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

这项研究将通过确定可能引发过去气候突变的原因，解决有关海洋古气候和古环流的基本问题。在世纪后期，乔治·纳雷斯爵士在北方埃尔斯米尔海岸外发现了厚达15-18米的不动冰层，冰层延伸了480公里。这些冰的特征与现在北冰洋上2-3米厚的冰有很大的不同。从这个时候其他北极探险家的类似帐户提供了深入了解什么肯定是一个更厚和更持久的冰覆盖在北冰洋在完整的冰川条件下比我们今天看到的。事实上，北极在冰川期的低生物生产力和极低或没有沉积物沉积表明，北冰洋中部和西部的部分地区被非常厚的常年冰层覆盖。这项研究将探索这些冰如何在冰川时期覆盖北冰洋的大部分地区，它可能有多厚，以及它的最终动员和消亡是否可能产生足够大的淡水输出到北大西洋，以削弱深水的形成并引发突然的气候冷却。该小组将使用一套复杂的、高分辨率的耦合数值模型实验来解决这些问题，并强调北极水文循环变化与全球气候之间的联系。每位研究人员都认真致力于教育和公众宣传，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小学和中学，无论是做演讲，雇用学生的夏天，指导科学公平的项目，或有助于课程开发。他们将通过开发一个基于网络的、互动的海冰学习工具来帮助正在进行的初中和高中科学教师培训活动，向学生们教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，与当地社区组织建立良好的关系将有助于促进公众对气候突变的了解。北极厚厚的海冰的想法有一种非凡的能力来捕捉公众的想象力，就像维多利亚时代一样，当探险家从北极回来时，他们带来了厚厚的不可穿透的冰的故事，传达北极在全球气候中扮演重要角色的概念。技术上，该项目的智力价值源于其建立北极物理系统之间联系的能力，（环流、海冰、冰山）和全球气候。数值模型最近表明，来自北极的淡水对气候的干扰效果是来自更南部来源的淡水的两倍，但到目前为止，淡水和气候突变的主题一直由对冰川湖爆发产生的融水洪水的讨论主导。确定海冰和相关的叠加冰从北极到北大西洋的出口是否可以为北欧海提供足够的淡水，从而导致地球气候变冷，这将为触发气候突变的机制提供新的见解。通过量化大西洋纬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（来自海冰融化和博福特环流的淡水输出）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型将以大约100000的分辨率解决海洋环流、海冰和冰山运输问题。0.17度（ca. 19公里），比现有的古气候模式高5-10倍，并有能力模拟对淡水沿沿着大陆边缘输送很重要的狭窄海岸边界流、陆架断裂和锋区，以及当前一代古气候模式没有捕捉到的其他特征。

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.