The Propagation and Evolution of Cyclonic Gulf Stream Rings

Mied, Richard P.; Lindemann, Gloria J.

doi:10.1175/1520-0485(1979)009<1183:tpaeoc>2.0.co;2

Cited by 85 publications

(47 citation statements)

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“…4 shows that all exhibit southwestward translation. The zonal speed is ~0.5 km day ' in the flat bottom case (B0) and analogous to the long Rossby wave phase speed of 0.56 km day -1 (= pR^.tid is internal Rossby radius), which is consistent with the results from a two-layer primitive equation model by Mied and Lindemann (1979) and a quasi-geostrophic model by McWilliams et al (1986). They reported that the westward translation speed increased toward pR\ with southward translation at a maximum of 1/4 pR\.…”

Section: Effect Of the Slope Steepnesssupporting

confidence: 85%

Topographic effects on the anticyclonic vortex evolution: A modeling study

Hyun

Hogan

2008

Continental Shelf Research

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Section: Effect Of the Slope Steepnesssupporting

confidence: 85%

Topographic effects on the anticyclonic vortex evolution: A modeling study

Hyun

Hogan

2008

Continental Shelf Research

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“…It should be also noticed that the northward shift shown in Fig. 7 is quite different from the westward shift of the isolated cyclonic Gaussian eddy examined in Part I, which is caused by the planetary β effect (e.g., McWilliam and Flierl, 1979;Mied and Lindemann, 1979). Because the planetary β effect is secondary in the present runs (Fig.…”

Section: Resultscontrasting

confidence: 51%

Topographic effect of a marine ridge on the spin-down of a cyclonic eddy

Sekine

1989

Journal of the Oceanographical Society of Japan

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The topographic effect of a meridional marine ridge on the spin-down of a cyclonic eddy, which is embedded in a zonal mean flow, is examined by use of a two layer numerical model. It is shown that the cyclonic eddy initially given on the eastern flank of the marine ridge decays in a short time. This result is common to all cases with the different volume transports of the mean flow (30 ~ 70 Sv) and of the cyclonic eddy (15 ~ 35 Sv). During the decay process, the cyclonic eddy shifts mainly northward into the shallower region, which is different from the dominant westward shift of the isolated cyclonic eddy. If the mean flow across over the marine ridge at the more northern latitude, the cyclonic eddy spins down more rapidly. A mean flow shifts zonal or south-eastward over a western side of the ridge, while it deflects north-eastward over an eastern side. The deflection angle of mean flow over the ridge depends on the intensity of lower layer velocity and density stratification. It is suggested that the topographic effect of the meridional marine ridge on the cyclonic eddy with mean flow is influenced both by the global phenomena that controls the inclination of the mean flow from zonal direction and by the local phenomena that controls the intensity of the topographic effect of the marine ridge. IntroductionIn Part I of this study (Sekine, 1989), the topographic effect of a meridional marine ridge on the spin-down of an isolated cyclonic eddy had been studied by use of a two-layer numerical model. It has been shown by Part I that a cyclonic eddy on the eastern flank of a marine ridge decays in a shorter time in comparison with those given on the western flank. The fast decay on the eastern side is attributable to the planetary β effect that carries the cyclonic eddy westward to a shallower region over the eastern flank of the ridge, in which significant spin-down is induced by shrink of a water column due to the conservation of absolute potential vorticity (e.g., Pedlosky, 1979;Gill, 1982). In contrast to this, because the westward shift by the planetary β effect carries a cyclonic eddy to a deeper region over a western flank of the ridge, a stretching of the cyclonic water column results in spin-up of the cyclonic eddy. On the basis of these results, it is inferred by Part I that a cyclonic eddy accompanied by a large meander of the Kuroshio on the eastern side of the Izu Ridge decays in a shorter time than that on the western side (Sekine et al., 1985).However, because a mean flow accompanying with the cyclonic eddy was not considered in Part I, the details of the spin-down was not fully discussed. In the present study, as a succeeding study of Part I, the effect of mean flow on the spin-down of a cyclonic eddy is examined with reference to the topographic effect of the meridional marine ridge.

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“…According to the linear theory, eddies of small amplitudes are expected to propagate westward due to the planetary β effect. As is well known and as will be shown later, the nonlinear effect of secondary eddies on a β plane tends to translate an isolated anticyclonic (cyclonic) eddy southwestward (northwestward) in the northern hemisphere (Firing and Beardsley, 1976;McWilliams and Flierl, 1979;Mied and Lindemann, 1979;Masuda et al, 1990). This mechanism alone, however, appears insufficient to explain the large speed and the almost southward direction of translation of meddies.…”

Section: Introductionmentioning

confidence: 76%

Mechanisms of the southward translation of meddies

Takahashi

Masuda

1998

J Oceanogr

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⋅ current-induced pseudo-topographic β effect, ⋅ nonlinear effect of secondary eddies. Meddies are warm and saline anticyclonic eddies found at the mid-depth of the Mediterranean Outflow in the Eastern North Atlantic. They are observed to move almost southward at average speeds as high as 1.3 ± 0.2 cm s -1 . This paper examines a mechanism which accelerates this curious translation to a reasonable speed when combined with nonlinearity and a suitable vertical eddy structure. This mechanism is the pseudo-topographic β effect due to the westward decrease in the thickness of the mid-layer induced by the surface southward mean current. The linear dispersion relation including this effect is shown to account for a quarter of the surface southward mean current or a fifth of the observed southward translation of meddies. Three-layer quasi-geostrophic experiments reveal that the surface southward mean current certainly enhances the southward translation velocity of meddies to a speed in agreement with observation, if the meddy has a current structure of plausible intensity and vertical coherence. In the light of the current-induced pseudo-topographic β effect, previous hypotheses are also re-examined through dynamic arguments together with numerical experiments; they are suggested to have some difficulty either in dynamics or in correspondence with observation. Thus the nonlinear effect due to secondary eddies combined with the current-induced pseudo-topographic β effect is the most likely mechanism responsible for the rapid southward translation of meddies among those examined in the paper. Mechanisms of the Southward Translation of Meddies

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The Propagation and Evolution of Cyclonic Gulf Stream Rings

Cited by 85 publications

References 0 publications

Topographic effects on the anticyclonic vortex evolution: A modeling study

Topographic effects on the anticyclonic vortex evolution: A modeling study

Topographic effect of a marine ridge on the spin-down of a cyclonic eddy

Mechanisms of the southward translation of meddies

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