17:15 〜 18:30
[MIS17-P16] 年輪δ18Oによるインドネシア・ジャワ島の古気候復元の可能性
キーワード：年輪、古気候、インド洋ダイポールモード
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.
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.