The zonal currents and transports at 35°W in the tropical Atlantic

Schott, Friedrich; Dengler, Marcus; Brandt, Peter; Affler, Karina; Fischer, Jürgen; Bourlès, Bernard; Gouriou, Yves; Molinari, Robert L.; Rhein, Monika

doi:10.1029/2002gl016849

Cited by 95 publications

(133 citation statements)

References 10 publications

(17 reference statements)

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“…[55] Our results also suggest that the EUC at 10°W is rather located under the thermocline, contrarily to the western EUC always found within the thermocline [Schott et al, 2003;Brandt et al, 2006]. Our results show a strong semiannual variability of the EUC transport and indicate that the hydrological structure varies strongly above and beneath the EUC velocity core.…”

Section: Discussionsupporting

confidence: 64%

“…These results suggest that, while the EUC transport significantly decreases from 35°W to 26°W and loses about 6 Sv, it decreases only modestly farther east, losing 1.7 Sv between 26°W and 10°W. From the 12.1 Sv EUC total transport, 0.4 Sv occurs in the surface layer, i.e., above s q = 24.5 (as previously defined by Schott et al [2003] and Brandt et al [2006]), and 11.7 Sv in the thermocline as follows: 2.5 Sv in the upper thermocline, 8.3 Sv in the lower thermocline layer, and 0.9 Sv in the deep thermocline above 250 m depth (Table 2). Brandt et al [2006] found at 26°W an EUC transport of 3.1 Sv above s q = 24.5 and 10.7 Sv below.…”

Section: Mean Flow At 10°wmentioning

confidence: 67%

“…It corresponds to the SEUC, also observed at 35°W and 26°W [Schott et al, 2003;Brandt et al, 2006]. The eastward velocities associated with the SEUC are found between 4°S and 7°S, revealing a large latitudinal extent for this mean current at that longitude.…”

Section: C06014mentioning

confidence: 85%

“…[60] An important aspect of the variability of the EUC core at 10°W is the disappearance of the salinity maximum, that characterizes the EUC at 35°W and 23°W in boreal summer [Schott et al, 2003;Brandt et al, 2006]. It is related to the boreal summer outcropping of the upper hydrological structure, associated with equatorial upwelling.…”

Section: Resultsmentioning

confidence: 99%

“…These mean sections are presented in Figure 2 and can be directly compared with mean equatorial sections previously presented at 35°W by Schott et al [2003] and around 26°W by Brandt et al [2006]. As summarized in Table 2, 3 cruises were carried out in boreal winter (i.e., from December to February), 2 in spring (March to May), 6 in summer (June to August) and 7 in fall (September to November).…”

Section: Mean Sections At 10°wmentioning

confidence: 99%

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Seasonal variability of the Equatorial Undercurrent at 10°W as inferred from recent in situ observations

Kolodziejczyk¹,

Bourlès²,

Marin³

et al. 2009

J. Geophys. Res.

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[1] Eighteen cross-equatorial shipboard current profiling sections along 10°W with conductivity-temperature-depth measurements taken between 1997 and 2007 are used to analyze the mean meridional structure and the seasonal variability of the Equatorial Undercurrent (EUC) at 10°W. Our analysis suggests a seasonal cycle for the EUC transport at 10°W, with a well-defined annual harmonic and some indication of a semiannual component, with a first maximum in January and a second stronger maximum from June to September. The mean EUC transport at 10°W is estimated to be 12.1 Sv and, compared to earlier estimates farther in the west, at 35°W (20.9 Sv) and 26°W (13.8 Sv). The eastward flow transport exhibits a strong variability at 10°W (with a total range of transports from 7.1 Sv to more than 31.7 Sv). The seasonal amplitude of the eastward flow variability is ±8.9 Sv, from a minimum of 8.2 Sv in November to 25.9 Sv in August. The eastward flows within the thermocline are divided in two parts: a permanent part within the s q = 24.5-26.5 isopycnal layer, with a semiannual cycle, known as the EUC, and a nonpermanent part in the deep thermocline (beneath s q = 26.5 isopycnal), associated with a strong eastward transport (up to 15 Sv) during the boreal summer, that is not observed during the rest of the year. The current at the equator in the deep thermocline is even westward during boreal fall. The disappearance of the salinity core of the EUC during the boreal summer, associated with the upwelling of the hydrological structure at 10°W, reveals that the saline subtropical waters carried by the EUC within the thermocline no longer flow into the Gulf of Guinea during the boreal summer. Our data also show the presence of the South Equatorial Undercurrent (SEUC) at 10°W in the Gulf of Guinea with a strong latitudinal and depth variability throughout the year. The mean SEUC at 10°W is centered near 5°S and is farther south than observed at 35°W and 26°W, suggesting its poleward shift from west to east.

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Section: Discussionsupporting

confidence: 64%

Section: Mean Flow At 10°wmentioning

confidence: 67%

Section: C06014mentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: Mean Sections At 10°wmentioning

confidence: 99%

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Seasonal variability of the Equatorial Undercurrent at 10°W as inferred from recent in situ observations

Kolodziejczyk¹,

Bourlès²,

Marin³

et al. 2009

J. Geophys. Res.

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Atlantic Ocean circulation changes preceded millennial tropical South America rainfall events during the last glacial

Bürckel

Waelbroeck

Gherardi

et al. 2015

Geophysical Research Letters

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During the last glacial period, Greenland's climate shifted between cold (stadial) and warm (interstadial) phases that were accompanied by ocean circulation changes characterized by reduced Atlantic Meridional Overturning Circulation (AMOC) during stadials. Here we present new data from the western tropical Atlantic demonstrating that AMOC slowdowns preceded some of the large South American rainfall events that took place during stadials. Based on 231 Pa/ 230 Th and Ti/Ca measurements in the same sediment core, we determine that the AMOC started to slowdown 1420 ± 250 and 690 ± 180 (1σ) years before the onset of two large precipitation events associated with Heinrich stadials. Our results bring unprecedented evidence that AMOC changes could be at the origin of the large precipitation events observed in tropical South America during Heinrich stadials. In addition, we propose a mechanism explaining the differences in the extent and timing of AMOC slowdowns associated with shorter and longer stadials.

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Annually-resolved propagation of CFCs and SF6 in the global ocean over eight decades

Cimoli

Gebbie

Purkey

et al. 2022

Preprint

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Oceanic transient tracers, such as chlorofluorocarbons (CFCs) and sulfur-hexafluoride (SF6), trace the propagation of intermediateto-abyssal water masses in the ocean interior. Their temporal and spatial sparsity, however, has limited their utility in quantifying the global ocean circulation and its decadal variability. The Time-Correction Method presented here is a new approach to leverage the available CFCs and SF6 observations to solve for the Green's functions describing the steady-state transport from the surface to the ocean interior. From the Green's functions, we reconstruct global tracer concentrations (and associated uncertainties) in the ocean interior at annual resolution (1940 to 2021). The spatial resolution includes 50 neutral density levels that span the water column along WOCE/GO-SHIP lines. The reconstructed tracer concentrations return a global view of CFCs and SF6 spreading into new regions of the interior ocean, such as the deep north-western Pacific. For example, they capture the southward spreading and equatorial recirculation of distinct NADW components, and the spreading of CFC-rich AABW out of the Southern Ocean and into the North Pacific, East Indian, and West Atlantic. The reconstructed tracer concentrations fit the data in most locations (˜75%), indicating that a steady-state circulation holds for the most part. Discrepancies between the reconstructed and observed concentrations offer insight into ventilation rate changes on decadal timescales. As an example, we infer decadal changes in Subantartic Mode Water (SAMW) and find an increase in SAMW ventilation from 1992 to 2014, highlighting the skill of the time-correction method in leveraging the sparse tracer observations.

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The zonal currents and transports at 35°W in the tropical Atlantic

Cited by 95 publications

References 10 publications

Seasonal variability of the Equatorial Undercurrent at 10°W as inferred from recent in situ observations

Seasonal variability of the Equatorial Undercurrent at 10°W as inferred from recent in situ observations

Atlantic Ocean circulation changes preceded millennial tropical South America rainfall events during the last glacial

Annually-resolved propagation of CFCs and SF6 in the global ocean over eight decades

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