Author(s): Anthony J. Gow
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Abstract: Several years observations of the crystalline structure of ice sheets forming on a number of New England lakes indicate that just two major types of congelation ice are formed during quiet (non-turbulent) freezing of lake water. These are: (1) ice sheets characterized by the growth of massive prismatic crystals exhibiting vertical or near-vertical c-axes probably equivalent to so-called S1 ice and (2) ice sheets composed predominantly of vertically elongated crystals exhibiting horizontally oriented c-axes, so-called columnar ice or S2 ice. In this context of quiet freezing of lakes it was also determined that columnar textures are always associated with horizontal c-axis orientations of the crystals, whereas the development of c-axis vertical orientation is invariably linked with the growth of massive crystals. These observations have fostered the concept of orientation textures. To ascertain how difference in orientation texture might be generated several ice sheets were grown in a test tank in which the water could be cooled uniformly to any desired temperature between 4°C and 0°C prior to freezing. Water that had been spray-seeded to initiate freezing always produced S2 type ice and this orientation texture developed regardless of the thermal condition of the water column. Unseeded or spontaneously nucleated ice growth always yielded macrocrystalline, S1 type ice. Results of these experiments strongly suggest that the crystalline structure of ice on quietly frozen lakes is pre-determined by meteorological events occurring immediately prior to freezing and, that atmospheric seeding leads to the formation of S2 ice with substantially horizontal c-axes and that lack of seeding (spontaneous nucleation) produces S1 ice exhibiting vertical c-axes.
Year: 1984