Vortex scaling ranges in two-dimensional turbulence

Burgess, B. H.; Dritschel, David G.; Scott, R. K.

doi:10.1063/1.4993144

Cited by 22 publications

(9 citation statements)

References 49 publications

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“…The numerous merger we studied, together with previous studies [6][7][8][9][10][11] , suggests that the merger of large mesoscale eddies are key for the transfer of heat and energy to large scales, through the mixing of water masses in surface and sub-surface. Recent studies suggested that, in the ocean, the number of vortex splitting is comparable to that of the vortex merger 30 .…”

Section: Discussionmentioning

confidence: 53%

Oceanic vortex mergers are not isolated but influenced by the β-effect and surrounding eddies

Marez

Carton

L’Hégaret

et al. 2020

Sci Rep

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Oceanic vortices are ubiquitous in the ocean. They dominate the sub-inertial energy spectrum, and their dynamics is key for the evolution of the water column properties. The merger of two like-signed coherent vortices, which ultimately results in the formation of a larger vortex, provides an efficient mechanism for the lateral mixing of water masses in the ocean. Understanding the conditions of such interaction in the ocean is thus essential. Here, we use a merger detection algorithm to draw a global picture of this process in the ocean. We show that vortex mergers are not isolated, contrary to the hypothesis made in most earlier studies. Paradoxically, the merging distance is well reproduced by isolated vortex merger numerical simulations, but it is imperative to consider both the β-effect and the presence of neighbouring eddies to fully understand the physics of oceanic vortex merger.Oceanic vortices, named eddies, impact biological activities 1 , tracer transport 2 , and properties of the water column 3 . It has become clear that the mesoscale (10-100 km) eddy field, is at least as energetic as the large scale circulation 2 , essential for the air-sea interactions 4 , and thus for the evolution of climate 5 . Eddy-eddy interactions therefore play a central role in the evolution of the ocean/atmosphere physics and biology. In particular, vortex merger -the physical process in which two like-signed coherent vortices collapse, ultimately resulting in a larger vortex-is of key importance for the distribution and the transfers of energy across scales in the ocean 6-11 . Since the 80's, an important effort has been undertaken to understand the physics of oceanic vortex merger, including in situ 12 , laboratory 13,14 , and numerical 15 observations, associated with intense theoretical debates [16][17][18] . Most fundamental studies addressed the 'isolated vortex merger' problem, omitting the influence of neighbouring eddies, large scale currents, or boundary, topographic, and planetary effects [19][20][21][22][23][24][25] . Efforts to include more physical effects in studies of vortex merger [26][27][28][29] were often impaired by the lack of general observations in the global ocean, or by the complexity of the resulting dynamical system. Despite recent trials 30 and pointwise observations 12,31-33 , a global description of vortex merger in the ocean is lacking.In this paper, we present an analysis of merging events in the global ocean, using a global 1/12° re-analysis dataset. This study was conducted over a five-year period, in five domains in the middle of each major oceanic basins -these domains a priori respect the hypothesis of isolated vortex merger studies: they are far away from the coastlines, topographic features, and strong currents, and are located at mid-latitudes (see Fig. 1). From 5,867 detected merging events, we infer the actual characteristics of mesoscale eddies that merge, and test the isolated vortex merger problem hypotheses. Further, we compare this analysis with the outcome of 1,600 idealized...

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Section: Discussionmentioning

confidence: 53%

Oceanic vortex mergers are not isolated but influenced by the β-effect and surrounding eddies

Marez

Carton

L’Hégaret

et al. 2020

Sci Rep

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“…However, Benzi et al (1988) suggest that the vortex population statistics obey a self-similar scaling that resembles the KBL scaling of the inertial ranges. This self-similarity, which is supported by the work of Burgess et al (2017), encourages the hope that the coherent vortices might yet fit within the standard model of two-dimensional turbulence. For a recent review of two-dimensional turbulence see Boffetta & Ecke (2012).…”

Section: Introductionmentioning

confidence: 58%

Entropy budget and coherent structures associated with a spectral closure model of turbulence

Salmon

2018

J. Fluid Mech.

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We ‘derive’ the eddy-damped quasi-normal Markovian model (EDQNM) by a method that replaces the exact equation for the Fourier phases with a solvable stochastic model, and we analyse the entropy budget of the EDQNM. We show that a quantity that appears in the probability distribution of the phases may be interpreted as the rate at which entropy is transferred from the Fourier phases to the Fourier amplitudes. In this interpretation, the decrease in phase entropy is associated with the formation of structures in the flow, and the increase of amplitude entropy is associated with the spreading of the energy spectrum in wavenumber space. We use Monte Carlo methods to sample the probability distribution of the phases predicted by our theory. This distribution contains a single adjustable parameter that corresponds to the triad correlation time in the EDQNM. Flow structures form as the triad correlation time becomes very large, but the structures take the form of vorticity quadrupoles that do not resemble the monopoles and dipoles that are actually observed.

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“…Using barotropic (2D) models is a common first step to evaluate coherent eddies in large-scale flows [52]. Inviscid decay (Landau damping) of asymmetric perturbations to stable vortices is responsible for the process of vortex axisymmetrication [53] and the energy transfer from a weak satellite at the periphery of a strong vortex due to curved stretching out [54].…”

Section: Discussionmentioning

confidence: 99%

How Oceanic Vortices can be Super Long-Lived

Sutyrin¹

2020

PhO

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The article is aimed at substantiating theoretically amazing longevity (up to 5 years) of the individual vortices in the World Ocean despite strong fluctuations of the ocean currents and regardless of the Rossby wave dispersion properties. Methods and Results. Evolution of the baroclinic vortices is considered in a hybrid two-layer ocean model over a topographic slope on the beta-plane. In the upper layer with strong potential vorticity anomalies, the currents are assumed to be balanced; in the lower layer at week potential vorticity anomalies, the currents are described in the traditional quasi-geostrophic approximation. Slow evolving almost circular vortices embedded in a vertically sheared current typical of the subtropical part of the ocean are described analytically. The theory shows how a baroclinic vortex is followed by the lee Rossby waves. The vortex drift across the mean current is caused mainly by the baroclinicdipole structure of the represented solution; while the vortex energy loss related to the Rossby wave radiation can be compensated by the energy stored in the mean currents. Conclusions. The constructed model provides reasonable estimates of the energy drift and transfer typical of the ocean vortices with strong anomalies of potential vorticity. Direct support of long-lived vortices by the energy of the baroclinic mean flows irrespective of their stability, is of great importance for better understanding the physical mechanisms relating to significant longevity of the geophysical vortices and their movement.

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Vortex scaling ranges in two-dimensional turbulence

Cited by 22 publications

References 49 publications

Oceanic vortex mergers are not isolated but influenced by the β-effect and surrounding eddies

Oceanic vortex mergers are not isolated but influenced by the β-effect and surrounding eddies

Entropy budget and coherent structures associated with a spectral closure model of turbulence

How Oceanic Vortices can be Super Long-Lived

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