Vigorous exchange between the Indian and Atlantic oceans at the end of the past five glacial periods

• Published in: Nature
• Main Authors: Peeters, Frank JC, Acheson, Ruth, Brummer, Geert-Jan A, de Ruijter, Wilhelmus P. M, Schneider, Ralph R, Ganssen, Gerald M, Ufkes, Els, Kroon, Dick
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2004
• Subjects: Vigorous Exchange; Indian Ocean; Atlantic Ocean; Oceanography; Glacial Periods; Agulhas; Indian; North Atlantic Deep Water; North Atlantic; South Atlantic Ocean
• Online Access: http://hdl.handle.net/1842/681; https://doi.org/10.1038/nature02785

The magnitude of heat and salt transfer between the Indian and Atlantic oceans through 'Agulhas leakage' is considered important for balancing the global thermohaline circulation1-3. Increases or reductions of this leakage lead to strengthening or weakening of the Atlantic meridional overturning and associated variation of North Atlantic Deep Water formation4-6. Here we show that modern Agulhas waters, which migrate into the south Atlantic Ocean in the form of an Agulhas ring, contain a characteristic assemblage of planktic foraminifera. We use this assemblage as a modern analogue to investigate the Agulhas leakage history over the past 550,000 years from a sediment record in the Cape basin. Our reconstruction indicates that Indian-Atlantic water exchange was highly variable: enhanced during present and past interglacials and largely reduced during glacial intervals. Coherent variability of Agulhas leakage with northern summer insolation suggests a teleconnection to the monsoon system. The onset of increased Agulhas leakage during late glacial conditions took place when glacial ice volume was maximal, suggesting a crucial role for Agulhas leakage in glacial terminations, timing of interhemispheric climate change7 and the resulting resumption of the Atlantic meridional overturning circulation6.