Deep Sea Research (1953)最新文献

Further considerations regarding the antiquity of the abyssal fauna suggest continued confusion regarding the terms ‘Ancient’ and ‘Deep’ with reference to the marine fauna.

Two hypotheses concerned with ecological conditions in the abyss of the oceans prevail. Zenkevitch and Birstein (1960) adhere to a belief in constancy of abyssal conditions with the passage of time. Assembled here are data suggesting changing abyssal conditions with time. These opposing views lead to quite different concepts of the antiquity of the abyssal fauna.

The available data suggest that abyssal depths are populated with recent as well as ancient types of organisms and also that the abyssal fauna is far more diverse than has been previously recognized. Arguments are presented in support of the validity of oxygen isotope measurements on benthic Foraminifera from abyssal sediments.

A plea is made for careful, critical studies on the zoology, paleontology, and geochemistry of long cores of submarine sediment as a means of obtaining additional evidence for the understanding of the present composition of the abyssal fauna.

Using box models, and the observed distribution of temperature, salinity and radiocarbon estimates are made of the origins and rate of flow of waters that make up the Common Water in the Pacific and Indian Oceans, and Antarctic Intermediate Water. Difficulties in extending the computation to Antarctic Bottom Water are described. Emphasis is placed upon questions of computational reliability and the occurrence of ‘ill-conditioned’ equations.

Oxygen isotopic analysis of Upper Cretaceous belemnites from Alaska and Siberia gave temperatures of about 14°C. Similar measurements on shells of calcareous benthonic Foraminifera from sections of Globigerina-ooze sediments of Tertiary age from the eastern equatorial Pacific gave a temperature of 10·4°C for the Middle Oligocene, decreasing to 2·2°C in the Late Pliocene. Thus, a temperature decrease of both surface water at high latitudes and abyssal-hadal water in open oceanic basins, amounting to about 12°C, appears to have occurred during the past 75 million years. This temperature decrease was probably not linear with time and, although very slow, may have had an important effect on the abyssal and hadal fauna. By comparison, temperatures similar to the present ones may have obtained throughout geologic time in at least some portions of the equatorial thermosphere. If constant temperature is more important for the survival of archaic forms than other factors, the equatorial pelagic fauna should show more archaic affinities than other marine faunas.

Data from a month of continuous surface observations across the Gulf Stream show a periodic time variation in the position of the current. The region studied is off Onslow Bay, North Carolina, where the current is close to the edge of the continental shelf. The dominant periods of the position variations correspond to the periods of the offshore winds, but no physical connection is apparent. The amplitude of these dominant variations, or meanders, is 10 km. Lunar components, either monthly or diurnal, have amplitudes which are, at most, small in comparison with those of the principal meanders.

Although the meanders off Onslow Bay may be analogous to the multiple currents found downstream, their periods eliminate them as incipient forms of the large-scale meanders. An average section of velocity and temperature during the month of observation is presented.

The geostrophic current components and the volume transports have been calculated under assumptions of three different reference levels. These computations are based on hydrographic sections obtained in April, 1930 by the Discovery II and in June 1958 by the Ob. Some evidence is presented for the possibility that a bottom current through the Drake Passage penetrates into the Pacific Ocean. The analysis suggests that the geostrophic transport of the Antarctic Circumpolar Current in this region is probably limited by 90 × 10⁶ m³ sec⁻¹ as an upper value and 45 × 10⁶ m³ sec⁻¹ as a lower value and that the actual transport is likely to be somewhere between these limits.

Cellulose acetate butyrate (CAB) core liners lose water through pores in the plastic. A wax bath has been developed to coat liners with a microcrystalline wax to retard water loss. Sealing properties of this wax are compared with those of paraffin and a combination of aluminum foil and microcrystalline wax. Over a 50-day period uncoated liners lost water at an average rate of 21·1 × 10⁻⁴ g/day/cm² of surface area, while liners coated with microcrystalline wax or with paraffin lost less than 3·3 × 10⁻⁴ g/day/cm². Liners coated with foil and wax did not lose water during the test.

Boron in the Gulf of Mexico, in the forms of total, inorganic and organic complexes, was evaluated using a mannitol titrometric method. Definite correlation between inorganic boron and chlorinity was observed for sea water, both vertically and horizontally, except in the oxygen minimum region. Similar, but less-defined correlation, is found to exist between the organic boron complexes and oxygen distribution.

A preliminary investigation using boron-chlorinity ratios for identification of water masses and possible detection of circulatory patterns was made on the deep water of the Caribbean. Data from the Venezuela, Columbia, Cayman, and Gulf basins all showed conservative boron-chloride ratios. Analysis of the data indicates a uniformity of deep basin waters of the American Mediterranean Sea, which suggests the existence of a single source of deep water or uniform mixing between the basins.

To arrive at an estimate of the role of the thermohaline circulation in the oceans, the magnitude and the implications of the various thermohaline effects are discussed numerically. From a consideration of the heat balance of the surface layer in lower latitudes it follows that the average ascending motion through the thermocline is limited to between 1 and 5 × 10⁻⁵ cm/sec. The discussion of the thermocline suggests a resultant downward heat flow in spite of the ascending motion, which is balanced by horizontal advection. A method for the calculation of the vertical exchange coefficient is given and shows that it has a pronounced minimum in the discontinuity layer. The discussion of the sinking processes of the Bottom Water and the Intermediate Waters indicates the existence of two nearly independent circulation systems in meridional direction. The deep meridional spreading of the different water masses cannot be explained satisfactorily by a two-layer model, but a four-layer model would be required. A model of a pure thermohaline circulation in an ocean covering the entire earth including frictional terms shows that a circumpolar current would exist in each hemisphere, carrying 134 × 10⁶ m³/sec, but that the strength of the meridional circulation across 45° latitude would be only 10 × 10⁶ m³/sec. This indicates that also in the actual ocean the thermohaline circulation can only be weak and its strength must be less than that of the wind driven circulation. In a detailed study of the deep circulation its influence, however, cannot be completely disregarded. A four-layer model of the wind driven and thermohaline circulation in a meridional plane is constructed, its implications are discussed and the results are found in agreement with the circulation pattern resulting from water mass analysis.