CAREER: Tree-Ring Based Reconstruction of Northern Hemisphere Jetstream Variability

北半球急流是一种高空狭窄的强风路径，蜿蜒环绕全球，是中纬度极端天气事件强度和持久性的关键因素。一些研究表明，随着正在进行和未来的气候变化，喷流可能会减缓并改变轨迹。加州干旱、美国东部极地涡旋以及2013-2014年冬季英格兰的冬季风暴都是这种行为的例证。近几十年来，北极放大（北半球高纬度地区比低纬度地区变暖更强烈）可能驱动急流变率，但人为气候变化在急流变率中的作用存在争议，而且仪器测量周期太短，无法对当前和未来的急流趋势得出确凿的结论。这项研究将利用树木年轮记录重建过去500多年来喷流的纬度位置。该项目将生成一个新的基于树木年轮的巴尔干夏季温度重建，并将其与欧洲西北部的代理数据结合起来，重建夏季北大西洋喷气机。对于冬季的北太平洋喷气机，这项工作将把来自北落基山脉的新的冬季气候敏感系列与来自加利福尼亚中部的年表结合起来。这两个500多年的区域急流重建将用于从历史的角度来看待当前的急流趋势。该职业奖教育部分的核心是开发一门新的全球变化分析课程，该课程将为亚利桑那大学广泛、跨学科的全球变化研究社区的学生提供定量方法的培训。该项目还包括一个多方面的推广方法，利用亚利桑那大学气候变化科学领域女性的偶然性，旨在激发后代对科学事业的兴趣。最后，该项目包括与保加利亚、斯洛文尼亚和瑞士的研究人员的国际合作和实地考察，包括技术知识转移（x射线密度测量），这将使美国具备新的能力。该项目由古气候计划和美国国家科学基金会国际科学与工程办公室共同支持。

The Northern Hemisphere Jet, a high altitude narrow path of strong winds that meanders around the globe, is a key factor in the strength and perseverance of mid-latitude extreme weather events. Some studies have suggested that the jet may slow and change trajectory with ongoing and future climate change. Such behavior has been exemplified by the California drought, the eastern US polar vortex, and the winter storms in England in the winter of 2013-2014. Arctic amplification (the stronger warming of high Northern Hemisphere latitudes compared to lower latitudes) may drive jet stream variability in recent decades, but the role of man-made climate change in jet stream variability is contested and the instrumental period of measurement is too short to draw firm conclusions about current and future jet stream trends.This research will reconstruct the latitudinal position of the jet over the last 500+ years using tree-ring records. The project will generate a new tree-ring based summer temperature reconstruction for the Balkans and combine it with proxy data from northwestern Europe to reconstruct the summer North Atlantic Jet. For the winter North Pacific Jet, the work will combine new winter climate-sensitive series from the northern Rockies with chronologies from central California. These two 500+ year-long regional jet stream reconstructions will be used to put current jet stream trends in a historical perspective.The centerpiece of the education component of this CAREER award is the development of a new Global Change Analysis course that would offer training in quantitative methods to students across the broad, interdisciplinary global change research community at the University of Arizona. The project also includes a multi-faceted outreach approach that capitalizes on the contingency of women in climate change science at the University of Arizona and is designed to excite future generations about science careers. Finally, the project includes international partnerships and field expeditions with researchers from Bulgaria, Slovenia, and Switzerland, including technology knowledge transfer (in x-ray densitometry) that will enable new capabilities in the US.This project is jointly supported by the Paleoclimate Program and NSF's office of International Science and Engineering.