AT, CONSTITUENT 



three variables may also be represented by nomo- 

 grams. (5) 



nomograph — See nomogram. 



nomographic chart — See nomogram. 



nonastacin carotenoid — Any of a group of plant 

 pigments, such as carotenes and xanthophylls. 

 exclusive of astacin carotenoids, which are also 

 animal pigments. The measurement of the con- 

 centration of these pigments in addition to vari- 

 ous chlorophylls is useful in estimating the rate 

 of photosynthesis (primary production) or as 

 an index of the standing crop (biomass) of 

 plant forms. 



nonharmonic constant — A tidal constant such 

 as a lunitidal interval, range, or inequality 

 which may be derived directly from high and 

 low water observations without regard to the 

 harmonic constituents of the tide. The term 

 is also applicable to tidal currents. (59) 



nonlinear waves — Waves in relatively shallow 

 water, with no superimposition of motion. ( 35 ) 



nontidal current — Any current that is caused by 

 other than tide-producing forces. This in- 

 cludes all permanentlj- established oceanic cur- 

 rents as well as all temporary ocean currents 

 caused by winds. (59) 



normal gravity — The value of gravity at sea level 

 accordmg to a theoretical formula which as- 

 sumes the earth to be a spherical or of some 

 similar regular shape. 



normal ripples — Simple asymmetrical ridges 

 made in sediments by water currents. 



normal stresses — The components of the stress 

 tensor which are normal to the faces of the 

 fluid element. 



normal temperature and pressure — (abbrevi- 

 ated N.T.P.). See standard temperature 

 pressure. 



normal water — (also called Copenhagen water, 

 standard sea- icater). A standard sea water 

 preparation, the chlorinity of which lies be- 

 tween 19.30 and 19.50 per mille and has been 

 determined to within ±0.001 per mille. 



Xormal water is used as a convenient compari- 

 son standard for cMorinit}' measurements of sea 

 water samples by titration. It is prepared by 

 the Hydrographical Laboratories, Copenhagen, 

 Denmark. (5) 



normal winter — Refers to normal ice season, that 

 is, the average ice conditions based on a num- 

 ber of recorded winters in a given area. 



North-About Route — The coastal route through 

 Melville Bugt from ITpernavik to Kap York. 

 Greenland, by going along the Greenland coastal 

 fast ice or floe leads. This passage usually 

 offers the earliest route to Thule and the "North 

 Open Water," and can generally be effected be- 

 fore the end of August, even m the worst season. 



North Atlantic Current — A wide slow-moving 

 continuation of the Gulf Stream originating in 

 the region east of the Grand Banks of Xew- 



foundland at about 40°N and 50°W. The 

 North Atlantic Current is often masked by shal- 

 low and variable wind-driven surface move- 

 ments. Branches of the Xorth Atlantic Cxirrent 

 form the Norway Current and the Irminger 

 Current. 



North Atlantic Drift — The weak, sluggish, north- 

 east part of the North Atlantic Current that is 

 easily influenced bj- winds: currents have been 

 observed to chaiige speeds and directions fre- 

 quently, and at times reverse directions. 



North Cape Current — A warm current flowing 

 northeastward and eastward around northern 

 Xorway, and cunning into the Barents Sea. The 

 Xorth Cape Current is a continuation of the 

 Norway Current. 



North Equatorial Current — Ocean currents 

 driven by the northeast trade winds blowing 

 over the tropical oceans of the Xorthem Hemi- 

 sphere. In the Atlantic Ocean it is known as 

 the Atlantic Xorth Equatorial Current and flows 

 west between the Atlantic Equatorial Counter- 

 current and the Sargasso Sea. 



In the Pacific Ocean it is known as the Pacific 

 Xorth Equatorial Current and flows westward 

 between 10° and 20°X. East of the Philippines 

 it divides, part turning south to join the Equa- 

 torial Countercurrent, and part going north to 

 form the Kuroshio. 



In the Xorth Indian Ocean there is no equa- 

 torial current : monsoon drifts dominate. 



northern lights — See aurora borealis. 



North Open Water — (or North Water). A con- 

 siderable area of open navigable water in north- 

 em Baffin Bay roughly oval in shape, with its 

 major axis oriental^ed north to south. It is 

 bounded by the fast ice of Smith Sound to the 

 north and by the Baffin Bay pack to the south. 

 Its southern botmdarj- is usually a little north 

 of the 75th parallel. Xorth Open Water usually 

 appears during April and May. (21) 



North Pacific Current — The warm branch of the 

 Kuroshio extension flowing eastward across 

 the Pacific Ocean. 



North Pole 1— (abbreviated XP-1). See drift 

 station. 



North Water — See North Open Water. 



Norway Current — (sometimes called Xorwegian 

 Current). A continuation of the North At- 

 lantic Drift, wliich flows northward along the 

 coast of Xorway. 



Norwegian Current — '<ee Norway Current. 



notch — A deep narrow cut in the base of a sea cliff 

 made by breaking wa\"es. See nip. 



Notice to Mariners — A periodic publication con- 

 tammg information affecting the safety of 

 navigation. 



N-2 constituent — The larger lunar elliptic semi- 

 diurnal constituent oi the theoretical tide- 

 producing forces. {See figure for partial 

 tide.) 



lU 



