Abstract
Abstract. We analyze the climate change signal in the Mediterranean Sea using the regionally coupled model REMO–OASIS–MPIOM (ROM; abbreviated from the regional atmosphere model, the OASIS3 coupler and the Max Planck Institute Ocean Model). The ROM oceanic component is global with regionally high horizontal resolution in the Mediterranean Sea so that the water exchanges with the adjacent North Atlantic and Black Sea are explicitly simulated. Simulations forced by ERA-Interim show an accurate representation of the present Mediterranean climate. Our analysis of the RCP8.5 (representative concentration pathway) scenario using the Max Planck Institute Earth System Model shows that the Mediterranean waters will be warmer and saltier throughout most of the basin by the end of this century. In the upper ocean layer, temperature is projected to have a mean increase of 2.7 ∘C, while the mean salinity will increase by 0.2 psu, presenting a decreasing trend in the western Mediterranean in contrast to the rest of the basin. The warming initially takes place at the surface and propagates gradually to deeper layers. Hydrographic changes have an impact on intermediate water characteristics, potentially affecting the Mediterranean thermohaline circulation in the future.
Highlights
The Mediterranean Sea is expected to be among the world’s most prominent and vulnerable climate change “hot spots” (Giorgi, 2006; Cramer et al, 2018)
Changes in the Mediterranean Sea under RCP8.5 conditions are estimated from the analysis of differences between the present climate (1976–2005, ROM_P1) and the climate projection (2070– 2099, ROM_P2) carried out by ROM driven by MPI-ESMLR
Those differences could be attributed partly to regional atmosphere model (REMO) parameterizations, but a more important role could be played by the deficiencies in the simulated ocean circulation in the North Atlantic, which result in a region of cold sea surface temperature (SST) bias centered east of the Flemish Cap
Summary
The Mediterranean Sea is expected to be among the world’s most prominent and vulnerable climate change “hot spots” (Giorgi, 2006; Cramer et al, 2018). The freshwater balance in the Mediterranean basin is negative since the evaporation exceeds precipitation and river runoff (SanchezGomez et al, 2011). This deficit is compensated for by a net inflow of water through the Strait of Gibraltar and the Dardanelles. The region is located in a transitional area between tropical and midlatitudes and presents a complex orography and coastlines, where intense air–sea and land–sea interactions take place These intense air–sea interactions together with the inflow of Atlantic Water drive the Mediterranean thermohaline circulation (MTHC) (Fig. 1), suggesting that atmosphere–ocean regionally coupled models (AORCMs) could be conducive to the study of atmospheric and oceanic processes in the Mediterranean Sea
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