Ice Accumulation on Ships
	See also: 'Operations In Polar Regions And Where Ice Is Prevalent'
	In certain weather conditions ice accumulation on the hulls and superstructures can be a serious danger to ships. Ice accumulation may occur from three causes: 1./ Fog with freezing conditions, including 'frost smoke'. 2./ Freezing drizzle or freezing rain. 3./ Sea spray or sea water breaking over the ship when the air temperature is below the freezing-point of sea water (about 29°F or -2°C). The weight of ice which can accumulate from causes 1 and 2 may increase to such an extent on the rigging that the ice is liable to fall and endanger those on deck. It is, however, small in comparison with the weight of ice accumulating in rough weather with low temperatures when large amounts of spray and often heavy seas break over a vessel. When the air temperature is below the freezing-point of sea water and the ship is in heavy seas, considerable amounts of water will freeze on to the superstructure and those parts of the hull which are sufficiently above the waterline to escape being frequently washed by the sea. The amount so frozen to surfaces exposed to the air will rapidly increase with falling air and sea temperatures and might in extreme cases lead to the capsizing of the vessel. The dangerous conditions are those in which gale-force winds last for several days in association with air temperatures of about 29°F / -2°C or lower. These conditions will normally occur when the wind direction lies between east and west through north, but the important datum is that the direction may be any that will transport sufficiently cold air. The prudent course in these circumstances is, therefore, to steer towards warmer water if possible or to seek shelter as soon as possible if a gale is anticipated in combination with such low temperatures.
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