Studies of Microstructural Features and Brine Drainage Networks in First-Year Sea Ice

第一年海冰的微观结构特征和盐水排放网络研究

• 批准号: 9872573
• 负责人: Lewis Shapiro
• 金额: $ 30.14万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-03-01 至 2003-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9872573&HistoricalAwards=false
• 关键词: Studies; Microstructural; Features; Brine; Drainage

ABSTRACTCole 9813221 and Shapiro/Eicken 9872573The objective of this 3-year project is to address gaps in knowledge ofthe development and evolution of some important macro- and microstructural features of first year sea ice by repeated measurements through the annual cycle from freezing to melting. Topics of study include:(1)the geometrical characteristics and spatial distribution of brine drainage networks and their relationship to the crystal structure of the ice, (2) the 3-dimensional characterization of brine and gas inclusions,(3)variations in permeability through the year and the resulting impact on heat and mass transfer through the ice, and (4)details of the relationship between c-axis fabrics and under-ice currents. Knowledge of these is important for studies of the optical and mechanical properties of sea ice, biological activity in sea ice, remote sensing applications, some aspects of climate modeling, and the entrainment and transport of contaminants. The main activity of this project will be the acquisition and analysis ofdetailed observations relevant to the structural features listed, along with in-situ permeability measurements. The samples and data will be collected periodically through the year from a study site on first-year sea ice near Barrow, Alaska. The site will be instrumented to continuously monitor the thermal regime of the ice, and other relevant parameters will be measured periodically through the year. The scale of the features to be studied ranges from individual brine inclusions (approximately 10-4 m) to the full thickness of the ice sheet. Current information on these subjects comes mainly from short-term field studies (although there are some notable exceptions) which often involve relatively thin ice, or studies on laboratory-prepared specimens. To some extent, this reflects the difficulty of obtaining information on natural first year ice sheets as they evolve through the year from initial freezing to melting. The main problems in this regard are the remoteness of the field areas and the expense of getting to them, coupled with the lack of appropriate methodologies for collecting samples other than by relatively small-diameter corers. However, this project makes use of recent advances in techniques for sampling, measuring and testing for the relevant parameters, some of which the investigators helped to develop. In addition, the presence of the Barrow Arctic Science Consortium (BASC) as a reliable source of local personnel to assist in data gathering allows frequent visits to the site to be made for routine data collection or sampling. These data collection efforts will maintain continuity between and after 3 additional field programs of approximately 10 days each, during which extensive data sets will be acquired. These programs will be timed to conduct detailed studies of the ice at the site shortly after it forms, under cold, mid-winter conditions, and at the start of the melt season. In addition to the usual salinity, density, grain size and c-axis fabric measurements, specialized observations will include the permeability measurements and associated detailed measurement of drainage pathways, sets of orthogonal micrographs (which yield size distributions of small-scale inclusions in 3-dimensions), ocean current measurements, and vertical sections through the entire thickness of the ice sheet. The latter provide a unique view of larger-scale features such as brine drainage networks and horizontal banding. The data will be used to develop or evaluate and improve existing salt-flux/thermodynamic ice growth models.

摘要Cole 9813221和Shapiro/艾肯9872573这个为期3年的项目的目标是通过对从冻结到融化的年度循环的重复测量，来解决第一年海冰的一些重要的宏观和微观结构特征的发展和演变的知识上的差距。研究主题包括：（1）盐水排水网络的几何特征和空间分布及其与冰的晶体结构的关系，（2）盐水和气体包裹体的三维特征，（3）全年渗透率的变化及其对冰中热量和质量传递的影响，以及（4）c轴结构和冰下电流之间关系的细节。这些知识对于海冰的光学和机械特性、海冰中的生物活动、遥感应用、气候建模的某些方面以及污染物的夹带和输送的研究都很重要。本项目的主要活动是采集和分析与所列结构特征相关的详细观测结果，沿着现场渗透率测量结果。这些样本和数据将在阿拉斯加巴罗附近的一个第一年海冰研究地点全年定期收集。该地点将安装仪器，以持续监测冰的热状况，并将全年定期测量其他相关参数。要研究的特征范围从单个盐水包裹体（约10-4米）到冰盖的整个厚度。目前关于这些主题的信息主要来自短期的实地研究（尽管有一些值得注意的例外），这些研究通常涉及相对较薄的冰，或对实验室制备的标本的研究。在某种程度上，这反映了获取关于自然冰盖从最初冻结到融化的第一年演变的信息的困难。这方面的主要问题是实地偏远，前往实地的费用高昂，加上除了使用直径较小的取样器之外，没有适当的方法收集样品。不过，该项目利用了有关参数的取样、测量和测试技术方面的最新进展，其中一些是调查人员帮助开发的。此外，巴罗北极科学联合会是协助数据收集的可靠的当地人员来源，因此可以经常访问该地点进行例行数据收集或取样。这些数据收集工作将在3个额外的现场项目之间和之后保持连续性，每个项目约10天，在此期间将获得大量数据集。这些计划将被安排在冰形成后不久、寒冷的仲冬条件下和融化季节开始时对该地点的冰进行详细研究。除了通常的盐度、密度、粒度和c轴组构测量外，专门的观测还将包括渗透率测量和相关的排水通道详细测量、正交显微照片集（产生三维小尺度夹杂物的尺寸分布）、洋流测量以及贯穿冰盖整个厚度的垂直截面。后者提供了一个更大规模的功能，如盐水排水网络和水平条带的独特视图。这些数据将用于开发或评估和改进现有的盐通量/热力学冰增长模型。