DOI: 10.25921/skaz-fm35
title: NOAA/WDS Paleoclimatology - Southern Mentawai Islands d18O and d13C Data and Indian Ocean Dipole reconstruction over the last millennium

description: The Indian Ocean Dipole (IOD) affects 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 twentieth century and may continue to intensify in a warming world. However, confidence in predictions of future IOD change is limited by known biases in model representations of the IOD and the lack of information on natural IOD variability before anthropogenic climate change. Here we use precisely dated and highly resolved coral records from the eastern equatorial Indian Ocean, where the signature of IOD variability is strong and unambiguous, 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 were rare before 1960. However, the most extreme event on record (1997) is not unprecedented, because at least one event that was approximately 27 to 42 per cent larger occurred naturally during the seventeenth century. We further show that a persistent, tight coupling existed between the variability of the IOD and the El Niño/Southern Oscillation during the last millennium. Indo-Pacific coupling was characterized by weak interannual variability before approximately 1590, which probably altered teleconnection patterns, and by anomalously strong variability during the seventeenth century, which was associated with societal upheaval in tropical Asia. A tendency towards clustering of positive IOD events is evident in our reconstruction, which-together with the identification of extreme IOD variability and persistent tropical Indo-Pacific climate coupling-may have implications for improving seasonal and decadal predictions and managing the climate risks of future IOD variability.
description: The coral IOD reconstruction data was compiled from one Porites coral record published in Abram et al. (2015), one Porites microatoll coral record published in Gagan et al. (2015), and seven Porites coral records published in this study. Note that this study extends the length of the record originally published in Abram et al. (2015). This study also adjusts the age model of the record originally published in Gagan et al. (2015) in order to reconstruct a physically plausible seasonal timing for positive IOD events that is consistent with the age model methods used for the other coral records used in the compilation. The coral IOD reconstruction compiled in this study also includes the coral Dipole Mode Index published in Abram et al. (2008), and derived from Porites coral data originally published in Abram et al. (2008), Charles et al. (1997), Charles et al. (2003), and Pfeiffer and Dullo (2006). For further details please refer to the methods published within Abram et al (2020, Nature). The d13C data from Si94-A-6 in Gagan et al (2015) was removed in July 2020 and can be found at: https://doi.org/10.25921/tkys-wd90. Provided Keywords: sea surface temperature, coral, Indian Ocean Dipole, last millennium