TOOTHED CETACEAN 



nel and Northwest Providence Channel and 

 trends southeast into the Great Bahama Bank, 

 terminating in a circidar cul-de-sac. (11) 



toothed cetacean — See toothed whale. 



toothed whale — (or odontocete, toothed cetacean) . 

 A member of the cetacean suborder Odontoceti, 

 which comprises the dolphins, porpoises, killer 

 whales, beaked whales, and sperm whales. 



tooth shell — ( or tu~sk shell, scaphopod) . One of a 

 class (Scaphopoda) of benthic marine mollusks 

 having tubular, tapering, slightly curved shells, 

 open at both ends ; the body has no distinct head 

 but possesses a foot. 



topographic correction — See terrain correction. 



topography — The configuration of a surface in- 

 cluding its relief. In oceanography the term is 

 applied to a surface such as the sea bottom or a 

 surface of given characteristics within the water 

 mass. 



torsion crack — A crack in sea ice, produced by 

 twisting of the ice beyond its elastic limit. (68) 



tosca — Applied in Argentina to a white calcareous 

 marl. In Colombia it is synonymous with vol- 

 canic tufa. (48) 



total internal reflection — In wave refraction 

 theory, a term analogous to the phenomenon of 

 the total internal reflection of light at a 45^5-90 

 prism. It occurs at a special type of caustic. 

 (73) 



total magnetic intensity — The vector resultant of 

 the intensity of the horizontal and vertical com- 

 ponents of the earth's magnetic field at a speci- 

 fied point. 



total pnosphorus — Includes both the soluble phos- 

 phonis (phosphate) and the organic phosphorus 

 contained in the plankton organisms and other 

 organic material in the water. (71) 



total scattering coefficient — See scattering coe- 

 ficient. 



tow — (or haul) . A single haul of a net. 



trace — 1. (sometimes called pr-o^Ze). A line drawn 

 on a graph which shows the variation of an 

 oceanographic element such as temperature and 

 salinity usually with depth. 



2. The indication of tlie recorded depth on an 

 echogram. 



tracer — A foreign substance mixed with (or at- 

 tached to a given substance) to enable the dis- 

 tribution or location of the latter to be deter- 

 mined subsequently. A radioactive tracer is a 

 physical or chemical tracer having radioactivity 

 as its distinctive property. An isotopic tracer 

 is a radionuclide used as a chemical tracer for 

 the element with which it is isotopic. (41) 



tracer studies — A technique for studying the role 

 of an element, a group of elements, or a com- 

 pound in a biological, chemical, or physical proc- 

 ess. In this technique an isotopic tracer is em- 

 ployed to follow the course of the bulk material 

 througli the process. (41) 



traction — See load. 



traction load — See load. 



trade winds — The wind system, occupying most 

 of the tropics, which blows from the subtropical 

 highs toward the equatorial trough; a major 

 component of the general circulation of the at- 

 mosphere. The winds are northeasterly in the 

 Northern Hemisphere and southeasterly in the 

 Southern Hemisphere. «S'ee antitrades. (5) 



traffic noise — The general disturbance caused by 

 ships not associated with a specific ship or, more 

 significant, which has no definite directional dis- 

 tribution relative to a given observation point 

 and which shows little change in intensity with 

 change in position. 

 (28) 



training wall — See jetty. 



transducer — A device that converts electrical en- 

 ergy to sound energy, or the converse. When 

 sound energy received through the water is con- 

 verted to electrical energy, the device is termed 

 a hydrophone; conversely, when electrical en- 

 ergy is converted to sound energy and trans- 

 mitted through the water, the device is termed 

 a sonar projector or echo sounder. 



transducer loss — The ratio of the available power 

 of the source to the power that the transducer 

 delivers to the load under specified operating 

 conditions. (6) 



transgressive reef — One of a series of reefs or 

 bioherms developed close to and parallel to the 

 shore, by a net movement of the sea over the 

 land. (2) 



transient thermocline — A small decrease in verti- 

 cal temperature observed above the thermo- 

 cline. It is a short-term phenomenon associated 

 primarily with diurnal heating and wind 

 mixing. 



transit — The passage of the moon over the local 

 meridian; it is designated as upper transit when 

 it crosses the observers meridian and as lower 

 transit when it crosses the same meridian but 

 180 degrees from the observer's location. When 

 specified, transit may be referred to the Green- 

 wich meridian. 



transitional water wave — A progressive gravity 

 wave in water whose depth is less than 14 but 

 more than 1^5 the wavelength. Often called a 

 shallow water wave. (73) 



transition zone — The water area between two op- 

 posing currents manifested by eddies, upwell- 

 ing, rips, and similar turbulent conditions oc- 

 curring either vertically or horizontally ; or a 

 zone between two water masses of differing phys- 

 ical characteristics such as temperature and/or 

 salinity. 



transmission anomaly — The difference (in deci- 

 bels) between the total transmission loss in 

 intensity and the reduction in intensity due to 

 an assumed inverse square divergence. 



transmission gain — Whenever the transmission 

 factor is a number greater than unity, as it is in 

 the case of an amplifier, the transmission loss 

 would have a negative sign. In such cases the 



168 



