### Abstract

A series of large eddy simulations is used to assess the transport properties of multi-scale ocean flows. In particular, we compare scale-dependent measures of Lagrangian relative dispersion and the evolution of passive tracer releases in models containing only submesoscale mixed layer instabilities and those containing mixed layer instabilities modified by deeper, baroclinic mesoscale disturbances. Visualization through 3D finite-time Lyapunov exponents and spectral analysis show that the small scale instabilities of the mixed layer rapidly lose coherence in the presence of larger-scale straining induced by the mesoscale motion. Eddy diffusivities computed from passive tracer evolution increase by an order of magnitude as the flow transitions from small to large scales. During the time period when both instabilities are present, scale-dependent relative Lagrangian dispersion, given by the finite-scale Lyapunov exponent (λ), shows two distinct plateau regions clearly associated with the disparate instability scales. In this case, the maximum value of λ over the submesocales at the surface flow is three times greater than λ at the mixed layer base which is only influenced by the deeper baroclinic motions. The results imply that parameterizations of submesoscale transport properties may be needed to accurately predict surface dispersion in models that do not explicitly resolve submesoscale turbulent features.

Original language | English (US) |
---|---|

Pages (from-to) | 16-30 |

Number of pages | 15 |

Journal | Ocean Modelling |

Volume | 56 |

DOIs | |

State | Published - Oct 2012 |

### Fingerprint

### Keywords

- Lagrangian sampling
- LES
- Transport

### ASJC Scopus subject areas

- Atmospheric Science
- Oceanography
- Geotechnical Engineering and Engineering Geology
- Computer Science (miscellaneous)

### Cite this

*Ocean Modelling*,

*56*, 16-30. https://doi.org/10.1016/j.ocemod.2012.07.004

**On multi-scale dispersion under the influence of surface mixed layer instabilities and deep flows.** / Ozgokmen, Tamay M; Poje, Andrew C.; Fischer, Paul F.; Childs, Hank; Krishnan, Harinarayan; Garth, Christoph; Haza, Angelique C.; Ryan, Edward.

Research output: Contribution to journal › Article

*Ocean Modelling*, vol. 56, pp. 16-30. https://doi.org/10.1016/j.ocemod.2012.07.004

}

TY - JOUR

T1 - On multi-scale dispersion under the influence of surface mixed layer instabilities and deep flows

AU - Ozgokmen, Tamay M

AU - Poje, Andrew C.

AU - Fischer, Paul F.

AU - Childs, Hank

AU - Krishnan, Harinarayan

AU - Garth, Christoph

AU - Haza, Angelique C.

AU - Ryan, Edward

PY - 2012/10

Y1 - 2012/10

N2 - A series of large eddy simulations is used to assess the transport properties of multi-scale ocean flows. In particular, we compare scale-dependent measures of Lagrangian relative dispersion and the evolution of passive tracer releases in models containing only submesoscale mixed layer instabilities and those containing mixed layer instabilities modified by deeper, baroclinic mesoscale disturbances. Visualization through 3D finite-time Lyapunov exponents and spectral analysis show that the small scale instabilities of the mixed layer rapidly lose coherence in the presence of larger-scale straining induced by the mesoscale motion. Eddy diffusivities computed from passive tracer evolution increase by an order of magnitude as the flow transitions from small to large scales. During the time period when both instabilities are present, scale-dependent relative Lagrangian dispersion, given by the finite-scale Lyapunov exponent (λ), shows two distinct plateau regions clearly associated with the disparate instability scales. In this case, the maximum value of λ over the submesocales at the surface flow is three times greater than λ at the mixed layer base which is only influenced by the deeper baroclinic motions. The results imply that parameterizations of submesoscale transport properties may be needed to accurately predict surface dispersion in models that do not explicitly resolve submesoscale turbulent features.

AB - A series of large eddy simulations is used to assess the transport properties of multi-scale ocean flows. In particular, we compare scale-dependent measures of Lagrangian relative dispersion and the evolution of passive tracer releases in models containing only submesoscale mixed layer instabilities and those containing mixed layer instabilities modified by deeper, baroclinic mesoscale disturbances. Visualization through 3D finite-time Lyapunov exponents and spectral analysis show that the small scale instabilities of the mixed layer rapidly lose coherence in the presence of larger-scale straining induced by the mesoscale motion. Eddy diffusivities computed from passive tracer evolution increase by an order of magnitude as the flow transitions from small to large scales. During the time period when both instabilities are present, scale-dependent relative Lagrangian dispersion, given by the finite-scale Lyapunov exponent (λ), shows two distinct plateau regions clearly associated with the disparate instability scales. In this case, the maximum value of λ over the submesocales at the surface flow is three times greater than λ at the mixed layer base which is only influenced by the deeper baroclinic motions. The results imply that parameterizations of submesoscale transport properties may be needed to accurately predict surface dispersion in models that do not explicitly resolve submesoscale turbulent features.

KW - Lagrangian sampling

KW - LES

KW - Transport

UR - http://www.scopus.com/inward/record.url?scp=84865517080&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84865517080&partnerID=8YFLogxK

U2 - 10.1016/j.ocemod.2012.07.004

DO - 10.1016/j.ocemod.2012.07.004

M3 - Article

AN - SCOPUS:84865517080

VL - 56

SP - 16

EP - 30

JO - Ocean Modelling

JF - Ocean Modelling

SN - 1463-5003

ER -