North Atlantic forcing of tropical Indian Ocean climate

• Published in: Nature (London) 2014-05, Vol.509 (7498), p.76-80
• Main Authors: Mohtadi, Mahyar, Prange, Matthias, Oppo, Delia W., De Pol-Holz, Ricardo, Merkel, Ute, Zhang, Xiao, Steinke, Stephan, Lückge, Andreas
• Format: Article
• Language: English
• Subjects: 140/58; 704/106/2738; 704/106/413; Africa, Eastern; Air; Atlantic Ocean; Borneo; Boundary conditions; Climate change; Climate models; Climatic changes; Cold; Cooling; Environmental aspects; Geologic Sediments - chemistry; Greenland; History, 19th Century; History, 20th Century; History, 21st Century; History, Ancient; Humanities and Social Sciences; Humidity; Hydroclimate; Hydrology; Ice Cover; Indian Ocean; Indonesia; Intertropical convergence zone; Lakes; letter; Meteorological research; Models, Theoretical; multidisciplinary; Oceans; Oxygen Isotopes; Precipitation; Rain; Salinity; Science; Sea surface temperature; Seasons; Seawater; Seawater - analysis; Seawater - chemistry; Temperature; Thermohaline circulation; Time Factors; Tropical Climate; Water Movements; Wind
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature13196

New sea surface temperature and oxygen isotope records, combined with climate modelling experiments, show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation. A 45,000-year eastern Indian Ocean climate record It is well known that North Atlantic cold events such as the Younger Dryas and Heinrich stadials influenced the broader climate system, but the response of the Indian Ocean to such events has remained unclear because of the lack of appropriate proxy records. This study presents high-resolution records from extremely well-dated sediments from the eastern Indian Ocean, covering the past 45,000 years. Together with state-of-the-art model simulations of the Heinrich events, the data reveal dramatic variations in tropical hydrology, remotely controlled by conditions in the North Atlantic. The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells 1 , 2 , 3 , 4 , 5 , but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during N