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Distinguished Lecture

Distinguished Lecture - IG

Nerilie ABRAM
Australian National University

Mon- 29 Jul, 12:00-12:30pm
MR 323, Level 3

"Tight Coupling of Tropical Indian and Pacific Climate Variability Through the Last Millennium"

The Indian Ocean Dipole (IOD) impacts climate and rainfall across the world, and most severely in nations surrounding the Indian Ocean. The frequency and intensity of positive IOD events increased during the 20th Century, and may continue to intensify in a warming world; however, confidence in future IOD changes is limited by known biases in model representations of the IOD and the limited information on natural IOD variability prior to anthropogenic climate change. Here we use precisely dated and highly resolved spliced fossil coral records from the eastern equatorial Indian Ocean, where the signature of IOD variability is optimised, to produce a semi-continuous reconstruction of IOD variability that covers five centuries of the last millennium. Our reconstruction demonstrates that extreme positive IOD events such as the 1997 strongest-on-record event are rare, but this event was not unprecedented with at least one event that was 20% larger occurring naturally during the 17th Century. High variability of the IOD during the 17th Century coincided with an anomalous interval where El Niño Southern Oscillation (ENSO) variability also exceeded the high variability observed in recent decades, and our reconstruction demonstrates for the first time that a persistent, tight coupling existed between variability of the IOD and ENSO during the last millennium including times prior to anthropogenic climate forcing. This tight coupling of tropical Indo-Pacific climate variability and a multi-decadal clustering of positive IOD events evident in our reconstruction have important implications for improving seasonal and decadal prediction schemes, with the potential to enable societal adaptation to the impacts of IOD variability.

Nerilie Abram is a Future Fellow at the Australian National University, and a Chief Investigator for the Centre of Excellence for Climate Extremes. She is also a Coordinating Lead Author for the special report on Ocean and Cryosphere in a Changing Climate being prepared by the Intergovernmental Panel on Climate Change (IPCC). Her research focuses on reconstructing climate variability and change over the last 1,000 years, using a variety of methods including the chemical analysis of Antarctic ice cores and tropical reef corals.