Consulta: subjectFacets:"Tropical Atlantic"
Registros recuperados: 14
Data/hora: 09/06/2024 05:01:40

Polychaete diversity at tropical Atlantic deep-sea sites: environmental effects
Provedor de dados: 5
Autores: Cosson-sarradin, Nathalie; Sibuet, Myriam; Paterson, Glj; Vangriesheim, Annick.
This study assesses how differences in nutrient flux and bottom currents affect the diversity and trophic structure of deep-sea polychaete communities from the tropical northeast Atlantic at 20 degrees to 21 degrees N latitude. Faunal assemblages were studied from 3 sets of USNEL box cores (0.25 m(2)) taken at depths of 1700, 3100 and 4600 m. In terms of primary productivity, the cores were taken beneath water which is eutrophic, mesotrophic and oligotrophic, respectively. Total polychaete abundance, abundance of dominant species, and faunal similarity and diversity were compared among the 3 sites. Polychaete abundance decreased with increasing depth. Community structure reflected environmental characteristics as well as the influence of coastal upwelling....
Tipo: Text
Palavras-chave: Deep sea; Tropical Atlantic; Diversity; Polychaete community; Environmental conditions.
Ano: 1998
URL: http://archimer.ifremer.fr/doc/00179/28978/27398.pdf

Sea Surface Salinity Signature of the Tropical Atlantic Interannual Climatic Modes
Provedor de dados: 5
Autores: Awo, F. M.; Alory, G.; Da-allada, Casimir Yelognisse; Delcroix, T.; Jouanno, J.; Kestenare, E.; Baloitcha, E.
The characteristic sea surface salinity (SSS) patterns associated with the tropical Atlantic meridional and equatorial interannual modes are extracted from in situ observations, by a statistical analysis performed on the 1980–2012 period. These SSS signatures of the interannual climatic modes are reproduced in a regional numerical simulation. For each mode, oceanic and/or atmospheric processes driving the SSS signature are identified through a mixed‐layer salt budget in the validated model. During a positive meridional mode in spring, a northward shift of the Intertropical Convergence Zone and related precipitation maximum creates a south‐north dipole of positive‐negative SSS anomalies around the equator. Western boundary currents strengthen and advect...
Tipo: Text
Palavras-chave: Sea surface salinity; Tropical Atlantic; Interannual climatic modes.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00463/57517/59694.pdf

Ocean Circulation Drives the Variability of the Carbon System in the Eastern Tropical Atlantic
Provedor de dados: 5
Autores: Lefèvre, Nathalie; Mejia, Carlos; Khvorostyanov, Dmitry; Beaumont, Laurence; Koffi, Urbain.
The carbon system in the eastern tropical Atlantic remains poorly known. The variability and drivers of the carbon system are assessed using surface dissolved inorganic carbon (DIC), alkalinity (TA) and fugacity of CO2 (fCO2) measured in the 12° N–12° S, 12° W–12° E region from 2005 to 2019. A relationship linking DIC to temperature, salinity and year has been determined, with salinity being the strongest predictor. The seasonal variations of DIC, ranging from 80 to 120 mol kg−1, are more important than the year-to-year variability that is less than 50 mol kg−1 over the 2010–2019 period. DIC and TA concentrations are lower in the northern part of the basin where surface waters are fresher and warmer. Carbon supply dominates over biological carbon uptake...
Tipo: Text
Palavras-chave: Carbon cycle; Tropical Atlantic; Dissolved inorganic carbon; Alkalinity.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00678/79046/81494.pdf

The mid-depth circulation of the northwestern tropical Atlantic observed by floats
Provedor de dados: 5
Autores: Lankhorst, Matthias; Fratantoni, David; Ollitrault, Michel; Richardson, Philip; Send, Uwe; Zenk, Walter.
A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600-1050dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200-2050dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW` mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g....
Tipo: Text
Palavras-chave: Equatorial currents; North Atlantic Deep Water; Antarctic Intermediate Water; Tropical Atlantic; Floats.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6815.pdf

Variation in structure and biomass of the benthic communities at three contrasting sites in the tropical Northeast Atlantic
Provedor de dados: 5
Autores: Galeron, Joelle; Sibuet, Myriam; Mahaut, Ml; Dinet, A.
Three major size classes of the benthic metazoan communities (megafauna, macrofauna and meiofauna) were investigated simultaneously at 3 sites in the tropical Northeast Atlantic. The sites varied in their level of surface primary productivity (eutrophic, mesotrophic and oligotrophic). Results for 3 cruises in 3 seasons (Eumeli 2, winter 1991; Eumeli 3, autumn 1991; Eumeli 4, spring 1992) are given for each size class in terms of taxonomic composition, density and biomass. The benthic communities did not exhibit evidence of seasonal variation, but there were substantial differences in the quantitative structure of the metazoan communities between the 3 sites. Total metazoan density and biomass, as well as density and biomass of each size class, decreased...
Tipo: Text
Palavras-chave: Deep sea; Tropical Atlantic; Meiofauna; Macrofauna; Megafauna; Taxonomic composition; Density; Biomass; Environmental conditions.
Ano: 2000
URL: http://archimer.ifremer.fr/doc/00000/10519/7602.pdf

Contribution of the Amazon River Discharge to Regional Sea Level in the Tropical Atlantic Ocean
Provedor de dados: 5
Autores: Giffard, Pierrick; Llovel, William; Jouanno, Julien; Morvan, Guillaume; Decharme, Bertrand.
Tipo: Text
Palavras-chave: Sea level; Amazon River; River plume; Salinity; Model; NEMO; Tropical Atlantic.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00591/70268/68327.pdf

SST Indexes in the Tropical South Atlantic for Forecasting Rainy Seasons in Northeast Brazil
Provedor de dados: 5
Autores: Hounsou-gbo, Gbekpo Aubains; Servain, Jacques; Araujo, Moacyr; Caniaux, Guy; Bourles, Bernard; Fontenele, Diogenes; Martins, Eduardo Savio P. R.
May-to-July and February-to-April represent peak rainy seasons in two sub-regions of Northeast Brazil (NEB): Eastern NEB and Northern NEB respectively. In this paper, we identify key oceanic indexes in the tropical South Atlantic for driving these two rainy seasons. In Eastern NEB, the May-to-July rainfall anomalies present a positive relationship with the previous boreal winter sea surface temperature anomalies (SSTA) in the southeast tropical Atlantic (20 degrees-10 degrees S; 10 degrees W-5 degrees E). This positive relationship, which spread westward along the southern branch of the South Equatorial Current, is associated with northwesterly surface wind anomalies. A warmer sea surface temperature in the southwestern Atlantic warm pool increases the...
Tipo: Text
Palavras-chave: Brazilian Northeast; Rainfall; Predictability; Tropical Atlantic.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00623/73547/73807.pdf

Proposal of a trophic relationship between Chaetognatha and Cnidaria based on Mitochondrial COI sequences
Provedor de dados: 5
Autores: Da Mota Melo, Danielle Caroline; Costa Brandao, Manoela; De Albuquerque, Simone Maria; Neumann-leitão, Sigrid.
This is the first study in Brazil to propose a trophic relationship between Chaetognatha and Cnidaria based on molecular data (COI gene - DNA barcode). Cnidaria COI sequences were detected in tissue samples from two specimens of Flaccisagitta enflata collected in the surroundings of Fernando de Noronha archipelago, Tropical Western Atlantic. The methodology used followed all the requirements for a safe molecular manipulation, making the possibility of contamination unlikely. A search carried in BLAST showed that both sequences provided here presented a combination of highest query coverage and match identity with Nemopilema nomurai (Cnidaria: Scyphozoa), supporting the hypothesis that they belong to a species of jellyfish. Since gelatinous taxa are known...
Tipo: Text
Palavras-chave: DNA barcode; Food item; Oceanic island; Tropical Atlantic; Zooplankton; Cytochrome oxidase subunit I gene.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00628/74057/73490.pdf

Subsurface fine scale patterns in an anticyclonic eddy off Cap-Vert peninsula observed from glider measurements
Provedor de dados: 5
Autores: Kolodziejczyk, Nicolas; Testor, Pierre; Lazar, Alban; Echevin, Vincent; Krahmann, Gerd; Chaigneau, Alexis; Gourcuff, Claire; Wade, Malick; Faye, Saliou; Estrade, Philippe; Capet, Xavier; Mortier, Laurent; Brehmer, Patrice; Schuette, Florian; Karstensen, Johannes.
Glider measurements acquired along 4 transects between Cap‐Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March‐April 2014 were used to investigate fine‐scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated north‐west towards the Cape Verde islands. At depth, between 100‐400 m, the isolated anticyclone core contained relatively oxygenated, low salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation of fine‐scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These...
Tipo: Text
Palavras-chave: Submesoscale; Stirring; Tropical Atlantic; Meoscale eddy; Glider measurements; OMZ.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00450/56162/57708.pdf

On the seasonal variations of salinity of the tropical Atlantic mixed layer
Provedor de dados: 5
Autores: Camara, I.; Kolodziejczyk, Nicolas; Mignot, Juliette; Lazar, Alban; Gaye, Amadou T.
The physical processes controlling the mixed layer salinity (MLS) seasonal budget in the tropical Atlantic Ocean are investigated using a regional configuration of an ocean general circulation model. The analysis reveals that the MLS cycle is generally weak in comparison of individual physical processes entering in the budget because of strong compensation. In evaporative regions, around the surface salinity maxima, the ocean acts to freshen the mixed layer against the action of evaporation. Poleward of the southern SSS maxima, the freshening is ensured by geostrophic advection, the vertical salinity diffusion and, during winter, a dominant contribution of the convective entrainment. On the equatorward flanks of the SSS maxima, Ekman transport mainly...
Tipo: Text
Palavras-chave: Salinity; Seasonal variation; Tropical Atlantic; Vertical mixing.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00624/73563/73200.pdf

Generation of tropical instability waves in the Atlantic Ocean - art. no. C08034
Provedor de dados: 5
Autores: Von Schuckmann, Karina; Brandt, P; Eden, C.
[1] The spatial and temporal distributions of tropical instability waves (TIWs) in the Atlantic Ocean are investigated using a combination of current observations with moored instruments deployed at the equator at 23 degrees W and a realistic eddy-resolving (1/12 degrees) general circulation model of the Atlantic Ocean. The meridional and vertical shears of the zonal current system contribute to the eddy production rates and thus to the generation of TIWs in the central tropical Atlantic Ocean. In the Southern Hemisphere, TIWs are forced only by baroclinic instability associated with the vertical shear of the central part of the South Equatorial Current (SEC). In the Northern Hemisphere, baroclinic instability due to the vertical shear of the northern SEC...
Tipo: Text
Palavras-chave: Barotropic and baroclinic instability; Tropical Atlantic; Tropical instability waves.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4554.pdf

Seasonal cycle of the salinity barrier layer revealed in the northeastern Gulf of Guinea
Provedor de dados: 5
Autores: Dossa, A. N.; Da-allada, C. Y.; Herbert, G; Bourles, Bernard.
The region located in the far northeast of the Gulf of Guinea (NEGG), eastern tropical Atlantic, remains poorly documented due to a lack of available in situ ocean data. Heavy rainfall and intense river discharges observed in this region induce a strong salinity stratification that may have a significant impact on the mixed layer depth and on sea surface temperatures, through the so-called barrier-layer effect. By using recent in situ data and climatological outputs from a numerical simulation, we reveal the existence of a barrier layer in the NEGG and describe its seasonal occurrence. In the NEGG, the barrier layer limits the mixed layer depth. From January to March, significant values for the barrier-layer thickness are observed mostly due to the...
Tipo: Text
Palavras-chave: Mixed layer depth; Niger River discharge; Numerical model; Oceanography; Sea surface salinity; Tropical Atlantic; Vertical stratification.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00509/62103/66273.pdf

Marine spatial planning and the risk of ocean grabbing in the tropical Atlantic
Provedor de dados: 5
Autores: Queffelec, Betty; Bonnin, Marie; Ferreira, Beatrice; Bertrand, Sophie; Teles Da Silva, Solange; Diouf, Fatou; Trouillet, Brice; Cudennec, Annie; Brunel, Adrien; Billant, Odeline; Toonen, Hilde; Flannery, Wesley.
Ocean grabbing occurs when traditional users, such as small-scale fishers, are pushed aside by new development activities. This grabbing must be prevented to avoid sea uses that maintain or increase social inequity. In this paper, we show that in tropical Atlantic countries, such as Brazil and Senegal, examples of ocean grabbing already occur. In this context, we analyse if Maritime Spatial Planning (MSP) may be an opportunity to limit ocean grabbing or, to the contrary, poses a risk to increase it. MSP calls for an ecosystem approach that requires integrated coastal and marine management and involves stakeholders in developing a shared vision of the future, where society and environment are preserved. However, recent studies have shown that MSP is a...
Tipo: Text
Palavras-chave: Brazil; Fisheries; Maritime spatial planning; Ocean grabbing; Senegal; Stakeholders; Tropical Atlantic.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00683/79487/82079.pdf

Seasonal and Interannual Mixed-Layer Heat Budget Variability in the Western Tropical Atlantic From Argo Floats (2007-2012)
Provedor de dados: 5
Autores: Nogueira Neto, A., V; Giordani, H.; Caniaux, G.; Araujo, M.
Oceanic and atmospheric processes were investigated in order to explore the causes of seasonal and interannual variability of sea surface temperatures (SST) in the western tropical Atlantic (WTA; 20 degrees S-20 degrees N, 15 degrees W-60 degrees W). A mixed-layer (ML) heat budget was performed by using Argo profiles and supplementary data sets based on satellite and atmospheric products during the period 2007-2012. The WTA is divided into four boxes which represent the main temporal and spatial heterogeneities of this region. An analysis of error of each term pointed out that the mean net surface heat fluxes are systematically underestimated by 20 W m(-2). A correction of this term provides realistic estimates of the vertical mixing which was obtained as...
Tipo: Text
Palavras-chave: Tropical Atlantic; Mixed-layer heat budget; Sea surface temperature; Argo floats.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00623/73551/73798.pdf