Indian Ocean Dipole variability during the last millennium
Abstract
The Indian Ocean Dipole (IOD) severely impacts rainfall patterns in nations surrounding the Indian Ocean. Climate model simulations indicate that the rainfall impacts of extreme positive IOD events will intensify in a warming world; however, confidence is limited by known biases in model representations of the IOD and 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 the extreme positive IOD event of 1997 was unusually strong but not unprecedented, with at least one event that was 70% larger occurring naturally during the last millennium. The frequent positive IOD events observed since the 1960s are similarly not unprecedented, with a particularly active period of positive IOD events occurring in the mid-17th Century and coinciding with an interval where El Niño Southern Oscillation (ENSO) variability also exceeded the high variability observed in recent decades. We observe that multi-decadal clustering of positive IOD events is a persistent characteristic of IOD variability during the last millennium. Although climate model simulations do not capture the magnitude of observed multi-decadal cycling between active and inactive phases of IOD variability, they do provide insights into the tropical ocean circulation and teleconnection processes responsible. The clustering of positive IOD events has significant implications for assessing climate risk and incorporation of this characteristic into seasonal and decadal prediction schemes has the potential to allow for societal adaptation to the impacts caused by IOD variability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP31A..01A
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 4914 Continental climate records;
- PALEOCEANOGRAPHYDE: 4928 Global climate models;
- PALEOCEANOGRAPHYDE: 4934 Insolation forcing;
- PALEOCEANOGRAPHY