The millennial-scale response and impact of climate variability in the eastern tropical Pacific to changing climate boundary conditions

随着全球变暖的证据变得越来越清楚，我们需要了解气候系统的自然运作变得越来越重要。必须了解人类活动对我们气候系统的影响，气候系统如何应对，以及未来将如何应对。因此，我们需要确定和了解气候变化的自然水平，并了解不同过程和区域系统相互作用的方式，从而为我们提供我们所知的“全球气候变化”。近年来，从冰芯和海洋沉积物中检索和分析非常高分辨率的档案表明，气候系统能够在百年和千年的时间尺度上发生非常迅速的变化。目前还不清楚控制这些变化的强制机制和反馈是什么。该项目的目的是提供热带太平洋在不同边界条件下的气候变化记录，从北方半球冰盖占主导地位的完整冰川阶段到与我们现代气候系统相当的最近全新世气候变化。我们将研究热带太平洋，因为从历史记录和最近的观测工作中得知，该区域的气候变化可以通过降水、温度和生态系统的变化产生巨大和深远的影响，这些变化可以延伸到热带区域以外。这些事件通常用厄尔尼诺/南方涛动（ENSO）来描述，它有几年的自然变化。我们将分析来自加州湾的一个非常高分辨率的核心，它提供了一个机会来评估ENSO系统在任何可能的人类活动干扰之前的“真实的”行为。通过比较这个系统之间的冰期和间冰期，我们还旨在研究系统的气候边界条件的变化，其中包括温室气体二氧化碳的变化的敏感性。然后，我们将能够评估热带太平洋可能通过反馈在将气候变化传播到气候系统的其他部分方面发挥了什么作用。我们建议将现有的和新的化学分析应用于沉积物，以重建过去热带太平洋气候系统的不同组成部分。我们使用现代ENSO系统作为模拟，并预测过去的ENSO样变率应与大的变化，海面温度，降水模式和生产的表面海洋。我们分析在沉积物中发现的化合物，这些化合物是生物产生的，即来自曾经生活过的生物。通过观察它们的相对丰度和稳定同位素组成，我们将能够以高分辨率重建热带太平洋气候系统过去的变化。最终，这些数据可以被建模者用来测试和改进目前用于了解气候系统如何运作的模型，以及它在人类活动影响下未来将如何表现。

As evidence for global warming becomes more clear, our need to understand the natural operation of the climate system becomes increasingly important. The impact that human activities have had on our climate system, how the climate system is responding and how it will respond in the future must be understood. Therefore we need to identify and understand the natural level of climate variability and understand the way in which different processes and regional systems interact to give us what we know as 'global climate change'. In recent years the retrieval and analysis of very high resolution archives from ice cores and marine sediments has shown that the climate system is capable of very rapid change, on centennial and millennial timescales. It is still not clear what the forcing mechanisms and feedbacks are that control these changes. This project aims to provide a record of climate variability in the tropical Pacific, under different boundary conditions ranging from a full glacial stage where ice-sheets dominated the northern hemisphere, to the more recent Holocene climate changes that are comparable to our modern climate system. We will examine the tropical Pacific because it is known from historical records and more recent observational work that climate changes in this region can have dramatic and far-reaching consequences through changes in precipitation, temperature and ecosystems that can extend beyond the tropical region. These events are commonly described by the El Nino/Southern Oscillation (ENSO), which has a natural variability of several years. We will analyse a remarkably high resolution core from the Gulf of California that provides an opportunity to assess what the 'real' behaviour of the ENSO system was before any possible interference by human activities. By comparing this system between a glacial and interglacial we also aim to examine the sensitivity of the system to changes in climatic boundary conditions, which include changes in the greenhouse gas carbon dioxide. We will then be able to assess what role the tropical Pacific may have played, via feedbacks, in propagating climate change to the rest of the climate system. We propose to apply both established and new chemical analyses to the sediments to reconstruct different components of the tropical Pacific climate system in the past. We use the modern ENSO system as an analogue, and predict that past ENSO-like variability should be associated with large changes to sea-surface temperatures, precipitation patterns and production in the surface ocean. We analyse compounds found in the sediments that are produced biologically i.e. from organisms that were once living. By looking at their relative abundances and stable isotope compositions, we will be able to reconstruct, at high resolution, the past variability of the tropical Pacific climate system. Ultimately, these data may be used by modellers to test and improve models that are currently used to understand both how the climate system works, but also how it will behave in the future under the influence of human activities.