DEEP CIRCULATION IN THE EASTERN SOUTH-ATLANTIC OCEAN

被引:56
作者
WARREN, BA [1 ]
SPEER, KG [1 ]
机构
[1] WOODS HOLE OCEANOG INST,WOODS HOLE,MA 02543
来源
DEEP-SEA RESEARCH PART A-OCEANOGRAPHIC RESEARCH PAPERS | 1991年 / 38卷
关键词
D O I
10.1016/S0198-0149(12)80014-8
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
Tracer properties on sections of closely spaced hydrographic stations across the Angola Basin of the South Atlantic Ocean along Lats 11-degrees and 24-degrees-S suggest a three-layer description of the deep circulation there. Below 4 km the basin is closed off in the south, so water enters only from the north; the interior flow is southward, and the western-boundary current (above the eastern flank of the Mid-Atlantic Ridge) is southward at 11-degrees-S, but northward at 24-degrees-S, as required by the Stommel-Arons dynamics. At depths roughly between 2400 and 4000 m the basin seems to be supplied only from the south, the western-boundary current is everywhere northward, and the interior flow is southward. Near the 2-km level the Mid-Atlantic Ridge is too deep to be an effective western boundary; the flow seems to be broadly southeastward across the full basin at 11-degrees-S, but at 24-degrees-S a topographically guided current flows northward above the ridge to supply southward interior flow. A hydrographic section along the Greenwich meridian illustrates an eastward jet at depths between 1300 and 3200 m that extends near Lat. 22-degrees-S from the western-boundary curent to a gap in the Walvis Ridge, through which the jet introduces water to the Cape Basin. Geostrophic estimates of the volume transports of these circulation elements, calculated with reference to zero-velocity surfaces construed from the tracer fields, are consistent in direction with the inferred flow patterns, but the values may be somewhat erroneously high, as they imply dubiously large upward velocities. A tongue of oxygen-poor, nutrient-rich water is found at depths between 3000 and 4500 m at 11-degrees-S but not at 24-degrees-S. It is strongest at the African continental rise, and extends some 1000 km westward. Its origin is attributed to decay within the sediment of detritus originating mainly from the Congo River plume, and its form to the deep horizontal flow field.
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页码:S281 / S322
页数:42
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