NEVE 



10= to 10= electron-volts: fast, greater than 0.1 



million-electron-volts. (70) 

 neve — Set firn, fim snow, 

 neve iceberg— An iceberg similar in appearance 



and color to a iceberg, but composed of neve 



(firn). (68) 



new ice — A general term which includes frazil 

 ice, sludge, medium winter ice, pancake ice, 

 and ice rind. (74) 



newly formed ice — (also called fresh ice). Ice in 

 the first stage of formation and development. 

 ■See young ice. (68) 



newly frozen ice — See newly formed ice. 



niggerhead — 1. Large blocks of coral torn loose 

 from the ourer face of a reef and tossed on to the 

 reef flat by storm waves or tsunamis. Tlie 

 blocks are blackened by a crust of lichens after 

 detachment from the reef. 

 2. See reef patch. 



night-sky light — See airglow. 



nilas — A Eussian term for gray or dark-colored 

 ice that forms in a sheet on a calm sea. 



nip — The cut made by waves in a shoreline of 

 emergence. (61) 



nipped — Pertaining to a ship which is icebound 

 and subjected to pressure from ice, sometimes to 

 the extent that the ship is damaged and even 

 sunk. (59) See beset. 



nipping — (or pinchijig). The closing of ice 

 aromid a ship so that the sliip is beset"and sub- 

 jected to pressure from the ice. (59) 



nitrate nitrogen — The most abundant and readily 

 assimilable form of nitrogen for marine orga- 

 nisms. Like phosphate, it^is an essential nutri- 

 ent. Estimates of primary productivity have 

 been made by determining the concentratmns of 

 nitrates in a water sample. 



nitrogen cycle — The series of chemical changes 

 that nitrogen imdergoes in its use by plants and 

 animals. Liorganic nitrogenous compounds 

 (nitrates, nitrites, and ammonium) and, to a 

 small extent, organic nitrogenous compounds 

 m the sea are utilized by marine plants, which 

 form other mtrogenous compotmds. such as 

 amino acids. More complex amino acids and 

 proteins are synthesized from these bv the ma- 

 rine animals, which feed on the plants. Final- 

 ly, these compounds, in the waste products and 

 the dead boclies of thie animals, are broken down 

 by bacteria into inorganic compounds and sim- 

 ple organic compounds, completing the cycle. 



nitrogen narcosis — (or rapture of the deep) . An 

 intoxicating or narcotic effect of gaseous nitro- 

 gen, produced in divers breathing air at depth. 

 Usually the effect first becomes noticeable at a 

 depth of 100 feet or more, although individuals 

 vary in their susceptibility. 



no-bottom — A notation appearing on nautical 

 charts indicating that the sounding did not reach 

 the bottom. 



Noctiluca — A genus of usually pale pink liuni- 

 nescent dinoflagellates large enough to be seen 

 by the unaided eye. This particular organism 

 is responsible for much of the sheet-type lumi- 

 nescence noted in coastal waters of various parts 

 of the world ocean. A green form occurring in 

 coastal regions of the Far East is not limii- 

 nescent. 



nocturnal radiation — Long-wave back radiation 

 from the sea surface. A misnomer since back 

 radiation is a continuous process. 



nodal line — In a tide area, the line about wliich 

 the tide oscillates and where there is little or no 

 rise and fall of the tide. (59) 



nodal point — See amphidromic point. 



nodal zone — An area at which the predominant 

 direction of the littoral transport changes. 

 (61) 



node — ^That part of a standing wave or clapotis 

 where the vertical motion is least and the hori- 

 zontal velocities are greatest. Xodes are associ- 

 ated with clapotis. and with seich action re- 

 sulting from resonant wave reflections in a har- 

 bor or bay. (61) 



node cycle — ^The time required for the regression 

 of the moon's nodes (the points where the plane 

 of the moou"s orbit intersects the ecliptic) to 

 complete a circuit of 360 degrees of longitude: 

 a period of approximateh- 18.6 years. It is ac- 

 companied by a corresponding cycle of chang- 

 ing inclination of the moon's orbit relative to 

 the plane of the earth's Equator, with resulting 

 inequalities in the rise and fall of the tide and 

 speed of the tidal current. (50) 



nodules — (or halobol'ite. pelugite). Concretion- 

 ary lumps of manganese, cobalt, iron, and nickel 

 found widely scattered on the ocean floor. 

 Eocks of various sizes and shapes often are en- 

 crusted with these metals. 



noise — Any undesired somid. By extension, noise 

 is any unwanted disturbance within a useful fre- 

 quency band, such as undesired electric waves 

 in a transmission channel or device. (69) 



noise level — The comparison of sound intensity, 

 usually measured in decibels, to a reference 

 level. Underwater sound pressures are com- 

 monly expressed in decibels or dynes per square 

 centimeter. 



noise spectrum — The relative amplitude of the 

 several frequencies present in a complex tone 

 (sound). 



nomogram — (or ulignment chart, also called 

 nomograph, nomographic chart). The graph- 

 ical representation of an equation of three 

 variables f{u. r. ir)=0. by means of three 

 graphical scales (not necessarily straight), ar- 

 ranged in such a manner that any straight line, 

 called an index line, cuts the scales in values of 

 V. V. and '.'• satisfying the equation. By in- 

 troducing auxiliary variables and constructing 

 auxiliary scales, equations containing more tlian 



110 



