Oceanic mesoscale eddies as revealed by Lagrangian coherent structures

Beron-Vera, F. J.; Olascoaga, M. J.; Goñi, Gustavo

doi:10.1029/2008gl033957

Cited by 162 publications

(146 citation statements)

References 20 publications

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“…7 and 9). The same region has been analyzed by Beron-Vera et al (2008), who showed that the finite-time Lyapunov exponent, a widely used Lagrangian diagnostic (Haller 2001;Peacock and Dabiri 2010), does not reveal coherent material eddies. More recently, the same area was also studied by Lehahn et al (2011), who reported observations of a nearly isolated mesoscale chlorophyll patch, FIG.…”

Section: Resultsmentioning

confidence: 91%

Objective Detection of Oceanic Eddies and the Agulhas Leakage

Beron-Vera

Wang

Olascoaga

et al. 2013

Journal of Physical Oceanography

153

156

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Mesoscale oceanic eddies are routinely detected from instantaneous velocities derived from satellite altimetry data. While simple to implement, this approach often gives spurious results and hides true material transport. Here it is shown how geodesic transport theory, a recently developed technique from nonlinear dynamical systems, uncovers eddies objectively. Applying this theory to altimetry-derived velocities in the South Atlantic reveals, for the first time, Agulhas rings that preserve their material coherence for several months, while ring candidates yielded by other approaches tend to disperse or leak within weeks. These findings suggest that available velocity-based estimates for the Agulhas leakage, as well as for its impact on ocean circulation and climate, need revision.

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Section: Resultsmentioning

confidence: 91%

Objective Detection of Oceanic Eddies and the Agulhas Leakage

Beron-Vera

Wang

Olascoaga

et al. 2013

Journal of Physical Oceanography

153

156

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show abstract

“…(b) EMC-CE interactions, distinguished by the moments when the surface volume transport is more than one standard deviation away from the mean represented in Fig. 15. material (Haller 2002(Haller , 2005Beron-Vera et al 2008;Samelson 2013). Here, we follow other works (e.g., Faghmous et al 2015) and treat these nearly circular SLAs as eddies, independent of their trapping ability.…”

Section: Discussionmentioning

confidence: 99%

The East Madagascar Current: Volume Transport and Variability Based on Long-Term Observations

Ponsoni

Aguiar‐González

Ridderinkhof

et al. 2016

Journal of Physical Oceanography

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This study provides a long-term description of the poleward East Madagascar Current (EMC) in terms of its observed velocities, estimated volume transport, and variability based on both ;2.5 yr of continuous in situ measurements and ;21 yr of satellite altimeter data. An array of five moorings was deployed at 238S off eastern Madagascar as part of the Indian-Atlantic Exchange in present and past climate (INATEX) observational program. On average, the EMC has a horizontal scale of about 60-100 km and is found from the surface to about 1000-m depth. Its time-averaged core is positioned at the surface, at approximately 20 km from the coast, with velocity of 79 (621) Results from wavelet analysis display a dominant nearly bimonthly (45-85 days) frequency band of transport variability, which explains about 41% of the transport variance. Altimeter data suggest that this band of variability is induced by the arrival of westward-propagating sea level anomalies, which in turn are likely represented by mesoscale cyclonic and anticyclonic eddies. Annual averages of the altimeter-derived surface transport suggest that interannual variabilities also play a role in the EMC system.

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“…Maps of FSLE are calculated weekly. An alternative to FSLE is the finite-time Lyapunov exponents (22,46). At the scales and parameters we are working no significant differences are expected for the locations of LCS by any of the 2 methods.…”

Section: Methodsmentioning

confidence: 99%

Top marine predators track Lagrangian coherent structures

Kai

Rossi

Sudre

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

234

157

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Meso-and submesoscales (fronts, eddies, filaments) in surface ocean flow have a crucial influence on marine ecosystems. Their dynamics partly control the foraging behavior and the displacement of marine top predators (tuna, birds, turtles, and cetaceans). In this work we focus on the role of submesoscale structures in the Mozambique Channel in the distribution of a marine predator, the Great Frigatebird. Using a newly developed dynamic concept, the finite-size Lyapunov exponent (FSLE), we identified Lagrangian coherent structures (LCSs) present in the surface flow in the channel over a 2-month observation period (August and September 2003). By comparing seabird satellite positions with LCS locations, we demonstrate that frigatebirds track precisely these structures in the Mozambique Channel, providing the first evidence that a top predator is able to track these FSLE ridges to locate food patches. After comparing bird positions during long and short trips and different parts of these trips, we propose several hypotheses to understand how frigatebirds can follow these LCSs. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biologic corridors. The birds being often associated with tuna schools around foraging areas, a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel.frigatebird ͉ finite-size Lyapunov exponent ͉ Mozambique Channel ͉ submesoscale

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Oceanic mesoscale eddies as revealed by Lagrangian coherent structures

Cited by 162 publications

References 20 publications

Objective Detection of Oceanic Eddies and the Agulhas Leakage

Objective Detection of Oceanic Eddies and the Agulhas Leakage

The East Madagascar Current: Volume Transport and Variability Based on Long-Term Observations

Top marine predators track Lagrangian coherent structures

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