During their seagoing careers, most mariners will never see ice and even fewer will have to navigate through it. In all its forms, whether land-generated or ocean-created, ice afloatis a fascinating sight in terms of colors, forms, and creation.
Land-based freshwater ice enters the oceans through the calving of glaciers at the point where they meet the sea, creating typical craggy icebergs. Ice shelves that flow from land over the ocean are another major source. Unlike glaciers, these ice sheets float on the ocean surface and can be massive. For example, the Antarctic's Ross Ice Shelf is the size of France. As the outer edges break off, huge tabular floes are created; some of them can be the size of small states or nations.
The Antarctic contains 90 percent of the world's freshwater ice, while Greenland ranks a distant second with 8.3 percent. The remainder is found in the world's other glaciers and ice cap. In the Arctic most icebergs are found along the west coast of Greenland, though a few also move southerly down its east coast. Primarily they come from "iceberg alley" between Greenland and Canada's Baffin Island and Labrador. Very few tabulars are found in the Arctic.
The berg that sank RMS Titanic in April 1912 was from this area. And it still happens. Since that time more than 500 ships have been seriously damaged or sunk because of collisions with ice.
Sea ice is formed from seawater through a cold distilling process that separates salt from the water. The heavy brine passes down through the ice and into the ocean below. First-year ice is just that, while the thicker and denser multiyear ice accumulates over more than one winter season. Both kinds can be found together.
The huge sea ice sheets move together or apart according to the effects of winds, swells, and currents. Icebergs are not formed by sea ice; however, ice ridges are created where the sheets collide. These can be tens of feet high and hundreds of feet deep underwater. Sometimes icebergs are entrained in sea ice.
It is impossible to offer a proper tutorial about ice found at sea in such a brief space, however, this is an annotated sampling of some of these fascinating "sea creatures."