Equatorial Undercurrent and North Equatorial Countercurrent at 38°W: A new perspective from direct velocity data

Urbano, D. F.; Almeida, Roberto A. F. de; Nobre, Paulo

doi:10.1029/2007jc004215

Cited by 36 publications

(42 citation statements)

References 41 publications

(82 reference statements)

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“…They found a strong exchange between the nNECC and the NECC/NEUC. The northern core of the NECC was noted by Urbano et al [2008] as well between 9° and 15°N farther west, during measurements at the PIRATA mooring position at 38°W. They found a meandering NECC and two cores developing when the ITCZ reaches its northernmost location.…”

Section: Discussionmentioning

confidence: 92%

On the spreading of South Atlantic Water into the Northern Hemisphere

et al. 2009

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[1] The upper branch of the meridional overturning circulation in the North Atlantic is fed by cross-equatorial transport of various water masses from the Southern Hemisphere. Here, we study the large-scale spreading of South Atlantic Water (SAW) into the western tropical North Atlantic from the equator to 25°N. The fractions of SAW in the upper ocean water masses are quantified using a water mass analysis applied on a data set of conductivity-temperature-depth data from the Hydrobase project and the Argo float program. To fill gaps in the data coverage and to gain insight into the mechanisms involved, the observations are complemented with results from the high-resolution Family of Linked Atlantic Model Experiments model ( 1 12°) , which has been shown to realistically simulate the inflow of SAW into the Caribbean. The analysis reveals the mean SAW propagation pathways in the North Atlantic and identifies the regions of largest variability. High SAW fractions in the thermocline and central water layers are limited to the region south of 10°N, where the water body consists of 80%-90% SAW. Thus, the zonal currents in the equatorial gyre are mainly formed of SAW. The weaker currents in the intermediate layer combined with a northward excursion of the North Equatorial Current allow the SAW in this layer to intrude farther north compared to the layers above. The transition into North Atlantic Water occurs gradually from 12°N to 20°N in the intermediate layer.

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Section: Discussionmentioning

confidence: 92%

On the spreading of South Atlantic Water into the Northern Hemisphere

et al. 2009

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“…The time-mean eastward surface velocity at 5 N between 40 and 20 W is approximately 0.2-0.25 mÁs 21 [Lumpkin and Garzoli, 2005]. But the eastward velocity of the NECC is stronger during early summer and exhibits strong interannual variation, for example, with a value of about 0.2 mÁs 21 in July 2004 and 0.4 mÁs 21 in July 2005 [Urbano et al, 2008]. The eastward propagation speed estimated from the Aquarius data in the second half of 2012 using Radon Transform is 0.81 mÁs 21 for the unfiltered data and 0.53 mÁs 21 for the 4-20 , 20-50 day band-pass filtered data.…”

Section: Spatial and Temporal Signature Of Tiws In Sss Sst And Sshmentioning

confidence: 99%

The influence of salinity on tropical Atlantic instability waves

et al. 2014

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Sea surface salinity (SSS) data derived from the Aquarius/SAC-D satellite mission are analyzed along with other satellite and in situ data to assess Aquarius' capability to detect tropical instability waves (TIWs) and eddies in the tropical Atlantic Ocean and to investigate the influence that SSS has on the variability. Aquarius data show that the magnitude of SSS anomalies associated with the Atlantic TIWs is 60.25 practical salinity unit, which is weaker than those in the Pacific by 50%. In the central equatorial Atlantic, SSS contribution to the mean meridional density gradient is similar to sea surface temperature (SST) contribution. Consequently, SSS is important to TIW-related surface density anomalies and perturbation potential energy (PPE). In this region, SSS influences surface PPE significantly through the direct effect and the indirect effect associated with SSS-SST covariability. Ignoring SSS effects would underestimate TIW-related PPE by approximately three times in the surface layer. SSS also regulates the seasonality of the TIWs. The borealspring peak of the PPE due to SSS leads that due to SST by about one month. Therefore, SSS not only affects the spatial structure, but the seasonal variability of the TIWs in the equatorial Atlantic. In the northeast Atlantic near the Amazon outflow and the North Brazil Current retroflection region and in the southeast Atlantic near the Congo River outflow, SSS accounts for 80-90% of the contribution to mean meridional density gradient. Not accounting for SSS effect would underestimate surface PPE in these regions by a factor of 10 and 4, respectively.

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“…Johns et al (2014) have recently shown that this is the case in the central Atlantic but not so in the eastern basin. Velocity measurements at moorings also suggest substantial seasonal changes in vertical structure, as the EUC shallows/deepens during the boreal spring/fall (Brandt et al, 2006;Urbano et al, 2008;Johns et al, 2014). Hüttl-Kabus and Böning (2008), using a high-resolution numerical model, found the NEUC to transport between 4 Sv and 7 Sv at 35°W (a predominant annual cycle) and the SEUC to range between 1.2 Sv and 4.5 Sv at 23°W (semiannual cycle).…”

Section: Seasonal Tropical Variabilitymentioning

confidence: 95%

“…The spatial structure of the mean surface tropical currents is characterized by zonal jets that alternate in latitude (Stramma and Schott, 1999;Schott et al, 2003Schott et al, , 2004Lumpkin and Garzoli, 2005;Hüttl-Kabus and Böning, 2008;Urbano et al, 2008;RosellFieschi et al, 2015). The predominant flow is the westward South Equatorial Current (SEC) but close to the Equator we find the eastward Equatorial Undercurrent (EUC) along 0°, flanked by its northern and southern branches (NEUC and SEUC) at latitudes between 3°and 4°.…”

Section: Mean Equatorial Surface Fieldsmentioning

confidence: 96%

“…Urbano et al (2006) used observational and numerical data at 35°W and found the NECC to reach maximum transports of 19 Sv during boreal summer and to reverse (4 Sv) during boreal winter. Urbano et al (2006Urbano et al ( , 2008 show that sometimes, when the ADT ridge widens, the NECC may partition into two jets, with the southern one sometimes merging with the NEUC.…”

Section: Seasonal Tropical Variabilitymentioning

confidence: 98%

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