Southern Ocean Dynamics A Strategy for Scientific Exploration, 1973-1983 (1974) / Chapter Skim
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DYNAMICS OF THE CIRCUMPOLAR CURRENT
DYNAMICS OF THE CIRCUMPOLAR CURRENT
Pages 12-24
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From page 12... ...
PRINCIPAL RECOMMENDATIONS 1. We recommend the initiation of planning for a measurement program, emphasizing presently available techniques, to study the large-scale, transient dynamics of the Antarctic Circumpolar Current (ACC)
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From page 13... ...
The width and intensity of this averaged current was found to vary greatly; constrictions occur south of New Zealand, at the Drake Passage, and near 145° W; the flow is relatively diffuse over the southeast and southwest Pacific basins. Wavelike patterns suggestive of the nonlinear, time-dependent dynamics seen in other currents at temperate latitudes appear to the lee of New Zealand and at 145° W
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From page 14... ...
found from a section across the Drake Passage that the relative pressure field was consistent with earlier measurements of the Soviet research ship Ob and British RRS Discovery and concluded that when the data are treated in the same way, three various sets of historical data (two from the Discovery, one from the Ob) and their own show remarkably similar results: a geostrophic transport relative to the bottom varying from 90 to 110 x 106 m3/s.
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From page 15... ...
by the variable-reference-level technique, this is the first estimate based on direct measurements of a significant westerly transport through the Drake Passage. On the basis of these observations, it is clear that the fundamental vorticity balance of the current involves contributions from several terms: wind stress, bottom topography, curvature, and time dependence.
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From page 16... ...
They discovered that the eastward current that would be produced by the observed surface wind stress is much stronger than observed, unless an unrealistically high value is assigned to frictional dissipation. They suggested that the retarding pressure of submarine ridges balances the stress exerted by the surface wind and that the easterly relative flow is caused by deep water in the Antarctic Ocean drifting toward the axis of the rotating earth.
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From page 17... ...
noted that propagating Rossby waves carrying momentum up-gradient into the weak current will cause baroclinic currents to be sharper where deeper water lies on the left, and he has used this fact to explain qualitatively Callahan's observations that the ACC is sharpest on the steeper slope of the Indian-Antarctic Ridge. Thompson suggests that concentrated currents might also be found at the northern end of the Albatross Cordillera (170° W to 140° W at 60° S)
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From page 18... ...
Such measurements have been of particular importance in local vorticity studies in the Gulf Stream and the Kuroshio Current. The flow patterns thus measured in conjunction with other properties of the current can reveal the relative importance of the bottom topography, timedependence, curvature, and planetary-vorticity terms in the vorticity-conservation equation.
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From page 19... ...
The choice between a linear and a two-dimensional array is to be determined by experience with moored arrays in other strong currents, e.g., the Gulf Stream. Later, more elaborate arrays could be supplemented by continuous vertical profiling instruments and bottom-mounted instruments (e.g., pressure gauges, electromagnetic-field recorders, and acoustic sounders capable of monitoring average properties of the flow)
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From page 20... ...
The flow path exhibits meanders that are superficially similar to those observed in the Gulf Stream or Kuroshio and would best be studied by the combination of techniques used in those areas. Accurate studies of meanders and local vorticity balance require both bottom current-meter arrays and path tracking by ship or airplane.
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From page 21... ...
In view of its importance in resolving the question of pressure gradients across the submarine ridges in the ACC, we recommend a feasibility study on the measurement of absolute dynamic topography on an east-west section from the South Sandwich Trench to the western end of Drake Passage.
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From page 22... ...
Aside from the straightforward extension of sensor ranges and necessary strengthening against ice and heavy weather, the development of sensors carried on in other oceans by other programs appears to be adequate. TABLE 3.1 RECOMMENDED PROGRAM STRUCTURE Dynamics of the Circumpolar Current Experiments and Goals Proposed Experiments and Theory Monitoring Experiments *
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From page 23... ...
,] collaboration 1 KriiKKe Technology v\ Satellite Data Aircraft Data collection Instrument Deployment Begin use I Merge Into International Hi mate Research Effort ^y Apply non-linear, timedependent jet dynanics to ACC Laboratory models of Begin planning use*
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From page 24... ...
1971. Velocity structure and flux of the Antarctic Circumpolar Current south of Australia.
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