Vertical structure, energetics, and dynamics of the Brazil Current System at 22 degrees S-28 degrees S

Autor(es)

Rocha, Cesar B. ^[1] ; da Silveira, Ilson C. A. ^[2] ; Castro, Belmiro M. ^[3] ; Lima, Jose Antonio M. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo. Inst Oceanog

^[2] Univ Sao Paulo. Inst Oceanog

^[3] Univ Sao Paulo. Inst Oceanog

^[4] Petr Brasileiro SA. Ctr Pesquisas & Desenvolvimento Leopoldo A Miguez

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS; v. 119, n. 1, p. 52-69, JAN 2014.
• Citações Web of Science: 16

Resumo

We use four current meter moorings and quasi-synoptic hydrographic observations in conjunction with a one-dimensional quasi-geostrophic linear stability model to investigate downstream changes in the Brazil Current (BC) System between 22 degrees S and 28 degrees S. The data set depict the downstream thickening of the BC. Its vertical extension increases from 350 m at 22.7 degrees S to 850 m at 27.9 degrees S. Most of this deepening occurs between 25.5 degrees S and 27.9 degrees S and is linked to the bifurcation of the South Equatorial Current at intermediate depths (Santos bifurcation), which adds the Antarctic Intermediate Water flow to the BC. Geostrophic estimates suggest that the BC transport is increased by at least 4.3 Sv (approximate to 70%) to the south of that bifurcation. Moreover, the Santos bifurcation is associated with a substantial increase in the barotropic component of the BC System. On average, the water column average kinetic energy (IKE) is 70% baroclinic to the north and 54% barotropic to the south of the bifurcation. Additionally, the BC shows conspicuous mesoscale activity off southeast Brazil. The water column average eddy kinetic energy accounts for 30-60% of the IKE. Instabilities of the mean flow may give rise to these mesoscale fluctuations. Indeed, the linear stability analysis suggests that the BC System is baroclinically unstable between 22 degrees S and 28 degrees S. In particular, the model predicts southwestward-propagating fastest growing waves (approximate to 190 km) from 25.5 degrees S to 27.9 degrees S and quasi-standing most unstable modes (approximate to 230 km) at 22.7 degrees S. These modes have vertical structures roughly consistent with the observed eddy field. Key Points <list list-type={''}bulleted{''}> The Brazil Current thickens substantially off southeast Brazil Most of this deepening is associated with the Santos bifurcation The BC becomes more barotropic to the south of the Santos bifurcation (AU)

• Processo FAPESP: 10/13629-6 - Reconstituição da Dinâmica de mesoescala da Corrente do Brasil a partir da temperatura da superfície do mar
• Beneficiário: César Barbedo Rocha
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 08/58101-9 - Impact of the Southwestern Atlantic Ocean on South American climate for the 20th and 21st centuries
• Beneficiário: Tercio Ambrizzi
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 12/02119-2 - Reconstrução da dinâmica de mesoescala da corrente do Brasil a partir da temperatura da superfície do mar
• Beneficiário: César Barbedo Rocha
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Mestrado