Title: The Indian Ocean Dipole and great earthquake cycle: Long-term perspectives for improved prediction
Abstract: Climatic extremes in the densely populated tropical Indian Ocean region are controlled by the interplay between the El NinoSouthern Oscillation (ENSO), Asian monsoon and Indian Ocean Dipole (IOD). Reliable instrumental records of the IOD only cover the last 50 years. To better understand IOD variability, we use a suite of Porites coral O/O records to extend the basin-wide index of IOD behaviour back to 1846 AD. Our analysis reveals a 3-fold increase in the frequency of IOD events since 1960, accompanied by the development of feedbacks between the IOD and Asian monsoon. We also use coupled Sr/Ca and O/O analysis of fossil corals to examine the character of prehistoric eastern IOD upwelling events. During the mid-Holocene, when the Asian monsoon was relatively strong and ENSO was weak, IOD events were characterised by more protracted cooling and droughts in the eastern Indian Ocean [1]. Together, the results suggest that any strengthening of the Asian monsoon in the future will lead to opposing east-west trends in rainfall across the Indian Ocean, with more severe IOD droughts in western Indonesia. An unanticipated “spin-off” of this work is the finding that skeletal C/C in Porites corals records vertical crustal deformation during earthquakes, such as the 2004 and 2005 events in Sumatra. Water column light intensity and skeletal C/C in symbiotic corals are inextricably linked. Our records show that C/C is sensitive to the increase in ambient light intensity when corals rise to shallower water during co-seismic uplift. We now have coral C/C time-series showing crustal deformation before, during, and after the 1797, 1907 and 1935 AD earthquakes in Sumatra. With further refinement, the coral “chemo-geodesy” technique could shed light on the recurrence intervals of great submarine earthquakes and tsunamis in island arc subduction zone settings throughout Australasia and the tropical western Pacific region.
Publication Year: 2008
Publication Date: 2008-01-01
Language: en
Type: article
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