Orbital to millennial-scale variability of the Southern Hemisphere Westerlies over the last glacial cycle

上一次冰期期间南半球西风带的轨道至千年尺度的变化

• 批准号: 2002546
• 负责人: Timothy Shanahan
• 金额: $ 40.22万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002546&HistoricalAwards=false
• 关键词: Orbital; millennial; scale; variability; Southern

The Southern Hemisphere westerly winds are a crucial component of the global climate system, playing an important role in controlling the weather of the Southern Hemisphere mid-latitudes through the seasonal transmission of precipitation-generating storm systems, as well as through their influence on the circulation of the Southern Ocean. It has been hypothesized that past changes in the position and strength of the westerlies may have also impacted the global carbon cycle through their influence on storage of carbon dioxide in the deep ocean, with impacts on global climate. Models also suggest that future warming will also result in changes in the westerlies, with the potential to drive changes in the storage or release of carbon dioxide from the Southern Ocean. However, the westerlies respond to a number of factors including regional, hemispheric and global patterns of warming, ocean circulation and Southern Ocean sea ice cover. In order to better understand how these factors influence the westerlies and their potential role in changing in the carbon cycle, this research project will generate a new reconstruction of the westerly wind response to a range of natural climate factors over the past ~140,000 years. In combination with the results of climate model simulations, the results of this study will provide a better understanding of how and why the westerlies change, and will thus provide a perspective from the geological past on how the westerlies will respond to future changes in global climate. The impacts of this research on society will be presented to the public through venues such the University of Texas Geoforce program, local community organizations, ongoing activities and outreach at local K-12 schools, through programs such as Girls Start and the Boy Scouts. This research will focus on the generation of a new high-resolution record of past westerly wind behavior using the laminated sediment record from Lake Orakei, a volcanic crater lake located on the North Island of New Zealand. Reconstructions will use the hydrogen isotope composition of sedimentary leaf waxes as a proxy for the position of the westerlies, an approach that is grounded in a study of modern isotope dynamics in this region. The reconstructions will be complemented by temperature reconstructions based on the MBT’5ME paleotemperature proxy and will focus on understanding the timing and nature of the westerly response to orbital forcing, the growth and retreat of the ice sheets and, over targeted intervals, the response to millennial-scale variability during Dansgaard-Oeschger and Heinrich stadials. A robust proxy-model comparison approach will be used to better understand the underlying climate dynamics driving the westerly wind response to these forcing mechanisms. This award is cofunded by the Division of Earth Sciences and the Division of Atmospheric and Geospace Sciences by way of the Paleo Perspectives on Climate Change Program.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.

南半球西风是全球气候系统的一个重要组成部分，通过产生降水的风暴系统的季节性传播以及对南大洋环流的影响，在控制南半球中纬度地区的天气方面发挥着重要作用。据推测，过去西风带位置和强度的变化也可能通过影响深海中二氧化碳的储存而影响全球碳循环，从而影响全球气候。模型还表明，未来的变暖也将导致西风带的变化，有可能导致南大洋二氧化碳储存或释放的变化。然而，西风带对许多因素作出反应，包括区域、半球和全球变暖模式、海洋环流和南大洋海冰覆盖。为了更好地了解这些因子如何影响西风带及其在碳循环变化中的潜在作用，本研究项目将对过去~14万年来西风对一系列自然气候因子的响应进行新的重建。结合气候模式模拟的结果，本研究的结果将更好地理解西风带变化的方式和原因，从而从过去的地质角度提供西风带如何响应未来全球气候变化的观点。这项研究对社会的影响将通过诸如德克萨斯大学地质部队计划、当地社区组织、正在进行的活动和当地K-12学校的外展活动等场所向公众展示，通过诸如女孩开始和童子军等项目。这项研究的重点是利用位于新西兰北岛的火山口湖奥拉凯湖的层状沉积物记录，生成新的高分辨率西风行为记录。重建将使用沉积叶蜡的氢同位素组成作为西风带位置的代表，这种方法是基于对该地区现代同位素动力学的研究。这些重建将辅以基于MBT’5ME古温度代理的温度重建，并将重点了解西风对轨道强迫响应的时间和性质，冰盖的生长和退缩，以及在目标间隔内对Dansgaard-Oeschger和Heinrich冰期千年尺度变率的响应。一种强有力的代理模式比较方法将用于更好地理解驱动西风对这些强迫机制响应的潜在气候动力学。这个奖项是由地球科学部和大气与地球空间科学部通过气候变化的古视角项目共同资助的。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。