ENSO flavors during the Last Glacial Maximum: Assessing spatial variability under varying climate background conditions

地球年际气候变异的最大来源是厄尔Niño南方涛动（ENSO），其特征是热带太平洋海面温度的明显空间格局。这些模式（或“味道”）通过强大的海洋-大气耦合相互作用与气候变化联系在一起，这种相互作用在全球范围内回响，并可能对人类社会产生不利影响。最近的观察表明，这些模式可能正在发生变化，从而限制了社会预测和减轻ENSO影响的能力。然而，ENSO的空间表达和气候效应的变化是否与背景气候条件（如全球平均温度或热带海洋表面和地下温度）有关尚不清楚。该项目将使用大约2万年前沉积的海洋沉积物来研究ENSO“风味”——温度的空间模式——在较冷的背景气候状态下是如何变化的。这些结果将促进我们对ENSO系统的理论认识，并使我们能够更好地预测未来气候条件下的全球ENSO影响。该项目将为本科生和研究生提供气候研究机会，并将促进在线内容的创建，以突出与enso相关的气候变率在区域和国家层面的重要性。背景气候条件与海洋温度异常模式（或厄尔Niño南方涛动（ENSO）特征的“风味”）之间关系的本质仍不清楚。本项目将验证以下假设：背景气候状态，如平均温度和热带太平洋表面和地下海洋条件，影响ENSO变化的空间格局，以及温跃层在调节ENSO中起关键作用。通过发展热带太平洋中部和东部关键地点跨越末次冰期极大期（2万年前）的变异性记录，将评估不同气候背景条件下热带太平洋的空间变异性。浮游有孔虫壳的地球化学分析将重建这些地点的海洋条件。单个贝壳的微量元素和稳定同位素比率的种群分布将提供对海洋表面和地下变化的估计。这些数据将重建末次盛冰期ENSO的空间表达，并测试背景气候和/或温跃层条件是否影响ENSO的“风味”。这项研究将促进我们对不同气候状态下气候系统过程、机制和海洋-大气动力相互作用的认识，并对预测未来ENSO行为具有重要意义。该项目结合了本科生和研究生的研究，并将为公共教育提供在线内容。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

ENSO flavors during the Last Glacial Maximum: Assessing spatial variability under varying climate background conditionsThe largest source of interannual climate variability on Earth is the El Niño Southern Oscillation (ENSO), characterized by distinct spatial patterns of tropical Pacific sea surface temperatures. These patterns (or ‘flavors’) are linked to climatic changes through powerful coupled ocean-atmosphere interactions that reverberate globally and can adversely affect human societies. Recent observations suggest these patterns may be changing, limiting societies’ ability to forecast and mitigate ENSO impacts. However, it remains unclear whether changes to ENSO’s spatial expression and climatic effects are related to background climate conditions such as mean global temperature or tropical ocean surface and subsurface temperatures. This project will use ocean sediments deposited approximately 20,000 years ago to study how ENSO ‘flavors’ – the spatial pattern of temperatures – change during a colder background climate state. The results will advance our theoretical understanding of the ENSO system and enable better predictions of global ENSO impacts under future climate conditions. This project will offer climate research opportunities for undergraduate and graduate students and will facilitate creation of online content to highlight the importance of ENSO-related climate variability at the regional and national level. The nature of the relationship between background climate conditions and the patterns of ocean temperature anomalies, or ‘flavors’ that characterize the El Niño Southern Oscillation (ENSO) remains unclear. This project will test hypotheses that background climate state, such as mean temperature and tropical Pacific surface and subsurface ocean conditions, influence the spatial pattern of ENSO variability, and that the thermocline plays a key role in modulating ENSO. The spatial variability of the tropical Pacific under differing climate background conditions will be assessed by developing records of variability spanning the last glacial maximum (20,000 years ago) from key locations in the central and eastern tropical Pacific. The geochemistry of planktic foraminifera shells will be analyzed to reconstruct oceanic conditions at these sites. Population distributions of trace elemental and stable isotopic ratios from individual shells will provide estimates of surface and subsurface ocean variability. These data will reconstruct ENSO’s spatial expression during the last glacial maximum and test whether background climate and/or thermocline conditions influence ENSO ‘flavors’. This research will advance our knowledge of climate system processes, mechanisms, and dynamical ocean-atmosphere interactions during different climate states with implications for predicting future ENSO behavior. This project incorporates undergraduate and graduate student research and will produce online content for public education.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.