FLOEBERG 



firn — (also called neve, fim snoiv). 1. See firn 

 snow (sense 1). 



2. Old snow that has become granular and 

 compacted (dense) as the result of various sur- 

 face metamorphoses, mainly melting and re- 

 freezing but also including sublimation. The 

 resulting particles are generally spherical and 

 rather uniform. Firnification is the first step 

 in tlie transformation of snow into land ice 

 (usually glacier ice) . Some authorities restrict 

 the use of firn to snow that has lasted through 

 one summer, thereby distinguishing it from 

 spring snow. (5) 



firnification — The process of firn formation. (5) 



firn snow — (also called neve). 1. According to 

 the adopted WMO definition, a snow which has 

 become coarse grained and compact through tem- 

 perature change, forming the transition stage 

 to glacier ice. (74) 

 2. See firn. 



First Approximation chart — See historical 

 chart. 



first ice — 1. The first appearance of ice in the 

 water at any particular location, whether locally 

 formed (grease ice, young ice) or formed else- 

 where (drift ice). 



2. Sometimes, the first appearance of locally 

 formed ice only. 



first reduction — A name formerly given to a high 

 and low water reduction in which the quantities 

 sought were the mean high and low water in- 

 tervals, the mean high and low water heights, 

 and the mean range of tide. (50) 



firth — ( or, frith ) . A long, narrow arm of the sea. 

 (68) See estuary. 



fish — 1. Any towed sensing device. 



2. A member of the class Pisces, which in- 

 cludes the true fishes (elasmobranchs excluded) 

 having a bony endoskeleton, paired fins, and an 

 operculum covering the gills. 



fission — The splitting of a nucleus into two more- 

 or-less equal fragments. Fission may occur 

 spontaneously or may be induced by capture of 

 bombarding particles. In addition to the fission 

 fragments, neutrons and gamma rays are usually 

 produced during fission. (41) 



fissionable — Having the propertj' of certain 

 atomic nuclei, such as some isotopes of uranium 

 and plutonium, of capturing neutrons and there- 

 upon splitting into two particles with great 

 kinetic energy. The term properly is applicable 

 to nuclei that undergo fission by neutrons of 

 thermal energies; but it sometimes is applied 

 loosely to cases where the neutron must be of 

 high energy, as in saying that U^^^ is fissionable 

 by fast neutrons. (41 ) 



fission fragments — The nuclear species which are 

 first produced when an atom such as U^^^ or 

 Pu"^ undergoes fission. In slow neutron fission 

 the fragments are seldom equal in mass but gen- 

 erally fall into a heavier group with masses 



around 140 and a lighter group with masses 

 around 95. The fragments are abnormally rich 

 in neutrons and decay to stability by successive 

 /3- emissions, in decay chains, averaging 3 to 4 

 members. (41) 



fission neutrons— Neutrons that are emitted as a 

 i-esult of nuclear fission. Prompt fission neu- 

 trons are those that are emitted during fissions. 

 Delayed fission neutrons are those emitted by 

 fission products. (41) 



fission products— The nuclides produced by the 

 fission of a heavy element nuclide such as 

 U235 oj, pu239 Thirty-five fission product ele- 

 ments from zinc through gadolinium have been 

 identified from slow neutron fission. (41) 



fix — A relatively accurate position determined 

 without reference to any former position. It 

 may be classed as visual, sonic, celestial, elec- 

 tronic, radio, hyperbolic, Loran, radar, etc., 

 depending upon the means of establishing it. A 

 pinpoint is a very accurate fix, usually estab- 

 lished by passing directly over or near an aid 

 to navigation or a landmark of small area. 

 (68) See dead reckoning. 



fjord — See fiord. 



flagellum — A whiplike process of protoplasm 

 which provides locomotion for a motile cell. 

 (13) 



flashing — The process of reducing the amount of 

 permanent magnetism in a ship by placing a 

 single coil horizontally around the ship and 

 energizing it. If the energized coil is moved up 

 and down along the sides of the ship, the process 

 is called wiping. (68) See deperming. 



flaw — A lead between fractured offshore ice and 

 landfastice. 



flaw ice — See fast ice. 



Fletcher's Ice Island— ^S^ee T-3. 



float — 1. An air sac or other light structure con- 

 taining air or gas serving to buoy up the body of 

 a pelagic animal (as the Portuguese man-of- 

 war) ; a pneumatophore. 



2. A hollow vesicle found in certain algae 

 (as of the genus Fucus) containing gases (as 

 carbon dioxide) and serving to buoy up the 

 plant. 



float gage — See box gage. 



floating ice — See drift ice. 



floe — Small aggregate of tiny sedimentary grains. 

 (2) 



flocculate — To aggregate into lumps, as when fine 

 or colloidal clay particles in suspension in fresh 

 water clump together upon contact with salt 

 water and settle out of suspension; a common 

 depositional process in estuaries. 



floe — See ice floe. 



floe belt — A belt consisting of ice floes. (68) 



floeberg — 1. See bergy bit. 



2. A mass of thick, heavily hummocked sea 

 ice resembling an iceberg or bergy bit. Floe- 

 bergs have been reported to be as high as 50 



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