A Millennial-Scale Reduction in Ventilation of the Deep South Atlantic During the Last Interglacial Period

Tuesday, 16 December 2014: 11:50 AM
Christopher T Hayes1, Alfredo Martinez-Garcia2, Adam Patrik Hasenfratz2, Sam Jaccard3, David A Hodell4, Daniel Mikhail Sigman5, Gerald Hermann Haug2 and Robert F Anderson6, (1)Massachusetts Institute of Technology, Earth Atmospheric and Planetary Sciences, Cambridge, MA, United States, (2)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (3)University of Bern, Bern, Switzerland, (4)University of Cambridge, Cambridge, United Kingdom, (5)Princeton University, Princeton, NJ, United States, (6)Lamont-Doherty Earth Obs, Palisades, NY, United States
During the last interglacial period, global temperatures were ~2°C warmer than present and sea level was 6-8 m higher. Southern Ocean sediments from ODP Site 1094 reveal a spike in authigenic uranium 127,000 years ago, within the last interglacial, reflecting decreased oxygenation of deep water by Antarctic Bottom Water (AABW). Increased deep storage of respired carbon due to this circulation event may explain an observed decline in atmospheric CO2 at this time. Unlike ice age reductions in AABW, the interglacial stagnation event appears decoupled from open ocean conditions and may have resulted from coastal freshening due to mass loss from the Antarctic ice sheet. AABW reduction coincided with increased North Atlantic Deep Water (NADW) formation, and the subsequent reinvigoration in AABW coincided with reduced NADW formation. Alternation of deep water formation between the Antarctic and the North Atlantic, believed to characterize ice ages, apparently also occurs in warm climates.