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The formation and nature of sea ice

2018-09-03  |   Editor : houguangbing  

Sea ice refers to the salt water ice that freezes directly into ice from sea water, also including continental glacier that comes into the sea, river ice and the ice of the lake. Salt water ice is a mixture of solid ice and brine and the salinity is 2% ~ 10 t lower than the water and its physical properties are different from fresh water ice.

The compressive strength of sea ice mainly depends on the salinity, temperature and the age of sea ice. Usually, the compressive strength of new ice is larger than old ice and the compressive strength of sea ice with low salinity degree is larger than sea ice with high salinity degree, so the density of the sea ice is not as hard as density of fresh water ice. In general, sea ice is about 75% firm of the fresh water ice. People can walk above the river ice safely in 5 cm thick can safely walk, while it is 7 cm thick ice for sea ice.

Of course, the colder the ice, the greater the compressive strength in 1969, during the Great ice age of Bohai, the air force dropped 30, 000 grams of powder on a 60cm thick ice to rescue ships. But the ice was not blowed up.

Large chunks of ice and icebergs floating on the ocean are driven by wind and ocean currents, and the thrust of the movement is related to the size and flow velocity of ice. According to the result of “Haierbing” platform in Bohai bay in the winter of 1971, If the flow rate is not too big, the thrust of an ice with 6000-meter square and height of 1.5 meters can reach up to 4000 tons, which is sufficient to push oil platform and other Marine engineering building. Sea ice is destructive to ports and ships at sea. Apart from these pressures, there is damage caused by the expansion of sea ice. It is calculated that when the sea ice temperature drops by 1.5 degrees, the sea ice of 1000 meters can expand by 0.45 meters, which can deform the ships in the ice. In addition, the vertical force of iceoften causes damage to the building foundation when frozen in sea ice is often driven by the vertical force caused by tidal fluctuation.

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