Marine Isotope Stage 11 in the Pacific sector of the Southern Ocean; a coccolithophore perspective

Abstract

This work aims to provide new insights into environmental conditions during late Pleistocene Marine Isotope Stage 11 (MIS 11) in the Southern Ocean. We generated a multi-proxy coccolithophore dataset based on sediment core PS75/059-2. This core was retrieved at the western flank of the southern East Pacific Rise crest at ∼3600 m water depth. Coccolithophore assemblage counts indicated that the coccolith fraction (CF; <20 μm) during MIS 11 was dominated by Gephyrocapsa caribbeanica and subsequently by small Gephyrocapsa. Coccolith accumulation rates, CF Sr/Ca data and temperature-corrected CF Sr/Ca records were consistent and showed a steep increase in coccolithophore productivity as well as apparent coccolith calcification during Termination V. Maximum values were reached during MIS 11. We explain this high coccolithophore production during MIS 11 by changes in sea surface temperature and nutrient regimes, due to a re-organisation of the surface circulation patterns and a southward migration of the frontal systems. Furthermore, the immense carbonate production of the coccolithophores may have contributed to increased atmospheric CO2 contents, causing a drawdown of the carbonate saturation and an increase in dissolution at the seafloor. However the atmospheric CO2 did not reach higher values probably due to the effective ballasting of organic matter by coccoliths.