RESUMEN
The Indian Ocean Dipole (IOD) affects climate and rainfall across the world, and most severely in nations surrounding the Indian Ocean1-4. The frequency and intensity of positive IOD events increased during the twentieth century5 and may continue to intensify in a warming world6. However, confidence in predictions of future IOD change is limited by known biases in IOD models7 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.
Asunto(s)
Antozoos/metabolismo , Cambio Climático/estadística & datos numéricos , Animales , Conjuntos de Datos como Asunto , El Niño Oscilación del Sur , Fósiles , Historia del Siglo XV , Historia del Siglo XVI , Historia del Siglo XVII , Historia del Siglo XVIII , Historia del Siglo XIX , Historia del Siglo XX , Historia del Siglo XXI , Historia Medieval , Océano Índico , Indonesia , Islas , Modelos Teóricos , Isótopos de Oxígeno , Océano Pacífico , Lluvia , Estaciones del Año , Clima TropicalRESUMEN
Records of relative sea-level change extracted from corals of the Mentawai islands, Sumatra, imply that this 700-kilometer-long section of the Sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years. The moment magnitude 8.4 earthquake of September 2007 represents the first in a series of large partial failures of the Mentawai section that will probably be completed within the next several decades.