Tracking via coccolithophores the East Asian Monsoon and carbonate production in the South China Sea during Marine Isotope Stage 5e

Coccolithophore analyses during Marine Isotope Stage (MIS) 5e and the preceding deglaciation phase (Termination II; T-II) provide key information into the paleoclimate and palaeoceanography of one of the best analogues for the current global warming, i.e., the MIS 5e. Here, we analyzed the fossil coccolithophore assemblages from Site U1501 in the South China Sea from 158 to 50 kyr (MIS 6-3) to assess coccolithophore abundance, community composition and calcium carbonate (CaCO3) production/accumulation. The assemblage indicates a sustained oligotrophic regime with a shallow nutricline and thermocline for this region. A systematic distinction between lightly and heavily calcified species, based on a quantitative threshold defined for the first time in this work, revealed that the latter (mainly Gephyrocapsa oceanica medium) contributed significantly during T-II and MIS 5e to the CaCO3 production. Variations in the coccolithophore abundance align with changes in the East Asian Monsoon (EAM) throughout the studied interval. Primary productivity indices suggest that EAM strengthening occurred during MIS 6, T-II, the cold substages of MIS 5, and MIS 4/3 transition, while weaker monsoons and reduced productivity characterized interglacial periods. Moreover, a comparison between data collected during T-II and MIS 5e and the future predicted scenarios for the SCS shows a strong similarity in the evolution of EAM dynamics, which predict reduced primary productivity and a weakened monsoon gyre, as well as some with future coccolithophores responses. These findings confirm the potential of coccolithophores in climate reconstructions and open interesting perspectives on the fate of coccolithophores in future oceans.