Deep Sea Research and Oceanographic Abstracts最新文献

Heat balance studies of the upper ocean layer require knowledge of the upwelling and downwelling irradiance through depths of interest: this requires an instrument with a flat spectral response. Measurements were made using commercially available pyranometers, but their glass domes produced large immersion errors (≈ 65% reductions) and careful calibrations were made to correct for this and also verify the cosine response of the pyranometers when underwater. Sample data obtained by towing uplooking and downlooking pyranometers on a sled at 5-m depth are given.

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.

Data obtained from the U.S. Coast Guard Environmental Buoy EBO-1 for the period of January 1971 to June 1972 are analyzed. The buoy, off the Virginia capes at approximately 36°30′N and 73°30′W, radioed hourly meteorological and oceanographic data to a shore station. Identification of water types at the buoy has been made by comparing the transmitted data with temperature-salinity diagrams. Concurrent observations of lateral shifts in the position of the Gulf Stream show a close correlation with changes in the amount, direction, and temperature-salinity characteristics of the flow at the buoy.

Six basalt samples from Josephine Seamount were dated by the K–Ar method. Their age ranged from 8 to 13 m.y. with increasing water depth. The Quaternary (and possibly Neogene) age of sediments overlying the basalt does not contradict those apparent ages.

Two basalt samples from the flank of the Great Meteor Seamount yielded ages of 11 and 16 m.y. Surf-rounded basalt pebbles with pocket-fillings of shallow-water limestone show that after the end of volcanic activity the basalt presently found at a water depth of about 600 m was only a few meters below sea level. Those data and assumptions about the age of underlying oceanic layer 2 (80 m.y.) allow inferences on the minimum volcanic production of Great Meteor Seamount (3.5 × 10⁵m³yr⁻¹). The volcanic activity of many eastern Atlantic seamounts ended about 10 m.y. ago.

Measurements from arrays of moored current meters taken during the Mid-Ocean Dynamics Experiment (MODE) are analyzed, using short-term spectral analysis. A weak variability in space and time is detected in the internal wave continuum, as well as some horizontal anisotropy. It is suggested that the observed anisotropy is induced by the weak interaction between internal waves and mesoscale motions in a manner consistent with the weak interaction theory of $\text{>u}\text{̈}$ (Hamburger Geophysikalische Einzelschriften23, 1974). The interaction appears to be essentially local in space and time. It is shown that the internal wave continuum contributes positively to the horizontal diffusion of mean flow momentum, and is characterized by a relaxation time of the order of 1 to 4 days in the vicinity of the main thermocline. From observed correspondences between the fluctuations in total internal wave energy and square mean vertical shear, an estimate of the vertical eddy viscosity v_ν induced by internal waves is attempted, suggesting a large value for v_ν in the mid-ocean thermocline, maybe as high as 10³ cm² s⁻¹.

The geographic variations in the oceanic baroclinic eddy field intensity, as indicated by the structure function of the dynamic height across the thermocline after seasonal and large scale trends are removed, is examined using historical data from the North Atlantic and North Pacific oceans. An inverse relationship between eddy field intensity and distance from the western boundary current is found in each region, confirming that the western boundary currents are major energy sources for baroclinic eddies in mid-ocean regions. Eddy energy is largely confined to the northern and western areas of the North Atlantic and North Pacific sub-tropical gyres, with significantly reduced energy levels both in the eastern areas and north of the Sub-Arctic Frontal Region. Dominant eddy field length scales of energy variability consistent in magnitude with those of more recently observed eddies also are confirmed for the North Pacific. Spatial statistics similarly computed from selected Mid-Ocean Dynamics Experiment (MODE-I) hydrographic data are consistent with those determined from the historical data. The statistical characteristics of the structure function are evaluated empirically to estimate the confidence levels of the historical data statistics.