[U-03] 人新世・第四紀の気候および水循環

[U03-01] Indian summer monsoon evolution during the last glacial termination

★Invited Papers

Sakonvan Chawchai¹、Xiaojing Du²、Hao-Cheng Wang^3,4、Hsun-Ming Hu^3,4、Liangcheng Tan⁵、Xiuyang Jiang⁶、Ryuji Asami⁷、Ruy Uemura⁸、Ludvig Löwemark⁹、Barbara Wohlfarth¹⁰、Yuji Sano¹¹、Yusuke Yokoyama¹²、Gideon M Henderson¹³、*Chuan-Chou Shen^3,4 (1.Department of Geology, The Faculty of Science, Chulalongkorn University, Bangkok, Thailand、2.Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA, USA、3.HISPEC, Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC、4.Research Center for Future Earth, National Taiwan University, Taipei, Taiwan, ROC、5.State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, China、6.Key Laboratory of Humid Subtropical Eco-geographical Processes, College of Geography Science, Fujian Normal University, Fuzhou, China、7.Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai, Japan、8.Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan、9.Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC、10.Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden、11.Center for Advanced Marine Core Research, Kochi University, Kochi, Japan、12.Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan、13.Department of Earth Sciences, University of Oxford, Oxford, UK)

キーワード：Indian Summer Monsoon, Last Glacial Termination, Stalagmite, sub-decadal to multi-decadal resolved records

The glacial-interglacial evolution of the Indian summer monsoon (ISM) in the late Quaternary is primarily influenced by northern hemispheric summer insolation, alongside forcings from high latitudes and sea level changes. However, the detailed ISM process during glacial terminations remains elusive due to lacks of high-resolved and well-dated records. Here, we present sub-decadal-to-multi-decadal oxygen isotope (δ¹⁸O) records of two stalagmites from Klang Cave (8.3°N, 98.7°E), southern Thailand, to decipher the transitional ISM behaviours during the last glacial termination from 23.0-13.2 thousand years ago (ka, relative to AD 1950). Through modern observations, previous studies, and alignment with records from multiple caves located within the monsoonal region, it is evident that Klang δ¹⁸O data capture regional precipitation patterns and ISM histories. The 10-kyr Klang records generally anti-correlate with Liang Luar records from Flores (8.5°S), attributed to shifts in the mean position of the intertropical convergence zone. During 16.0-14.3 ka, Klang records, anchored by 35 U-Th ages with 2-sigma precision of ±10s years, exhibit four abrupt stepwise enhancements of ISM at 15.5, 15.1, 14.7, and 14.3 ka, spanning from sub-decadal to multi-decadal scales. These climate shifts could be either induced by North Atlantic climate change or forcings from bi-hemispheric low/high latitudes. We hypothesize that the accumulation of oceanic heat content might be the key for triggering the observed non-linear ISM changes during the last glacial termination.