Pan-hemispheric synchrony/asynchrony of D/O events: replication of Suigetsu chronology and extension of Japanese lateglacial event stratigraphy

点击翻译按钮获取中文摘要

Global warming is a very important issue for modern human society. One efficient way of understanding the nature and mechanism of such rapid global climate change is to use changes in past climate as analogues of what is happening today. The last termination, i.e. the end of the last Glacial period, and the trend of climate changes towards the Holocene is often considered to be a good analogue for contemporary global warming. Comparison of climate changes between different regions is particularly important because it provides a key for identifying the trigger of climate changes and the mechanism of inter-regional linkage. In particular, the chronological lag and lead of common climatic events between regions is an important information source because the lag and lead can often be considered to be representing the relationship of trigger and response. Lake Suigetsu (Japan) is one of only a few study sites (together with some North Atlantic sites) which are suitable for this purpose because of its undisturbed sediment and high-potential for high-resolution age determination (at centennial to decadal scales). Previous studies of the Lake Suigetsu pollen record have revealed that some short-term (millennial scale) climate oscillations common in the N. Atlantic have their counterparts in Japan, but frequently these changes are asynchronous either leading or lagging those in the N Atlantic by a few centuries and often display different amplitude (Nakagawa et al., 2003). In order to check if these patterns are consistent over time, it is necessary to re-core the lake and extend the work to the older time slices. We plan to obtain a pair of 25 m long sediment cores and establish an accurate chronology using both annual lamination counting and intensive 14C dating. High-resolution pollen analysis will be used to reconstruct glacial to early Holocene climate changes (the last 30,000 years). The principal goals of our study are to (i) establish an event stratigraphy in Japan using an independent age scale, (ii) compare it to other climate proxy curves from other regions, and (iii) detect synchrony/asynchrony and differences in amplitude of climatic events between different regions (most typically Japan, N. Atlantic and Antarctica). Very careful age-based correlation of the climate proxy curves from different regions should provide insights into the mechanisms involved in global climate changes.