Deep Sea Research and Oceanographic Abstracts最新文献

Measurement of the activity of dissolved oxygen based on its rate of reaction with the excited singlet state of pyrene-1-butyric acid indicates that it is not changed by hydrostatic pressures up to 1000 atm. The partial pressure of dissolved oxygen will thus have the same relation to concentration at abyssal depths as at the surface.

The regional coverage of Lamont nephelometer data in the North and South Atlantic can be used to map seawater turbidity at all depths. At the level of the clearest water, in the mid-depth regions, the turbidity distribution primarily reflects the pattern of productivity in the surface waters. This suggests that the ‘background’ turbidity level in the oceans is largely a function of biogenic fallout. The bottom waters of the western Atlantic generally exhibit large increases in turbidity. The most intense benthic nepheloid layers are in the southwestern Argentine basin and northern North American basin; the lowest bottom water turbidity in the western Atlantic is in the equatorial regions. Both the Argentine and North American basin bottom waters appear to derive their high turbidity largely from local resuspension of terrigenous input in these basins. In contrast to the west, the eastern Atlantic basins show very low turbidities with the exception of three regions: the Mediterranean outflow area, the Cape basin, and the West European basin.

Depth soundings before and during the Mid-Ocean Dynamics Experiment (MODE-I) are integrated to produce bathymetric charts of the MODE-I region at scales of 1:500,000 and 1:250,000. Seven undersea features are named. The southwestern portion of the Bermuda Rise is characterized by rugged bottom topography generally striking north-northeast to south-southwest. Southeast of the Blake Bahama Outer Ridge, a zone of morphology paralleling the regional contours of the lower continental rise and associated deeps along many of the steep slopes on the Bermuda Rise suggest that the submarine terrain may be influenced by erosion by bottom currents.

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.

Horizontal and vertical diffusion coefficients are calculated by fitting different types of diffusive-advective models to the scales of a specified anomaly in the salinity field near the Subtropical Convergence. Comparison of the calculated coefficients with those in the literature reveal the balance in the mixed layer near the convergence is between horizontal diffusion and northward advection. Below the mixed layer at the convergence the balance is between southwards and upward advection and mainly horizontal diffusion. A tongue of saline water extends south from the convergence with its core at a depth of about 100 m. The balance in this tongue is consistent with a uniform slow northwards flow with parabolic shear and horizontal and vertical diffusion.