The Forced Annual Reversal of the Atlantic North Equatorial Countercurrent

Garzoli, Silvia L.; Katz, Eli Joel

doi:10.1175/1520-0485(1983)013<2082:tfarot>2.0.co;2

Cited by 127 publications

(91 citation statements)

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“…The peak in positive WSC occurs in September (not shown) and leads to an overall peak in the WSC difference in August (Figure 3d). The several month lag of the NECC transport to this cycle is consistent with expected delays due to Rossby wave propagation at this latitude [e.g., Garzoli and Katz, 1983].…”

Section: The Nbcr Necc and The Wind Fieldsupporting

confidence: 80%

“…Some studies indicate that during the boreal summer, when the ITCZ is located at its northernmost position, the maximum velocities in the eastward flow of the NECC are observed [Richardson and Reverdin, 1987]. During the spring, when the ITCZ is located at its southernmost location, the NECC becomes weak and may be replaced by a westward flow [Garzoli and Katz, 1983;Garzoli and Richardson, 1989].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the North Brazil Current retroflection and North Equatorial Countercurrent variability

Fonseca

Goñi

Johns³

et al. 2004

Geophysical Research Letters

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Eight years of TOPEX/Poseidon altimeter‐derived sea height anomaly and climatological hydrographic data are used to investigate the temporal and spatial variability of the North Brazil Current (NBC) retroflection and the North Equatorial Countercurrent (NECC). The NBC retroflection exhibits a mean position of 6.6°N ± 2.0°, with a strong annual signal and year‐to‐year variability. The annual cycle of its location follows the meridional migration of the ITCZ and the strength of the wind stress curl over the equatorial Atlantic. A marked shift in the annual mean location of the NBC retroflection is observed in 1998–1999 that appears to be linked to an increase in wind stress curl during this period. The mean latitude of the NECC is estimated to be 6.0°N ± 1.3°, with a semiannual cycle showing maximum northerly locations in February and August. The baroclinic transport of the NECC varies predominantly on an annual cycle with maximum transport of 12 Sv occurring in November.

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Section: The Nbcr Necc and The Wind Fieldsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Investigation of the North Brazil Current retroflection and North Equatorial Countercurrent variability

Fonseca

Goñi

Johns³

et al. 2004

Geophysical Research Letters

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“…The NECC is highly variable, featuring a strong annual cycle (see e.g. Garzoli and Katz, 1983) and significant inter-annual variability in its mean location and strength (Hormann et al, 2012). In fact, the NECC includes a seasonal reverse cycle in the east-westward direction (see e.g.…”

Section: J M Magalhaes Et Al: Internal Solitary Waves Off the Amazmentioning

confidence: 99%

“…In fact, the NECC includes a seasonal reverse cycle in the east-westward direction (see e.g. Garzoli and Katz, 1983, for further details), which will be shown to have a major influence in the propagation of ISWs.…”

Section: J M Magalhaes Et Al: Internal Solitary Waves Off the Amazmentioning

confidence: 99%

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

et al. 2016

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Abstract. Synthetic aperture radar (SAR) imagery from the Amazon shelf break region in the tropical west Atlantic reveals for the first time the two-dimensional horizontal structure of an intense Internal Solitary Wave (ISW) field, whose first surface manifestations are detected several hundred kilometres away from the nearest forcing bathymetry. Composite maps and an energy budget analysis (provided from the Hybrid Coordinate Ocean Model -HYCOM) help to identify two major ISW pathways emanating from the steep slopes of a small promontory (or headland) near 44 • W and 0 • N, which are seen to extend for over 500 km into the open ocean. Further analysis in the SAR reveals propagation speeds above 3 m s −1 , which are amongst the fastest ever recorded. The main characteristics of the ISWs are further discussed based on a statistical analysis, and seasonal variability is found for one of the ISW sources. This seasonal variability is discussed in light of the North Equatorial Counter Current. The remote appearance of the ISW sea surface manifestations is explained by a late disintegration of the internal tide (IT), which is further investigated based on the SAR data and climatological monthly means (for stratification and currents). Acknowledging the possibility of a late disintegration of the IT may help explain the remote-sensing views of other ISWs in the world's oceans.

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“…The dominant feature south of the TANWA is the eastward flowing North Equatorial Countercurrent (NECC) extending over a latitudinal range from 3 • N to about 10 • N. It has a pronounced seasonal cycle with maximum strength in boreal summer and autumn, when the ITCZ reaches its northernmost position. During that period the NECC is a continuous zonal flow across the entire tropical Atlantic (e.g., Garzoli and Katz, 1983;Richardson and Reverdin, 1987;Stramma and Siedler, 1988;Polonsky and Artamonov, 1997). When approaching the African coast, the current is partly deflected to the north feeding a sluggish northward flow along the coast.…”

Section: Introductionmentioning

confidence: 99%

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

2016

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Abstract. Coherent mesoscale features (referred to here as eddies) in the tropical northeastern Atlantic Ocean (between 12-22 • N and 15-26 • W) are examined and characterized. 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 sea surface salinity (SSS) anomalies are obtained from composites of all snapshots around identified eddy cores. Anticyclones/cyclones are identified by an elevation/depression of SLA and enhanced/reduced SST and SSS in their cores. However, about 20 % of all anticyclonically rotating eddies 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 with a minimum lifetime of 7 days are identified (52 % cyclones, 39 % anticyclones, 9 % ACMEs) with rather similar mean radii of about 56 ± 12 km. Based on concurrent in situ temperature and salinity profiles (from Argo float, shipboard, and mooring data) taken inside of eddies, distinct mean vertical structures of the three eddy types are determined. Most eddies are generated preferentially in boreal summer and along the West African coast at three distinct coastal headland regions and carry South Atlantic Central Water supplied by the northward flow within the Mauretanian coastal current system. Westward eddy propagation (on average about 3.00 ± 2.15 km d −1 ) is confined to distinct zonal corridors with a small meridional deflection dependent on the eddy type (anticyclones -equatorward, cyclones -poleward, ACMEs -no deflection). Heat and salt fluxes out of the coastal region and across the Cape Verde Frontal Zone, which separates the shadow zone from the ventilated subtropical gyre, are calculated.

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The Forced Annual Reversal of the Atlantic North Equatorial Countercurrent

Cited by 127 publications

References 0 publications

Investigation of the North Brazil Current retroflection and North Equatorial Countercurrent variability

Investigation of the North Brazil Current retroflection and North Equatorial Countercurrent variability

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

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

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