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Exploring subsurface waves with neutrally buoyant floats I.S.A.
Oceanographic Abstracts
569
tests, with a view to collecting comparative material, such as would hint at the most appropriate solution of ship design--from the practical point of view. MORDUKnAI-BOLxOVS~:OY F. D. 1962. Appearance of a representative of Mediterranean polyphemids in the Caspian Sea. Zool. Zh. Akad. Nauk SSSR. 41 (2): 289-290. In the catches of Caspian plankton in 1958 a Mediterranean (more exactly, a widely distributed in open seas) polyphemid species, Podon polyphemoides was found. This species seems to have penetrated into the Caspian Sea about 1957 through the Volga-Don canal. NORTNROP J. and M. RANSONE 1962. Some seismic profiles near the Western end of the Puerto Rico trench. J. Gen. Physiol., 45 (4) Pt. 2: 243-251. (Volume is published in honour of John Howard Northrop). A cooperative program of seismic refraction profiling was complete in the vicinity of the Fuerto Rico Trench by Hudson Laboratories, Woods Hole, Lamont, and Texas A. & M. Profiles completed near the western end of the Trench were analysed at Hudson Laboratories. Five seismic layers are indicated below the water layer. The thickness/velocity relationships are as follows: 5.1 km of l "5 km/sec. (water); 1 km of 1.7 kin/see. (sediment); 1.5 km of 3 km/sec. (metamorphics?); 2 km of 5'5 km/sec. (basement); and 2 km of 7-1 km/sec. (high speed basement). Below these, typical Moho velocities of 8-1 km/sec, were measured. Total depth to Moho ranges from 9 to 12 k m below sea level, the greatest variation occurring in the basement layers. The least depth was measured 65 miles north of the Puerto Rico Trench. POCnAPSKV T. E. 1961. Exploring subsurface waves with neutrally buoyant floats I . S . A . J . , lnstrum. Soc., .4mer, (Oct.): 4 pp. These submarine-like instrumented floats follow and measure the turbulence and internal wave motions at prescribed depths in the ocean. After recording their data on a built-in camera or telemetering it acoustically to a ' listening' ship, the floats are recovered for future use. POSTMA H. 1961. Suspended matter and Secchi disk visibility in coastal waters. Netherlands J. Sea Res. 1 (3): 359-390. From experiments in the laboratory with artificially prepared sand and clay suspensions a simple equation could be derived, which gives the quantitative relation between visibility range, determined by means of a Secchi disc and the amounts and the grainsizes of the suspended materials. This relation, however, cannot directly be applied to natural waters, because in the latter nearly always an important part of the suspended matter is organic. It could be shown that a certain amount of organic matter intercepts the light more effectively than the same amount of inorganic matter, not only if particle sizes are equal, but also if the settling velocities are the same, although in the latter case organic particles are considerable larger than inorganic ones. In this connection it appeared useful to introduce " o p t i c a l grainsize," defined as the grainsize determined from visibility range and suspended matter content by means of the above equation, for convenience assuming that all material is inorganic. Measurements in fresh and salt natural waters show that they should be divided into two groups: those where the concentrations of suspended matter are not appreciably influenced by the tides and those where tidal action is predominant. The data of the first group indicate that for one distinct mass of water a simple straight line relation exists between the reciproque value of the Secchi disc readings and the concentration of suspended matter, the line passing through the origin. However, different water bodies have a different relation. In other words, within one water mass sediment assemblages have the same optical grainsize, but this size is different from one entity to the other. This may be due to true grainsize differences, but it is most probably caused partly by differences in organic matter content. The data of the second group show that in areas with strong tidal currents no simple relation in the above sense is to be found. If only measurements at one fixed point during a tidal period are considered, there is again a straight line correlation between the reciprocal value of disc visibility and suspended matter; this line, however, does not pass through the origin. This may be explained by assuming the presence of a certain amount of finely divided suspended matter which remains in suspension at slack tide and to which increasing quantities of coarser materials are added by increasing current velocities. It is concluded that Secchi disc measurements are a valuable source for additional information concerning the properties of suspended matter. POSXMA H. 1961. Transport and accumulation of suspended matter in the Dutch Wadden Sea. Netherlands 7. Sea Res. 1 (1/2): 148-190. Previous observations in various parts of the Dutch Wadden Sea have established the existence of a gradient of fine-grained suspended matter from the tidal inlets, where concentrations are comparatively low, towards the coast. Since the water masses in the Wadden Sea, owing to intensive tidal movements, are rapidly renewed by N o r t h Sea water this gradient must favour transport of material towards the North Sea. Actually, no appreciable residual transport takes place in that direction; hence, the existence of a factor must be assumed which causes a compensating movement of finegrained material towards the coast.
569
tests, with a view to collecting comparative material, such as would hint at the most appropriate solution of ship design--from the practical point of view. MORDUKnAI-BOLxOVS~:OY F. D. 1962. Appearance of a representative of Mediterranean polyphemids in the Caspian Sea. Zool. Zh. Akad. Nauk SSSR. 41 (2): 289-290. In the catches of Caspian plankton in 1958 a Mediterranean (more exactly, a widely distributed in open seas) polyphemid species, Podon polyphemoides was found. This species seems to have penetrated into the Caspian Sea about 1957 through the Volga-Don canal. NORTNROP J. and M. RANSONE 1962. Some seismic profiles near the Western end of the Puerto Rico trench. J. Gen. Physiol., 45 (4) Pt. 2: 243-251. (Volume is published in honour of John Howard Northrop). A cooperative program of seismic refraction profiling was complete in the vicinity of the Fuerto Rico Trench by Hudson Laboratories, Woods Hole, Lamont, and Texas A. & M. Profiles completed near the western end of the Trench were analysed at Hudson Laboratories. Five seismic layers are indicated below the water layer. The thickness/velocity relationships are as follows: 5.1 km of l "5 km/sec. (water); 1 km of 1.7 kin/see. (sediment); 1.5 km of 3 km/sec. (metamorphics?); 2 km of 5'5 km/sec. (basement); and 2 km of 7-1 km/sec. (high speed basement). Below these, typical Moho velocities of 8-1 km/sec, were measured. Total depth to Moho ranges from 9 to 12 k m below sea level, the greatest variation occurring in the basement layers. The least depth was measured 65 miles north of the Puerto Rico Trench. POCnAPSKV T. E. 1961. Exploring subsurface waves with neutrally buoyant floats I . S . A . J . , lnstrum. Soc., .4mer, (Oct.): 4 pp. These submarine-like instrumented floats follow and measure the turbulence and internal wave motions at prescribed depths in the ocean. After recording their data on a built-in camera or telemetering it acoustically to a ' listening' ship, the floats are recovered for future use. POSTMA H. 1961. Suspended matter and Secchi disk visibility in coastal waters. Netherlands J. Sea Res. 1 (3): 359-390. From experiments in the laboratory with artificially prepared sand and clay suspensions a simple equation could be derived, which gives the quantitative relation between visibility range, determined by means of a Secchi disc and the amounts and the grainsizes of the suspended materials. This relation, however, cannot directly be applied to natural waters, because in the latter nearly always an important part of the suspended matter is organic. It could be shown that a certain amount of organic matter intercepts the light more effectively than the same amount of inorganic matter, not only if particle sizes are equal, but also if the settling velocities are the same, although in the latter case organic particles are considerable larger than inorganic ones. In this connection it appeared useful to introduce " o p t i c a l grainsize," defined as the grainsize determined from visibility range and suspended matter content by means of the above equation, for convenience assuming that all material is inorganic. Measurements in fresh and salt natural waters show that they should be divided into two groups: those where the concentrations of suspended matter are not appreciably influenced by the tides and those where tidal action is predominant. The data of the first group indicate that for one distinct mass of water a simple straight line relation exists between the reciproque value of the Secchi disc readings and the concentration of suspended matter, the line passing through the origin. However, different water bodies have a different relation. In other words, within one water mass sediment assemblages have the same optical grainsize, but this size is different from one entity to the other. This may be due to true grainsize differences, but it is most probably caused partly by differences in organic matter content. The data of the second group show that in areas with strong tidal currents no simple relation in the above sense is to be found. If only measurements at one fixed point during a tidal period are considered, there is again a straight line correlation between the reciprocal value of disc visibility and suspended matter; this line, however, does not pass through the origin. This may be explained by assuming the presence of a certain amount of finely divided suspended matter which remains in suspension at slack tide and to which increasing quantities of coarser materials are added by increasing current velocities. It is concluded that Secchi disc measurements are a valuable source for additional information concerning the properties of suspended matter. POSXMA H. 1961. Transport and accumulation of suspended matter in the Dutch Wadden Sea. Netherlands 7. Sea Res. 1 (1/2): 148-190. Previous observations in various parts of the Dutch Wadden Sea have established the existence of a gradient of fine-grained suspended matter from the tidal inlets, where concentrations are comparatively low, towards the coast. Since the water masses in the Wadden Sea, owing to intensive tidal movements, are rapidly renewed by N o r t h Sea water this gradient must favour transport of material towards the North Sea. Actually, no appreciable residual transport takes place in that direction; hence, the existence of a factor must be assumed which causes a compensating movement of finegrained material towards the coast.