Glacial termination hydroclimate in the Indo-Pacific Warm Pool

Thursday, 18 December 2014
Shufang Yuan1, Xianfeng Wang1, Hong-Wei Chiang2, Satria Bijaksana3, Xiuyang Jiang4, Andi Muhammad Imran5 and Satrio A Wicaksono6, (1)Earth Observatory of Singapore, Singapore, Singapore, (2)Nanyang Technological University, Singapore, Singapore, (3)Bandung Institute of Technology, Bandung, Indonesia, (4)Fujian Normal University, Fuzhou, China, (5)Hasanuddin University, Makassar, Indonesia, (6)Brown University, Providence, RI, United States
Hydroclimatic change in the Indo-Pacific Warm Pool (IPWP), the largest center of atmospheric deep convection on Earth, can have a profound influence on the global moisture and energy budgets. Although it has been extensively studied, the history of IPWP hydroclimate remains elusive, partially due to the scarcity of well-resolved hydroclimiate records from the region.

Here we report a U/Th dated, high-resolution, calcite d18O record on IPWP hydroclimatic change, spanning the last glacial termination (termination-I or T-I) and the interval of time from the Marine Isotope Stage (MIS) 12 to MIS11 (termination-V or T-V). The record was obtained using speleothems collected from Southwest Sulawesi (S5o1’, E119o44’), Indonesia. During T-I, the Sulawesi speleothem δ18O shows a few millennial-scale events, possibly a drier climate during the Younger Dryas (YD) and Heinrich Stadial 1 (HS1), but a relatively wet climate during the last glacial maximum (LGM) and the Bolling-Allerod (B-A). The pattern resembles those registered in the speleothem records from eastern China and Borneo. However, the Sulawesi d18O varies from ~ -5.8‰ to ~ -7.3‰ during the last termination, which is much smaller than the magnitudes shown in China and Borneo cave samples (~ 4‰). On the other hand, the Sulawesi cave record is anti-correlated with the Flores speleothem record in terms of their millennial-scale events. Yet, the two Indonesian records share a similar, small d18O variation (~1.5‰). Such observations therefore suggest that the Intertropical Convergence Zone (ITCZ) probably became narrower when responding to the northern high-latitude climatic forcing during the T-I, and it centered zonally between the two Indonesian locations.

Interestingly, Sulawesi speleothem d18O has a larger magnitude of shift during T-V, from ~ -5.7‰ in MIS12 to ~ -8.7‰ at the peak of MIS11. Given that Sulawesi cave d18O is not sensitive to sea level change and orbital forcing, we suspect that a much lower d18O observed in MIS11 could be attributed to a higher temperature in the IPWP accompanying with a regional higher rainfall.