Interfacial Premelting and Geophysical Implications

界面预熔和地球物理意义

• 批准号: 0440841
• 负责人: John Wettlaufer
• 金额: --
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440841&HistoricalAwards=false
• 关键词: Interfacial; Premelting; Geophysical; Implications

This project is a three-year continuation of a theoretical and experimental study of the dynamics of liquid water existing at the boundaries of ice crystal at temperatures below the freezing point of pure water. This process, called premelting, has significant consequences in the redistributing of brine in sea ice, the apparent migrating of contaminants through glacier ice, and the rate of frost heave and weathering in soils and rocks. Premelting is common to virtually all types of materials, but has been most extensively studied in ice. It can be caused by adsorption forces, wetting, size effects, or substrate disorder, and involves many aspects of surface physics and phase transition phenomena. The macroscale consequences of these molecular-scale processes include the relationship between seasonal freezing and the oceanic thermohaline circulation, and the quantitative interpretations of paleoclimate proxy records. On the longer climatic time scales, the overall features of recent glacial-interglacial cycles have been revealed in the Antarctic ice cores, but higher resolution is required to decipher the mechanisms that drive abrupt climate changes. The accuracy of any higher resolution paleoclimatic information derived from ice cores will have to rely on the proper treatment of processes that affect the trace constituents during their long (100 kyr) residence times in the ice sheets. Grain-boundary melting is believed to be the primary process controlling the rate of material transport through the premelted-liquid networks of veins and nodes that line the grain intersections of glacier ice. Moreover, the role of grain-boundary melting can further increase the liquid content and enhance trace-constituent mobility.The project has three distinct, but interrelated components. Direct measurements of premelting of grain boundaries in the presence of different impurities will be made as a function of temperature and grain mismatch, and experiments on instabilities that are predicted to occur at the growing sea ice/ocean interface in the presence of a shear flow will be conducted. Both will be complemented by theoretical calculations to prove experimental issues and to pursue the implications of premelting in numerous contexts.

该项目是对在低于纯水冰点的温度下存在于冰晶边界处的液态水的动力学进行的理论和实验研究的三年延续。 这一过程被称为预融，对海冰中盐水的重新分布、污染物通过冰川冰的明显迁移以及土壤和岩石中的冻胀和风化速率具有重要影响。预融是常见的几乎所有类型的材料，但已被最广泛的研究在冰。 它可以由吸附力、润湿、尺寸效应或基底无序引起，并且涉及表面物理和相变现象的许多方面。 这些分子尺度过程的宏观后果包括季节性冻结和海洋温盐环流之间的关系，以及古气候代用记录的定量解释。在较长的气候时间尺度上，南极冰芯已经揭示了最近冰川-间冰期循环的总体特征，但需要更高的分辨率来破译驱动气候突变的机制。从冰芯中获得的任何更高分辨率的古气候信息的准确性将不得不依赖于对影响痕量成分在冰盖中长时间（100 kyr）停留期间的过程的适当处理。 晶界融化被认为是控制物质通过脉和节点的预熔液体网络传输速率的主要过程，这些脉和节点排列在冰川冰的颗粒交叉点上。此外，晶界熔化的作用可以进一步增加液体含量和增强微量成分的流动性。 在不同杂质的存在下，晶界的预熔的直接测量将作为温度和晶粒失配的函数，和实验的不稳定性，预计将发生在不断增长的海冰/海洋界面的剪切流的存在下，将进行。 两者都将通过理论计算来补充，以证明实验问题，并在许多情况下追求预熔的影响。