ICE POINT 



ice point — ^The true freezing point of water ; the 

 temperature at which a mixture of air-saturated 

 pure water and pure ice may exist in equilibrium 

 at a pressure of one standard atmosphere. 



The ice point is often used as one fiducial 

 point (0°C or 32°F) in establishing a thermo- 

 metric scale because it is reproduced relatively 

 easily under laboratory conditions. 



The ice point is frequently called the freezing 

 point, but the latter term should be reserved for 

 the much broader reference to the solidification 

 of any kind of liquid under various conditions. 



ice pole — (or fole of inaccessibility). The area 

 round which the more consolidated part of the 

 arctic ice pack is located and therefore the most 

 difficult point to reach by surface travel. At 

 present its location is about 84°N and 160 °"W". 

 (59) 



ice port — An embayment in an ice front, often 

 of a temporary nature, where ships can tie up 

 and unload directly onto the ice shelf or thick 

 sea ice. 



ice potential — The potential amount of ice that 

 would be formed in a given water mass if sur- 

 face heat loss provided the thermohaline cir- 

 culation. 



icequake — The concussion attending the breaking 

 up of masses of ice. ( 68 ) 



ice rafting — The transportation of sediments and 

 rock fragments of all sizes by floating ice. Such 

 material is widely distributed in marine sedi- 

 ments along the paths of melting icebergs and 

 is identified by glacial abrasion marks, composi- 

 tion, angularity (in contrast to rounded, water- 

 worn alluvial-marine sediments), and size too 

 large for any but ice-rafting method of trans- 

 portation. 



ice rind — (or glass ice., ice crust) . A thin, elastic, 

 shining crust of ice, formed by the freezing of 

 ice slush or sludge on a quiet sea surface. It 

 has varying degrees of whiteness depending on 

 its age, thickness, and the rapidity of freezing. 

 It is easily broken by wind or swell, and is gen- 

 erally less than 5 centimeters (2 inches) in thick- 

 ness. (74) 



ice routing — Optimal routes for ships in ice-in- 

 fested water provided through forecasting fu- 

 ture ice conditions. 



ice run — See debacle. 



ice sheet — Any large area of continuous ice overly- 

 ing a land surface. ( 65 ) 



ice shelf — (also called shelf ice; formerly harrier 

 ice) . 1. A thick ice formation with a fairly level 

 surface, formed along a polar coast and in shal- 

 low bays and inlets, where it is fastened to the 

 shore and often reaches bottom. It may grow 

 hundreds of miles out to sea. It is usually an 

 extension of land ice, and the seaward edge 

 floats freely in deep water. 



The calving of an ice shelf forms tabular ice- 

 bergs and ice islands. ( 5 ) 



2. More specifically, a level ice formation 

 over 2 meters (6.6 feet) above the sea surface 

 which originates from annual accumulations 

 of firn snow layers on bay ice or on the seaward 

 extension of a glacier. (74) 



ice skylight — From the point of view of the sub- 

 mariner, thin places of the ice canopy, usually 

 less than 1 meter thick and appearing from be- 

 low as relatively light translucent patches in 

 dark surroundings. The undersurface of an ice 

 skylight is normally flat. Ice skylights are 

 called large if big enough for a submarine to 

 attempt to surface through them (120 meters or 

 393.7 feet) or small if not. (7) See lead. 



ice slush — An accumulation on the water surface 

 of ic« needles that are frozen togetlier; it forms 

 patches or a thin compact layer of a grayish or 

 leaden-tinted color. The surface of the area 

 covered with ice slush has a dim tint. (74) 



ice stream^l. A glacier, usually an outlet 

 glacier, located on the periphery of an ice cap. 

 2. See strip. 



ice strip — See strip. 



ice table — A mass of level ice. ( 68 ) 



ice tongue — Any narrow extension of a glacier or 

 ice shelf, such as a projection floating in the sea 

 or an outlet glacier of an ice cap. (5) 



ice tongue afloat — A terminal extension of a 

 glacier which extends so far into the sea that its 

 end is buoyed. This is primarily an antarctic 

 phenomenon but occurs occasionally in the 

 arctic. (59) 



ice wall — See ice front. 



ice yowling^A long, high-pitched sound accom- 

 panying the formation of contraction cracks in 

 ice. (59) 



icing — 1. The formation of ice on aircraft sur- 

 faces, within aircraft engines, or on ships. 



2. Glaze. 

 (59) 



ideal sea level — The theoretical sea surface which 

 is everywhere normal to the plumb line. Refer- 

 ence of all depth soundings to this level would 

 make them all comparable. 



ideal transducer — A hypothetical passive trans- 

 ducer that transfers the maximum possible 

 power from the source to the load, in regard to 

 connecting a specified source to a specified load. 



igneous rock — Rock formed by solidification of 

 molten material or magma. (2) 



illite — (or hydromical) . A group of clay minerals 

 composed of interlayered mica and montmoril- 

 lonite and intermediate between muscovite and 

 montmorillonite. 



illuminance — The total luminous flux received on 

 a unit area of a given real or imaginary surface, 

 expressed in such units as the foot-candle, lux, 

 or phot. 



The only difference between this term and illu- 

 mination is that the latter always refers to light 

 incident upon a material surface. 



84 



