Deep Sea Research (1953)最新文献

The oceanography of the Greenland-Norwegian Sea which was described by Norwegian oceanographers in the early part of the present century is reviewed in the light of recent winter data.

The dynamic topography and two-hundred metre temperatures indicate a circulation generally similar to that given in the earlier descriptions except that the cyclonic movement in the Norwegian Sea appears to be further west and the Norwegian Current appears to be much broader than it was previously considered to be.

Deep water identical to that of the Norwegian Sea and appreciably warmer than that of the Greenland gyral core lies on at least three sides of that gyral, and it is suggested that this is the major source of Polar Basin deep-water. It is probably formed within the Norwegian gyral. Deep-water in the Greenland-Norwegian Sea may not be formed each winter but only during particularly cold seasons. Deep-water which is formed within the Greenland gyral eventually loses its cold identity through gradual mixing with the surrounding water from the Norwegian gyral.

A temperature-depth diagram demonstrates two distinct types of intermediate and deep-water as well as two groups of stations showing some of the characteristics of each type within a single water column. Bottom topography is believed to play a significant role in the distribution of this type of station.

Further field studies, especially in the western part of the Greenland Sea, are needed to fill the large gaps in our knowledge of the circulation pattern.

Measurements of surface light intensity, water transparency and concentration of chlorophyll a were made in the northern coastal waters of South America during October and November 1958. Phytoplankton collections were made simultaneously. The highest gross production rates were encountered in the Gulf of Cariaco (3·75 g C/m²/day), over the Cariaco Trench (2·30 g C/m²/day), in Lake Maracaibo (1·23 g C/m²/day) and the Gulf of Venezuela (1·20 g C/m²/day). Upwelling appears to be the source of nutrients for production in the Gulfs of Cariaco and Venezuela. This relationship is less well established over the Cariaco Trench. High silt concentrations limit light for photosynthetic production in the Gulf of Darien, at the mouth of the Magdalena River and to the east of Margarita Island. Phytoplankton reduces materially the light available for photosynthesis in Lake Maracaibo.

The 1958 survey provided the data for a preliminary synoptic study of the complicated dynamic phenomena of the Strait of Gibraltar. For this purpose, attention was focused near the boundary surface of the deep layer of pure Mediterranean water east of the sill. West of the sill this dense layer loses its character in a process of turbulent mixing with the lighter Atlantic water.

The survey of the thermal microstructure of the sill area was made possible by the use of the new towed thermistor chain of the Woods Hole Oceanographic Institution (Richardson and Hubbard 1959). In 66 crossings of the Strait (north to south) above the sill and one passage (west to east) along the axis, the following were the most interesting findings:

• 1.

  (1) - The boundary between deep Mediterranean water and Atlantic water oscillates vertically with tidal periods.

• 2.

  (2) - The boundary layer was found to slope down sharply at the centre of the channel at the time of internal high tide.

• 3.

  (3) - Vertical motions of the isotherms of semi-diurnal period and in phase with the moon transits were dominat.

• 4.

  (4) - Fluctuations of high amplitude and non-tidal period were superimposed on the dominant motions.

• 5.

  (5) - Solitary rapid depth variations of some isotherms were recorded more frequently over the southern portion of the sill. The maximum depth change recorded was 80 m.

• 6.

  (6) - The surface temperature is warmer on the Spanish than on the African side of the Strait. A four degree Centrigrade difference was found at one time along the four-mile long transverse above the sill.

Total phosphorus was determined on some 170 samples from eleven stations in the Bering Sea, the Aleutian Trench, and the Gulf of Alaska. Samples ranged in depth from the surface to 7000 m. In these samples organic phosphorus, estimated as the difference between total and inorganic phosphorus, bears an inverse relationship to the distribution of inorganic phosphorus. Surface waters, generally low in inorganic phosphorus, contain up to 1·0 μg. at./L organic phosphorus, with a grand average of 0·27 μg. at./L for the upper 200 m. The amount of organic phosphorus present in surface waters reaches values as high as 47 per cent of the total. On the other hand, waters below about 200 m. have little or no measurable amounts of organic phosphorus. In its vertical distribution, total phosphorus varies at the most by a factor of three and is more or less uniform with depth compared to the inorganic phosphorus. Inferences are drawn concerning the nature of organic matter and the state of organic phosphorus in deep waters. The observed distribution of various forms of phosphorus substantiates the theory that the major part of the phosphorus cycle is enacted in the surface layers.