由泰國Klang洞穴石筍紀錄探討過去兩萬三千年以來亞洲季風變化

Abstract

亞洲季風是全球氣候系統的重要系統之一，前人的研究認為亞洲季風不止與北半球高緯度地區變化有關，同時也受到南半球赤道地區變化所影響，前人已經透過中國和印度的氧同位素記錄重建了亞洲季風過去的變化，並顯示此一強度變化主要受控於北半球高緯度地區夏季日照量影響。然而，末次冰期以來洞穴石筍紀錄卻鮮少來自於低緯度地區，因此在亞洲季風演化過程的解釋上可能造成些許不確定。透過七支採集自泰國南部Klang洞穴（8°1'N，98°48'E）的石筍樣本，並利用其氧同位素紀錄，我們重建了過去兩萬三千年以來低緯度地區亞洲季風的變化。此研究結果支持了前人在此時間段的亞洲季風研究成果，包含末次冰期、Heinrich event 1、新仙女木事件（YD）等氣候皆有同步變化的現象。亞洲季風區洞穴石筍氧同位素變化的一致性說明過去亞洲季風的強弱主要跟隨北半球日照量而改變，但Klang洞穴記錄在Termination 1、新仙女木事件（YD）等氣候事件的變化幅度上卻是中國石筍的二到三倍，根據現代降雨觀測及雨水氧同位素值顯示，我們認為此一現象不只與亞洲夏季季風有關，同時也受到亞洲冬季季風的影響。

The Asian monsoon (AM) is an important component of the global climate system. Its past variability, revealed by Chinese and Indian cave carbonate records, was paced by solar forcing and strongly influenced by changes in northern high-latitude climatic condition. However, only a few absolutely dated records are available from low latitude. Here, I present a replicated and spliced stalagmite record covering the past twenty-three thousand years from Klang Cave in southern Thailand (8°1'N, 98°48'E). Synchroneity of climate changes recorded in different Asian caves and in the Greenland oxygen isotope record support previous assumptions of orbital and high-latitudinal forcings. However, the respective enrichment and depletion in δ18O values over the Younger Dryas and Termination 1 of Klang record are 2-3 times greater than those registered in the Chinese cave records. On the basis of modern monthly rainfall data and their oxygen isotopic values, I propose that Klang Cave stalagmite δ18O variability is not only associated with the Asian summer monsoon, but also with the Asian winter monsoon.