Collaborative Research: Deformation of Arctic Sea Ice Cover: Formation and Action of Failure Zones

ABSTRACTSchulsonOPP-0328605HiblerOPP-0328728The首席研究人员描述了新的数值和实验室实验，这些实验应该阐明每年北冰洋冰盖内形成的断裂带的形成和随后的行为背后的物理机制。断裂区，被称为。线性运动学特征(LKF)通常出现在横跨北极盆地很大一部分的次平行断层的共轭集合中。一旦形成，冰盖通常会略微膨胀，随后发生振荡，从而加强热量从海洋向大气的转移，并随着新的冰在开阔水域形成而增加海洋盐通量。LKF./断层最有可能影响冰层厚度分布，因为在随后的冰包汇聚时，会发生压力隆起。线状结构(和其他大型断裂特征)在外观上类似于实验室样品中看到的较小规模的压剪断层，这表明，当考虑到冰破裂的分形性时，断裂的物理性质与尺度无关。将进行三组不同的数值实验。在第一个系列中，将进行理想化和数值网格实验，以检验不同流动规则对断层形成和随之而来的背包减弱的影响。在第二组中，将使用具有非均匀初始强度和实验室产生的流动规则的理想化空间变化风强迫来研究变形断层的特征开合以及它们的交角。在第三个系列中，将使用全厚度冰分布公式执行高分辨率的盆地范围模拟。这些模拟将与最近获得的各种形变数据进行比较，最值得注意的是与最近解密的向上俯视海底声纳观测的厚度分布数据进行比较。这样的比较将考察这项研究对气候数值调查的空气-冰-海洋数值模式的实用性和适用性。五套系统的双轴压缩实验将在实验室进行。智力上的优点：这项研究集中于发展与尺度无关的海冰模式，特别适用于空间分辨率低于10公里的空间分辨率和断裂带/断层的分辨，为海冰动力学提供了一种新的范式。在这种模式下，导致局部破裂的高内部冰应力在短时间内发生，并随着断层的形成而迅速下降。这与目前气候数值研究中使用的传统公式(冰包及其厚度分布)有很大不同，传统公式隐含地假设在时间和空间上都有一个平滑变化的形变场。人们期望新模式能更真实地反映海冰厚度的分布，从而在气候及其对极地海冰覆盖的敏感性的数值模拟中更加有用。更广泛的影响：这项研究将在两所活跃于极地研究的大学的研究生的帮助下，构成一项紧张的智力调查。它将有助于新一代调查人员的智力发展，以及改善两个机构的研究环境。此外，通过揭示和了解新的物理效应，这项研究将丰富首席调查员的本科生和研究生教学。这项活动还将有助于达特茅斯大学和阿拉斯加大学在极地研究方面的工作伙伴关系。为增进对科学和技术的了解，将通过在讲习班和社会会议上的介绍以及对技术和科学文献的贡献，广泛传播工作成果。还计划撰写一篇评论文章或一本书的章节。

ABSTRACTSchulsonOPP-0328605HiblerOPP-0328728The Principal Investigators describe new numerical and laboratory experiments that should elucidates the physical mechanisms that underlie the formation and subsequent behavior of failure zones that form within the annual arctic sea ice cover. The failure zones, termed. linear kinematic features (LKFs), often occur in conjugate sets of sub-parallel faults that traverse a large fraction of the arctic basin. Upon formation, the ice cover generally dilates somewhat and subsequently oscillates, thereby enhancing transfer of heat from the ocean to the atmosphere as well as increasing oceanic salt flux as new ice forms on open water. The LKF.s/faults most probably affect the ice thickness distribution in that, upon subsequent convergence of the ice pack, pressure ridging occurs. The lineaments (and other large-scale fracture features) are similar in appearance to smaller-scale compressive shear faults seen in laboratory specimens, suggesting, when the fractal character of ice breakup is also taken into account, that the physics of fracture is scale independent. Three different sets of numerical experiments will be performed. In the first series, idealized and numerical grid experiments will be carried out to examine the effect of different flow rules on fault formation and on the attendant weakening of the pack. In the second set, idealized spatially-varying wind forcing will be used with heterogeneous initial strength and a laboratory-generated flow rule to investigate the characteristic opening and closing of deformation faults as well as their angle of intersection. In the third series, high-resolution basin-wide modeling will be performed using a full-thickness ice distribution formulation. These simulations will be compared with a variety of recently acquired deformation data, most notably with recently declassified thickness-distribution data from upward-looking submarine sonar observations. Such comparisons will access the utility and applicability of this research to numerical air-ice-ocean models for the numerical investigation of climate. Five sets of systematic biaxial compressive experiments will be performed in the laboratory on blocks of salt-water ice.Intellectual Merit: In focusing on the development of a scale-independent sea-ice model, particularly applicable to spatial resolutions less than 10 kilometers and to the resolution of failure zones/faults, this research represents a new paradigm for sea ice dynamics. Under this paradigm, high internal ice stresses leading to localized fracture occur over short periods of time and rapidly decrease as a fault is formed. This differs significantly from conventional formulations (of the ice pack and its thickness distribution) which are used in current numerical investigations of climate and which implicitly assume a smoothly-varying deformation field in both time and space. The expectation is that the new model will more realistically capture the distribution in sea ice thickness and, thus, will be more useful in the numerical modeling of climate and its sensitivity to the polar sea ice cover. Broader Impacts: The research will constitute an intense intellectual enquiry carried out with the assistance of graduate students at two universities active in polar research. It will contribute to the intellectual development of a new generation of investigators, as well as enhance the research environment of the two institutions. In addition, through the revelation and understanding of new physical effects, the study will enrich both the undergraduate and graduate teaching of the Principal Investigators. The activity will contribute also to a working partnership in polar studies between Dartmouth and The University of Alaska. To enhance scientific and technical understanding, the results of the work will be disseminated broadly, through presentations to workshops and societal meetings and through contributions to the technical and scientific literature. A review article or book chapter is also planned.