Deglacial Southern Ocean change: a cold-water coral investigation

Abstract

Over the past decades, great progress has been made in understanding the transition of Earth’s climate from the last ice age to the present day, in particular the importance of Southern Ocean processes and their impact on transfer of heat and carbon. This work explores deglacial ocean change through the lens of a new collection of cold-water corals from an understudied region, the southwest Indian Ocean alongside existing palaeo records including two other unpublished cold-water coral collections to form a broader picture of ventilation and structure of the deglacial Southern Ocean. A compelling peak in abundance of solitary scleractinians in the southwest Indian Ocean, as well as at other sites in the Southern Ocean during the late deglacial hints at widespread oceanic controls on habitat suitability. Neodymium isotope analysis reveals maintained Atlantic influence at intermediate depths throughout the record, and particularly strong connectivity at the most southerly sampling site, which records rapid fluctuations in seawater chemistry during the Younger Dryas. Radiocarbon data provides new evidence in support of a Southern Ocean source of atmospheric CO2 early in Heinrich Stadial 1, and potential transfer of old carbon to the upper cell at the end of the Younger Dryas. Overall, regional hydrographic changes appear to have played a significant role in the ventilation and water mass history of the southwest Indian Ocean.