Hydrographic section with closely spaced stations, occupied in the southern Weddell Sea during the International Weddell Sea Oceanographic Expedition aboard the USCGC Glacier in austral summer 1973, were used to investigate the mixing in the frontal zone near the shelf break. The Warm Deep Water is modified by mixing with Winter Water before it intrudes on the shelf. This Modified Warm Deep Water then mixes with highly saline Western Shelf Water to form cold Weddell Sea Bottom Water. Formation of bottom water probably takes place on the southern shelf of the Weddell Sea west of somewhere between 29 and 40°W. The classically defined Antarctic Bottom Water forms when the Weddell Sea Bottom Water mixes with the Warm Deep Water above as it flows out of the sea to the east.
The spectra of either temperature, salinity or vertical velocity which might be measured by a sensor moving through a field of salt fingers are considered. A theoretical calculation is presented which attempts to incorporate the deviations from squareness and perfect orientation of the salt fingers. The resulting spectra rise to a peak close to ω = (√2)kv and decrease rapidly for larger ω, where ω is the temporal frequency of the spectrum, k the dominant wave number of the salt fingers and ν the horizontal velocity of the sensor. A spectrum of vertical velocity of laboratory-generated salt fingers is shown to be in close agreement with the theoretical prediction.
Field studies and tow basin experiments of Longhurst-Hardy Plankton Recorder (LHPR) biases were conducted by injecting various types of particles into an LHPR having a variety of net and recorder box configurations. Tow speed and clogging were also considered. The following factors contributed to biases: (1) low recorder gauze aperture area to throat area ratios, causing backing up of flow into the net cod end, (2) tunnel gauze slot design, allowing significant losses of particles; (3) steep side angles of the net at the recorder entrance due to bagging or radial stretching; (4) clogging of the neta head of the LHPR; (5) short nets; and (6) tow speeds greater than about 125 cm s−1. Experiments with an LHPR modified to minimize biases showed that resolution to 15 m in oligotrophic waters is possible. In eutrophic waters, we doubt it is feasible to use a net with the LHPR.
Thin-film X-ray fluorescence, using an energy dispersive system, allows for the determination of the major rock-forming elements (Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe) in suspended phases of marine particulate matter. The method is rapid, non-destructive, entails no pre-analysis treatment of the sample, and requires as little as 25 to 50 μg of sample. Particulate samples for this and other analyses are filtered quickly and without post-collection transfer of the water sample by a simple pressure filtration technique employing standard plastic sampling bottles.
Phytoplankton net samples from all oceans were examined by advanced light microscopy or electron microscopy for the presence of 26 diatom species, and the records plotted on eight distribution maps. Some of the species are classified as cosmopolitan, some as warm-water species and some as cold-water species. The cold-water species belong either to the Northern Hemisphere or to the Southern Hemisphere, or are suggested as being bipolar, having a disjunct distribution. Some of the smallest marine planktonic diatoms collected have a cosmopolitan distribution. Thalassiosira species, forming gelatinous masses, seem to be most prominent in coastal waters where upwelling occurs. The distribution patterns of T. gravida and T. rotula indicate that they may be modifications of the same species. The finding of morphologically and taxonomically closely related species in distinctly different biogeographic regions emphasizes the importance of reliable identification at the specific level.
Temperature and temperature-gradient records made as a freely-falling probe hit bottom show an extremely well-mixed layer on the Oregon continental shelf in September, 1974. Temperatures were uniform to within a few millidegrees in a 10-m deep layer. A reverse gradient of one to four times the adiabatic was found in the last 5 m or so, larger than the geothermal flux could maintain. The layer depth is similar to that of a turbulent Ekman layer. On vertical temperature-gradient spectra several subranges are seen. Estimates of eddy diffusivity by the Cox-Osborn-Hacker method agree within a factor of two with estimates calculated from the level of an assumed inertial sub-range in temperature gradient spectra. Possibly the layer is stabilized by a salinity gradient too small to be observed by the conductivity-temperature-depth probe, or by sediment load. Calculations of heat flux caused by the thermal storage of the sediments yield a flux of the correct order, but the opposite sign, of the calculated flux.
The formation and exchange of deep water in the Greenland and Norwegian seas are modeled by a time-dependent box model. Using tritium and radiocarbon data, primarily from the Geochemical Sections (GEOSECS) 1972 operation, the time scale for deep convective mixing in the Greenland Sea is estimated to be about 30 years, which implies that about 100 m of surface water are mixed down annually. The time scale for exchange between the deep Greenland Sea and the deep Norwegian Sea is estimated to be at least 100 years. It appears, on the basis of tritium data, that the formation and exchange of deep water in the Greenland and Norwegian seas are essentially isolated from the formation of the dense overflow waters of the Denmark Strait and the Iceland-Faroe Passage.
The authors conducted a detailed quantitative analysis of dissolved and particulate hydrocarbons in the surface microlayer of the oceans, sampled by a metallic screen, with respect to the underlying water. The n-alkane content varies from 0.11 to 5.66 μg 1−1 in the underlying water: much higher concentrations are encountered in the microlayer, reaching as high as 1200 μg 1−1. On the average, the n-alkanes account for 10% of total hydrocarbons in the underlying water and 15% of these in the surface microlayer. The hydrocarbons are in general of biological origin (distribution of n-alkanes centred around n C27 to n C29, approaching that of algae). Of note is the contribution of petroleum pollution. The remarkable fact is the accumulation of hydrocarbons in the surface microlayer, with an enrichment factor averaging 50.
-A technique for the objective analysis of oceanic data has been developed and used on simulated data. The technique is based on a standard statistical result--the Gauss-Markov Theorem--which gives an expression for the least square error linear estimate of some physical variable (velocity, stream function, temperature, etc.) given measurements at a limited number of data points, the statistics of the field being estimated in the form of space-time spectra, and the measurement errors. An expression for the r.m.s, error expected in this estimate is also derived and illustrated in the form of 'error maps'. Efficient sampling arrays can be designed through trial-and-error adjustment of array configurations until a suitable balance of mapping coverage and accuracy, as measured by the error maps, is achieved. Examples of the mapping ability of some simple arrays are given. Using statistics inferred from the preliminary Mid Ocean Dynamics Experiments various realizations of likely flow fields were simulated. The 16 element MODE-I array was tested by comparison of the simulated fields and the objective maps based on inferred 'measurements' at the array points. The reliability of statistics inferred from observations was estimated by comparing correlations derived from limited observations of the simulated fields with the known statistics. Correlations derived from two realizations differed significantly but most calculations reproduced the known statistics moderately well. An intercomparison of Eulerian measurements (current meters) and Lagrangian measurements (neutrally buoyant drifters) was also carried out using the objective interpolation method.
On a cruise of the R.V. Meiring Naude´, wave records wer taken in and ou the Agulhas Current. These have been analysed using the standards methods of spectral analysis and the energy increase in a frequency band from 0.067 to 0.02 Hz determined. Rough agreemeent with theory is found up to maximum current speeds of 1.6 m s−1.
Current observations at the southeastern edge of the Faroe-Shetland Channel, north of Scotland, have been used along with hydrographic measurements to investigate the transfer of ‘Atlantic’ water on to the continental shelf. Although currents are predominantly parallel to the bottom contours, the observations suggest that cross-slope currents of about 2 cm s−1 can be generated at the shelf break by disturbances propagating along the channel from the southwest.
Two Pacific Ocean manganese nodules, one from the ocean basin and one from a sea-mount, were examined in transmission electron microscopes at 100 and 650 kV. Of the many specimens examined, ten electron diffraction crystal spot patterns were identified. Sodium birnessite was observed six times and todorokite, Giavanoli's synthetic birnessite, hydrohausmanite and γ-Fe2O3 one time each. Ferric hydroxide was synthesized in the laboratory and shown to be the same as the primary iron mineral observed in the manganese nodules. The ferric hydroxide had a particle size range from 30 to 450 Å. Manganese oxide particles were frequently embedded in a mass of smaller ferric hydroxide particles.
Deep western boundary currents are wider by about an order of magnitude than such currents of the upper water as the Gulf Stream. Their structure is discussed here within the framework of a linear, continuously stratified model with lateral diffusion of density and momentum. They are treated as boundary layer corrections to interior fields, where the interior field is presumed given by observation, and the density-depth variation at the western boundary is taken (also from observation) as a prescribed boundary condition. A level bottom is assumed. For parameter values appropriate to the deep ocean, the lateral diffusion of density severely limits the geostrophic velocities and thus requires a relatively broad flow field. For a mixing coefficient of 1·2 × 107 cm2 s−1 and suitable boundary conditions, a detailed calculation for the deep current at Lat. 28°S in the western South Pacific reproduces the scale and other gross features of the density field there and accounts qualitatively, in terms of the associated flow field, for prominent features in the distributions of dissolved oxygen and silicate.
This is the first known report of the midwater capture of a species of macrourid that lives on the abyssal plain. Four Coryphaenoides filifer were caught in an Isaacs-Kidd midwater trawl over 500 m above the 2700- to 2800-m sea floor in the northeastern Pacific Ocean off central Oregon. Such behavior helps to explain the presence of pelagic organisms in the stomachs abyssobenthic macrourids and may accelerate transport of energy and elements to the deep-sea benthos.
A complete set of linearly independent relationships among the different cross spectral components obtained from pairs of moored instruments is derived which can be utilized to test whether or not the observed fluctuations within the internal wave frequency band represent a field of propagating internal waves. A further complete set of relationships is derived which enables to test whether or not the internal wave field is horizontally isotropic and (or) vertically symmetric. These relations are compared with corresponding relations for alternative models (standing internal wave modes, three-dimensional isotropic turbulence) and their capability to discriminate between the various models is investigated. The tests are applied to a set of data for which it is found that the observed fluctuations are consistent with both propagating and standing internal waves whereas isotropic turbulence must be rejected for the most part of the internal wave frequency band.
A formula for the conversion of in situ measurements of conductivity to salinity suitable for use with small computers or calculators is presented which agrees with the UNESCO International Oceanographic Tables for converting conductivity ratio to salinity at 15°C and atmospheric pressure. The formula is applicable over the range of conditions found in most of the world's seas and oceans. The accuracy is estimated as 0·0042‰ r.m.s., but the possibility remains that there may be systematic errors as great as 0·01‰
An analytical model for the interaction of a broad, eastward baroclinic current with shallow topographic features in an unbounded β-plane ocean is developed and solved for three types of topography: a meridionally oriented ridge as is found in the central South Pacific and South Atlantic sectors of the Southern Ocean, a zonally oriented ridge as is found south of Australia and Africa, and an isolated plateau or seamount. The meridional ridge causes a stationary wave pattern similar to that believed to occur in the southeast Pacific Ocean. The zonal ridge causes a current intensification on the equatorward side of the ridge crest, with intermittent slowed or reversed flow and a string of stationary warm core eddies on the poleward side. Comparison is made to Callahan's (1971, Journal of Geophysics Research, 76, 5859–5870) observations of the flow along the ridge south of Australia. The isolated seamount forces a Taylor column (warm core anticyclonic eddy) above it, and has a stationary meandering wake downstream, sometimes with embedded eddies.
In four sedimentary environments off North Carolina 209 species of free-living marine nematodes were identified. Of these, 106 were restricted to one of four habitats. Clayey-silts (800 to 2500 m) contained the most stenotopic species (49). Quartz-algal sands (50 to 100 m) contained 35, foraminiferan sands (250 to 500 m) 17, and sandy silts (500 to 800 m) only 5 stenotopic species.
Current-meter observations near 39°N, 70°W, on the continental rise, provide evidence that the motions with periods of 1 to 2 weeks are dominated by baroclinic topographic Rossby waves which decay upward from the bottom. Temperature and up-slope velocity are coherent and in quadrature at these frequencies, as predicted. The kinetic energy structure versus depth is consistent with horizontal wavelengths of 100 to 200 km. The spectra drop abruptly for periods shorter than a week, the shortest period the model says the slope and stratification around Site D can maintain. The principal axis of the velocity shifts from nearly perpendicular to the isobaths at 1-week period to nearly along the isobaths at long periods, in satisfactory quantitative agreement with the model.
Employing the Knudsen-Ekman formulation for specific anomaly, a five-term expression is found relating depth and pressure in the ocean. The first four terms provide the conversion in a standard ocean and the remaining term is proportional to the dynamic height anomaly in the water column. In the conversion the importance of the variation of gravity with both latitude and depth is illustrated.
