Interfacial Melting and Frost Heave in Ice

该项目是对存在于冰晶边界的液态水在低于纯水冰点温度下的动力学进行为期三年的理论和实验研究的延续。这一过程被称为预融化，在海冰中盐水的重新分配、污染物通过冰川的明显迁移、土壤和岩石的冻胀和风化速率等方面具有重要影响。预熔对几乎所有类型的材料都是常见的，但对冰的研究最为广泛。它可以由吸附力、润湿、尺寸效应或衬底紊乱引起，并涉及表面物理和相变现象的许多方面。研究计划将包括观察受污染溶液中的冰晶生长；不冻结的水在晶体之间的运输作为温度和温差的函数，以及在冰晶和各种基质之间的研究。一个重要的目标将是开发在自然条件下冰生长和杂质输送的有用模型，以评估晶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海冰电磁特性的演变（这在遥感中很重要）、极地平流层云颗粒对氯的吸收（这在臭氧破坏的化学过程中很重要）、冰芯中杂质的迁移（影响地层等时线估计）以及大气污染物对永久冻土和冻土的渗透。

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.