PP34A-06
The Glacial-Interglacial Monsoon Recorded by Speleothems from Sulawesi, Indonesia

Wednesday, 16 December 2015: 17:15
2012 (Moscone West)
Alena Kay Kimbrough1, Michael K Gagan2, Gavin B Dunbar3, Claire Krause1, Wahyoe S. Hantoro4, Hai Cheng5,6, R. Lawrence Edwards6, Chuan-Chou Shen7, Hailong Sun8, Binggui Cai7, John Charles Hellstrom9 and Hamdi Rifai10, (1)Australian National University, Canberra, Australia, (2)Australian National University, Canberra, ACT, Australia, (3)Victoria University of Wellington, Antarctic Research Centre, Wellington, New Zealand, (4)Indonesian Institute of Sciences, Research Center for Geotechnology, Bandung, 40135, Indonesia, (5)Xi'an Jiaotong University, Institute of Global Environmental Change, Xian, China, (6)University of Minnesota, Minneapolis, MN, United States, (7)NTU National Taiwan University, Taipei, Taiwan, (8)Chinese Academy of Sciences, The State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Guiyang, China, (9)University of Melbourne, Parkville, Australia, (10)State University of Padang, Department of Physics, Padang, Indonesia
Abstract:
The Indo-Pacific Warm Pool is a primary source of heat and moisture to the global atmosphere and a key player in tropical and global climate variability. There is mounting evidence that atmospheric convection and oceanic processes in the tropics can modulate global climate on orbital and sub-orbital timescales. Glacial-interglacial cycles represent the largest natural climate changes over the last 800 kyr with each cycle terminated by rapid global warming and sea level rise. Our understanding of the role and response of tropical atmospheric convection during these periods of dramatic warming is limited.

We present the first speleothem paleomonsoon record for southwest Sulawesi (5ºS, 119ºE), spanning two glacial-interglacial cycles, including glacial termination IV (~340 kyr BP) and both phases of termination III (~248 and ~220 kyr BP). This unique record is constructed from multiple stalagmites from two separate caves and is based on a multi-proxy approach (δ18O, δ13C, Mg/Ca, Sr/Ca) that provides insight into the mechanisms controlling Australian-Indonesian summer monsoon variability.

Speleothem δ18O and trace element data indicate a rapid increase in rainfall at glacial terminations and wet interglacials. Terminations IV, III, and I are each characterized by an abrupt 3‰ decrease in δ18O. Variability in δ18O leading-in to glacial terminations is also similar, and corresponds to October insolation. Prior to deglaciation, there is a distinct shift to higher δ18O that is synchronized with weak monsoon intervals in Chinese speleothem records. The remarkably consistent pattern among terminations implies that the response of tropical convection to changing background climates is well regulated.

Furthermore, we find that speleothem δ13C leads δ18O by ~5 kyr during glacial terminations. The early decrease in speleothem δ13C may reflect the response of tropical vegetation to rising atmospheric CO2 and temperature, rather than regional changes in rainfall.

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