[U-03] 人新世・第四紀の気候および水循環

[U03-P10] Meridional migrations of the Intertropical convergence Zone during the last deglaciation in the Timor Sea detected by extensive radiocarbon dating

*根本 夏林^1,2、横山 祐典^1,2,3,4,5、堀池 智之¹、オブラクタ スティーブン⁶、宮入 陽介¹ (1.東京大学大気海洋研究所、2.東京大学大学院理学系研究科地球惑星科学専攻、3.東京大学総合文化研究科、4.海洋研究開発機構、5.オーストラリア国立大学、6.秋田大学大学院国際資源科学研究科)

キーワード：ITCZ、ベリリウム、退氷期、放射性炭素年代測定

At the Intertropical Convergence Zone (ITCZ), the northern and southern Tradewinds converge, and this region is characterized by low atmospheric pressure and high precipitation. The climate in the Timor Sea is characterized by seasonal precipitation changes driven by meridional migrations of the ITCZ and the monsoonal front. The ITCZ shifts in response to changes in the thermal balance between the northern and southern hemispheres. Thus, reconstruction of paleo-precipitation in the Timor Sea is expected to reveal past changes in both regional and global climate, the latter through inference of the ITCZ position. To reconstruct paleo-precipitation in the Timor Sea, we performed extensive radiocarbon analysis on both planktonic foraminifera and total organic carbon (TOC), which is derived from terrestrial and marine sources. Increased precipitation enhances the fraction of relatively old, terrestrial carbon to the core site, which in turn increases the difference between the ages of TOC and planktonic foraminifera. Variations in radiocarbon ages reveal that during northern hemisphere cooling intervals such as Heinrich Stadial 1 and the Younger Dryas, the ITCZ was in a southern position, thus increasing precipitation in the Timor Sea. However, the Timor Sea was dryer during the Bølling–Allerød warming as the ITCZ shifted northward.