Deep Sea Research (1953)最新文献

A gently rolling surface of very soft folded sediment lies at the anomalously shallow deep-sea depth of 1900 fathoms east of Guadalupe Island. Sub-bottom echoes occur at a uniform depth of 6–8 metres over most of the area and photographs reveal organisms vigorously reworking much of the upper ten centimetres of sediment. At present, the region is surrounded by a deeper sea floor and cannot receive bottom-transported sediment. The origin of this anticlinorium is indeterminate. Geomagnetic profiles reveal north-south anomalies which are typical of the oceanic crust of the northeastern Pacific Ocean basin and which parallel the folds though are not necessarily related to them. Large tectonic features surround the area such as volcanoes, ridges, basins and deeps. Compared to these features, it is relatively deformed and appears to have a normal oceanic crust because it has (1) a long depositional history, (2) north-south magnetic anomalies and (3) a normal thickness.

The inductive salinometer is an instrument for measuring the salinity of sea water to an accuracy of approximately 0·003 parts per mille. The instrument is portable and does not require a temperature-controlled bath for the samples. The general design and operation of the instrument are described, and test results are summarized.

The magnetisation of a ship may be divided into a permanent and an induced part. If the induced part is a linear function of the field components and the permanent part is independent of them, the disturbance of the total force by the ship contains a term independent of magnetic heading and terms proportional to the sine and cosine of the heading and of twice the heading, the sine terms being less than a tenth of the cosine terms.

The variation with distance astern of the ship is similar to that due to a pole near the bow and one near the stern plus a line of vertical dipoles.

These results are verified by experiment. The disturbance of the field by Discovery II and by Sarsia is less than 10 γ at a distance of 2 ship's lengths astern. It is believed that this result will hold for most ships. A method for the determination of the principal coefficients and their variation with distance is described.

The effects of enriching surface water samples from the Sargasso Sea upon the rate of C¹⁴ assimilation was investigated. The addition of nitrate, phosphate and vitamins, added separately or in combination, had no stimulatory effect, while addition of a trace metal mixture increased C¹⁴ uptake by several-fold. The effective component of the trace metal mix found to be iron, which alone enhanced C¹⁴ uptake for 24 hours but which required the addition of nitrogen and phosphorus to produce a comparable effect of over a three-day period.

Net and gross primary production, measure at two-week intervals over a period of three years, show annual variations during the winter period (November–April) which are directly related to the degree of mixing of the surface water and may be directly attributed to the severity of the winter as revealed by air temperature and wind strength. Seasonal and year-to-year changes were observed in the ratio net : gross production, as indicated by changes in the relationship between C¹⁴ assimilation and chlorophyll.

A simple means of recording hydrophone depth by connection into an echo-sounding system is described. The small corrections occasionally necessary and the practical working of the system are discussed.

The quantitative distribution of heterotrophs in the water column of the Atlantic Ocean between Greenland and the Tropic of Capricorn (along 30°W), in the Norwegian, and in the Greenland Seas was studied. In the tropics the abundance of micro-organisms which assimilate slightly decomposed, non-humus organic matter is great, while in the subarctic and arctic areas it is low.

Equatorial-tropical water, rich in heterotrophs, was identified in the subatropic and subantarctic zones of the Atlantic Ocean, in the Norwegian and in the Greenland Seas at various depths. It occurred not only down to 1000 m but also much deeper at 2000–2500–3000 m.

Judging by the finding of equatorial-tropical water layers or ‘islands’ in the Atlantic Ocean, in the western Norwegian Sea and in the Greenland Sea at the same levels, it may be supposed that the circulation of these waters at certain depths is stable over extensive areas.

Most of the Atlantic Water (along 30 °W) from Denmark Strait to the Tropic of Cancer, is of arctic origin, i.e., water with few heterotrophs. These waters penetrate into the tropics and cross the equator. However, in the equatorial-tropical zone they do not form as thick a layer as Defant (1957) estimates.

Microbiological data indicate that waters in the equatorial-tropical zone of the Atlantic are significantly enriched by slightly decomposed, non-humus organic matter. In this respect they are similar to the Equatorial Water Masses of the Indian and Pacific Oceans. They, therefore, cannot be considered as merely transitional between the Central Water Masses of the northern and southern Atlantic.