Circulation in the central equatorial Atlantic: Mean and intraseasonal to seasonal variability

Brandt, Peter; Schott, Friedrich; Provost, Christine; Kartavtseff, Annie; Hormann, Verena; Bourlès, Bernard; Fischer, Jürgen

doi:10.1029/2005gl025498

Cited by 65 publications

(125 citation statements)

References 17 publications

Supporting

Mentioning

108

Contrasting

Order By: Relevance

“…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°wsupporting

confidence: 58%

“…[2003] at 35°W, and to the 20.0 Sv and 13.8 Sv obtained at 35°W and around 26°W, respectively, by Brandt et al [2006]. 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.…”

Section: Mean Flow At 10°wmentioning

confidence: 67%

“…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. Thus, between 26°W and 10°W, the EUC loses about 2.7 Sv above s q = 24.5 but gains 1.0 Sv below.…”

Section: Mean Flow At 10°wmentioning

confidence: 88%

“…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: 96%

“…[2] Although the ocean circulation and the Equatorial Undercurrent (EUC) are rather well described and begin to be well understood in the western and central parts of the equatorial upper Atlantic Ocean [Schott et al, 1998;Bourlès et al, 1999;Stramma and Schott, 1999;Brandt et al, 2006], the EUC in the Gulf of Guinea (GG) suffers from a lack of recent observations and studies.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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.

View full text Add to dashboard Cite

[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.

show abstract

Section: Mean Flow At 10°wsupporting

confidence: 58%

Section: Mean Flow At 10°wmentioning

confidence: 67%

Section: Mean Flow At 10°wmentioning

confidence: 88%

Section: Mean Sections At 10°wmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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.

View full text Add to dashboard Cite

show abstract

Mixed layer heat and salinity budgets during the onset of the 2011 Atlantic cold tongue

Schlundt

Brandt

Dengler

et al. 2014

J. Geophys. Res. Oceans

Self Cite

View full text Add to dashboard Cite

The mixed layer (ML) temperature and salinity changes in the central tropical Atlantic have been studied by a dedicated experiment (Cold Tongue Experiment (CTE)) carried out from May to July 2011. The CTE was based on two successive research cruises, a glider swarm, and moored observations. The acquired in situ data sets together with satellite, reanalysis, and assimilation model data were used to evaluate box-averaged ML heat and salinity budgets for two subregions: (1) the western equatorial Atlantic cold tongue (ACT) (23 -10 W) and (2) the region north of the ACT. The strong ML heat loss in the ACT region during the CTE was found to be the result of the balance of warming due to net surface heat flux and cooling due to zonal advection and diapycnal mixing. The northern region was characterized by weak cooling and the dominant balance of net surface heat flux and zonal advection. A strong salinity increase occurred at the equator, 10 W, just before the CTE. During the CTE, ML salinity in the ACT region slightly increased.Largest contributions to the ML salinity budget were zonal advection and the net surface freshwater flux. While essential for the ML heat budget in the ACT region, diapycnal mixing played only a minor role for the ML salinity budget. In the region north of the ACT, the ML freshened at the beginning of the CTE due to precipitation, followed by a weak salinity increase. Zonal advection changed sign contributing to ML freshening at the beginning of the CTE and salinity increase afterward.

show abstract

Biological production, export efficiency, and phytoplankton communities across 8000 km of the South Atlantic

Howard

Durkin

Hennon

et al. 2017

Global Biogeochemical Cycles

View full text Add to dashboard Cite

In situ oxygen tracers (triple oxygen isotope and oxygen/argon ratios) were used to evaluate meridional trends in surface biological production and export efficiency across~8000 km of the tropical and subtropical South Atlantic in March-May 2013. We used observations of picophytoplankton, nanophytoplankton, and microphytoplankton to evaluate community structure and diversity and assessed the relationships of these characteristics with production, export efficiency, and particulate organic carbon (POC) fluxes. Rates of productivity were relatively uniform along most of the transect with net community production (NCP) between 0 and 10 mmol O 2 m À2 d À1, gross primary production (GPP) between 40 and 100 mmol O 2 m À2 d À1 , and NCP/GPP, a measure of export efficiency, ranging from 0.1 to 0.2 (0.05-0.1 in carbon units). However, notable exceptions to this basin-scale homogeneity included two locations with highly enhanced NCP and export efficiency compared to surrounding regions. Export of POC and particulate nitrogen, derived from sediment traps, correlated with GPP across the transect, over which the surface community was dominated numerically by picophytoplankton. NCP, however, did not correlate with POC flux; the mean difference between NCP and POC flux was similar to published estimates of dissolved organic carbon export from the surface ocean. The interrelated rates of production presented in this work contribute to the understanding, building on the framework of better-studied ocean basins, of how carbon is biologically transported between the atmosphere and the deep ocean.Plain Language Summary Photosynthesis in the ocean results in the drawdown of atmospheric carbon dioxide. In this study, we use biological and chemical data from a cruise transiting 8000 km of the South Atlantic Ocean in order to study how biological communities in the surface ocean produced oxygen and took up carbon dioxide from the atmosphere in order to grow and how that carbon was consumed or transferred to greater depths away from the atmosphere. Specifically, we used dissolved gases to measure phytoplankton respiration and photosynthesis and sediment traps to collect falling particles; we also determined phytoplankton community structure at 5 m of water depth. This combination of information about the biological community, production, and export across a large region provides insights into the relationships underlying carbon cycling in the South Atlantic.

show abstract

Circulation in the central equatorial Atlantic: Mean and intraseasonal to seasonal variability

Cited by 65 publications

References 17 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

Mixed layer heat and salinity budgets during the onset of the 2011 Atlantic cold tongue

Biological production, export efficiency, and phytoplankton communities across 8000 km of the South Atlantic

Contact Info

Product

Resources

About