BT SLUG 



(roarinj? forties). They are associated with 

 the strong pressure iiradient on the equatorial 

 side of tiie frequent depressions passing east- 

 ward in subpohar temperate latitudes; hence 

 they fluctuate mainly between southwest and 

 northwest. (5) 



Brazil Current — The warm ocean current that 

 flows southward along the Brazilian coast below 

 Natal. 



Its origin is in the westward flowing South 

 Equatorial Current, part of which turns south 

 and flows along the South American coast as 

 the Brazil Current. At about 35° S it meets the 

 cold north-setting Falkland Current and the 

 two turn to set eastward across the South 

 Atlantic Ocean. 



breaker — A wave breaking on the shore, over a 

 reef, etc. Breakers may be roughly classified 

 into three kinds, although the categories may 

 overlap : 



Spilling breakers break gradually over a con- 

 siderable distance; 

 Plunging breakers tend to curl over and break 



with a crash ; and 

 Surging breakers peak up, but then instead 

 of spilling or plunging they surge up on 

 the beach face. 

 In the figure on the following page, the 

 sketches consist of a series of profiles of the wave 

 form as it appeal's before, during, and after 

 breaking. The niunbers opposite the profile 

 lines indicate the relative times of occurrence. 

 (61) 



breaker depth — (also called breaking depth). 

 The still water depth at the point where a wave 

 breaks. («S'eefigurefor surf zone.) (61) 



breaker zone — Generally used for surf zone. 



breaking depth — See breaker depth. 



breakup — In general, the spring melting of snow, 

 ice, and frozen ground. Specifically, the 

 destruction of the ice cover on rivere and seas 

 during the spring thaw ; or applied to the time 

 when the solid sheet of ice breaks into pieces that 

 move with the current. 



Breakup connotes the end of winter to a resi- 

 dent of the north. (59) 



breakwater — A structure protecting a shore area, 

 harbor, anchorage, or basin from waves. (61 ) 



breccia — (or agglomerate) . A fragmental rock 

 whose components are angular and therefore, as 

 distinguished from conglomerates, are not wa- 

 terworn. There are friction or fault-breccias, 

 talus-breccias, and eruptive or volcanic brec- 

 cias. (2) 



bridge — A light formation of snow or ice join- 

 ing two heavier formations. See ramp. ( 65 ) 



brightness — See luminance. 



brine — Sea water containing a higher concentra- 

 tion of dissolved salt than that of the ordinary 

 ocean. 



Brine is produced by the evaporation or freez- 

 ing of sea water, for, in the latter case, the sea ice 



formed is much less saline than the initial liquid, 

 leaving the adjacent unfrozen water witli in- 

 creased salinity. The liquid remaining after 

 sea water has been concentrated by evaporation 

 until salt has crystallized is called bittern. (5) 



brine slush — A mixture of ice crystals and salt 

 water, which retards or prevents complete freez- 

 ing, often found between young sea ice and a 

 cover of newly fallen snow. (59) 



brit — (sometimes spelled britt) . 1. The young of 

 the common herring; any of certam small 

 herring. 



2. The plankton upon which the right whales 

 feed. 



3. Any of the silversides. 



British thermal unit — (abbreviated B.T.U., 

 Btu). A unit of energy defined as the heat re- 

 quired to raise the temperature of one pound 

 of water one degree Fahrenlieit; it is equal to 

 252.1 calories or 1,055 Joules. (5) 



brittle star — One of a class (Ophiuroidea) of 

 echinoderms having five, sometimes six, rarely 

 seven or eight, elongate, slender, cylindrical 

 arms radiating from a flat central disc; they 

 range from shallow water to great depths. 



broad ice field — A Russian term for an ice field 

 of more than 10 kilometers (5.4 n. miles) in 

 width. It corresponds to the current WMO 

 definition of vast ice floe. 



broken belt — The transition zone between open 

 water and consolidated ice. (68) 



broken ice — ^(also called loose ice, loose pach ice, 

 open ice, open pack ice, slack ice). Ice that: 

 covers from 5-tenths to 8-tenths of the sea sur- 

 face. See open pack ice. ( 68 ) 



Note: This term is being superceded by the 

 term open pack ice by '\'\rMO. 



broken water — Water ha^'ing a surface covered 

 with ripples or eddies, and usually surrounded 

 by calm water. (68) 



brown alga — One of a division or phylum (Phae- 

 ophyta) (the Phyophyceae of another scheme) 

 of greenish yellow to deep brown, filamentous to 

 inassively complex plants, in which the color is 

 imparted by the predominance of carotenes and 

 xanthophylls over the chlorophylls. This 

 group includes the rockweeds, gulfweeds, and 

 the large kelp. Brown algae are most abundant 

 in the cooler waters of the world. 



bryozoan — (or polyzoan, moss animal, sea mat). 

 One of a phylum (Bryozoa or Polyzoa) of mi- 

 nute, mostly colonial, aquatic animals with body 

 walls often hardened by calcium carbonate and 

 growing attached to aquatic plants, rocks, and 

 other firm surfaces. Colonies may be encrust- 

 ing, creeping, or erect and branching. Encrust- 

 ing colonies may be white, yellowish, or brick 

 red and consist of many tiny,"beautifully formed 

 shells. Members of this phylmn are widespread 

 and notable fouling organisms. 



BT slug — See airborne expendable bathyther- 

 mograph. 



25 



