Dominant Spatio-Temporal Modes of Mediterranean Heat Budget Variability

Understanding the Mediterranean Sea heat budget is crucial for assessing regional climate variability and warming responses. In this work, we analyse the spatio-temporal structure of heat budget components using atmospheric (ERA5) and ocean reanalysis (ORAS5). Heat budget analyses are compared to sea surface temperature (SST) and salinity (SSS), total water column ocean heat content (TOHC), and complemented by heat fluxes at the atmosphere-ocean interface (Qnet) and oceanic advective terms. Climatological SST reveals a strong west-east gradient, with the Levantine Basin exhibiting the highest temperatures. TOHC is maximal  in the eastern region and lower in shallow basins such as the Adriatic and Gulf of Lion. SSS increases from 35–37 PSU in colder and deeper basins in the western part of the Mediterranean to values in excess of 40 PSU in the Levantine Sea, due to positive evaporation and stratification. Net fluxes at the interface range from winter heat loss (-150 to -200 Wm⁻²) to summer heat gain (+150 to +200 Wm⁻²), with maximum variability in the eastern Mediterranean. Preliminary trend analysis indicates steady increments in TOHC and SSS since the 1980s, with accelerated heat accumulation in the Eastern Mediterranean. An EOF analysis of monthly TOHC anomalies reveals a dominant basin-wide warming mode and secondary east-west dipole structures connected with regional circulation features. The role of advective fluxes in determining these regional circulation features is discussed.  

Keywords: Mediterranean Sea, Spatio-temporal analysis, Heat budget components, Seasonal variability, Decadal trends, EOF analysis.