Oxygen depletion recorded in upper waters of the glacial Southern Ocean

• Published in: Nature Communications
• Main Authors: Lu, Zunli, Hoogakker, Babette A. A., Hillenbrand, Claus-Dieter, Zhou, Xiaoli, Thomas, Ellen, Gutchess, Kristina M., Lu, Wanyi, Jones, Luke, Rickaby, Rosalind E. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2016
• Subjects: General Physics and Astronomy; General Biochemistry, Genetics and Molecular Biology; General Chemistry; Antarctic; Southern Ocean; The Antarctic; Antarc*; Planktonic foraminifera
• Online Access: http://dx.doi.org/10.1038/ncomms11146; http://www.nature.com/articles/ncomms11146.pdf; http://www.nature.com/articles/ncomms11146

Abstract Oxygen depletion in the upper ocean is commonly associated with poor ventilation and storage of respired carbon, potentially linked to atmospheric CO 2 levels. Iodine to calcium ratios (I/Ca) in recent planktonic foraminifera suggest that values less than ∼2.5 μmol mol −1 indicate the presence of O 2 -depleted water. Here we apply this proxy to estimate past dissolved oxygen concentrations in the near surface waters of the currently well-oxygenated Southern Ocean, which played a critical role in carbon sequestration during glacial times. A down-core planktonic I/Ca record from south of the Antarctic Polar Front (APF) suggests that minimum O 2 concentrations in the upper ocean fell below 70 μmol kg −1 during the last two glacial periods, indicating persistent glacial O 2 depletion at the heart of the carbon engine of the Earth’s climate system. These new estimates of past ocean oxygenation variability may assist in resolving mechanisms responsible for the much-debated ice-age atmospheric CO 2 decline.