The Structure of an East Australian Current Anticyclonic Eddy

Andrews, John C.; Scully‐Power, Paul

doi:10.1175/1520-0485(1976)006<0756:tsoaea>2.0.co;2

Cited by 47 publications

(21 citation statements)

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“…As in the Agulhas case, anticyclonic eddies are detached from the EAC by the pinching-off of poleward meanders. However, in contrast to the present day Agulhas case, the eddies often coalesce with the EAC again (Nilsson et al, 1977;Andrews and Scully-Power, 1976;Nilsson and Cresswell, 1981;Sokolov and Rintoul, 2000).…”

Section: The Glacial-interglacial Hypothesismentioning

confidence: 91%

Agulhas ring injection into the South Atlantic during glacials and interglacials

Zharkov

Nof

2008

Ocean Sci.

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Abstract. Recent proxies suggest that, at the end of the last glacial, there was a significant increase in the injection of Agulhas rings into the South Atlantic (SA). This brought about a dramatic increase in the salt-influx (from the Indian Ocean) into the SA helping re-start the then-collapsed meridional overturning cell (MOC), leading to the termination of the Younger Dryas (YD). Here, we propose a mechanism through which large variations in ring production take place.Using nonlinear analytical solutions for eddy shedding, we show that there are restricted possibilities for ring detachment when the coast is oriented in the north-south direction. We define a critical coastline angle below which there is rings shedding and above which there is almost no shedding. In the case of the Agulhas region, the particular shape of the African continent implies that rings can be produced only when the retroflection occurs beyond a specific latitude where the angle is critical. During glaciation, the wind stress curl (WSC) vanished at a latitude lower than that of the critical angle, which prohibited the retroflection from producing rings. When the latitude at which the WSC vanishes migrated poleward towards its present day position, the corresponding coastline angle decreased below the critical angle and allowed for a vigorous production of rings.Simple process-oriented numerical simulations (using the Bleck and Boudra model) are in satisfactory agreement with our results and enable us to affirm that, during the glacials, the behavior of the Agulhas Current (AC) was similar to that of the modern East Australian Current (EAC), for which the coastline slant is supercritical.

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Section: The Glacial-interglacial Hypothesismentioning

confidence: 91%

Agulhas ring injection into the South Atlantic during glacials and interglacials

Zharkov

Nof

2008

Ocean Sci.

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“…They originate by a 'pinching off' process from warm subtropical waters of the Coral Sea (Nilsson et al, 1977), and migrate slowly southwards as far as the eastern end of Bass Strait (Cresswell and Golding, 1979). Their main structural features are strong surface currents (3.5-4 knots) in the form of a ring, with deep isothermal layers (up to 300 m) in the eddy centre (Andrews and Scully-Power, 1976). They occur in the deep waters seaward from the edge of the continental shelf, and can have a lifetime of 6-12 months (Hamon and Golding, 1979).…”

Section: Introductionmentioning

confidence: 99%

Studies of Phytoplankton Species and Photosynthetic Pigments in a Warm Core Eddy of the East Australian Current. I. Summer Populations

Jeffrey¹,

Hallegraeff²

1980

Mar. Ecol. Prog. Ser.

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Summer phytoplankton populations in a warm core eddy of the East Australian Current were studied by thin-layer chromatography for pigments and by microscopy of living samples for species identification. Small differences in phytoplankton populations at the eddy centre compared to surrounding waters were observed. These included higher subsurface chlorophyll maxima (0.49-0.89 pg 1-' eddy centre; 0.33-0.38 pg 1-' eddy edge; 0.27-0.34 yg I-' midway positions) due to increased diatom abundance, a lower proportion of nanoplankton chlorophyll (52 % eddy centre; 73 % eddy edge), a dominance change from Rhizosolenia alata (eddy edge) to Nitzschia seriata (eddy centre), and a decreased number of dinoflagellate species.

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“…The East Australian current is very variable and is characterized by a net southward flow and a series of intense meanders and eddies, which typically have wavelengths of about 200-250 km and drift speeds of 5-10km/day (Hamon et al, 1975;Andrews and Scully-Power, 1976). To model this current we again use (5.1), choosing L=80km, a=0.6 and V=O.19 (representative of the summer mean current) or V=O.11 (representative of the winter mean current).…”

Section: Discussion and Applicationsmentioning

confidence: 77%

Stable and unstable barotropic shelf waves in a coastal current

Collings

Grimshaw

1984

Geophysical & Astrophysical Fluid Dynamics

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We consider the linearized stability of a barotropic coastal current flowing parallel to a straight coastline over a continental shelf and slope whose depth varies monotonically with distance from the coast. Some necessary conditions for stability and various semi-circle theorems are reviewed for general current profiles and bottom topography. A criterion for topography to be a destabilizing influence is derived. Some general results for stable waves are also described. Analytic solutions are obtained for a piece-wise linear current profile and the exponential depth profile (Buchwald and Adams, 1968). Dispersion diagrams are obtained for a monotonic current profile, where it is shown that the effect of topography is destabilizing, and for a triangular current profile. The dispersion diagrams generally contain a finite number (usually one or two) of unstable waves, and a set of stable waves, which may be infinite in number. The results are applied to some specific coastal regimes.

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The Structure of an East Australian Current Anticyclonic Eddy

Cited by 47 publications

References 0 publications

Agulhas ring injection into the South Atlantic during glacials and interglacials

Agulhas ring injection into the South Atlantic during glacials and interglacials

Studies of Phytoplankton Species and Photosynthetic Pigments in a Warm Core Eddy of the East Australian Current. I. Summer Populations

Stable and unstable barotropic shelf waves in a coastal current

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