When was Summit, Greenland last ice-free: 81Kr dating of dirty ice at the bottom of the GISP2 ice core

格陵兰岛萨米特最后一次无冰是什么时候：GISP2冰芯底部脏冰的81Kr测年

• 批准号: 2052958
• 负责人: Michael Bender
• 金额: $ 13.59万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-15 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2052958&HistoricalAwards=false
• 关键词: When; was; Summit; Greenland; last

Ice sheets melt as Planet Earth becomes warmer. This melting causes sea level to rise, constituting one of the most serious problems resulting from global warming. Complete melting of the Greenland Ice Sheet would raise the average level of the oceans by 7 meters, with significant consequences for cities and towns along the coasts of the world. Understanding how extensively the Greenland Ice Sheet melted in the past will help us predict how fast it will melt in the future. The investigators will determine the age of ice at the very bottom of the ice sheet. The measurements will be made on ice from a site called “GISP2”, in central Greenland, where a hole has been drilled through the 3053-meter thick ice sheet. The ice at the bottom of the hole is likely to be the oldest ice on Greenland and the dating of this bottom ice will tell us the last time that Greenland was not covered by a big ice sheet. By comparing the time when Greenland was ice-free with global climate events that occurred in the past, we hope to learn why the Greenland Ice Sheet melted in the past, and what human activities might cause it to melt in the future. This work will have 2 major benefits to society. First, it will lead to a better understanding of how human activities are likely to affect sea level in the future. Second, it will lead to the training of a postdoctoral fellow, who will collect most of the data, understand the results, and develop research skills that will complete her training as an outstanding independent scientist.The great planetary ice sheets may melt due to global warming, causing sea level to rise. Complete melting of the East Antarctic ice sheet would raise sea level by 53 m, melting of the West Antarctic Ice Sheet would lead to a 5 m rise, and melting of Greenland would cause a 7 m rise. The Greenland ice sheet is generally regarded as most susceptible to melting and therefore of greatest concern. Melting of the Greenland Ice Sheet would lead to a catastrophic rise in sea level, causing flooding of coastal cities as well as lowlands near the ocean. A premise of this proposal is that, if we determine when Greenland was last ice-free, we will have new information which will help us predict the rate of melting in the future, and, consequent rate of sea level rise. The investigators will determine the age of ice at the very bottom of the ice sheet. We will do this using a method called “krypton 81 dating”. Krypton 81 is a form of krypton that is radioactive and gradually changes into another element. The lower the krypton-81 concentration in air trapped in ancient ice, the older the ice. The measurements will be made on ice from a site called “GISP2”, in central Greenland, where a hole has been drilled through the 3053-meter thick ice sheet. The dating measurements will be made at the University of Science and Technology of China, in Hefei. This University has the one instrument in the world capable of measuring the abundance of 81Kr with the required accuracy. Having dated the oldest ice, we will examine the age in the context of known global climate events that occurred around the same time. For example, climate was particularly warm at several times in the past, including 400,000 years ago and 1,070,000 years ago. A date near one of those 2 times would suggest that the planetary warming was sufficient to melt the Greenland Ice Sheet, after which the planet cooled and Greenland was continuously glaciated. This information would challenge global climate models to account for global warming at the appropriate time and would clarify what is required for the melting and regrowth of the ice sheet. This new insight would, in turn, improve our ability to estimate the melting trajectory of the Greenland Ice Sheet on human-relevant timescales (say, thousands to hundreds of thousands of years). It would also improve our ability to understand past climate events and the role of Greenland melting. A Postdoctoral Fellow will be directly responsible for most aspects of the project, including preparing ice core samples for analysis, extracting dissolved gases, interpreting the results, preparing a paper reporting the data, and submitting the results to the NSF Arctic Data Center. The post doctoral scientist will be mentored by the PI and provide support for becoming an independent scientist playing an important role in moving the field forward.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.

随着地球变暖，冰盖融化。这种熔化导致海平面上升，这构成了全球变暖引起的最严重的问题之一。格陵兰冰盖的完全融化将使海洋的平均水平提高7米，这对世界上的城市和城镇产生了重大影响。了解格陵兰冰盖过去融化的广泛程度将有助于我们预测未来融化的速度。调查人员将确定冰盖底部的冰时代。该测量值将在格陵兰中部的一个名为“ GISP2”的地点在冰上进行，在那里已经通过3053米厚的冰盖钻了一个孔。孔底部的冰可能是格陵兰岛上最古老的冰，而这种底部冰的日期会告诉我们上次格陵兰岛不被大型冰盖覆盖。通过比较格陵兰岛与过去发生的全球气候事件无冰的时间，我们希望了解为什么格陵兰冰盖过去融化了，以及人类的活动可能会导致其将来融化。这项工作将对社会有2个主要利益。首先，它将更好地了解未来人类活动可能如何影响海平面。其次，这将导致对博士后研究员的培训，后者将收集大多数数据，了解结果并发展研究技能，以完成她作为杰出的独立科学家的培训。伟大的行星冰盖可能由于全球变暖而融化，导致海平面上升。东南极冰盖的完全融化将使海平面提高53 m，南极冰盖的融化将导致5 m的上升，而格陵兰岛的融化将导致7 m上升。格陵兰冰盖通常被认为最容易受到融化的影响，因此最引起人们的关注。格陵兰冰盖的融化将导致海平面灾难性上升，导致沿海城市以及海洋附近的低地泛滥。该提议的前提是，如果我们确定格陵兰岛何时无冰，我们将拥有新的信息，这将有助于我们预测将来的融化速度，并有助于海平面上升的速度。调查人员将确定冰盖底部的冰时代。我们将使用称为“ K 81约会”的方法来做到这一点。 K k 81是一种k的形式，它是放射性的，并逐渐变成另一个元素。在古代冰中被困在空气中的K k81浓度越低，冰年龄较大。该测量值将在格陵兰中部的一个名为“ GISP2”的地点在冰上进行，在那里已经通过3053米厚的冰盖钻了一个孔。日期测量将在Hefei的中国科学技术大学进行。该大学拥有世界上一种能够以所需准确性来测量81kr的抽象。与最古老的冰约会后，我们将在同一时间发生的已知全球气候事件的背景下检查年龄。例如，过去几次气候特别温暖，包括400，000年前和1,070，000年前。在这两次中，约会的日期表明，行星变暖足以融化格陵兰冰盖，然后行星冷却，格陵兰岛不断冰川。这些信息将挑战全球气候模型，以在适当的时间考虑全球变暖，并阐明冰盖融化和改革所需的内容。反过来，这种新的见解将提高我们估计与人类相关的时间尺度上格陵兰冰盖融化轨迹的能力（例如，数千至数十万年）。这也将提高我们了解过去气候事件的能力和格陵兰融化的作用。博士后研究员将直接负责项目的大多数方面，包括准备分析冰核样本，提取溶解的气体，解释结果，准备报告数据并将结果提交给NSF北极数据中心。 PI将召集博士后科学家，并为成为独立科学家的支持提供了支持，该奖项反映了NSF的法定任务，并通过使用基金会的知识分子和更广泛的影响审查标准来评估NSF的法定任务。