tamlnated melt water obtained from them l8 fresh. 



The settling out of the brine gives sea ice a 

 honeycomb structure which greatly hastens its dis- 

 integration when the temperature rises above freez- 

 ing. In this state, when it is called ROTTEN ICE, 

 much more surface is exposed to warm air and water, 

 and the rate of melting is Increased. In a day's 

 time, a floe of apparently solid ice several inches 

 thick may disappear completely. (12) 



SALINITY-TEMPERATURE-DEPTH RECORDER . The STD 

 (Salinity-Temperature-Depth Recorder) measures tem- 

 perature by means of a nickel-resistance thermometer. 

 Utilizing the conductivity, salinity can be com- 

 piled automatically in situ . This instrument de- 

 veloped at Woods Hole, measures the conductivity 

 of sea water between two platinum electrodes spaced 

 a few inches apart . This is combined with the tem- 

 perature by an electromechanical computer in the 

 recorder to give salinity. The sensing elements 

 are towed behind the ship while a recorder aboard 

 ship shows the temperature, salinity, and depth. 

 Although this instrument is not as accurate as 

 desired, it is excellent for rapid surveys, and is 

 adequate for surveys in estuarine waters. (35) 



SALINOMETER . Any device or instrument for deter- 

 mining salinity, especially one based on electrical 

 conductivity methods . (24) 



SALP . See TUNICATES . 



SALTATION . That method of sand movement in a fluid 

 in which individual particles leave the bed by 

 bounding nearly vertically and, because the motion 

 of the fluid is not strong or turbulent enough to 

 retain them in suspension, return to the bed at 

 some distance downstream. The travel path of the 

 particles is a series of hops and bounds. (11) 



SALT ERROR . In determining the pH of sea water 

 by indicators an error is introduced by the fact 

 that neutral ions in the solution have a pronounced 

 effect upon the color and, hence, upon the apparent 

 pH. (13) 



SALT HAZE . A haze created by the presence of fine- 

 ly divided particles of sea salt in the air, usual- 

 ly derived from the evaporation of sea spray. (12) 



SAND . Loose detrital material consisting of small 

 but easily distinguishable separate grains ranging 

 between 0.0025 and 0.0787 inch (0.0625 and 2.0000 

 millimeters) in diameter. (16) 



SAND REEF . Same as BAR. 



SANDSTONE . A cemented or otherwise compacted detri- 

 tal sediment composed predominantly of quartz 

 grains, the grades of the latter being those of 

 sand (See SAND) . Mineralogical varieties such as 

 feldspatic and glauconltic sandstones are recog- 

 nized,, and also argillaceous, siliceous, calcareous, 

 ferruginous and other varieties according to the 

 nature of the binding or cementing material. 

 (Holmes, 1928) (28) 



SAPROPHYTIC . Living on and obtaining food from 

 dead or decaying matter in the soil or from the 

 dead parts of living plants. (18) 



SARGASSO . A certain type of seaweed, or more 

 generally, a large floating mass of this seaweed. 

 (17) 



SARGASSO SEA . A region of the north Atlantic Ocean 

 occupying the central space within a huge ellipse 

 bounded by the GULF STREAM, the SOUTHEAST DRIFT 

 CURRENT, the CANARIES CURRENT, and the NORTH EQUA- 

 TORIAL CURRENT. It is located approximately be- 

 tween lat. 20°N. and 40°N. and long. 30°W. and 

 70°W, and is characterised by the presence of large 

 quantities of gulf weed and the absence of any well- 

 marked currents. (14) 



SARGASSUM . A marine alga which grows attached to 

 the bottom in tropical and subtropical waters and 

 becomes detached to form extensive drifts, some- 

 times called gulfweed. (15) 



SATURABLE REACTOR . See FLUX-GATE MAGNETOMETER, 



SATURATION . When a person resides at sea level, 

 his blood and all his tissues become saturated 

 with dissolved nitrogen at a tension (partial pres- 

 sure of dissolved gas) equal to the partial pres- 

 sure of nitrogen in his lung ALVEOLI - about 570 

 mm. Kg. If the person is then exposed to a breath- 

 ing medium other than air or is taken to altitude 

 or depth, this will change the partial pressure 

 of nitrogen in his alveoli. His blood and tissues 

 must then either lose or take up nitrogen in order 

 to reach equilibrium (state of balance) with the 

 new alveolar nitrogen pressure. 



SAVONIUS ROTOR . A Magnetic Pickup Rotor (having 

 very low threshold speeds) which is used as a flow 

 sensing device. It was introduced into Oceano- 

 graphy by J. M. Snodgrass in 1954. 



In the Savonius Current Meter, the meter uses 

 a magnetic compass to originate an electric signal 

 which is proportional to direction. (35) 



SCANNING SONAR . Echo-ranging system in which the 

 ping is transmitted simultaneously throughout the 

 entire angle to be searched, and a rapidly rotat- 

 ing narrow beam scans for the returning echoes . (6) 



SCAR . Special Committee on Antarctic Research. 



SCARP . See ESCARPMENT. 



SCATTERING . Modifications of the direction in 

 which acoustic energy is propagated caused by 

 reflections from foreign bodies (in the medium, 

 and including the bottom and surface interface) 

 are said to be due to scattering. (4) 



SCATTERING CROSS SECTION . The acoustic scattering 

 cross section of an object is an area equal to 4ir 

 times the product of the mean-square sound pressure 

 scattered by the object, averaged over a sphere of 

 unit radius surrounding the object, and the square 

 of the unit radius, divided by the square of the 

 sound pressure of the plane wave incident upon the 

 object. The unit of the cross section is the 

 square of the unit radius. (2) 



SCATTERING DIFFERENTIAL . The scattering differen- 

 tial is the amount by which the level of the scat- 

 tered mean-square sound pressure averaged over all 

 directions at a specified unit distance from the 

 effective acoustic center of the object exceeds the 

 plane-wave free-field pressure level of the sound 

 incident upon the object. The scattering differen- 

 tial of an object is ten times the logarithm to the 

 base ten of the ratio of the scattering cross sec- 

 tion to the area of the sphere of unit radius sur- 

 rounding the object. (2) 



SCATTERING LOSS . Scattering loss is that part of 

 the transmission loss which is due to scattering 

 within the medium or due to roughness of any 

 reflecting surfaces. (9) 



SCG. Scientific Committee for Inter-Union Coopera- 

 tion in Geophysics. 



SCHLIEREN . (German, 'streaks', 'striae'.) 



1. Regions of different density in a fluid, es- 

 pecially as shown by special apparatus. 



2. A method or apparatus for visualizing or photo- 

 graphing regions of varying density in a field of 

 flow. (31) 



SCOOPFISH (UNDERWAY SAMPLER) . This device consists 

 of a sampling cup which is mounted in a hollow bar- 

 rel attached to a tail-piece. When cocked ready 



1Q3 



