Recent research published in Science Advances sheds light on the role of the Southern Ocean in controlling global oceanic oxygenation during the last deglaciation. The study, conducted by Yi Wang, Kassandra M. Costa, Wanyi Lu, Sophia K. V. Hines, and Sune G. Nielsen, presents a comprehensive reconstruction of ocean dissolved oxygen (DO) using thallium isotopes.

The findings reveal lower global DO levels during the Last Glacial Maximum (19 to 23 thousand years before the present) compared to the Holocene. Additionally, the research highlights periods of reoxygenation during the Heinrich Stadial 1 (approximately 14.7 to 18 thousand years before the present) and the Younger Dryas (11.7 to 12.9 thousand years before the present), along with deoxygenation during the Bølling-Allerød (12.9 to 14.7 thousand years before the present).

Importantly, the study suggests that the deglacial DO changes were independent of North Atlantic Deep Water formation rates, indicating that Southern Ocean ventilation played a crucial role in controlling ocean oxygen levels. The coherence between global DO and atmospheric CO2 on millennial timescales underscores the significant impact of the Southern Ocean on the rise of atmospheric CO2 during the deglaciation period.

These findings have significant implications for understanding the marine carbon cycle and its influence on global climate change. By providing insights into the relationship between marine carbon storage and DO, the research contributes to our understanding of the glacial-interglacial variability of atmospheric CO2 levels.

The study’s comprehensive analysis of DO proxy records, including laminations, foraminiferal assemblages, redox-sensitive metals, bulk sedimentary nitrogen isotopes, and carbon isotopic composition records, contributes to a more nuanced understanding of the intricate dynamics between marine carbon storage and oceanic oxygenation.