Collaborative Research: Kr-86 as a Proxy for Barometric Pressure Variability and Movement of the SH Westerlies during the last Deglaciation

合作研究：Kr-86 作为上次冰消期期间南半球西风带气压变化和运动的代理

• 批准号: 1543267
• 负责人: Edward Brook
• 金额: $ 16万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-15 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1543267&HistoricalAwards=false
• 关键词: Collaborative; Research; Kr; 86; Proxy

Brook 1543267Approximately half of the human caused carbon dioxide emissions to the atmosphere are absorbed by the ocean, which reduces the amount of global warming associated with these emissions. Much of this carbon uptake occurs in the Southern Ocean around Antarctica, where water from the deep ocean comes to the surface. How much water "up-wells," and therefore how much carbon is absorbed, is believed to depend on the strength and location of the major westerly winds in the southern hemisphere. These wind patterns have been shifting southward in recent decades, and future changes could impact the global carbon cycle and promote the circulation of relatively warm water from the deep ocean on to the continental shelf, which contributes to enhanced Antarctic ice melt and sea level rise. Understanding of the westerly winds and their role in controlling atmospheric carbon dioxide levels and the circulation of ocean water is therefore very important. The work supported by this award will study past movement of the SH westerlies in response to natural climate variations. Of particular interest is the last deglaciation (20,000 to 10,000 years ago), when the global climate made a transition from an ice age climate to the current warm period. During this period, atmospheric carbon dioxide rose from about 180 ppm to 270 parts per million, and one leading hypothesis is that the rise in carbon dioxide was driven by a southward movement of the southern hemisphere westerlies. The broader impacts of the work include a perspective on past movement of the southern hemisphere westerlies and their link to atmospheric carbon dioxide, which could guide projections of future oceanic carbon dioxide uptake, with strong societal benefits; international collaboration with German scientists; training of a postdoctoral investigator; and outreach to public schools. This project will investigate whether the abundance of a noble gas, krypton-86, trapped in Antarctic ice cores, records atmospheric pressure variability, and whether or not this pressure variability can be used to infer past movement of the Southern Hemisphere westerly winds. The rationale for the project is that models of air movement in the snow pack (firn) in Antarctica indicate that pressure variations drive air movement that disturbs the normal enrichment in krypton-86 caused by gravitational settling of gases. Calculations predict that the krypton-86 deviation from gravitational equilibrium reflects the magnitude of pressure variations. In turn, atmospheric data show that pressure variability over Antarctica is linked to the position of the southern hemisphere westerly winds. Preliminary data from the West Antarctic Ice Sheet (WAIS) Divide ice core show a large excursion in krypton-86 during the transition from the last ice age to the current warm period. The investigators will perform krypton-86 analysis on ice core and firn air samples to establish whether the Kr-86 deviation is linked to pressure variability, refine the record of krypton isotopes from the WAIS Divide ice core, investigate the role of pressure variability in firn air transport using firn air models, and investigate how barometric pressure variability in Antarctica is linked to the position/strength of the SH westerlies in past and present climates.

Brook 1543267 人类排放到大气中的二氧化碳大约有一半被海洋吸收，从而减少了与这些排放相关的全球变暖量。 大部分碳吸收发生在南极洲周围的南大洋，那里深海的水流到地表。有多少水“上升”，以及有多少碳被吸收，被认为取决于南半球主要西风的强度和位置。 近几十年来，这些风型一直在向南转移，未来的变化可能会影响全球碳循环，并促进相对温暖的海水从深海循环到大陆架，从而导致南极冰川融化和海平面上升。因此，了解西风及其在控制大气二氧化碳水平和海水循环方面的作用非常重要。 该奖项支持的工作将研究南半球西风带过去的运动对自然气候变化的响应。特别令人感兴趣的是最后一次冰消期（20,000 至 10,000 年前），当时全球气候从冰河时代气候过渡到当前的温暖期。 在此期间，大气中的二氧化碳含量从约 180 ppm 上升至百万分之 270，一个主要假设是二氧化碳的上升是由南半球西风带向南移动所致。 这项工作的更广泛影响包括对南半球西风过去运动及其与大气二氧化碳的联系的看法，这可以指导未来海洋二氧化碳吸收的预测，具有强大的社会效益；与德国科学家的国际合作；培训博士后研究员；以及向公立学校进行推广。 该项目将调查南极冰芯中惰性气体氪86的丰度是否记录了大气压力的变化，以及这种压力变化是否可以用来推断南半球西风过去的运动。该项目的基本原理是，南极洲积雪中的空气运动模型表明，压力变化会驱动空气运动，从而扰乱由气体重力沉降引起的氪 86 的正常富集。 计算预测氪86与重力平衡的偏差反映了压力变化的幅度。 反过来，大气数据表明，南极洲的压力变化与南半球西风的位置有关。来自西南极冰盖 (WAIS) 分水岭冰芯的初步数据显示，在从最后一个冰河时代到当前温暖时期的过渡期间，氪 86 发生了大幅偏移。 研究人员将对冰芯和冷空气样本进行氪 86 分析，以确定 Kr-86 偏差是否与压力变化有关，完善 WAIS Divide 冰芯的氪同位素记录，研究冷空气中压力变化的作用。使用冷空气模型进行航空运输，并研究南极洲的气压变化与过去和现在气候中南半球西风带的位置/强度之间的关系。