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

人类排放到大气中的二氧化碳大约有一半被海洋吸收，这减少了与这些排放相关的全球变暖。大部分碳吸收发生在南极洲附近的南大洋，那里有来自深海的水进入海面。据信，有多少水“上井”，因此有多少碳被吸收，这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，并促进相对温暖的水从深海流向大陆架，从而促进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过去SH西风带对自然气候变化的反应。特别令人感兴趣的是最后一次冰川消融(20,000至10,000年前)，当时全球气候从冰河时代的气候过渡到目前的暖期。在此期间，大气中的二氧化碳从百万分之180左右上升到270ppm，一个主要的假设是，二氧化碳的上升是由南半球西风带向南移动所推动的。这项工作的更广泛影响包括：透视南半球西风带过去的移动及其与大气二氧化碳的联系，这可指导对未来海洋二氧化碳吸收的预测，具有强大的社会效益；与德国科学家开展国际合作；培训一名博士后研究员；与公立学校开展外联活动。该项目将调查困在南极冰芯中的惰性气体氪-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的过去移动。该项目的基本原理是，南极洲积雪(FIRN)中的空气运动模型表明，气压变化驱动空气运动，而空气运动扰乱了由于气体重力沉降而导致的氪-86的正常浓缩。计算预测，氪-86偏离引力平衡反映了压力变化的大小。反过来，大气数据显示，南极洲上空的气压变化与南半球西风的位置有关。来自西南极冰盖(WAIS)冰芯的初步数据显示，在从上一个冰期到当前暖期的过渡期间，氪-86有很大的漂移。研究人员将对冰芯和降雪空气样本进行氪-86分析，以确定Kr-86偏差是否与气压变异性有关，改进来自WAIS分隔冰芯的氪同位素记录，使用降雪空气模型调查气压变异性在降雪空气输送中的作用，并调查南极洲的气压变异性如何与过去和现在气候中SH西风的位置/强度有关。

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.