Reference work entry
Sea Ice – formed in seas due to the freezing of seawater. Its specific properties are salinity and porosity. It represents a smooth mass of Arctic ice with lower density as compared with freshwater ice (from 0.85 to 0.94 g/cm3); because of their small areas, floes rise up to 1/7–1/10 of their thickness above the water surface. The sea ice formation starts at a temperature below 0 °C, the melting at a temperature above −2.3 °C. Water in the Arctic seas with the highest salinity (approx. 35 ‰) begins to freeze at a temperature of −1.9 °C. S. I. is more flexible and more difficult to get crushed into pieces than freshwater ice. By its structure, S. I. may be needlelike, spongy, and grainy. The sea area covered by ice varies from month to month and from year to year, depending on the amount of heat in the ocean, the duration of sea cooling, ice melting, etc. A S. I. condition is important for shipping.
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