Interfacial Melting and Frost Heave in Ice

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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.