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

全球变暖是现代人类社会的一个非常重要的问题。理解如此快速的全球气候变化的本质和机制的一个有效方法是用过去的气候变化作为今天正在发生的事情的类比。最后一次终止，即末次冰期的结束，以及气候变化走向全新世的趋势通常被认为是当代全球变暖的一个很好的类比。不同区域间气候变化的比较尤其重要，因为它为确定气候变化的触发因素和区域间联系机制提供了一把钥匙。特别是，区域间常见气候事件的时间滞后和铅是一个重要的信息源，因为滞后和铅通常可以被认为代表了触发和响应的关系。日本的绥越湖（Lake Suigetsu）是为数不多的适合用于这一目的的研究地点之一（以及北大西洋的一些地点），因为它的沉积物未受干扰，并且具有高分辨率年龄测定（百年至十年尺度）的高潜力。先前对水越湖花粉记录的研究表明，北大西洋常见的一些短期（千年尺度）气候振荡在日本也有对应的变化，但这些变化往往是不同步的，要么领先北大西洋几个世纪，要么落后于北大西洋几个世纪，而且往往表现出不同的幅度（Nakagawa et al., 2003）。为了检查这些模式是否随着时间的推移而保持一致，有必要对湖泊进行重新取样，并将工作扩展到更早的时间片。我们计划获得一对25米长的沉积物岩心，并利用年度层压计数和密集的14C测年建立准确的年表。高分辨率花粉分析将用于重建冰川到全新世早期的气候变化（过去3万年）。我们研究的主要目标是：(i)使用独立的年龄尺度在日本建立事件地层学，（ii）将其与其他地区的其他气候代理曲线进行比较，以及（iii）检测不同地区（最典型的是日本，北大西洋和南极洲）气候事件振幅的同步/非同步和差异。对来自不同地区的气候代理曲线进行非常仔细的基于年龄的相关性分析，将有助于深入了解全球气候变化的机制。

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.