Collaborative Research: Reconstructing Climate Linkages Across the Tropical Oceans Over the Last Millennium

热带海洋温度的年复一年变化影响着世界各地的气候和天气。最明显的例子是热带太平洋的厄尔尼诺-南方涛动(ENSO)系统。与ENSO相关的变暖和降温模式对干旱、洪水和热带风暴有重大影响。热带大西洋和印度的温度也以同样的方式影响天气。不仅如此，这三个大洋盆地可以相互作用，因为大气将它们连接在一起。例如，热带大西洋的变暖往往会导致风的模式，然后使热带太平洋降温。这意味着，要预测未来气候变化可能如何变化，人们必须了解热带海洋之间的联系。然而，众所周知，这些关系会随着时间的推移(几十年)而变化，而热带地区的温度记录很短，而且很少。因此，这一问题很难用传统的观测方法(如温度计)来研究。取而代之的是，这个项目将使用长寿珊瑚的地球化学性质来产生温度记录。通过比较太平洋、大西洋和印度洋的珊瑚数据，这项研究将展示这些海洋在过去几个世纪里是如何相互作用的。将20世纪与前几个世纪进行比较，将会揭示出最近气候变暖的影响。这项工作探索了这些模式是否出现在用于理解未来气候变化的气候模型中，以及涉及哪些物理过程。将使用几个不同的模型组进行比较。学生和博士后也将参与这项研究。最后，该项目将开发培训材料，使那些没有高度技术背景的人更容易获得数据和模型结果。热带海洋年际到数十年的变化导致极端气候，对世界各地的自然和人类系统产生影响。赤道太平洋ENSO系统特别重要，最近的工作突出表明，大西洋和印度洋的多变性影响了ENSO极端事件的重现和强度。这些相互作用受自然和人为强迫的影响，受到多种机制的驱动。然而，每种机制的相对重要性仍然未知，流域间遥相关的时间历史也是未知的。缩小这一知识差距对于了解外部强迫如何影响盆地间相互作用和提高热带及其他地区未来模型预测的准确性至关重要。这项研究将利用热带北大西洋(TNA)和西印度洋(WIO)数百年前殖民地的珊瑚骨骼材料的元素和同位素组成，创造新的海洋表面温度(SST)古气候记录。这些数据将与已公布的数据结合起来，以重建这些区域的仪器前SST，并评估盆地间的相互作用。这项研究还将探索这些模式与外部强迫的关系。该项目将评估流域间相互作用在相关模型模拟中的明显程度。来自珊瑚替代物的见解将通过启用同位素的上一个千年整体模拟来探索：这项研究将分析现有的iCESM输出，包括诊断个体外部影响对气候和同位素变异性的“单一强迫”实验，并进行有针对性的敏感性实验，分离与特定动力学机制相关的同位素特征。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Year-to-year changes in the temperatures of the tropical oceans impact climate and weather around the world. The clearest example of this is the El Niño-Southern Oscillation (ENSO) system in the tropical Pacific. Warming and cooling patterns related to ENSO have major effects on droughts, floods, and tropical storms. The temperature of the tropical Atlantic and Indian also affects weather in the same types of ways. Not only that, the three ocean basins can interact with each other since the atmosphere connects them all. For example, warming in the tropical Atlantic tends to lead to wind patterns that then cool off the tropical Pacific. This means that to predict how climate variations may change in the future, one must understand the connections between the tropical oceans. However, those relationships are known to change over long timescales (multiple decades), and temperature records are short and scarce in the tropics. As a result, this problem is difficult to study with traditional observations (e.g. thermometers). Instead, this project will produce records of temperature using the geochemistry of long-lived corals. By comparing data from corals in the Pacific, Atlantic, and Indian oceans, this research will show how these oceans have interacted over the past several centuries. Comparison of the 20th century with previous centuries will reveal the influence of recent warming. This work explores whether these patterns appear in the climate models used to understand future climate change, and what physical processes are involved. Several different model groups will be used for comparison. Students and postdocs will also participate in this research. Finally, the project will develop training materials to make data and model results more accessible to those without a highly technical background. Interannual to multidecadal variability in the tropical oceans drives climate extremes that impact natural and human systems around the world. The equatorial Pacific ENSO system is particularly important, and recent work highlights that Atlantic and Indian ocean variability impact the recurrence and intensity of ENSO extremes. Multiple mechanisms drive these interactions, which are affected by natural and anthropogenic forcing. Yet the relative importance of each mechanism remains unknown, as does the time history of the inter-basin teleconnections. Closing this knowledge gap is fundamental to understanding how inter-basin interactions are influenced by external forcing and improving the accuracy of future model projections in the tropics and beyond. This study will create new paleoclimate records of sea surface temperature (SST) using the elemental and isotopic composition of coral skeletal material, in cores from centuries-old colonies in the Tropical North Atlantic (TNA) and Western Indian Ocean (WIO). These data will be combined with published data to reconstruct pre-instrumental SST for these regions and assess inter-basin interactions. The study will also explore the relationship of these patterns to external forcing. The project will evaluate the degree to which interbasin interactions are manifest across relevant model simulations. Insights from coral proxies will be explored with the ensemble of isotope-enabled Last Millennium Ensemble simulations: the study will analyze existing iCESM output, including ‘single forcing’ experiments to diagnose individual external influences on climate and isotopic variability, and perform targeted sensitivity experiments isolating the isotopic signatures associated with particular dynamical mechanisms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.