the SAMPA system with respect to the regional IBI solution (in which SAMPA is nested), providing an objective measure of the potential added values introduced by the SAMPA downscaling solution in the Alboran Sea.