NSFGEO-NERC: Understanding Trans-Hemispheric Modes of Climate Variability: A Novel Tree-Ring Data Transect spanning the Himalaya to the Southern Ocean

控制跨半球气候联系以及热带和高纬度之间气候联系的机制还没有得到很好的理解，特别是在人类活动时期之前。因此，知识上的差距限制了我们对年际到年代际和更长时间尺度上更广泛的气候遥相关的理解。与美洲西部不同的是，由于两个半球在地理上的相似性，可以观察到对称性和共同的振荡模式，而西太平洋缺乏这种对称性，该地区大部分地区的高分辨率、准确年代的古记录的数据覆盖范围有限。我们建议改变现有的从喜马拉雅到南大洋的树木年轮数据样带的用途，基于我们从更广泛的季风亚洲到中纬度南部收集的档案中的木材样本。通过创建一个侧重于早材(EW)和晚材(LW)宽度以及最大和最小蓝色强度(BI)的新数据网络，这些数据将用于加强几乎完全基于单一总年轮宽度(RW)参数的先前气候分析。BI是相对木材密度的间接替代物，已被证明在低成本和低工作量下可能比单独使用TRW对温度和水文气候更敏感。这一扩展的数据样带将用于模拟和重建南北半球(NH和SH)之间的关键大气-海洋变率模式。NSF-NERC项目PI共同开创了热带和SH中纬度BI和EW-LW研究的先河。概念验证数据显示，几种喜马拉雅、热带和中纬度SH针叶树的BI、EW和LW参数有力地反映了气候变化，使我们的研究团队处于独特的地位，可以扩大我们对整个地区温度和水文气候变化的知识。这套新的数据将提供机会模拟和重建这一样带的大气-海洋环流动态的关键指标，热带印度-太平洋是一个关键的感兴趣的区域，其中厄尔尼诺-南方涛动(ENSO)、热带辐合带(ITCZ)和印度洋偶极子是具有全球影响的气候变异性的主要来源。火山活动扰乱了两个半球的气候，而南环状模式或南极涛动则影响着我们样带南端的中纬度地区的气候。新的数据覆盖范围、参数、分析和重建将使我们能够解决几个悬而未决的研究问题，包括：1.热带和南半球火山事件对气候的影响？2.过去500-1000年来，整个研究区域的ITCZ和ENSO是如何变化的？3.南环型在过去的千年中有何变化，它是由热带强迫驱动的吗？要了解全球对气候的响应，需要来自热带和上海的强大的、高分辨率的古气候数据，我们的拟议样带将提供这一数据。该项目将有助于更好地理解在本文提出的东半球样带的气候敏感但数据稀少的地区的过去变异性，这些地区是全球气候最脆弱的地区。这些数据将通过国际树轮数据库和其他场所向更广泛的社区传播，并将纳入未来的亚洲季风干旱地图集。教育也将是该项目的重要组成部分。来自该项目的数据将用于哥伦比亚大学(CU)由首席PI讲授的硕士课程和RU PI在Rider大学(RU)教授的本科生课程。RU的学生将参与这个项目，并往返于RU和CU之间的教育活动。RU、CU和外国合作伙伴的学生将定期进行虚拟学生交流。

The mechanisms that govern trans-hemispheric climate linkages and those between the tropics and higher latitudes are not well understood, especially before the Anthropogenic period. Hence there are gaps in knowledge that limit our understanding of broader-scale climate teleconnections on interannual to decadal and longer time scales. Unlike the western Americas, where symmetries and common oscillatory modes are observed due to geographic similarities between the two hemispheres, the western Pacific lacks such symmetry, and data coverage of high resolution, well-dated paleorecords is limited over much of the region. We propose to repurpose an existing tree-ring data transect spanning from the Himalaya to the Southern Ocean, based on wood samples from our archives collected from broader monsoon Asia down to southern middle latitudes. By creating a new data network that focuses on earlywood (EW) and latewood (LW) width and maximum and minimum Blue Intensity (BI), these data will be used to enhance prior climate analyses based almost entirely on the single total ring-width (RW) parameter. BI is an indirect proxy of relative wood density and has been shown to be potentially more responsive to temperature and hydroclimate than TRW alone at low cost and effort. This expanded data transect will be used to model and reconstruct key modes of atmosphere-ocean variability between the northern and southern hemispheres (NH and SH).The NSF-NERC project PIs have jointly pioneered BI and EW-LW research in the tropics and SH mid-latitudes. Proof of concept data show that BI, EW and LW parameters for several Himalayan, tropical and mid-latitude SH conifers are robustly reflective of climate variability, placing our research team in a unique position to expand our knowledge of temperature and hydroclimate variability across the region. This new suite of data will provide the opportunity to model and reconstruct key indicators of atmosphere-ocean circulation dynamics across this transect, the tropical Indo-Pacific is a key region of interest, where the El Niño-Southern Oscillation (ENSO), Intertropical Convergence Zone (ITCZ), and Indian Ocean Dipole are dominant sources of climate variability with global impact. Volcanism perturbs climate across both hemispheres, while the Southern Annular Mode or Antarctic Oscillation impacts climate towards the SH mid latitudes at the southern end of our transect. The new data coverage, parameters, analyses and reconstructions will allow us to address several outstanding research questions, including: 1. What are the climatic impacts of volcanic events in the tropics and Southern Hemisphere? 2. How have the ITCZ and ENSO varied of the past 500-1000 years as expressed across our study region? And 3. How has the Southern Annular Mode varied over the past millennium, and is it driven by tropical forcing? To understand the global response to climate requires robust, high-resolution paleoclimate data from the tropics and SH, which our proposed transect will provide.This project will lead to an improved understanding of past variability in climate-sensitive, yet data-sparse regions of the Eastern Hemisphere transect proposed herein, some of the most climatically vulnerable regions of the globe. These data will be disseminated to the broader community via the International Tree-Ring Data Bank and other venues and will be included in a future iteration of the Monsoon Asia Drought Atlas. Education will be an important component of this project as well. Data from this project will be used for instructional purposes in a Masters level class taught at Columbia University (CU) by the lead PI and an undergraduate level course at Rider University (RU) by the RU PI. RU students will participate in this project and travel between RU and CU for educational activities. Regular virtual student exchanges will take place between students from RU, CU and foreign partners.