Physical Properties of Glacial and Ground Ice

Vasil’chuk, Y.K.

Автор: Vasil’chuk Yu K.
Сборник: Encyclopedia of Life Support Systems (EOLSS). Ed.: M.G. Khublaryan
Том: 2
Год издания: 2009
Первая страница: 237
Последняя страница: 264
Аннотация: Glacier ice covers about ten per cent of the Earth’s land surface at the present time and covered about three times as much during the ice ages. The great ice sheets are of Greenland and Antarctica. Classification of glaciers is according to ice temperature and mount of surface melting. Very few glaciers show the entire sequence: dry snow zone, percolation zone, wet-snow zone, superimposed-ice zone. The transformation of snow to ice in the percolation and wet snow zones differs from that in the dry snow zone. A superimposed–ice zone represents the extreme case. Density increase in ice results from compression of air bubbles by the overburden pressure. Crystal size increases at a constant rate if the temperature remains constant. A single ice crystal deforms under an applied stress. A single ice crystal normally deforms by gliding on its basal planes. In glaciers and ice sheets, the ice is deformed for hundreds or thousand of years, to total strains of perhaps 10 or more. Ablation includes all processes by which snow and ice are lost from the glacier. Ice in glaciers is re-crystallizing continuously. Crystal size of the ice depends on salinity. The petrofabric analysis of ground ice may help to infer growth processes and conditions. The ice grain diameter, density and shear modulus increase with the increase of the depth. Porosity of solid transparent ice is as high as 1 kg (cm3/kg) and of solid sea ice is 1–50 cm3/kg. Effective thaw heat of sea ice decreases abruptly with increase of salinity. Regelation is movement of heavy objects through the ice without any disturbances to the ice. Due to molecular thermal oscillations and defects of ice crystals the water molecules can diffuse. The electrical properties of ice are distinguished by the fact that the charge carriers in ice are protons. The dynamics of glaciers and other large ice masses, temperature regime of glaciers, glaciers’ balance and detail study of glaciers’ physical properties have been considered in detail by Budd and Paterson. Modern study of glaciers is based on detail investigations of their microphysical properties (Hondoh, Fukuda, Mae, Watanabe and others), deformation, texture, and grain growth (Alley, Budd, Gow, Woods, Duval, Dahl-Jensen, Langway, Goodman, Thorsteinsson, and others) isotope (Dansgaard, Grootes, Johnsen, Jouzel, Lorius, Kotlyakov, Merlivat, Petit, Stuiver, Thompson, Vasil’chuk) and physical properties, electrical properties and chemistry, palaeoclimate and palaeoatmosphere (Dansgaard, Grootes, Hammer, Jouzel, Thompson, Yu.Vasil’chuk), firn densification, close-off and air bubbles and clathrate hydrate
Добавил в систему: Васильчук Юрий Кириллович

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