Productivity and dissolved oxygen controls on the Southern Ocean deep‐sea benthos during the Antarctic Cold Reversal

• Published in: Paleoceanography and Paleoclimatology
• Main Authors: Stewart, Joseph A., Li, Tao, Spooner, Peter T., Burke, Andrea, Chen, Tianyu, Roberts, Jenny, Rae, James W.B., Peck, Victoria, Kender, Sev, Liu, Qian, Robinson, Laura F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2021
• Subjects: Antarctic; Southern Ocean; The Antarctic; Drake Passage; Antarc*; Sea ice
• Online Access: http://nora.nerc.ac.uk/id/eprint/531210/; https://nora.nerc.ac.uk/id/eprint/531210/1/2021PA004288.pdf; https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021PA004288

The Antarctic Cold Reversal (ACR; 14.7 to 13 thousand years ago; ka) phase of the last deglaciation saw a pause in the rise of atmospheric CO2 and Antarctic temperature, that contrasted with warming in the North. A re-expansion of sea ice and a northward shift in the position of the westerly winds in the Southern Ocean are well-documented, but the response of deep-sea biota and the primary drivers of habitat viability remain unclear. Here we present a new perspective on ecological changes in the deglacial Southern Ocean, including multi-faunal benthic assemblage (foraminifera and cold-water corals) and coral geochemical data (Ba/Ca and δ11B) from the Drake Passage. Our records show that, during the ACR, peak abundances of thick-walled benthic foraminifera Uvigerina bifurcata and corals are observed at shallow depths in the sub-Antarctic (∼300 m), while coral populations at greater depths and further south diminished. Our ecological and geochemical data indicate that habitat shifts were dictated by (i) a northward migration of food supply (primary production) into the Subantarctic Zone and (ii) poorly oxygenated seawater at depth during this Antarctic cooling interval.