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行变得越来越重要。必须了解人类活动对我们的气候系统产生的影响，气候系统是如何应对的，以及它未来将如何应对。因此，我们需要识别和了解气候变化的自然水平，并了解不同进程和区域系统相互作用的方式，以给我们带来我们所知的‘全球气候变化’。近年来，对冰芯和海洋沉积物的极高分辨率档案的检索和分析表明，气候系统能够在百年和千年的时间尺度上非常迅速地变化。目前还不清楚控制这些变化的强迫机制和反馈是什么。该项目旨在记录热带太平洋在不同边界条件下的气候变化，从北半球以冰盖为主的完全冰川阶段，到可与我们的现代气候系统相媲美的最近的全新世气候变化。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知道，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戏剧性和深远的后果，这些变化可以延伸到热带地区以外。这些事件通常被描述为厄尔尼诺/南方涛动(ENSO)，它具有几年的自然变化。我们将分析加利福尼亚州海湾的一个非常高分辨率的岩心，它提供了一个机会来评估在任何可能的人类活动干扰之前ENSO系统的“真实”行为是什么。通过比较冰期和间冰期这一系统，我们还旨在检查该系统对气候边界条件变化的敏感性，包括温室气体二氧化碳的变化。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。我们建议对沉积物进行现有的和新的化学分析，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系统作为类比，并预测过去类似ENSO的变化应该与海面温度、降水模式和表层海洋生产的巨大变化有关。我们分析在沉积物中发现的化合物，这些化合物是由生物产生的，即来自曾经活着的有机体。通过观察它们的相对丰度和稳定的同位素组成，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异性。最终，这些数据可能会被建模人员用来测试和改进模型，这些模型目前被用来理解气候系统是如何工作的，以及它未来在人类活动影响下的表现。

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.