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On the use of acoustics for studying suspended oceanic sediment and for determing the onset of the shallow thermocline
Oceanographic Abstracts
293
correspond to interglacial and glacial conditions in the Colombia Basin. The oceanographic conditions represented by these assemblages were deduced from the present faunal distributions in the North Atlantic Ocean. The interglacial assemblage has maximum abundances in the equatorial zone, which is characterized by moderate salinities, strong currents, and high nutrients and productivity The glacial assemblage occurs today in the distinctive southern Sargasso Sea water of high salinity, low nutrients, and low productivity. The alternation between interglacial-equatorial and glacial-Sargasso Sea assemblages in the Colombia Basin suggests that during glacial periods, Sargasso type water was formed in situ within the Colombia Basin. Paleotemperature estimates derived by the Imbrie and Kipp technique (1971) reveal only 2 ° to 3°C average temperature changes between interglacial and glacial stages. During glacial stages, however, seasonal contrast (Ts-Tw) was increased; the winters had much larger variations (4 ° to 5°C) than did the summers (1 ° to 2°C). Because the evaporation/precipitation ratio (E/P) is greatest today during the Caribbean winter, increased seasonal contrast during glacial stages may have increased the E/P, resulting in high salinities similar to present Sargasso water. The increased E/P suggests that the Intertropical Convergence Zone was on the average located over South America more during the glacial stages than at present. PRONI J.R., F. C. NEWMAN, D. C. RONA, D. E. DRAKE, G. A. BERBERIAN, C. A. LAUTER Jr. and R. L. SELLERS, 1976. On the use of acoustics for studying suspended oceanic sediment and for determining the onset of the shallow thermocline. Deep-Sea Res., 23 (9): 831-837. Acoustic observations of a low-density sediment flow originating from a dredge operating in the main Miami shipping channel have been made. The flow proceeded seaward alc,ng layered thermal gradients at the top of the shallow thermocline and at greater depths. Acoustic, thermal, salinity, chemical, and transmissivity measurements were made during summer and winter in 1974. PROPP M.V., V. A. DENISOV, V. M. POGREBOV and V. I. RYABUSHKO, 1975. The ecological system of a fiord of the Barents Sea. 1. Hydrobiological and hydrochemical characteristics. (Russian original.) BioL mor., 1 (3): 44-56. Translation: Soy. ,L mar. BioL, 1 (3): 201-212. We investigated the hydrological (tides, water temperature, penetration of light, water exchange between the bay and the sea, shore drainage) and hydrochemical (salinity, oxygen, nitrites, nitrates, organic nitrogen, phosphates, organic phosphorus) regimes in a fiord and the coastal region of the sea. Characteristics of waters of the sea matched the mean data for many years. Waters of the fiord to a depth of 20 m mix with sea waters ovel a period of 7 - 10 days and differ little from the latter. The deep part is characterized by low water temperature, reduced oxygen content (to 1.8 ml/liter), and increased concentration of nitrogen and phosphorus. Mixing occurs during the winter season. The bottom layer of water in the deep part is enriched with nitrates, total nitrogen, phosphorus, and oxygen. Conditions favorable for benthonic organisms are preserved throughout the entire fiord. However, the surface layers of water are phosphate-poor, a circumstance which limits primary production. The fiord is of interest as a water body convenient for modeling conditions of a marine ecosystem and for studying the ways in which processes of biological production are regulated. RABINOWITZ P. D., 1976. Geophysical study of the continental margin of southern Africa. Bull. geol. Soc. Am., 87 (11): 1643-1653. Marine gravity and magnetic anomalies determine a model for the boundary between oceanic and continental basement off southern Africa. A nearly linear high-amplitude positive magnetic anomaly (about 300 to 800 7) is coincident with an isostatic gravity anomaly where the Agulhas fracture zone is bounded to the north by the African continent. The magnetic anomaly is interpreted as a magnetic "edge effect" separating oceanic basement in the south from continental basement in the north. Where deep ocean lies on either side of the fracture zone, negative magnetic anomalies occur that are modeled by assuming a broad zone of zero magnetization within the fracture zone. Mesozoic mag4aetic lineations M0 ( ~ 108 m y B.P.) through MI2 ( ~ 128 m y B.P.) are adjacent to the western margin of southern Africa (Cape Sequence). West of the Orange River, the magnetic anomaly amplitudes are attenuated, which is attributed to a partial demagnetization of basement rocks due to an increase in sediment overburden. A prominent magnetic anomaly (anomaly G) borders the Cape Sequence on its landward side and is coincident with an isostatic gravity anomaly. Anomaly G is interpreted as a magnetic edge-effect anomaly separating oceanic from continental basement, simila~ to the magnetic anomaly associated with the Agulhas fracture zone. Southwest of Capetown, anomaly G is located on the continental slope, implying that continental basement has subsided to form the slope. Farther north, anomaly G lies nearly 125 km landward of the shelf break; this implies that the shelf break in the north was formed by a prograding of sediment over an oceanic basement, in general agreement with available seismic (sonobuoy) measurements. RAMABHADRAN T. E., 1975. A mathematical theory of estuarine particle dynamics. Proc. Indian natn. Sci. Acad., (A) 41 (5): 470-484. A dynamic model of particulate behaviour in an estuary is proposed. The model includes all the physical and chemical processes involved including sedimentation, dissolution, advecdon, coagulation, and chemical transformation. Defining an appropriate phase space, a general population balance is derived. To use the idea of dynamic similarity, a simplified form of the general population balance equation is used and the existence of self-preserving size distributions is demonstrated.
293
correspond to interglacial and glacial conditions in the Colombia Basin. The oceanographic conditions represented by these assemblages were deduced from the present faunal distributions in the North Atlantic Ocean. The interglacial assemblage has maximum abundances in the equatorial zone, which is characterized by moderate salinities, strong currents, and high nutrients and productivity The glacial assemblage occurs today in the distinctive southern Sargasso Sea water of high salinity, low nutrients, and low productivity. The alternation between interglacial-equatorial and glacial-Sargasso Sea assemblages in the Colombia Basin suggests that during glacial periods, Sargasso type water was formed in situ within the Colombia Basin. Paleotemperature estimates derived by the Imbrie and Kipp technique (1971) reveal only 2 ° to 3°C average temperature changes between interglacial and glacial stages. During glacial stages, however, seasonal contrast (Ts-Tw) was increased; the winters had much larger variations (4 ° to 5°C) than did the summers (1 ° to 2°C). Because the evaporation/precipitation ratio (E/P) is greatest today during the Caribbean winter, increased seasonal contrast during glacial stages may have increased the E/P, resulting in high salinities similar to present Sargasso water. The increased E/P suggests that the Intertropical Convergence Zone was on the average located over South America more during the glacial stages than at present. PRONI J.R., F. C. NEWMAN, D. C. RONA, D. E. DRAKE, G. A. BERBERIAN, C. A. LAUTER Jr. and R. L. SELLERS, 1976. On the use of acoustics for studying suspended oceanic sediment and for determining the onset of the shallow thermocline. Deep-Sea Res., 23 (9): 831-837. Acoustic observations of a low-density sediment flow originating from a dredge operating in the main Miami shipping channel have been made. The flow proceeded seaward alc,ng layered thermal gradients at the top of the shallow thermocline and at greater depths. Acoustic, thermal, salinity, chemical, and transmissivity measurements were made during summer and winter in 1974. PROPP M.V., V. A. DENISOV, V. M. POGREBOV and V. I. RYABUSHKO, 1975. The ecological system of a fiord of the Barents Sea. 1. Hydrobiological and hydrochemical characteristics. (Russian original.) BioL mor., 1 (3): 44-56. Translation: Soy. ,L mar. BioL, 1 (3): 201-212. We investigated the hydrological (tides, water temperature, penetration of light, water exchange between the bay and the sea, shore drainage) and hydrochemical (salinity, oxygen, nitrites, nitrates, organic nitrogen, phosphates, organic phosphorus) regimes in a fiord and the coastal region of the sea. Characteristics of waters of the sea matched the mean data for many years. Waters of the fiord to a depth of 20 m mix with sea waters ovel a period of 7 - 10 days and differ little from the latter. The deep part is characterized by low water temperature, reduced oxygen content (to 1.8 ml/liter), and increased concentration of nitrogen and phosphorus. Mixing occurs during the winter season. The bottom layer of water in the deep part is enriched with nitrates, total nitrogen, phosphorus, and oxygen. Conditions favorable for benthonic organisms are preserved throughout the entire fiord. However, the surface layers of water are phosphate-poor, a circumstance which limits primary production. The fiord is of interest as a water body convenient for modeling conditions of a marine ecosystem and for studying the ways in which processes of biological production are regulated. RABINOWITZ P. D., 1976. Geophysical study of the continental margin of southern Africa. Bull. geol. Soc. Am., 87 (11): 1643-1653. Marine gravity and magnetic anomalies determine a model for the boundary between oceanic and continental basement off southern Africa. A nearly linear high-amplitude positive magnetic anomaly (about 300 to 800 7) is coincident with an isostatic gravity anomaly where the Agulhas fracture zone is bounded to the north by the African continent. The magnetic anomaly is interpreted as a magnetic "edge effect" separating oceanic basement in the south from continental basement in the north. Where deep ocean lies on either side of the fracture zone, negative magnetic anomalies occur that are modeled by assuming a broad zone of zero magnetization within the fracture zone. Mesozoic mag4aetic lineations M0 ( ~ 108 m y B.P.) through MI2 ( ~ 128 m y B.P.) are adjacent to the western margin of southern Africa (Cape Sequence). West of the Orange River, the magnetic anomaly amplitudes are attenuated, which is attributed to a partial demagnetization of basement rocks due to an increase in sediment overburden. A prominent magnetic anomaly (anomaly G) borders the Cape Sequence on its landward side and is coincident with an isostatic gravity anomaly. Anomaly G is interpreted as a magnetic edge-effect anomaly separating oceanic from continental basement, simila~ to the magnetic anomaly associated with the Agulhas fracture zone. Southwest of Capetown, anomaly G is located on the continental slope, implying that continental basement has subsided to form the slope. Farther north, anomaly G lies nearly 125 km landward of the shelf break; this implies that the shelf break in the north was formed by a prograding of sediment over an oceanic basement, in general agreement with available seismic (sonobuoy) measurements. RAMABHADRAN T. E., 1975. A mathematical theory of estuarine particle dynamics. Proc. Indian natn. Sci. Acad., (A) 41 (5): 470-484. A dynamic model of particulate behaviour in an estuary is proposed. The model includes all the physical and chemical processes involved including sedimentation, dissolution, advecdon, coagulation, and chemical transformation. Defining an appropriate phase space, a general population balance is derived. To use the idea of dynamic similarity, a simplified form of the general population balance equation is used and the existence of self-preserving size distributions is demonstrated.