The impact of mesoscale eddies on the phytoplankton community in the South Atlantic Ocean: HPLC-CHEMTAX approach

Abstract. Three methods for automatic detection of mesoscale coherent structures are applied to Sea Level Anomaly (SLA) fields in the South Atlantic. The first method is based on the wavelet packet decomposition of the SLA data, the second on the estimation of the Okubo-Weiss parameter and the third on a geometric criterion using the winding-angle approach. The results provide a comprehensive picture of the mesoscale eddies over the South Atlantic Ocean, emphasizing their main characteristics: amplitude, diameter, duration and propagation velocity. Five areas of particular eddy dynamics were selected: the Brazil Current, the Agulhas eddies propagation corridor, the Agulhas Current retroflexion, the Brazil-Malvinas confluence zone and the northern branch of the Antarctic Circumpolar Current (ACC). For these areas, mean propagation velocities and amplitudes were calculated. Two regions with long duration eddies were observed, corresponding to the propagation of Agulhas and ACC eddies. Through the comparison between the identification methods, their main advantages and shortcomings were detailed. The geometric criterion presents a better performance, mainly in terms of number of detections, duration of the eddies and propagation velocities. The results are particularly good for the Agulhas Rings, that presented the longest lifetimes of all South Atlantic eddies.

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Comparison between three implementations of automatic identification algorithms for the quantification and characterization of mesoscale eddies in the South Atlantic Ocean

Ocean Science ◽

10.5194/os-7-317-2011 ◽

2011 ◽

Vol 7 (3) ◽

pp. 317-334 ◽

Cited By ~ 71

Author(s):

J. M. A. C. Souza ◽

C. de Boyer Montégut ◽

P. Y. Le Traon

Keyword(s):

Atlantic Ocean ◽

Wavelet Packet ◽

Mesoscale Eddies ◽

South Atlantic ◽

South Atlantic Ocean ◽

Automatic Identification ◽

The South ◽

Geometric Criterion ◽

Comprehensive Picture ◽

Propagation Velocities

Abstract. Three methods for automatic detection of mesoscale coherent structures are applied to Sea Level Anomaly (SLA) fields in the South Atlantic. The first method is based on the wavelet packet decomposition of the SLA data, the second on the estimation of the Okubo-Weiss parameter and the third on a geometric criterion using the winding-angle approach. The results provide a comprehensive picture of the mesoscale eddies over the South Atlantic Ocean, emphasizing their main characteristics: amplitude, diameter, duration and propagation velocity. Five areas of particular eddy dynamics were selected: the Brazil Current, the Agulhas eddies propagation corridor, the Agulhas Current retroflexion, the Brazil-Malvinas confluence zone and the northern branch of the Antarctic Circumpolar Current (ACC). For these areas, mean propagation velocities and amplitudes were calculated. Two regions with long duration eddies were observed, corresponding to the propagation of Agulhas and ACC eddies. Through the comparison between the identification methods, their main advantages and shortcomings were detailed. The geometric criterion presents the best performance, mainly in terms of number of detections, duration of the eddies and propagation velocities. The results are particularly good for the Agulhas Rings, which have the longest lifetimes of all South Atlantic eddies.

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A Numerical Study of the Impact of Greenhouse Gases on the South Atlantic Ocean Climatology

Climatic Change ◽

10.1023/b:clim.0000043143.32099.ec ◽

2004 ◽

Vol 66 (1/2) ◽

pp. 163-189 ◽

Cited By ~ 7

Author(s):

Ilana Wainer ◽

Andrea Taschetto ◽

Bette Otto-Bliesner ◽

Esther Brady

Keyword(s):

Atlantic Ocean ◽

Greenhouse Gases ◽

Numerical Study ◽

South Atlantic ◽

South Atlantic Ocean ◽

The South ◽

The Impact

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Rockhopper penguins and other marine life threatened by driftnet fisheries at Tristan da Cunha

Oryx ◽

10.1017/s0030605300035109 ◽

1991 ◽

Vol 25 (2) ◽

pp. 76-79 ◽

Cited By ~ 7

Author(s):

Peter G. Ryan ◽

John Cooper

Keyword(s):

Atlantic Ocean ◽

Large Scale ◽

Fishing Effort ◽

South Atlantic ◽

South Atlantic Ocean ◽

Target Species ◽

The South ◽

Tristan Da Cunha ◽

The Pacific ◽

The Impact

The oriental driftnet fleet, which is responsible for the large-scale mortality of non-target species in the Pacific Ocean, has extended its range to include the South Atlantic Ocean. Relatively little is known about the areas of operation and impacts of driftnetting in the South Atlantic as yet, but it is emerging that driftnetting is equally devastating to the fauna of this ocean. This paper reviews the impact of the driftnet fishery on non-target species in the central South Atlantic Ocean. Several lines of evidence suggest that fishing effort is focused on Tristan da Cunha, apparently resulting in considerable mortality of rockhopper penguins Eudyptes chrysocome and other marine organisms. Britain should take steps to curb this destructive fishing technique in Tristan waters.

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