Assessing the role of millennial-scale variability in glacial-interglacial climate change

地球的气候变化的时间尺度从几十年到几千万年不等。一旦这种模式的变化是有关的变化，在地球的轨道围绕太阳。这被称为“轨道时间尺度”的变化，具有数万至数十万年的特征时间尺度，从而产生了众所周知的晚更新世冰川周期。叠加在这种冰川-间冰期变化上的是另一种气候变化模式，称为“千年尺度”气候变化（以数百至数千年的时间尺度变化为特征）。这两种气候变率模式都受到了重要的科学研究，因为它们涉及全球气候的重大变化，但它们的基本机制仍然是谜。然而，最近的研究表明，这些表面上独立的机制实际上可能是密切相关的。因此，增进我们对一个方面的了解应能促进对另一个方面的了解。在这里，我们试图调查千年尺度的气候变率在更广泛的变化与冰川间冰期气候变化的潜在作用。具体来说，我们将研究海洋/大气环流的突然变化所产生的影响，这些变化可能在冰期气候向间冰期气候的转变中发挥作用。（例如最后一次冰川消退，发生在20到10000年前）人们认为，海洋环流和相关大气现象的变化可引起剧烈的温度波动，如格陵兰冰所记录的温度波动。在末次冰期和冰消期的岩芯。值得注意的是整个南极洲记录的相应温度变化，这表明气候系统可能像一种跷跷板;当环流强烈时，格陵兰岛（和西北欧）温暖，南极洲变冷。减弱的环流导致格陵兰岛的寒冷天气，而南极洲则出现变暖。这种所谓的“两极跷跷板”的一个重要副作用是，每当环流处于减弱状态时，大气中的二氧化碳似乎就会上升。与这一提议特别相关的是在上一次冰川消退期间发生的二氧化碳上升，这与两极跷跷板的明显振荡有关。此外，在末次冰期期间还发生了其他几次跷跷板振荡，这也导致了二氧化碳的增加，但没有导致冰川消退。我们希望找出为什么某些双极跷跷板振荡（终端振荡）显然会导致冰川消退，而其他（非终端振荡）则不会。这些事件有什么特别之处吗？或者它们与冰川消退的联系仅仅是巧合？为了回答这个问题，我们将把联合收割机定量数据分析与最先进的气候系统计算机模型结合起来。我们将分析气候记录跨越几个冰川周期，以提供一个统计表示的“终端”和“非终端”的两极跷跷板振荡。然后，我们将使用计算机模型来研究如何在各种背景条件下的跷跷板操作。我们的最终目标是找出是什么，如果有的话，使终端振荡特殊。这样做，我们将提供重要的制约机制的冰川消退。

Earth's climate varies on timescales ranging from decades to tens of millions of years. Once such mode of variability is that related to changes in the Earth's orbit around the Sun. This is known as 'orbital-timescale' variability and has characteristic timescales of tens to hundreds of thousands of years, giving rise to the well known glacial cycles of the Late Pleistocene. Superimposed on this glacial-interglacial variability is another mode of climate change, known as 'millennial-scale' climate variability (characterised by changes on a timescale of hundreds to a few thousands of years). Both of these modes of climate variability have received significant scientific enquiry because they involve major changes in global climate and yet both remain enigmatic in their underlying mechanisms. However, recent studies have suggested that these apparently separate mechanisms may in fact be intimately related. As such, improving our understanding of one should promote understanding in the other. Here we seek to investigate the potential role of millennial-scale climate variability in the wider changes associated with glacial-interglacial climate change. Specifically we will examine the effects that occur in response to abrupt changes in ocean/atmosphere circulation that may play a role in the transition from glacial to interglacial climate (such as the last deglaciation, which occurred between 20 and 10 thousand years ago).It is thought that changes in ocean circulation and related atmospheric phenomena can give rise to dramatic temperature fluctuations such as those recorded by Greenland ice cores during the last glacial and deglacial periods. Of note is the corresponding temperature variations recorded across Antarctica, which suggest that the climate system may act like a sort of seesaw; when circulation is strong, Greenland (and north western Europe) is warm and Antarctica cools. A weakened circulation gives rise to cold conditions across Greenland while warming occurs across Antarctica. An important side effect of this so-called 'bipolar seesaw' is that atmospheric carbon dioxide appears to rise every time the circulation is in a weakened state. Of particular relevance to this proposal is the rise in carbon dioxide that occurred during the last deglaciation, which was associated with a distinct oscillation of the bipolar seesaw. Moreover, several other seesaw oscillations occurred during the last glacial period, which also gave rise to increases in carbon dioxide but did not lead to deglaciation.We wish to find out why certain bipolar seesaw oscillations (terminal oscillations) apparently lead to deglaciation while others (non-terminal oscillations) do not. Is there anything special about these events or is their affiliation with deglaciation merely coincidence? In order to answer to this question we will combine quantitative data analysis with state-of-the-art computer models of the climate system. We will analyse climate records spanning several glacial cycles in order to provide a statistical representation of 'terminal' and 'non-terminal' oscillations of the bipolar seesaw. We will then use computer models to investigate how the seesaw operates under a variety of background conditions. Our ultimate goal is to find out what, if anything, makes terminal oscillations special. In so doing we will provide important constraints on the mechanism of deglaciation.