Young Ice. Applied to all unhummocked ice up to about a foot in thickness. Owing to the fibrous or platy structure, the floes crack easily, and where the ice is not over thick a ship under steam cuts a passage without much difficulty. Young ice may originate from the coalescence of “pancakes,” where the water is slightly ruffled or else be a sheet of “black ice,” covered maybe with “ice-flowers,” formed by the freezing of a smooth sheet of sea-water.
In the Arctic it has been the custom to call this form of ice “bay-ice”; in the Antarctic, however, the latter term is wrongly used for land-floes (fast-ice, etc.), and has been so misapplied consistently for fifteen years. The term bay-ice should possibly, therefore, be dropped altogether, especially since, even in the Arctic, its meaning is not altogether a rigid one, as it may denote firstly the gluey “slush,” which forms when sea-water freezes, and secondly the firm level sheet ultimately produced.
Land floes. Heavy but not necessarily hummocked ice, with generally a deep snow covering, which has remained held up in the position of growth by the enclosing nature of some feature of the coast, or by grounded bergs throughout the summer season when most of the ice breaks out. Its thickness is, therefore, above the average. Has been called at various times “fast-ice,” “coast-ice,” “land-ice,” “bay-ice” by Shackleton and David and the Charcot Expedition; and possibly what Drygalski calls Schelfeis is not very different.
Floe. An area of ice, level or hummocked, whose limits are within sight. Includes all sizes between brash on the one hand and fields on the other. “Light-floes” are between one and two feet in thickness (anything thinner being “young-ice”). Those exceeding two feet in thickness are termed “heavy floes,” being generally hummocked, and in the Antarctic, at any rate, covered by fairly deep snow.
Field. A sheet of ice of such extent that its limits cannot be seen from the masthead.
Hummocking. Includes all the processes of pressure formation whereby level young ice becomes broken up and built up into
Hummocky Floes. The most suitable term for what has also been called “old pack” and “screwed pack” by David and Scholleneis by German writers. In contrast to young ice, the structure is no longer fibrous, but becomes spotted or bubbly, a certain percentage of salt drains away, and the ice becomes almost translucent.
The Pack is a term very often used in a wide sense to include any area of sea-ice, no matter what form it takes or how disposed. The French term is banquise de derive.
Pack-ice. A more restricted use than the above, to include hummocky floes or close areas of young ice and light floes. Pack-ice is “close” or “tight” if the floes constituting it are in contact; “open” if, for the most part, they do not touch. In both cases it hinders, but does not necessarily check, navigation; the contrary holds for
Drift-ice. Loose open ice, where the area of water exceeds that of ice. Generally drift-ice is within reach of the swell, and is a stage in the breaking down of pack-ice, the size of the floes being much smaller than in the latter. (Scoresby’s use of the term drift-ice for pieces of ice intermediate in size between floes and brash has, however, quite died out). The Antarctic or Arctic pack usually has a girdle or fringe of drift-ice.