Occurrence and characteristics of mesoscale eddies in the tropical northeast Atlantic Ocean

Schütte, Florian, Brandt, Peter and Karstensen, Johannes (2016) Occurrence and characteristics of mesoscale eddies in the tropical northeast Atlantic Ocean Ocean Science, 12 (3). pp. 663-685. DOI 10.5194/os-12-663-2016.

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Abstract

Coherent mesoscale features (referred to here as eddies) in the tropical northeast Atlantic (between 12–22° N and 15–26° W) are examined and characterised. The eddies' surface signatures are investigated using 19 years of satellite derived sea level anomaly (SLA) data. Two automated detection methods are applied, the geometrical method based on closed streamlines around eddy cores, and the Okubo–Weiß method based on the relation between vorticity and strain. Both methods give similar results. Mean eddy surface signatures of SLA, sea surface temperature (SST) and salinity (SSS) are obtained from composites of all snapshots around identified eddy cores. Anticyclones/cyclones are associated with elevation/depression of SLA and enhanced/reduced SST and SSS patterns. However, about 20 % of all detected anticyclones show reduced SST and reduced SSS instead. These kind of eddies are classified as anticyclonic mode-water eddies (ACMEs). About 146 ± 4 eddies per year are identified (52 % cyclones, 39 % anticylones, 9 % ACMEs) with rather similar mean radii of about 56 ± 12 km. Based on concurrent in-situ temperature and salinity profile data (from Argo float, shipboard and mooring data) inside of the three eddy types, their distinct differences in vertical structure is determined. Most eddies are generated preferentially in boreal summer and along the West African coast at three distinct coastal headland region and carry South Atlantic Central Water that originates from the northward transport within the Mauretania coastal current system. Westward eddy propagation (on average about 3.00 ± 2.15 km d−1) is confined to distinct corridors with a small meridional deflection dependent on the eddy type (anticyclones – equatorward, cyclones – poleward, ACMEs – no deflection). Heat and salt flux out of the coastal region and across the Cap Verde Frontal Zone, which separates the shadow zone from the ventilated gyre, are calculated.

Document Type: Article
Additional Information: WOS:000379347400004
Keywords: RV POSEIDON; RV METEOR; RV Maria S. Merian; L'Atalante; Pos320; M68/2; M68/3; Pos347; Pos348; Ata3; Ata4; MSM8; MSM10; Pos399; M80/1; M80/2; M81/1; M83/1; MSM18/2; MSM18/3; MSM22; MSM23; M96; M97
Research affiliation: OceanRep > SFB 754
OceanRep > SFB 754 > A5
OceanRep > SFB 754 > A4
OceanRep > SFB 754 > B9
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
DOI etc.: 10.5194/os-12-663-2016
ISSN: 1812-0784
Related URLs:
Projects: AWA, SFB754, FOR1740
Expeditions/Models:
Date Deposited: 18 Dec 2015 14:11
Last Modified: 19 Dec 2017 12:51
URI: http://eprints.uni-kiel.de/id/eprint/30689

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