Variability of Black Sea Physical Processes from 1950 to 2100

Climate change and climate variability have significant effects on atmospheric and oceanic processes, with semi-enclosed basins such as the Black Sea being particularly vulnerable due to their unique physical and chemical structure. In recent decades, the basin has experienced pronounced changes in temperature, salinity, and circulation, with important consequences for its biogeochemical and ecological functioning. Understanding the mechanisms driving these changes and their future evolution is therefore essential. This study investigates the historical and projected variability of key physical processes in the Black Sea over the period 1950-2100 using a high-resolution regional ocean model (NEMO). Temperature, salinity, mixed layer depth, and Cold Intermediate Layer (CIL) dynamics are analyzed, using atmospheric forcings from reanalysis data (ERA5) and a regional climate model (MAR) forced by a global climate model (EC-Earth). Future projections are conducted under two IPCC Shared Socioeconomic Pathways (SSP1-2.6 and SSP5-8.5). The historical simulations (1950-2020) are validated against in situ CTD observations and satellite-derived sea surface temperature and sea surface height, demonstrating good skill in reproducing the observed thermal and haline structure of the basin. Results from the historical simulations show a progressive weakening of the CIL and a shift toward stronger upper sea stratification. Future simulations aim to quantify how different climate change pathways will modify temperature and salinity dynamics. Together, the results provide new insight into the atmospheric drivers controlling Black Sea hydrodynamics and offer projections of regional climate change impacts on this highly sensitive system.