Interfacial Melting and Frost Heave in Ice

该项目是对冰晶边界上存在的液态水在低于纯水冰点的温度下的动力学的理论和实验研究的三年的延续。这个被称为预融的过程对海冰中卤水的重新分布、污染物在冰川中的明显迁移以及土壤和岩石中的冻胀和风化速率都有重要的影响。预融几乎对所有类型的材料都是常见的，但在冰中得到了最广泛的研究。它可能是由吸附力、润湿、尺寸效应或衬底无序引起的，涉及表面物理和相变现象的许多方面。该研究计划将包括观察受污染的溶液中冰晶的生长；未冻结水在晶体之间的传输随温度和温差的函数，以及冰晶和各种基质之间的这种研究。一个重要的目标将是开发在自然条件下冰生长和杂质运输的有用模型，以便评估颗粒界面如何作为化学管道。这些分子尺度过程的宏观后果包括对遥感很重要的海冰电磁性质的演变，对破坏臭氧的化学很重要的极地平流层云颗粒对氯的吸收，影响地层等时线估计的冰芯中杂质的迁移，以及大气污染物对永久冻土和积雪的渗透。

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 study program will include the observing of ice crystal growth from a contaminated solution; of unfrozen water transport between crystals as functions of temperature and temperature differences, as well as such studies between ice crystals and various substrates. An important objective will be the development of useful models for ice growth and impurity transport under natural conditions in order to assess how grain interfaces may serve as chemical conduits. The macroscale consequences of these molecular-scale processes include the evolution of the electromagnetic properties of sea ice which are important in remote sensing, the uptake of chlorine on polar stratospheric cloud particles which are important in the chemistry of ozone destruction, the migration of impurities in ice cores which affect the stratigraphic isochrone estimates, and the penetration of atmospheric pollutants into permafrost and firn.