Westward Motion of Mesoscale Eddies

Cushman-Roisin, Benoı̂t; Tang, Benyang; Chassignet, Eric P.

doi:10.1175/1520-0485(1990)020<0758:wmome>2.0.co;2

Cited by 222 publications

(159 citation statements)

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“…The mean westward propagation speed of anticyclonic and cyclonic rings was 2.59 cm s -1 and 3.44 cm s -1 , respectively. This zonal propagation speed is consistent with the theory (e.g., McWilliams and Flierl 1979;Cushman-Roisin et al 1990) and previous observational results (e.g., Ebuchi and Hanawa 2001;Itoh and Yasuda 2010). There was no significant difference of the westward propagation speed between the upstream and downstream regions (not shown).…”

Section: Climatological Mean Featuresmentioning

confidence: 98%

Climatological mean features and interannual to decadal variability of ring formations in the Kuroshio Extension region

Sasaki

Minobe

2016

“Hot Spots” in the Climate System

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This study examines the climatological mean features of oceanic rings shed from the Kuroshio Extension (KE) jet and their interannual to decadal variability using satellite altimeter observations from October 1992 to December 2010. To objectively capture a ring shedding from the KE jet, a new method that consists of the detection of the jet length changes and the tracking of a ring is proposed. A spatial distribution of the ring formations in the KE region indicates that cyclonic (cold-core) rings were most frequently formed in the upstream region between 143°-147°E around the steady meander of the KE jet. In contrast, most of anticyclonic (warm-core) rings formed in the downstream region west of the Shatsky Rise. These pinched-off rings in both the upstream and downstream regions generally propagated westward, but about two-third of the rings was reabsorbed by the jet. Nevertheless, about one-fourth of the meridional eddy heat transport at the latitude of the KE resulted from the rings that are not reabsorbed by the jet. The number of ring formations showed substantial interannual to decadal variability. In the upstream and downstream KE region, decadal and interannual variability was dominant, respectively. These fluctuations of the ring formations were negatively correlated with the strength of the KE jet. It is also revealed that the ring formation variations play an important role in sea surface temperature changes north of the KE jet.

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Section: Climatological Mean Featuresmentioning

confidence: 98%

Climatological mean features and interannual to decadal variability of ring formations in the Kuroshio Extension region

Sasaki

Minobe

2016

“Hot Spots” in the Climate System

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“…Given the smallness of the scales of motion relative to planetary scales and the strength of the bottom slope, the ␤ effect is not expected to play a large role in determining the rate of eddy formation. Once formed, the ␤ effect would cause the eddies to drift westward out of the gap with speed c Ϸ ␤R 2 d (see, e.g., Cushman-Roisin et al 1990 and the references therein). For the region under consideration, this speed is so slow that the eddies are expected to drift less than 10 km in the time it takes them to transit the gap, reaffirming the fact that the ␤ effect is negligible in this system.…”

Section: Comparison With Oceanic Observationsmentioning

confidence: 99%

Laboratory Experiments on Eddy Generation by a Buoyant Coastal Current Flowing over Variable Bathymetry*

Wolfe

Cenedese

2006

Journal of Physical Oceanography

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Irminger rings are warm-core eddies formed off the west coast of Greenland. Recent studies suggest that these eddies, which are implicated in the rapid springtime restratification of the Labrador Sea, are formed by an internal instability of the West Greenland Current (WGC), triggered by bathymetric variations. This study seeks to explore the effect of the magnitude and downstream length scale of bathymetric variations on the stability of a simple model of the WGC in a series of laboratory experiments in which a buoyant coastal current was allowed to flow over bathymetry consisting of piecewise constant slopes of varying magnitude. The currents did not form eddies over gently sloping bathymetry and only formed eddies over steep bathymetry if the current width exceeded the width of the sloping bathymetry. Eddying currents were immediately stabilized if they flowed onto gently sloping topography. Bathymetric variations that persisted only a short distance downstream perturbed the flow locally but did not lead to eddy formation. Eddies formed only once the downstream length of the bathymetric variations exceeded a critical scale of about 8 Rossby radii. These results are consistent with the observed behavior of the WGC, which begins to form Irminger rings after entering a region where the continental slope abruptly steepens and becomes narrower than the WGC itself in a region spanning about 20-80 Rossby radii of downstream distance.

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“…Under the transcription of notations-while we called the total depth of the shallow-water system H · ͑1+h͒, 25 …”

Section: The Geostrophic Balance: Covariant and Conventional Formmentioning

confidence: 99%

“…For Gulf Stream rings, where L is twice to three times R d , 25 this would amount to a correction of 6%-13%. This explains published results from numerical experiments, based on reduced gravity, single-layer, shallow-water dynamics 25 that showed that ͑regular͒ anticyclones drift systematically faster than predicted by geostrophic formula ͑86͒: Gulf-Stream ring-like anticyclones turned out to drift 5%-9% faster than predicted by geostrophic expression ͑86͒ of the drift speed.…”

Section: E Effect Of Centrifugal Correction On Drift Velocitymentioning

confidence: 99%

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Angular momentum dynamics and the intrinsic drift of monopolar vortices on a rotating sphere

Toorn

Zimmerman

2010

Journal of Mathematical Physics

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On the basis of the angular momentum equation for a fluid shell on a rotating planet, we analyze the intrinsic drift of a monopolar vortex in the shell. Central is the development of a general angular momentum equation for Eulerian fluid mechanics based on coordinate-free, general tensorial representations of the underlying fluid dynamics on the one hand, and an appropriate representation of the Lie algebra so͑3͒ of rotations on the other hand. We show that angular momentum fluid dynamics concisely describes the motion of vortices along the sphere and explains why both geostrophic cyclones and anticyclones drift in retrograde direction ͑west-ward͒, why anticyclones do so faster than cyclones, and why this difference is enhanced by a cyclostrophic correction. Technically, the analysis is based on a tensorial representation of the integral angular momentum equation for the fluid shell as a whole, and, derived from this, a coordinate representation with respect to coordinates which may move with the vortex along the surface of the planet. Depicting the angular momentum balance of cyclones and anticyclones in terms of vector diagrams, we present an overview of the results achieved.

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Westward Motion of Mesoscale Eddies

Cited by 222 publications

References 0 publications

Climatological mean features and interannual to decadal variability of ring formations in the Kuroshio Extension region

Climatological mean features and interannual to decadal variability of ring formations in the Kuroshio Extension region

Laboratory Experiments on Eddy Generation by a Buoyant Coastal Current Flowing over Variable Bathymetry*

Angular momentum dynamics and the intrinsic drift of monopolar vortices on a rotating sphere

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