Australia: The Land Where Time Began

A biography of the Australian continent 

Indo-Pacific Warm Pool - Oscillation in its Southern Extent During the Middle Holocene

The Indo-Pacific Warm Pool (IPWP) has an influence on the global distribution of heat and water vapour, which is why it is believed to have a key role in the propagation and amplification of climate changes, though little is known about changes in the past of the size and position of the IPWP. According to the authors1 in this study they used a total of 48 modern and fossil records obtained from the Mentawai Islands, Sumatra, Indonesia and the Muschu/Koil Islands, Papua New Guinea, to reconstruct the oscillations of the extent of the IPWP since the mid-Holocene. This study shows that by using fossil corals, reliable estimates of mean sea surface temperature (SST) can be obtained by low-resolution Sr/Ca analysis of a suite of corals to overcome the large uncertainties that are associated with the mean  Sr/Ca-SST estimates of individual coral colonies. It was found that between 5,500-4,300 BP it is indicated by the coral records that the southeastern and southwestern margins of the IPWP were cooler than at present, about 1.2 ± 0.3o C, and before about 6,800 BP the temperatures were as cool as at the present,. An abrupt, short-lived shift to mean SSTs that were warmer than at present between 6,600-6,300 BP, punctuated the cooling of the mid-Holocene, about 1.3 ± 0.3o C, and conditions that were similarly warm may have existed after about 4,300 BP. The authors1 suggest that at their study sites cooling in the mid-Holocene resulted from contraction of the southeastern and southwestern margins of the IPWP that were associated with the change in position of the Inter-tropical Convergence Zone (ITCZ) that accompanied strengthening of the Asian summer monsoon in the mid-Holocene. The authors1 suggest it appears abrupt episodes of warming correspond with widespread episodes of weakening of the monsoon, accompanied by migration to the south of the ITCZ that caused the expansion of the IPWP beyond the sites where they obtained the coral for their study. Intervals of a stronger Asian monsoon, and cooling in the southwestern IPWP, that occurred in the mid-Holocene, are suggested by the authors1 to apparently correspond with a more positive Indian Ocean Dipole (IOD)-like mean configuration across the tropical Indian Ocean, which suggests that the interaction of the Asian monsoon-IOD on interannual timescales also continues into centennial and millennial scales. It is also suggested that associated mean changes in the Pacific ENSO mode may have occurred in the mid-Holocene. It has been suggested that during the mid-Holocene  the dynamic and inter-connected behaviour of the IPWP with tropical climate systems highlights how important the warm pool region is for understanding climate change throughout the tropics and beyond.


Sources & Further reading

  1. Abram, Nerilie J., Helen V. McGregor, Michael K. Gagan, Wahyoe S. Hantoro, and Bambang W. Suwargadi. "Oscillations in the Southern Extent of the Indo-Pacific Warm Pool During the Mid-Holocene." Quaternary Science Reviews 28, no. 2526 (12// 2009): 2794-803.


Author: M. H. Monroe
Last updated: 30/03/2013

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