Modeled Export of Ancient, Thick Sea Ice from the Arctic, and its Role in Abrupt Climate Change

模拟北极古代厚海冰的输出及其在气候突变中的作用

• 批准号: 1855918
• 负责人: Alan Condron
• 金额: $ 12.67万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-02-15 至 2020-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1855918&HistoricalAwards=false
• 关键词: Modeled; Export; Ancient; Thick; Sea

NontechnicalThis research will address fundamental questions regarding both paleo-climate and paleo-circulation of the ocean by identifying what may have triggered past abrupt climate change. In the late nineteenth century, Sir George Nares came across 15-18 m thick, immobile, ice extending 480 km off the northern Ellesmere coast. The characteristics of the ice were very different from the 2-3 m thick ice now circulating the Arctic Ocean. Similar accounts from other arctic explorers from this time provided insight into what must surely have been a far thicker and more persistent ice cover over the Arctic Ocean during full glacial conditions than we see today. Indeed, low biological productivity and extremely low, or absent, sediment deposition in the Arctic during glacial periods suggest that parts of the central and western Arctic Ocean were covered by very thick, perennial ice. This research will explore how such ice could have covered much of the Arctic Ocean during glacial periods, how thick it could have been, and whether its eventual mobilization and demise could have produced freshwater output to the North Atlantic large enough to weaken the deep water formation and trigger abrupt climate cooling. Using a suite of sophisticated, high-resolution, coupled numerical model experiments, this group will address these questions and highlight the connection between changes in the Arctic hydrological cycle and global climate.Each investigator has a serious commitment to education and public outreach, and the project will support and train a graduate student who will work with the investigators in all aspects of the research. Each investigator has been involved with local primary and secondary schools, either by making presentations, hiring students for the summer, mentoring science fair projects, or contributing to curriculum development. They will contribute to the on-going middle and high school science teacher training activities by developing a web-based, interactive, sea ice-learning tool to teach school children about the mechanisms behind sea ice formation and how ice will change as the arctic climate warms. In addition, well-developed relationships with local community organizations will help promote public understanding of abrupt climate change. The idea of thick sea ice in the Arctic has a remarkable ability to capture the public imagination in much the same way as it did in the Victorian period when explorers returned from the Arctic with tales of thick impenetrable ice, conveying the concept of the important role that the Arctic plays in global climate.TechnicalThe intellectual merit of this project stems from its ability to establish a link between the physical arctic system (circulation, sea ice, icebergs) and global climate. Numerical models have recently shown that freshwater sourced from the Arctic is twice as effective at disrupting climate than freshwater released from more southerly sources, but to the present the subject of freshwater and abrupt climate change has been dominated by discussion of meltwater floods emanating from glacial lake outbursts. Determining whether the export of sea ice and associated superimposed ice from the Arctic to the North Atlantic could supply enough freshwater to the Nordic Seas to cause the Earth's climate to cool will provide new insight into the mechanisms that trigger abrupt climate change. By quantifying the sensitivity of Atlantic meridional overturning circulation to arctic freshwater forcing the researchers will also be able to better examine whether changes in the arctic hydrological cycle in the near future (from sea ice melt and freshwater export from the Beaufort Gyre) pose a threat to the stability of modern-day climate and human society. In addition, the numerical model developed for this project will resolve ocean circulation, sea ice, and iceberg transport at a resolution approx. 0.17 degrees (ca. 19 km), 5-10 times higher than that of existing paleo-climate models, and have the capability of simulating narrow coastal boundary currents, shelf-breaks, and frontal zones important for freshwater transport along the continental margins, and other features not captured by the current generation of paleo-climate models.

非技术性这项研究将通过确定过去突然的气候变化可能引发的因素来解决有关古气候和古海洋环流的基本问题。19世纪末，乔治·纳雷斯爵士在埃尔斯米尔北部海岸外发现了厚15-18米、静止不动的冰，绵延480公里。这些冰的特征与目前在北冰洋循环的2-3米厚的冰有很大的不同。从那时起，其他北极探险家的类似描述为我们提供了洞察，在冰川条件比我们今天看到的全面冰川条件下，北冰洋上空肯定有更厚、更持久的冰盖。事实上，北冰洋生物生产力低，冰川时期北冰洋沉积物沉积极低或没有，这表明北冰洋中部和西部的部分地区被非常厚的常年冰覆盖。这项研究将探索这样的冰层如何在冰川时期覆盖北冰洋的大部分地区，它可能有多厚，以及它最终的移动和消失是否会产生足够大的淡水输出到北大西洋，从而削弱深水形成并引发气候突然冷却。利用一套复杂的、高分辨率的、耦合的数值模式实验，这个小组将解决这些问题，并强调北极水文循环的变化与全球气候之间的联系。每个研究人员都认真致力于教育和公共宣传，该项目将支持和培训一名研究生，他将在研究的各个方面与研究人员合作。每个调查员都参与了当地的中小学，要么做报告，要么雇佣学生参加暑期活动，要么指导科学博览会项目，要么为课程开发做出贡献。他们将为正在进行的初中和高中科学教师培训活动做出贡献，开发一个基于网络的、互动的海冰学习工具，向学生传授海冰形成背后的机制，以及随着北极气候变暖，冰将如何变化。此外，与当地社区组织发展良好的关系将有助于促进公众对突然的气候变化的了解。北极厚厚的海冰的概念具有非凡的能力，能够激发公众的想象力，就像维多利亚时代一样，当时探险家们从北极带着厚厚的不可穿透的冰的故事回来，传达了北极在全球气候中扮演的重要角色的概念。技术上，这个项目的学术价值来自于它能够在物理北极系统(环流、海冰、冰山)和全球气候之间建立联系。最近的数值模型表明，来自北极的淡水在破坏气候方面的效果是来自更南端的淡水的两倍，但到目前为止，淡水和气候突然变化的主题一直被关于冰川湖暴发引发的融水洪水的讨论所主导。确定从北极向北大西洋出口海冰和相关的叠加冰是否可以向北欧海洋提供足够的淡水，从而导致地球气候变冷，这将为触发气候突然变化的机制提供新的见解。通过量化大西洋经向翻转环流对北极淡水强迫的敏感性，研究人员还将能够更好地研究在不久的将来北极水文循环的变化(来自海冰融化和来自波弗特环流的淡水输出)是否对现代气候和人类社会的稳定构成威胁。此外，为该项目开发的数值模式将以大约分辨率解析海洋环流、海冰和冰山输送。0.17度(约19公里)，比现有的古气候模型高5-10倍，并有能力模拟狭窄的沿海边界流、陆架断裂和对大陆边缘淡水运输重要的锋面带，以及当代古气候模型未能捕捉到的其他特征。