Yoshimine Ikeda

A corrente do Brasil ao largo da costa leste brasileira

Existe limitada e esparsa informacao na literatura sobre a Corrente do Brasil, a corrente de contorno que fecha o Giro Subtropical do Atlântico Sul em sua borda oeste. Neste artigo, compilamos as informacoes atualmente disponiveis na literatura para fornecer uma visao dos aspectos cinematicos e dinâmicos desta corrente, enquanto flui ao largo do Leste Brasileiro. Discutimos sua composicao em termos de massas de agua e de sua extensao vertical em diversas latitudes. Tambem apresentamos levantamento atualizado sobre aspectos cinematicos desta corrente, tanto em termos de velocidades observadas e geostroficas como de transportes de volume. Informacoes sobre o meandramento e formacao de vortices na Corrente do Brasil, ao largo da costa Sudeste, e seu provavel papel na penetracao da Agua Central do Atlântico Sul. na quebra da plataforma continental, igualmente sao abordados.

Geostrophic transport in the Brazil current region north of 20°S

Geostrophic volume transports in the upper 500 m are computed from historical hydrographic data for the area off the Brazilian coast west of 30°W and between 7° and 20°S. On the basis of water mass distributions, potential density surfaces of σθ = 27.05 kg m−3 (360–670 m) and σθ = 27.6 kg m−3 (∼1200 m) are used for referencing the meridional and zonal components of the geostrophic shears, respectively. Near 15°S a northwestward flow of 8 Sv crosses 30°W. This current reaches the shelf near 10°S in February and March, the only two months for which observations are available near that latitude along the coast; of the 8 Sv, about 4 Sv continue towards the northwest into the North Brazil Current while another branch also carrying 4 Sv turns southward as the beginning of the Brazil Current. Between 10° and 20°S the Brazil Current does not appear to strengthen appreciably, but because of the likely existence of flow on the shelf these transport values represent lower limits to the actual ones. At 30°W, another westward flow of approximately 8–10 Sv enters the area near 10°S and serves to strengthen the North Brazil Current. The total transfer of 12 Sv or more from the South Equatorial Current into the North Brazil Current and later to other currents and the northern hemisphere may be an important factor contributing to the well-known weakness of the Brazil Current in its more northerly latitudes.

Observations on stages of upwelling in the region of Cabo Frio (Brazil) as conducted by continuous surface temperature and salinity measurements

A brief outline is given of the results of surface temperature and salinity to the west and southwest of Cabo Frio obtained in August of 1971 with a continuous recording Thermo-Salinograph (Bissett-Berman, Model 6600T). A rapid change was observed in the field distribution of temperature from 21.5-21.9oC to 15-21oC, and similary change in the distribution of salinity from 34.1-35.0o/oo to 35.3-36.0o/oo, over a time scale of seven days. The changes were accredited to the process of upwelling at the coastal region under the influence of E and NE winds. The occurrence of a surface counter-current moving upwind was detected. This anomaly, not explained on the basis of the Ekmans classical theory, was qualitatively explained as the result of a horizontal divergence in the wind-stress field.

Variações em escala média da temperatura e da salinidade do mar na região entre a Baía de Guanabara e Cabo Frio (17/08 a 26/08/1971)

Um aspecto importante a ser apontado no presente trabalho e o fato de se ter acompanhado de um modo ininterrupto, durante 10 dias, as anomalias nas distribuicoes das propriedades fisicas da agua do mar. Os resultados experimentais obtidos na regiao costeira a oeste de Cabo Frio durante esse pe riodo mostraram a preponderância dos processos advectivos e difusivos que alteram a distribuicao da temperatura e da salinidade na superficie do mar. Essa anomalia pode ser indicada por nuvens do tipo cumulos formada por conveccao penetrante, fato verificavel pela comparacao dos dados termicos de superficie, com fotografias obtidas pelo satelite ERTS.

Note on the occurrence of saline fronts in the Ilha Grande (RJ) region

Continuous records of temperature and salinity were obtained on the surface waters as function of the horizontal distances around Ilha Grande region, on June 21, 1975; an outflow of less saline (S~33.10o /oo ) and slightly warmer water was detected throughout the region between Ponta de Castelhanos and Ponta Grossa da Marambaia and a visible manifestation of a saline front was observed in the interaction of this outflow with the coastal and more saline water (S~ 35.4 to 35.6o /oo). The recorded salinity values in the east region of Ilha Grande, suggest that the source of less saline water is the runoff in the Baia de Sepetiba.

Seasonal characteristics of hydrography, turbulence and dispersion near Ilha Grande (RJ), Brazil, based on R/V "Prof. W. Besnard" data

Seasonal differences in sigma-t (1.8)3 temperature (4.0oC) and salinity (0.9‰) were observed during February/June 1976 in the vicinity of Ilha Grande off the coast of Brazil Estimates of static and dynamic stability were made through the calculation of Brunt-Vaisala frequencies and Richardson numbers, respectively. Both static and dynamic stability values were larger in February than in June for the same location and suggest a greater column stability in February than in June. Stations located in the northern and western channels of Ilha Grande, however, contained greater density reversals than to the east of the Island. Small scale dispersion studies were made using Rhomamine B dye to determine horizontal diffusion coefficients (K) east of the Island and in an embayment of the Island. The estimate for K was 9X103 cm2 s-1 east of the Island, about 2.6 times greater than the value estimated for the protected embayment.

Time series analysis of NOAA-4 sea surface temperature (SST) data

Abstract Through time series analysis of GOSSTCOMP satellite data, time differences in the occurrence of maximum and minimum mean monthly SSTs off the coast of Brazil were observed in the region of 20–28° S by 34–47° W and showed the maximum surface water temperature to lag the coastal land station (Cananeia) by two months and the minimum by one month. For annual components of SST, maximum amplitudes were observed at Cabo Frio (influenced by upwelling) and Cananeia (influenced by Malvinas current) and minimum amplitudes at coastal and oceanic area between Ubatuba and Santos, a more thermally stable area.

Estimation of annual heat flux balance at the sea surface from SST (NOAA-Satellite) and ships drift data off southeast Brazil

The objective of this work is to study the possibility of estimating the heat flux balance at the sea surface from GOSSTCOMP (Global Ocean Sea Surface Temperature Computation) developed by NOAA/NESS, USA, and sea surface current data based from ships drift information obtained from Pilot Charts, published by the Diretoria de Hidrografia e Navegacao (DHN, Brazilian Navy). The annual mean value of the heat flux balance at the sea surface off southeast Brazil for 1977, is estimated from data on the balance between the heat transported by the currents and that transported by eddy diffusion for each volume defined as 2o x 2o (Lat. x Long.) square with a constant depth equivalent to an oceanic mixed layer, 100 m thick. Results show several oceanic areas where there are net flows of heat from atmosphere towards the sea surface. In front of Rio de Janeiro the heat flow was downward and up to 70 ly day-1 and is probably related to the upwellirug phenomenon normally occurring in that area. Another coastal area between Lat. 25oS to 28oS indicated an downward flow up to 50 ly day-1; and for an area south of Lat. 27oS, Long. 040oW - 048oW an downward flow up to 200 ly day-1, where the transfer was probably due to the cold water of a nortward flux from the Falkland (Malvinas) Current. Results also show several oceanic areas where net flows of heat (of about -100 ly day-1) were toward the atmosphere. In the oceanic areas Lat. 19oS - 23oS and Lat. 24oS - 30oS, the flows were probably due to the warm water of a southward flux of the Brazil Current. The resulting fluxes from the warm waters of the Brazil Current when compared with those from warm waters of the Gulf Stream and Kuroshio, indicate that the Gulf Stream carries about 3.3 times and the Kuroshio 1.7 times more heat than the Brazil Current. These values agree with those of data available on the heat fluxes of the above mentioned Currents calculated by different methods (Budyko, 1974).

Distribuição da temperatura na superfície do mar obtida através do uso de sensores remotos na área compreendida entre Itanhaém e a Ilha de São Sebastião (SP)

The use of remote sensing in oceanography, has been largely increased, mainly because the synoptic look, the accuracy of the data as well as the economics aspects. This paper shows the features and the first results of some experiments performed in the offshore region near Santos Bay and Sao Sebastiao Island, in the southeast coast of Brazil. The technique seems to be powerfull in coastal circulation studies, as well as, in every process that uses the temperature as a natural tracer. The tide currents seem to have large influence in the area near the Santos Bay, with a surface mean speed of about 1.2 m/s, which can reach distances of about 50 n.m. One can note that the area can be divided, at least in surface terms, in two subareas, with different thermal behaviours, with the interface standing normal to the coast in front of Santos.