ROOT-MEAN-SQUARE SOUND PRESSURE . 

 SOUND PRESSURE. 



See EFFECTIVE 



ROPAK . A pinnacle or slab of heavy SEA ICE which 

 has been forced to stand on edge and thus extend 

 vertically upward. The crests may rise 25 feet 

 above the surrounding ice. (25) 



ROSS EL CURRENT . A seasonal Pacific Ocean current 

 flowing westward and northwestward along both the 

 southern and northeastern coasts of New Guinea, 

 the southern part flowing through Torres Strait 

 and losing its identity in the Arafura Sea, and the 

 northern part curving northeastward to join the 

 EQUATORIAL COUNTERCURRENT of the Pacific Ocean. 

 The Rossel current is a weak branch of the SOUTH 

 EQUATORIAL CURRENT. During the northern hemisphere 

 winter it is replaced by an easterly-flowing cur- 

 rent from the Indian Ocean. (17) 



ROTARY CURRENT . A tidal current that flows con- 

 tinually with the direction of flow changing through 

 all points of the compass during the tidal period. 

 Rotary currents are usually found offshore where 

 the direction of flow is not restricted by any 

 barriers. The tendency for the rotation in direc- 

 tion has its origin in the deflecting force of the 

 earth's rotation, and unless modified by local con- 

 ditions the change is clockwise in the Northern 

 Hemisphere and counterclockwise in the Southern 

 Hemisphere. The velocity of the current usually 

 varies throughout the tidal cycle, passing through 

 2 maxima in approximately opposite directions and 

 2 minima with the direction of the current at ap- 

 proximately 90° from the direction at time of maxi- 

 mum velocity. (14) 



ROTATIONAL WAVE . See SHEAR WAVE. 



ROTTEN ICE . Old ice which has become honeycombed 

 in the course of melting and which is in an advanced 

 stage of disintegration. Rotten ice may appear 

 black through saturation with sea water. (Thin 

 sheets of newly- formed, very thin ice also appear 



black, and may easily be confused with rotten 

 ice when met in the ICE PACK.) (25) 



RSO . Research SHIP OF OPPORTUNITy. 



RUBBER ICE . A type of sludge with an elastic 

 quality, not strong enough to bear the weight of 

 a man. (17) 



RUBBER SUIT . A partial or complete diving suit 

 designed primarily for the purpose of insulation 

 (preservation) of body heat. The suits are classi- 

 fied as "wet" and "dry". Wet suits are usually 

 made of foam neoprene and are so designed to permit 

 a thin insulating layer of water to contact the 

 divers skin. The "Dry" or rubber sheet suits are 

 designed so as to prohibit such a contact. 



RUBBLE , 

 a beach. 



Loose angular water-worn stones along 



rock. 



2. Rough, irregular fragments of broken 

 (11) 



RUBBLE-MOUND STRUCTURE . A mound of random-shaped 

 and random-placed stones protected with a cover 

 layer of selected stones or specially shaped con- 

 crete armor units . (armor units in primary cover 

 layer may be placed in orderly manner or dumped at 

 random.) (11) 



RUM . Remote Underwater Manipulator. 



RUNNEL . A corrugation (trough) of the FORESHORE 

 (or the bottom just offshore) , formed by wave and/ 

 or tidal action. Larger than the trough between 

 RIPPLE MARKS. (11) 



RUN-UP (UPRUSH) . The rush of water up a structure 

 on the breaking of a wave. The amount of run-up 

 is the vertical height above still water level 

 that the rush of water reaches. (11) 



R/V . 1. Research Vessel 

 2. Reentry Vehicle. 



s 



SAC . Indentation in the contour lines of equal 

 depth showing submarine relief; analogous to a gulf 

 on the surface. The opposite is submarine peninsu- 

 la. (17) 



SAC I . South Atlantic Cooperative Investigations. 



SACLANTCEN . Supreme Allied Command for the Atlan- 

 tic Center (ASW Research Center, LaSpezia, Italy.) 



SADDLE . A low point on a RIDGE or between SEA- 

 MOUNTS. (26) 



SALINITY . A measure of the quantity of dissolved 

 salts in sea water. It is formally defined as the 

 total amount of dissolved solids in sea water in 

 parts per thousand (0/00) by weight when all the 

 carbonate has been converted to oxide, the bromide 

 and iodide to chloride, and all organic matter is 

 completely oxidized. These qualifications result 

 from the chemical difficulty in drying the salts 

 in sea water. In practice, salinity is not deter- 

 mined directly but is computed from chlorinity, 

 electrical conductivity, refractive index, or some 

 other property whose relationship to salinity is 

 well established. 



The relationship between chlorinity CI and 

 salinity S as set forth in Knudsen's tables is 

 S = 0.03 + 1.805 CI. In 1940, however, Lyman and 

 Fleming found that the relationship between total 

 dissolved salts S and chlorinity was better ex- 

 pressed by S = 0.07 + 1.811 CI. (24) 



SALINITY BRIDGE . An Instrument for determining 

 salinity of water (a salinometer) by measuring 

 electrical conductivity of the water sample with 

 a Wheatstone bridge. (24) 



SALINITY OF SEA ICE . Sea ice forms first as salt- 

 free crystals near the surface of the sea. As the 

 process continues, these crystals are joined to- 

 gether and, as they do so, small quantities of 

 brine are trapped within the ice. On the average, 

 new ice six inches thick contains five to ten parts 

 of salt per thousand. With lower temperature, 

 freezing takes place faster and a greater amount 

 of salt is trapped in the ice. 



Depending upon the temperature, the trapped 

 brine may either freeze or remain liquid, but 

 because its density is greater than that of the 

 pure ice, it tends to settle down through the 

 pure ice. As it does so the ice gradually freshens, 

 becoming clearer, stronger, and more brittle. At 

 an age of one year sea ice is sufficiently fresh 

 that its melt water, if found in puddles of suf- 

 ficient size, and not contaminated by spray from 

 the sea can be used to replenish the fresh water 

 supply of a ship. When sea ice reaches an age of 

 about two years, virtually all of the salt has been 

 eliminated. Icebergs contain no salt, and uncon- 



102 



