[M-IS17] Paleoclimatology and paleoceanography

[MIS17-P16] On the possibility of tree-ring δ¹⁸O in Java, Indonesia for paleoclimate proxy

*Ryo Hisamochi¹, Yumiko Watanabe¹, Naoyuki Kurita², Masaki Sano³, Takeshi Nakatsuka³, Miyuki Matsuo⁴, Hiroyuki Yamamoto⁴, Junji Sugiyama⁵, Toshitaka Tsuda⁵, Takahiro Tagami¹ (1.Graduate School of Science, Kyoto University, 2.Graduate School of Environmental Studies, Nagoya University, 3.Research Institute for Humanity and Nature, 4.Graduate School of Bioagricultural Sciences, Nagoya University, 5.Research Institute for Sustainable Humanosphere, Kyoto University)

Keywords:tree-ring, paleoclimate, Indian Ocean Dipole

The Indonesian region plays a key role in global climate system because active convection in this region is considered as a heat and moisture source which drives global circulation. Although δ¹⁸O in tree-ring has been used to reconstruct hydroclimatic and atmospheric circulation, there are only a few paleoclimate reconstruction based on δ¹⁸O in tree-ring in Indonesia (Schollaen et al., 2013, Poussart et al., 2004). In this study, we measured tree-ring δ¹⁸O in Java Island to explore the possibility of tree-ring δ¹⁸O as proxy.
We used four teak (Tectona grandis) samples collected at Sumedang, Western Java. Samples were cut into annual rings after cellulose extraction. δ¹⁸O of individual rings were measured by TCEA-IRMS.
We analyzed 59 years (1940-1998). Time series variation of δ¹⁸O are correlated between the four samples, and EPS (expressed population signal) values are 0.89-0.93. In addition, the δ¹⁸O time series of this study (Western Java) are very similar to that of Schollaen et al.(2013) (Eastern Java). This suggests common climate signals preserved in teak tree-ring in Java Island. δ¹⁸O time series of our samples shows positive correlation with that of precipitation in the last dry season and negative correlation with that of precipitation in rainy season (growing season). Schollaen et al. (2013) suggests this is because dry season precipitation has relatively high δ¹⁸O compared with rainy season precipitation.
We checked the correlation with DMI (Dipole Mode Index). The results show tree-ting δ¹⁸O in Western Java has a negative correlation with last dry season DMI. This is probably because DMI has a negative correlation with dry season precipitation in Java Island (Ashok et al., 2003).
For future plan, we are going to analyze using tree-ring isotope model, in order to assess the reliability of tree-ring δ¹⁸O as climate proxy in Java.