Collaborative Research: P2C2--A Model/Proxy Synthesis of Walker Circulation Trends During the Last Millennium

太平洋沃克环流改变了世界各地的极端天气和气候，但它对外部气候强迫的敏感性尚不清楚。特别是，对20世纪沃克环流趋势的观测估计提供了相互矛盾的结果，一些人提出了加强的趋势，另一些人则认为趋势减弱或没有趋势，这使得将这些趋势归因于任何特定的强迫变得复杂。古气候记录可以通过提供更长期的背景来改进趋势的探测和归属，但由于缺乏涵盖上一个千年的多指标综合产品和气候模型模拟，这些记录的使用受到阻碍。该项目旨在使用最近建立的PAGES Iso2k数据库创建多个Walker循环指标的新的定量重建，并使用共同体地球系统模型最后一个千年集合(LME)和其同位素使能补体(ILME)的新模拟来评估这些指标中的可变性和趋势的机制。这项研究试图应用这些新工具来回答一个核心问题：从上个千年到20世纪，沃克环流变化和趋势背后的机制是什么，外部强迫和内部变化的相对作用是什么？潜在的更广泛的影响(B.I.)包括强大的科学和教育方面。热带太平洋的气候变异性影响着社会和生态系统；因此，了解沃克环流的长期变异性对于改进对21世纪气候变化影响的预测至关重要。这个科学跨学科的研究团队完全由职业生涯早期的研究人员组成，其中两人是女性。该项目将资助一名研究生和博士后研究员。来自人口结构偏低的高中生将通过一项针对STEM多样性的计划，招募他们参加暑期实习和辅导。最后，该项目将产生热带太平洋气候变异性和iLME整体成员的多代理综合重建，所有这些都将作为资源提供给更广泛的科学和民间社区。该奖项反映了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。

The Pacific Walker circulation alters weather and climate extremes around the world, but its sensitivity to external climate forcings remains unknown. In particular, observational estimates of 20th century trends in the Walker circulation provide conflicting results, with some suggesting a strengthening and others a weakening or no trend, complicating the attribution of these trends to any specific forcing. Paleoclimate records can improve the detection and attribution of trends by providing longer-term context, but their use has been hindered by the lack of multi-proxy synthesis products and climate model simulations covering the last millennium. This project aims to create new quantitative reconstructions of multiple Walker circulation metrics using the recently constructed PAGES Iso2k database, and to evaluate the mechanisms for variability and trends in these metrics using the Community Earth System Model Last Millennium Ensemble (LME) and new simulations with its isotope-enabled complement (iLME). The research seeks to apply these new tools to answer one central question: What are the mechanisms underlying Walker circulation variability and trends from the Last Millennium through the 20th century, and what are the relative roles of external forcings and internal variability?The potential Broader Impacts (B.I.) includes strong science and educational aspects. Climate variability in the tropical Pacific affects societies and ecosystems; understanding long-term variability of the Walker circulation is thus critical for improving projections of the impacts of 21st century climate change. This scientifically-interdisciplinary research team is composed entirely of early-career researchers, two of whom are female. The project will support a graduate student and postdoctoral researcher. High school students from underrepresented demographics will be recruited for summer internships and mentoring through a program that targets diversity in STEM. Finally, the project will produce multi-proxy synthesis reconstructions of tropical Pacific climate variability and iLME ensemble members, all of which will be made available as resources to the wider scientific and civil communities.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.