Modeling Carbon Budgets and Acidification in the Mediterranean Sea Ecosystem Under Contemporary and Future Climate

We simulate and analyze the effects of a high CO2 emission scenario on the Mediterranean Sea biogeochemical state at the end of the XXI century, with a focus on carbon cycling, budgets and fluxes, within and between the Mediterranean sub-basins, and on ocean acidification. As a result of the overall warming of surface water and exchanges at the boundaries, the model results project an increment in both the plankton primary production and the system total respiration. However, productivity increases less than respiration, so these changes yield to a decreament in the concentrations of total living carbon, chlorophyll, particulate organic carbon and oxygen in the epipelagic layer, and to an increment in the DIC pool all over the basin. In terms of mass budgets, the large increment in the dissolution of atmospheric CO2 results in an increment of most carbon fluxes, including the horizontal exchanges between eastern and western sub-basins, in a reduction of the organic carbon component, and in an increament of the inorganic one. The eastern sub-basin accumulates more than 85% of the absorbed atmospheric CO2. A clear ocean acidification signal is observed all over the basin, quantitatively similar to those projected in most oceans, and well detectable also down to the mesopelagic and bathypelagic layers.

Automated summary

This study simulates and analyzes the impact of a high CO2 emission scenario on the Mediterranean Sea ecosystem. It reveals that under this scenario, plankton primary production and total system respiration increase. However, the increase in productivity is smaller than that of respiration, resulting in decreased concentrations of total living carbon, chlorophyll, particulate organic carbon, and oxygen in the surface layer, and increased DIC pool throughout the basin. Additionally, the dissolution of atmospheric CO2 leads to increased carbon fluxes, reduced organic carbon, and increased inorganic carbon. The eastern sub-basin accumulates more than 85% of the absorbed atmospheric CO2. A clear signal of ocean acidification is observed in the entire basin, similar to other oceans, and can be detected even in the deep layers.