Beyond Greenland: Extending the record of abrupt climate variability

格陵兰岛的冰芯记录对我们理解千年尺度的气候变率和所谓的“突变”气候变化至关重要（美国国家气候突变研究委员会将这种变化定义为气候系统在一个比负责任的强迫更快的时间尺度上向另一种模式的转变，这种转变发生得如此之快和出乎意料，以至于人类或自然系统难以适应）。格陵兰岛的第一个长冰芯是在1966年钻取的，但直到20世纪80年代和90年代，随着更多高质量记录的产生，人们才完全认识到在次千年时间尺度上可能发生的自然气候变化的幅度。例如，在末次冰期的部分时期，记录显示格陵兰岛的温度可能在几十年内上升16摄氏度。这些温度变化被称为丹斯加德-奥斯格振荡，被认为与海洋环流的变化有关。自从在冰芯记录中发现这种突变以来，古气候学家从各种气候档案中得出了大量的记录，试图更多地了解气候突变的全球表现，并扩展格陵兰冰提供的记录，这些记录通常只能追溯到距今10万年左右。然而，许多尚未解决的问题仍然存在，包括：气候突变振荡与地球气候的长期变化（即大冰期旋回）之间的联系是什么？这种关系在中更新世过渡（大约100万年前，当冰期周期从~41kyr转变为~100kyr）之前是否成立？气候突变的幅度如何取决于背景气候状态？在气候突变和深海环流变化之间是否存在一致的关系？在这个项目中，我们将通过产生追溯到170万年前的第一个连续的气候突变记录来解决这些问题。我们将建立北大西洋海表条件的长期代理记录，并用深海洋流变化记录补充这些记录。我们的项目符合NERC“地球系统科学”的科学主题，并与“气候系统”主题相关。特别是，我们对突变的关注，它与海洋环流的关系及其随时间的演变，解决了NERC的挑战，即“增加对驱动全球变化的力量和反馈的了解”。通过实现我们的目标，我们将创造一个标志性的记录，为未来许多关于气候突变的研究提供一个基准。

Ice core records from Greenland have been pivotal in our understanding of millennial-scale climate variability and so-called 'abrupt' climate change (the US National Research Council Committee on Abrupt Climate Change defines such a change as a transition of the climate system into a different mode on a timescale that is faster than the responsible forcing and one that takes place so rapidly and unexpectedly that human or natural systems have difficulty adapting to it). The first long Greenland ice core was drilled in 1966 but it was not until the 1980's and '90's, as more high quality records were produced, that the magnitude of natural climate change possible on sub-millennial timescales was fully realised. For example, during parts of the last glacial period, the records suggest that temperatures over Greenland could rise by up to 16 degrees Celsius within decades. These temperature shifts, known as a Dansgaard-Oeschger oscillations, are thought to be associated with changes in ocean circulation.Since the discovery of such abrupt changes in the ice core record, paleoclimatologists have produced a huge array of records from various climate archives in their attempts to learn more about the global manifestation of abrupt climate change and to extend the records provided by Greenland ice, which typically reach back only to about 100 thousand years before present. However, many unanswered questions remain, including: What is the association between abrupt climate oscillations and longer term changes in Earth's climate (i.e. the great glacial cycles)? Did this relationship hold prior to the Mid Pleistocene Transition (an interval about 1 million years ago, when the glacial cycles changed from ~41kyr to ~100kyr periodicity)? How does the amplitude of abrupt climate variability depend on the background climate state? Is there a consistent relationship between abrupt climate shifts and changes in deep ocean circulation? Within this project we will address these questions by producing the first continuous record of abrupt climate variability stretching back 1.7 million years. We will construct long proxy records of sea surface conditions in the North Atlantic and supplement these with records of deep ocean current variability. Our project fits within the NERC science theme of 'earth system science' and is of relevance to the 'climate system' theme. In particular, our focus on abrupt change, its relation to ocean circulation and its evolution through time addresses NERC's challenge of 'increasing knowledge of the forces and feedbacks that drive global change'. By meeting our objectives we will have produced an iconic record that will provide a benchmark for many future studies on abrupt climate change.