Mediterranean Sea warming, nutrient decline, primary production increase, deoxygenation and acidification during the 21st century from high resolution physical and biogeochemical projections under emission scenarios RCP4.5 and RCP8.5

Eddy-resolving projections of the physical and biogeochemical state of the Mediterranean Sea under the Representative Concentration Pathway (RCP) 4.5 and 8.5 are here analyzed to assess the impacts of climate change on the Mediterranean marine ecosystems in the middle and at the end of the 21st century. The projections were produced through the offline coupling between the physical model MFS16 and the transport-biogeochemical reactor OGSTM-BFM. The analysis shows during the 21st century an overall warming and an increase in the stratification of the water column, resulting in a weakening of the thermohaline circulation of the basin. The biogeochemical projections show a decline in the dissolved nutrients content and organic matter stock of the euphotic and intermediate layers of the basin and an increase in the net primary production and phytoplankton respiration. Moreover, the projected warming of the water column and the increase in the respiration community will drive a quite uniform surface and subsurface reduction in the oxygen concentration. Finally an acidification of the upper and intermediate layers of the basin driven by the CO₂ absorption from the atmosphere is projected. All the projected changes are found to be stronger in the eastern part of the Mediterranean basin.