A Possible 20th-Century Slowdown of Southern Ocean Deep Water Formation

• Published in: Science
• Main Authors: Broecker, Wallace S., Sutherland, Stewart, Peng, Tsung-Hung
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 1999
• Subjects: Southern Ocean
• Online Access: http://dx.doi.org/10.1126/science.286.5442.1132; https://www.science.org/doi/pdf/10.1126/science.286.5442.1132

Chlorofluorocarbon-11 inventories for the deep Southern Ocean appear to confirm physical oceanographic and geochemical studies in the Southern Ocean, which suggest that no more than 5 × 10 6 cubic meters per second of ventilated deep water is currently being produced. This result conflicts with conclusions based on the distributions of the carbon-14/carbon ratio and a quasi-conservative property, PO 4 * , in the deep sea, which seem to require an average of about 15 × 10 6 cubic meters per second of Southern Ocean deep ventilation over about the past 800 years. A major reduction in Southern Ocean deep water production during the 20th century (from high rates during the Little Ice Age) may explain this apparent discordance. If this is true, a seesawing of deep water production between the northern Atlantic and Southern oceans may lie at the heart of the 1500-year ice-rafting cycle.