Satellite infra-red images in the Agulhas Current System

Harris, T.F.W.; Legeckis, Richard; Forest, D. van

doi:10.1016/0146-6291(78)90642-2

Cited by 73 publications

(23 citation statements)

References 6 publications

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“…18). Along the eastern edge of this bank the Agulhas Current starts to develop meanders (Harris et al, 1978) very similar to those found on the comparable Gulf Stream. These meanders have been shown to grow downstream (Lutjeharms et al, 1989b) and have attendant cyclonic eddies and warm water plumes.…”

Section: Southern Agulhas Currentmentioning

confidence: 75%

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Three decades of research on the greater Agulhas Current

Lütjeharms

2007

Ocean Sci.

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Abstract. The greater Agulhas Current has been shown to be a key link in the global thermohaline circulation and an increased understanding of this current system is therefore of more than just local interest. Knowledge on the Agulhas Current system has in fact increased enormously over the past 30 years. This review covers some aspects of what has been learnt on the northern and the southern parts of the Agulhas Current proper and their influence on the waters and circulation of the adjoining continental shelf. It also discusses the Natal Pulse and new information that has been gained on how it is triggered and what influence it has. It deals with the Agulhas retroflection, the shedding of Agulhas rings and the movement and characteristics of these rings that contributes to the meridional overturning circulation of the global ocean. The Agulhas Return Current forms part of the final outflow of the system and current knowledge on that current is appraised. The sources of the Agulhas Current have been a controversial subject for many years and this dispute continues. This is described and discussed, based on what information has been gained from research over the past three decades. Building on what is currently known, some suggestions are given on the most important remaining knowledge gaps and how these could most efficaciously be filled.

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Section: Southern Agulhas Currentmentioning

confidence: 75%

“…With the advent of satellite remote sensing it was soon discovered (Harris et al, 1978;Lutjeharms, 1981) that the Agulhas Current can be considered to consist of a northern Agulhas Current and a southern Agulhas Current. These two parts have distinctly different trajectorial behaviours.…”

Section: Agulhas Currentmentioning

confidence: 99%

Three decades of research on the greater Agulhas Current

Lütjeharms

2007

Ocean Sci.

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“…Although sample collection over a large area was limited to the surface using a relatively coarse station grid, the information obtained suggests that coccolithophores reflect the general oceanographic environment, and can thus supplement other methods such as buoy drift experiments (Grundlingh, 1977;Grundlingh & Lutjeharms, 1979) or satellite image methods (Harris et al, 1978), in determining hydrographic regimes. …”

Section: Discussionmentioning

confidence: 98%

“…This situation is thought to have been relatively stable since the MioceneiPliocene boundary ( 5 my Bp, Martin, 1981). South of 34" S, the current diverges from the continental shelf edge and turns east at about 15"E to form the Agulhas Return Current (Grundlingh, 1977;Harris et al, 1978). The interaction of the western boundary currents with the upwelling regime occurring around the south and southwest coast produces a region of complicated dynamic interaction and eddy formation (retroflexion regime) that is in a continuous state of flux (Lutjeharms, 1981).…”

Section: Oceanographymentioning

confidence: 98%

Distribution of modern coccolithophore assemblages in the southwest Indian Ocean off southern Africa

Friedinger¹,

Winter²

1987

J. Micropalaeontol.

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Abstract. Living coccolithophore assemblages were investigated in 35 surface water samples taken from the Natal Valley (southwest Indian Ocean) in January and November, 1983 and February, 1984. Fifty-nine species were recognised using a scanning electron microscope (S.E.M.). Cluster analysis revealed four different species assemblages dominated by Emiliania huxleyi, Umbilicosphaera hulburtiana, Umbellosphaera tenuis and Gephyrocapsa oceanica. Significant differences in species composition between the sampling periods are attributed to seasonal fluctuations. The regional distribution of the assemblages reflects two different océanographic regimes: 1) The Agulhas Current, which is a nearly stable feature and 2) the area of the Agulhas Return Current, characterised by rapidly changing hydrographic and ecological conditions.

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“…The magnitude of the transfer between the Indian and Atlantic Oceans in the Agulhas Retroflection region is uncertain and a topic of active debate, as discussed in detail in Section 4. The flow in this region varies on a range of temporal and spatial scales: the retroflection occurs in one of two modes, one at 13°E, or more commonly at 19°E (Harris et al, 1978); the retroflection itself often pinches off to form large eddies, which may drift to the northwest and enter the South Atlantic (Lutjeharms, 1981); and cyclonic eddies are occasionally formed inshore of the current core (Lutjeharms and Baker, 1980). Recently Gordon (1985) has presented evidence of 13.5 Sv of Indian Ocean water entering the Atlantic southwest of Cape Town; depending on the path of the return flow , this could result in a large flux of heat and other properties between the oceans.…”

mentioning

confidence: 99%

Mass, heat and nutrient fluxes in the Atlantic Ocean determined by inverse methods

Rintoul¹

1988

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Inverse methods are applied to historical hydrographic data to address two aspects of the general circulation of the Atlantic Ocean. The method allows conservation statements for mass and other properties, along with a variety of other constraints, to be combined in a dynamically consistent way to estimate the absolute velocity field and associated property transports.The method is first used to examine the exchange of mass and heat between the South Atlantic and the neighboring ocean basins. The Antarctic Circumpolar Current (ACC) carries a surplus of intermediate water into the South Atlantic through Drake Passage which is compensated by a surplus of deep and bottom water leaving the basin south of Africa. As a result, the ACC loses .25±.18x10 15 W of heat in crossing the Atlantic. At 32°S the meridional flux of heat is .25±.19x10 15 W equatorward, consistent in sign but smaller in magnitude than other recent estimates. This heat flux is carried primarily by a meridional overturning cell in which the export of 17 Sv of North Atlantic Deep Water (NADW) is balanced by an equatorward return flow equally split between the surface layers, and the intermediate and bottom water. No "leak" of warm Indian Ocean thermocline water is necessary to account for the equatorward heat flux across 32°S; in fact, a large transfer of warm water from the Indian Ocean to the Atlantic is found to be inconsistent with the present data set. Together these results demonstrate that the Atlantic as a whole acts to convert intermediate water to deep and bottom water, and thus that the global thermohaline cell associated with the formation and export of NADW is closed primarily by a "cold water path," in which deep water leaving the Atlantic ultimately returns as intermediate water entering the basin through Drake Passage.The second problem addressed concerns the circulation and property fluxes across 24°and 36°N in the subtropical North Atlantic. Conservation statements are considered for the nutrients as well as mass, and the nutrients are found to contribute significant information independent of temperature and salinity. Silicate is particularly effective in reducing the indeterminacy of circulation estimates based on mass conservation alone. 2In turn, the results demonstrate that accurate estimates of the chemical fluxes depend on relatively detailed knowledge of the circulation.The zonal-integral of the circulation consists of an overturning cell at both latitudes, with a net export of 19 Sv of NADW. This cell results in a poleward heat flux of 1. 3±.2x10 15 Wand an equatorward oxygen flux of 2900±180 kmol S-l across each latitude. The net flux of silicate is also equatorward: 138±38 kmol s -1 and 152±56 kmol s -1 across 36°and 24°N, respectively. However, in contrast to heat and oxygen, the overturning cell is not the only important mechanism responsible for the net silicate transport. A horizontal recirculation consisting of northward flow of silica-rich deep water in the eastern basin balanced by southward flow of low si...

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Satellite infra-red images in the Agulhas Current System

Cited by 73 publications

References 6 publications

Three decades of research on the greater Agulhas Current

Three decades of research on the greater Agulhas Current

Distribution of modern coccolithophore assemblages in the southwest Indian Ocean off southern Africa

Mass, heat and nutrient fluxes in the Atlantic Ocean determined by inverse methods

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