MODELING THE SOUTH ATLANTIC OCEAN FROM MEDIUM TO HIGH RESOLUTION

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Mariela Gabioux ◽  
Vladimir Santos da Costa ◽  
Joao Marcos Azevedo Correia de Souza ◽  
Bruna Faria de Oliveira ◽  
Afonso De Moraes Paiva
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Large Scale ◽  
South Atlantic ◽  
Surface Relaxation ◽  
The South ◽  
Small Surface ◽  
Basic Model ◽  
Basic Set ◽  
Set Up

Results of the basic model configuration of the REMO project, a Brazilian approach towards operational oceanography, are discussed. This configuration consists basically of a high-resolution eddy-resolving, 1/12 degree model for the Metarea V, nested in a medium-resolution eddy-permitting, 1/4 degree model of the Atlantic Ocean. These simulations performed with HYCOM model, aim for: a) creating a basic set-up for implementation of assimilation techniques leading to ocean prediction; b) the development of hydrodynamics bases for environmental studies; c) providing boundary conditions for regional domains with increased resolution. The 1/4 degree simulation was able to simulate realistic equatorial and south Atlantic large scale circulation, both the wind-driven and the thermohaline components. The high resolution simulation was able to generate mesoscale and represent well the variability pattern within the Metarea V domain. The BC mean transport values were well represented in the southwestern region (between Vitória-Trinidade sea mount and 29S), in contrast to higher latitudes (higher than 30S) where it was slightly underestimated. Important issues for the simulation of the South Atlantic with high resolution are discussed, like the ideal place for boundaries, improvements in the bathymetric representation and the control of bias SST, by the introducing of a small surface relaxation. In order to make a preliminary assessment of the model behavior when submitted to data assimilation, the Cooper & Haines (1996) method was used to extrapolate SSH anomalies fields to deeper layers every 7 days, with encouraging results.

scholarly journals MODELING THE SOUTH ATLANTIC OCEAN FROM MEDIUM TO HIGH-RESOLUTION

2013 ◽  
Vol 31 (2) ◽  
pp. 229 ◽  
Author(s):  
Mariela Gabioux Gabioux ◽  
Vladimir Santos Da Costa ◽  
João Marcos Azevedo Correia de Souza ◽  
Bruna Faria de Oliveira ◽  
Afonso De Moraes Paiva
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Large Scale ◽  
South Atlantic ◽  
Surface Relaxation ◽  
Brazilian Coast ◽  
Western Boundary ◽  
The South ◽  
Basic Set ◽  
Set Up

ABSTRACT. The standard REMO (a Brazilian approach towards operational oceanography) model configuration is tested, and results of two numerical simulations with HYCOM are presented and discussed. This configuration consists basically of a high-resolution eddy-resolving, 1/12 degree model for the Metarea V (latitudes from 7◦N to 35◦50’S, and longitudes between 20◦W and the Brazilian coast), nested in a medium-resolution eddy-permitting, 1/4 degree model of the Atlantic Ocean. These simulations aim for: a) creating a basic set-up for implementation of assimilation techniques leading to ocean prediction; b) the development of hydrodynamic bases for environmental studies; and c) providing boundary conditions for regional domains with increased resolution. This is the first time HYCOM is applied in high-resolution and particularly tailored for this region of the ocean. The 1/4 degree simulation was able to simulate realistic Equatorial and South Atlantic large scale circulation, both the wind-driven and the thermohaline components. The high-resolution introduces realistic mesoscale activity, in particular that associated with the dynamics of western boundary currents, and captures also both the continental shelf and the upper-ocean modes of variability associated with atmospheric synoptic forcing. Important issues for the simulation of the South Atlantic with high-resolution are discussed, like the ideal place for boundaries, improvements in the bathymetric representation, and the control of SST bias by the introduction of surface relaxation. In order to make a preliminary assessment of the model behavior when submitted to data assimilation, the Cooper & Haines (1996) method was used to extrapolate SSH anomalies fields to deeper layers every 7 days, with encouraging results.Keywords: numerical simulation, nesting, southwest Atlantic, Brazil Current. RESUMO. Neste trabalho são apresentados e discutidos resultados de duas simulações numéricas realizadas com o model HYCOM e que representam a configuração padrão do projeto REMO (Rede de Modelagem e Observação Oceanográfica), uma abordagem brasileira para a oceanografia operacional. Esta configuração consiste em um modelo em alta resolução (1/12 de grau, que resolve a mesoescala) da região denominada de Metarea V (latitudes de 7◦N a 35◦50’S e longitudes desde 20◦W até a costa brasileira), aninhado em um modelo em média-resolução (1/4 de grau, que resolve apenas parcialmente a mesoescala) do oceano Atlântico. Estas simulações tem como objetivos: a) a geração de um set-up básico para implementação de técnicas de assimilação visando a previsão oceânica; b) o desenvolvimento de bases hidrodinâmicas para estudos ambientais; e c) a geração de condições de contorno para domínios regionais com maior resolução. Esta é a primeira vez que o HYCOM é aplicado em alta resolução e especialmente configurado para esta região do oceano. A simulação em 1/4 de grau simulou de forma realista a circulação de larga escala no Atlântico Sul e Equatorial, tanto a componente eólica quanto a termohalina. A simulação em alta resolução foi capaz de introduzir também de forma realista a mesoescala, em particular aquela associada à dinâmica das correntes de contorno oeste, e de capturar a variabilidade da porção superior do oceano e da plataforma continental associada à forçante atmosférica em escala sinótica. Aspectos importantes para a simulação do Atlântico Sul em alta resolução são discutidos, como o posicionamento dos contornos, a representação da batimetria e o controle de possíveis tendências na TSM pela introdução de um termo de relaxamento para climatologia em superfície. Uma avaliação preliminar do comportamento do modelo submetido à assimilação de dados foi realizada com o método de Cooper & Haines (1996), capaz de extrapolar campos de anomalias de elevação da superfície para camadas mais profundas a cada 7 dias, com resultados promissores.Palavras-chave: simulação numérica, aninhamento, Atlântico sudoeste, Corrente do Brasil.

scholarly journals THE BIFURCATION OF THE WESTERN BOUNDARY CURRENT SYSTEM OF THE SOUTH ATLANTIC OCEAN

2014 ◽  
Vol 32 (2) ◽  
pp. 241 ◽  
Author(s):  
Janini Pereira ◽  
Mariela Gabioux ◽  
Martinho Marta Almeida ◽  
Mauro Cirano ◽  
Afonso M. Paiva ◽  
...  
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Ocean Circulation ◽  
South Atlantic ◽  
Western Boundary Current ◽  
South Atlantic Ocean ◽  
Western Boundary ◽  
Intermediate Water ◽  
Boundary Current ◽  
The South

ABSTRACT. The results of two high-resolution ocean global circulation models – OGCMs (Hybrid Coordinate Ocean Model – HYCOM and Ocean Circulation andClimate Advanced Modeling Project – OCCAM) are analyzed with a focus on the Western Boundary Current (WBC) system of the South Atlantic Ocean. The volumetransports are calculated for different isopycnal ranges, which represent the most important water masses present in this region. The latitude of bifurcation of the zonalflows reaching the coast, which leads to the formation of southward or northward WBC flow at different depths (or isopycnal levels) is evaluated. For the Tropical Water,bifurcation of the South Equatorial Current occurs at 13◦-15◦S, giving rise to the Brazil Current, for the South Atlantic Central Water this process occurs at 22◦S.For the Antarctic Intermediate Water, bifurcation occurs near 28◦-30◦S, giving rise to a baroclinic unstable WBC at lower latitudes with a very strong vertical shearat mid-depths. Both models give similar results that are also consistent with previous observational studies. Observations of the South Atlantic WBC system havepreviously been sparse, consequently these two independent simulations which are based on realistic high-resolution OGCMs, add confidence to the values presentedin the literature regarding flow bifurcations at the Brazilian coast.Keywords: Southwestern Atlantic circulation, water mass, OCCAM, HYCOM. RESUMO. Resultados de dois modelos globais de alta resolução (HYCOM e OCCAM) são analisados focando o sistema de Corrente de Contorno Oeste do Oceano Atlântico Sul. Os transportes de volume são calculados para diferentes níveis isopicnais que representam as principais massas de água da região. É apresentada a avaliação da latitude de bifurcação do fluxo zonal que atinge a costa, permitindo a formação dos fluxos da Corrente de Contorno Oeste para o sul e para o norte emdiferentes níveis de profundidades (ou isopicnal). Para a Água Tropical, a bifurcação da Corrente Sul Equatorial ocorre entre 13◦-15◦S, originando a Corrente do Brasil, e para a Água Central do Atlântico Sul ocorre em 22◦S. A bifurcação daÁgua Intermediária Antártica ocorre próximo de 28◦-30◦S, dando um aumento na instabilidade baroclínica da Corrente de Contorno Oeste em baixas latitudes e com um forte cisalhamento vertical em profundidades intermediárias. Ambos os modelos apresentamresultados similares e consistentes com estudos observacionais prévios. Considerando que as observações do sistema de Corrente de Contorno Oeste do Atlântico Sul são escassas, essas duas simulações independentes com modelos globais de alta resolução adicionam confiança aos valores apresentados na literatura, relacionadosaos fluxos das bifurcações na costa do Brasil.Palavras-chave: circulação do Atlântico Sudoeste, massas de água, OCCAM, HYCOM.

scholarly journals Large-scale distribution of microbial and viral populations in the South Atlantic Ocean

2016 ◽  
Vol 8 (2) ◽  
pp. 305-315 ◽  
Author(s):  
Daniele De Corte ◽  
Eva Sintes ◽  
Taichi Yokokawa ◽  
Itziar Lekunberri ◽  
Gerhard J. Herndl
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South

scholarly journals Latitudinal distribution of <i>Trichodesmium</i> spp. and N<sub>2</sub> fixation in the Atlantic Ocean

2010 ◽  
Vol 7 (2) ◽  
pp. 2195-2225 ◽  
Author(s):  
A. Fernández ◽  
B. Mouriño-Carballido ◽  
A. Bode ◽  
M. Varela ◽  
E. Marañón
Keyword(s):  
Atlantic Ocean ◽  
N2 Fixation ◽  
Large Scale ◽  
Strong Association ◽  
Absolute Magnitude ◽  
South Atlantic ◽  
Equatorial Region ◽  
Latitudinal Distribution ◽  
Dust Deposition ◽  
The South

Abstract. We have determined the latitudinal distribution of Trichodesmium spp. abundance and community N2 fixation in the Atlantic Ocean along a meridional transect from ca. 30° N to 30° S in November–December 2007 and April–May 2008. The observations from both cruises were highly consistent in terms of absolute magnitude and latitudinal distribution, showing a strong association between Trichodesmium abundance and community N2 fixation. The highest Trichodesmium abundances (mean = 220 trichomes L−1) and community N2 fixation rates (mean = 60 μmol m−2 d−1) occurred in the Equatorial region between 5° S–15° N. In the South Atlantic gyre, Trichodesmium abundance was very low (ca. 1 trichome L−1) but N2 fixation was always measurable, averaging 3 and 10 μmol m2 d−1 in 2007 and 2008, respectively. We suggest that N2 fixation in the South Atlantic was sustained by other, presumably unicellular, diazotrophs. Comparing these distributions with the geographical pattern in atmospheric dust deposition points to iron supply as the main factor determining the large scale latitudinal variability of Trichodesmium spp. abundance and N2 fixation in the Atlantic Ocean. We observed a marked South to North decrease in surface phosphate concentration, which argues against a role for phosphorus availability in controlling the large scale distribution of N2 fixation. Scaling up from all our measurements (42 stations) results in conservative estimates for total N2 fixation of ~6 TgN yr−1 in the North Atlantic (0–40° N) and 1.2 TgN yr−1 in the South Atlantic (0–40° S).

scholarly journals Latitudinal distribution of <i>Trichodesmium</i> spp. and N<sub>2</sub> fixation in the Atlantic Ocean

2010 ◽  
Vol 7 (10) ◽  
pp. 3167-3176 ◽  
Author(s):  
A. Fernández ◽  
B. Mouriño-Carballido ◽  
A. Bode ◽  
M. Varela ◽  
E. Marañón
Keyword(s):  
Atlantic Ocean ◽  
N2 Fixation ◽  
Large Scale ◽  
Strong Association ◽  
Absolute Magnitude ◽  
South Atlantic ◽  
Equatorial Region ◽  
Latitudinal Distribution ◽  
Dust Deposition ◽  
The South

Abstract. We have determined the latitudinal distribution of Trichodesmium spp. abundance and community N2 fixation in the Atlantic Ocean along a meridional transect from ca. 30° N to 30° S in November–December 2007 and April–May 2008. The observations from both cruises were highly consistent in terms of absolute magnitude and latitudinal distribution, showing a strong association between Trichodesmium abundance and community N2 fixation. The highest Trichodesmium abundances (mean = 220 trichomes L−1,) and community N2 fixation rates (mean = 60 μmol m−2 d−1) occurred in the Equatorial region between 5° S–15° N. In the South Atlantic gyre, Trichodesmium abundance was very low (ca. 1 trichome L−1) but N2 fixation was always measurable, averaging 3 and 10 μmol m2 d−1 in 2007 and 2008, respectively. We suggest that N2 fixation in the South Atlantic was sustained by other, presumably unicellular, diazotrophs. Comparing these distributions with the geographical pattern in atmospheric dust deposition points to iron supply as the main factor determining the large scale latitudinal variability of Trichodesmium spp. abundance and N2 fixation in the Atlantic Ocean. We observed a marked South to North decrease in surface phosphate concentration, which argues against a role for phosphorus availability in controlling the large scale distribution of N2 fixation. Scaling up from all our measurements (42 stations) results in conservative estimates for total N2 fixation of ∼6 TgN yr−1 in the North Atlantic (0–40° N) and ~1.2 TgN yr−1 in the South Atlantic (0–40° S).

scholarly journals Modulation of Midtropospheric CO2 by the South Atlantic Walker Circulation*

2015 ◽  
Vol 72 (6) ◽  
pp. 2241-2247 ◽  
Author(s):  
Xun Jiang ◽  
Edward T. Olsen ◽  
Thomas S. Pagano ◽  
Hui Su ◽  
Yuk L. Yung
Keyword(s):  
South America ◽  
Atlantic Ocean ◽  
Large Scale ◽  
Climate Models ◽  
Walker Circulation ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Strong Impact ◽  
The South ◽  
Near Surface

Abstract Midtropospheric CO2 data from the Atmospheric Infrared Sounder (AIRS) are used in this study to explore the variability of CO2 over the South Atlantic Ocean. It was found that the area-averaged CO2 over the South Atlantic Ocean is less than that over South America by about 1 ppm during December–March. This CO2 contrast is due to the large-scale vertical circulation over this region. During December–March, there is sinking motion over the South Atlantic Ocean. The sinking motion brings high-altitude air with a slightly lower concentration of CO2 to the midtroposphere. Meanwhile, air rising over South America brings near-surface air with a higher concentration of CO2 to the midtroposphere. As a result, the AIRS midtropospheric CO2 concentration is lower over the South Atlantic Ocean than over South America during December–March. The detrended AIRS midtropospheric CO2 difference correlates well with the inverted and detrended 400-hPa vertical pressure velocity difference between the South Atlantic and South America. Results obtained from this study demonstrate the strong impact of large-scale circulation on the vertical distribution of CO2 in the free troposphere and suggest that midtropospheric CO2 measurements can be used as an innovative observational constraint on the simulation of large-scale circulations in climate models.

scholarly journals Rockhopper penguins and other marine life threatened by driftnet fisheries at Tristan da Cunha

Oryx ◽  
1991 ◽  
Vol 25 (2) ◽  
pp. 76-79 ◽  
Author(s):  
Peter G. Ryan ◽  
John Cooper
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
Fishing Effort ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Target Species ◽  
The South ◽  
Tristan Da Cunha ◽  
The Pacific ◽  
The Impact

The oriental driftnet fleet, which is responsible for the large-scale mortality of non-target species in the Pacific Ocean, has extended its range to include the South Atlantic Ocean. Relatively little is known about the areas of operation and impacts of driftnetting in the South Atlantic as yet, but it is emerging that driftnetting is equally devastating to the fauna of this ocean. This paper reviews the impact of the driftnet fishery on non-target species in the central South Atlantic Ocean. Several lines of evidence suggest that fishing effort is focused on Tristan da Cunha, apparently resulting in considerable mortality of rockhopper penguins Eudyptes chrysocome and other marine organisms. Britain should take steps to curb this destructive fishing technique in Tristan waters.

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