Three-Dimensional Chaotic Advection by Mixed Layer Baroclinic Instabilities

Mukiibi, Daniel; Badin, Gualtiero; Serra, Nuno

doi:10.1175/jpo-d-15-0121.1

Cited by 9 publications

(11 citation statements)

References 108 publications

(130 reference statements)

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“…Due to the availability of satellite‐derived altimetric observations from 1993 to present and the well‐studied relationship between sea level anomalies (SLAs) and geostrophic currents, most global eddy tracking algorithms have exclusively utilized gridded SLA fields (Chaigneau et al, ; Chelton et al, ; Williams et al, ; Yi et al, ). However, a more complete analysis requires consideration of other parameters such as SST and sea surface salinity (SSS), which can have local impacts on ocean stirring and mixing processes (Dong et al, ; d'Ovidio et al, ; Mukiibi et al, ; Pasquero, ). Before the satellite era, the salinity and temperature characteristics of Arabian Sea eddies relied on survey observations (Fischer et al, ; Schott & Garternicht, ).…”

Section: Introductionmentioning

confidence: 99%

Eddy‐Induced Temperature and Salinity Variability in the Arabian Sea

Trott

Subrahmanyam

Chaigneau

et al. 2019

Geophysical Research Letters

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The eddy field in the Arabian Sea experiences seasonal wind‐driven intensification during the summer monsoon season from June through September. These strong eddies strengthen local currents like the Somali Current and strongly impact regional upper‐level vertical and lateral advection. To investigate the multivariate response to eddying, we apply a closed‐contour eddy‐tracking algorithm to sea level anomaly maps and then examine sea surface temperature and salinity of the identified eddies to infer whether they are surface or subsurface intensified in the Arabian Sea during the summer monsoon. A complete understanding of the temperature and salinity signatures reveals how Arabian Sea eddies alter upper‐ocean stratification. Though both intensification types are identified, we find a dominance of likely surface‐intensified eddies characterized by relatively warm and fresh cores for anticyclonic eddies and relatively cool and saline cores for cyclonic eddies, particularly in the northwestern Arabian Sea and Somali Current region.

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Section: Introductionmentioning

confidence: 99%

Eddy‐Induced Temperature and Salinity Variability in the Arabian Sea

Trott

Subrahmanyam

Chaigneau

et al. 2019

Geophysical Research Letters

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“…The latter results in the formation of fronts, which in turn are important for the mixing of passive tracers [19]. In the ocean, SQG dynamics may shed light on the formation of submesoscale dynamics [20], which again are important for the mixing of passive tracers [21][22][23]. For a study on the relationship between quasi geostrophic (QG) and SQG turbulence, see e.g.…”

Section: Introductionmentioning

confidence: 99%

Collapse of generalized Euler and surface quasigeostrophic point vortices

Badin

Barry

2018

Phys. Rev. E

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Point-vortex models are presented for the generalized Euler equations, which are characterized by a fractional Laplacian relation between the active scalar and the stream function. Special focus is given to the case of the surface quasigeostrophic (SQG) equations, for which the existence of finite-time singularities is still a matter of debate. Point-vortex trajectories are expressed using Nambu dynamics. The formulation is based on a noncanonical bracket and allows for a geometrical interpretation of trajectories as intersections of level sets of the Hamiltonian and Casimir. Within this setting, we focus on the collapse of solutions for the three-point-vortex model. In particular, we show that for SQG the collapse can be either self-similar or non-self-similar. Self-similarity occurs only when the Hamiltonian is zero, while non-self-similarity appears for nonzero values of the same. For both cases, collapse is allowed for any choice of circulations within a permitted interval. These results differ strikingly from the classical point-vortex model, where collapse is self-similar for any value of the Hamiltonian, but the vortex circulations must satisfy a strict relationship. Results may also shed a light on the formation of singularities in the SQG partial differential equations, where the singularity is thought to be reached only in a self-similar way.

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“…If −λ α = λ E ω 0 , (49) reduces to (29) aside for the fact that the angular impulse has not been here considered as a constraint.…”

Section: The Delta Prior Distribution and The Point-vortex Statisticsmentioning

confidence: 99%

Statistical Measures and Selective Decay Principle for Generalized Euler Dynamics: Formulation and Application to the Formation of Strong Fronts

Conti

Badin

2020

J Stat Phys

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We investigate the statistical mechanics of a family of two dimensional (2D) fluid flows, described by the generalized Euler equations, or α-models. These models describe both nonlocal and local dynamics, with one example of the latter one given by the Surface Quasi Geostrophy (SQG) model, for which the existence of singularities is still under debate. We aim to study the equilibrium mechanics, using initially a point-vortex approximation and then exploiting the full continuous equations, invoking the maximization of appropriate entropy functionals. The point-vortex approximation highlights an important difference between the 2D turbulence and local dynamics models. In the latter, it is in fact possible to derive a statistical measure only considering two conserved quantities as constraints for the maximization problem, the Hamiltonian and the angular impulse. This result does not hold for 2D turbulence. Both the continuous and the point vortex approximation allow for the derivation of mean field equations that act as constraints for the functional relation between the streamfunction and the active scalar of the model considered. Further, the analysis of the continuous equations suggests the existence of a selective decay principle for the whole family of models. To test these ideas we use numerical simulations of the partial differential equations of the α-models starting from different sets of initial conditions (i.c.s). For random i.c.s, all the solutions tend to a dipolar structure. The functional relation between the active scalar and the streamfunction shows an increase of nonlinearity with a decrease of the locality of the dynamics. We then test the evolution of the specific case of SQG for i.c.s in the form of a hyperbolic saddle, that is a candidate for the possible formation of singularity through a self-similar cascade though secondary instabilities. Results show the presence of a scale dependent selective decay associated to the breaking of the frontal structures emerging from the flow, suggesting a relation with the change of topology of the flow.

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Three-Dimensional Chaotic Advection by Mixed Layer Baroclinic Instabilities

Cited by 9 publications

References 108 publications

Eddy‐Induced Temperature and Salinity Variability in the Arabian Sea

Eddy‐Induced Temperature and Salinity Variability in the Arabian Sea

Collapse of generalized Euler and surface quasigeostrophic point vortices

Statistical Measures and Selective Decay Principle for Generalized Euler Dynamics: Formulation and Application to the Formation of Strong Fronts

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