Persistence and material coherence of a mesoscale ocean eddy
Ocean eddies play an important role in the transport and mixing processes of the ocean due to their ability to transport material, heat, salt, and other tracers across large distances. They exhibit at least two timescales; an Eulerian lifetime associated with persistent identifiable signatures in gr...
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ftdatacite:10.48550/arxiv.2111.08351 2023-05-15T18:21:13+02:00 Persistence and material coherence of a mesoscale ocean eddy Denes, Michael C. Froyland, Gary Keating, Shane R. 2021 https://dx.doi.org/10.48550/arxiv.2111.08351 https://arxiv.org/abs/2111.08351 unknown arXiv arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Fluid Dynamics physics.flu-dyn Dynamical Systems math.DS FOS Physical sciences FOS Mathematics Article CreativeWork article Preprint 2021 ftdatacite https://doi.org/10.48550/arxiv.2111.08351 2022-03-10T13:30:59Z Ocean eddies play an important role in the transport and mixing processes of the ocean due to their ability to transport material, heat, salt, and other tracers across large distances. They exhibit at least two timescales; an Eulerian lifetime associated with persistent identifiable signatures in gridded fields such as vorticity or sea-surface height, and multiple Lagrangian or material coherence timescales that are typically much shorter. We propose a method to study the multi-timescale material transport, leakage, and entrainment by eddies with their surroundings by constructing sequences of finite-time coherent sets, computed as superlevel sets of dominant eigenfunctions of dynamic Laplace operators. The dominant eigenvalues of dynamic Laplace operators defined on time intervals of varying length allows us to identify a maximal coherence timescale that minimizes the rate of mass loss over a domain, per unit flow time. We apply the method to examine the persistence and material coherence of an Agulhas ring, an ocean eddy in the South Atlantic ocean, using particle trajectories derived from a $0.1^\circ$ global numerical ocean simulation. Using a sequence of sliding windows, the method is able to identify and track a persistent eddy feature for a time much longer than the maximal coherence timescale, and with considerably larger material transport than the corresponding eddy feature identified from purely Eulerian information. Furthermore, the median residence times of fluid in the identified feature far exceed the timescale over which fully material motion is guaranteed. Through residence time calculations, we find that this particular eddy does not exhibit a long-lived coherent inner core and that the bulk of material transport is performed by the quasi-coherent outer ring of the eddy. : 34 pages, 13 figures Article in Journal/Newspaper South Atlantic Ocean DataCite Metadata Store (German National Library of Science and Technology) Laplace ENVELOPE(141.467,141.467,-66.782,-66.782) |
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DataCite Metadata Store (German National Library of Science and Technology) |
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language |
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topic |
Fluid Dynamics physics.flu-dyn Dynamical Systems math.DS FOS Physical sciences FOS Mathematics |
spellingShingle |
Fluid Dynamics physics.flu-dyn Dynamical Systems math.DS FOS Physical sciences FOS Mathematics Denes, Michael C. Froyland, Gary Keating, Shane R. Persistence and material coherence of a mesoscale ocean eddy |
topic_facet |
Fluid Dynamics physics.flu-dyn Dynamical Systems math.DS FOS Physical sciences FOS Mathematics |
description |
Ocean eddies play an important role in the transport and mixing processes of the ocean due to their ability to transport material, heat, salt, and other tracers across large distances. They exhibit at least two timescales; an Eulerian lifetime associated with persistent identifiable signatures in gridded fields such as vorticity or sea-surface height, and multiple Lagrangian or material coherence timescales that are typically much shorter. We propose a method to study the multi-timescale material transport, leakage, and entrainment by eddies with their surroundings by constructing sequences of finite-time coherent sets, computed as superlevel sets of dominant eigenfunctions of dynamic Laplace operators. The dominant eigenvalues of dynamic Laplace operators defined on time intervals of varying length allows us to identify a maximal coherence timescale that minimizes the rate of mass loss over a domain, per unit flow time. We apply the method to examine the persistence and material coherence of an Agulhas ring, an ocean eddy in the South Atlantic ocean, using particle trajectories derived from a $0.1^\circ$ global numerical ocean simulation. Using a sequence of sliding windows, the method is able to identify and track a persistent eddy feature for a time much longer than the maximal coherence timescale, and with considerably larger material transport than the corresponding eddy feature identified from purely Eulerian information. Furthermore, the median residence times of fluid in the identified feature far exceed the timescale over which fully material motion is guaranteed. Through residence time calculations, we find that this particular eddy does not exhibit a long-lived coherent inner core and that the bulk of material transport is performed by the quasi-coherent outer ring of the eddy. : 34 pages, 13 figures |
format |
Article in Journal/Newspaper |
author |
Denes, Michael C. Froyland, Gary Keating, Shane R. |
author_facet |
Denes, Michael C. Froyland, Gary Keating, Shane R. |
author_sort |
Denes, Michael C. |
title |
Persistence and material coherence of a mesoscale ocean eddy |
title_short |
Persistence and material coherence of a mesoscale ocean eddy |
title_full |
Persistence and material coherence of a mesoscale ocean eddy |
title_fullStr |
Persistence and material coherence of a mesoscale ocean eddy |
title_full_unstemmed |
Persistence and material coherence of a mesoscale ocean eddy |
title_sort |
persistence and material coherence of a mesoscale ocean eddy |
publisher |
arXiv |
publishDate |
2021 |
url |
https://dx.doi.org/10.48550/arxiv.2111.08351 https://arxiv.org/abs/2111.08351 |
long_lat |
ENVELOPE(141.467,141.467,-66.782,-66.782) |
geographic |
Laplace |
geographic_facet |
Laplace |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_rights |
arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
op_doi |
https://doi.org/10.48550/arxiv.2111.08351 |
_version_ |
1766200371000115200 |